What Are Common E39 OBD2 Diagnostic Issues And Solutions?

The E39 Obd2 system serves as a crucial interface for diagnosing and maintaining your BMW E39. Understanding the intricacies of BMW E39 OBD2 diagnostics empowers owners and technicians to accurately troubleshoot issues. At MERCEDES-DIAGNOSTIC-TOOL.EDU.VN, we provide a comprehensive resource for mastering E39 diagnostics, enhanced scan tools, and E39 hidden features unlocking.

1. What is the E39 OBD2 Port and Where is it Located?

The E39 OBD2 (On-Board Diagnostics II) port is a standardized interface used to access the vehicle’s diagnostic data. This port allows mechanics and car owners to connect scan tools to retrieve diagnostic trouble codes (DTCs) and monitor various parameters of the vehicle’s systems. It is typically located under the dashboard on the driver’s side. The OBD2 port’s standardized nature makes it compatible with a wide range of diagnostic tools. Understanding its location and function is the first step in effective E39 BMW diagnostics.

The location of the OBD2 port in the E39 BMW is typically under the dashboard on the driver’s side, making it easily accessible for diagnostic procedures. Its function allows connectivity with various diagnostic tools, facilitating the retrieval of trouble codes and monitoring of vehicle parameters.

1.1 Why is the OBD2 Port Important for E39 Diagnostics?

The OBD2 port is crucial for E39 diagnostics because it offers a standardized way to communicate with the vehicle’s computer systems. This allows technicians to quickly identify problems, monitor performance, and verify repairs.

• Standardized Communication: The OBD2 port provides a universal interface, enabling different scan tools to interact with the vehicle’s computer.
• Trouble Code Retrieval: Diagnostic trouble codes (DTCs) are stored in the vehicle’s computer when a fault is detected. These codes can be read through the OBD2 port, pinpointing the source of the issue.
• Parameter Monitoring: Live data, such as engine temperature, RPM, and sensor readings, can be monitored in real-time via the OBD2 port, aiding in diagnosing intermittent issues.
• Emissions Testing: The OBD2 system monitors emissions-related components, and the port is used to verify compliance during inspections.
• Resetting Systems: After repairs, the OBD2 port can be used to reset diagnostic codes and clear warning lights.

1.2 Common Locations for the E39 OBD2 Port

While the OBD2 port location is standardized, it can vary slightly among different models and years of the E39. Generally, you can find it in one of these locations:

• Under the Dashboard (Driver’s Side): The most common location is beneath the dashboard on the driver’s side. You may need to crouch down and look under the steering column to find it.
• Near the Center Console: In some E39 models, the port might be located near the center console, close to the driver’s side.
• Behind a Panel: Occasionally, the OBD2 port is hidden behind a small removable panel.

1.3 How to Identify the OBD2 Port

The OBD2 port is a 16-pin, D-shaped connector. This specific shape and pin configuration are standardized, making it easy to identify. You can also refer to the vehicle’s owner’s manual for a precise location.

2. What Types of E39 OBD2 Scanners Are Available?

There are several types of E39 OBD2 scanners available, ranging from basic code readers to advanced professional-grade tools. Basic code readers are inexpensive and can read and clear diagnostic trouble codes (DTCs). More advanced scanners offer features such as live data streaming, freeze frame data, and bidirectional control. Professional-grade tools provide even more advanced capabilities, including module programming and detailed system diagnostics. Selecting the right tool depends on your needs and budget.

The types of E39 OBD2 scanners available range from basic to professional, each offering different levels of functionality. Basic code readers are suitable for simple diagnostics, while advanced scanners provide more in-depth analysis and capabilities.

2.1 Basic OBD2 Code Readers

Basic OBD2 code readers are entry-level tools designed for simple tasks such as reading and clearing diagnostic trouble codes (DTCs). These devices are typically inexpensive and easy to use, making them suitable for car owners who want to perform basic diagnostics.

• Functionality:
  • Read diagnostic trouble codes (DTCs)
  • Clear DTCs and reset the check engine light
  • View basic freeze frame data
• Pros:
  • Affordable
  • Easy to use
  • Compact and portable
• Cons:
  • Limited functionality
  • May not support advanced diagnostics or live data
  • Often lack vehicle-specific features
• Use Cases:
  • Diagnosing common issues indicated by the check engine light
  • Clearing codes after performing minor repairs
  • Verifying repairs after a mechanic’s work

2.2 Enhanced OBD2 Scanners

Enhanced OBD2 scanners offer more advanced features compared to basic code readers. These scanners often include capabilities such as live data streaming, freeze frame data, and the ability to perform some bidirectional tests.

• Functionality:
  • Read and clear DTCs
  • View live data streams (e.g., engine temperature, RPM, sensor readings)
  • Access freeze frame data (snapshot of data when the DTC was recorded)
  • Perform some bidirectional tests (e.g., turning on/off certain components)
  • Support vehicle-specific codes and diagnostics
• Pros:
  • More comprehensive diagnostics
  • Ability to monitor real-time data
  • Enhanced troubleshooting capabilities
• Cons:
  • More expensive than basic code readers
  • May require some technical knowledge to use effectively
• Use Cases:
  • Diagnosing more complex issues
  • Monitoring engine performance
  • Troubleshooting sensor-related problems
  • Performing basic component testing

2.3 Professional-Grade Diagnostic Tools

Professional-grade diagnostic tools are high-end devices designed for professional mechanics and advanced DIYers. These tools offer extensive capabilities, including module programming, advanced system diagnostics, and bidirectional control.

• Functionality:
  • Read and clear DTCs
  • View live data streams
  • Perform bidirectional control (activate/deactivate components)
  • Module programming and coding
  • Advanced system diagnostics (ABS, SRS, transmission, etc.)
  • Vehicle-specific diagnostics and functions
  • Access to technical service bulletins (TSBs)
• Pros:
  • Comprehensive diagnostic capabilities
  • Ability to perform advanced functions
  • Access to vehicle-specific data and procedures
• Cons:
  • Expensive
  • Requires extensive technical knowledge and training
  • Can be complex to use
• Use Cases:
  • Diagnosing and repairing complex issues
  • Programming and coding vehicle modules
  • Performing advanced system diagnostics
  • Accessing and utilizing technical service bulletins

2.4 Comparison Table of OBD2 Scanner Types

Feature	Basic Code Reader	Enhanced Scanner	Professional-Grade Tool
DTC Reading/Clearing	Yes	Yes	Yes
Live Data Streaming	No	Yes	Yes
Freeze Frame Data	Limited	Yes	Yes
Bidirectional Control	No	Limited	Yes
Module Programming	No	No	Yes
Vehicle-Specific Codes	Limited	Yes	Yes
Cost	Low	Medium	High
Ease of Use	High	Medium	Low
Technical Knowledge Needed	Low	Medium	High

3. How to Use an OBD2 Scanner on an E39 BMW?

Using an OBD2 scanner on an E39 BMW involves a few straightforward steps. First, locate the OBD2 port, typically found under the dashboard on the driver’s side. Turn on the ignition without starting the engine. Plug the scanner into the port and follow the scanner’s prompts to read diagnostic trouble codes (DTCs). Record any codes and use them to diagnose the issue. Once repairs are made, clear the codes using the scanner. Always refer to your scanner’s manual for specific instructions.

To use an OBD2 scanner on an E39 BMW, follow these steps: locate the OBD2 port, connect the scanner, turn on the ignition, read the codes, diagnose the issue, and clear the codes after repairs. Proper use of an OBD2 scanner can greatly assist in diagnosing and resolving vehicle issues.

3.1 Step-by-Step Guide to Connecting and Using an OBD2 Scanner

Here’s a detailed step-by-step guide on how to connect and use an OBD2 scanner on your E39 BMW:

1. Locate the OBD2 Port:
   • The OBD2 port is usually located under the dashboard on the driver’s side. It may be near the steering column or center console.
2. Prepare the Vehicle:
   • Turn off the ignition.
   • Ensure the vehicle is parked in a safe location.
3. Connect the OBD2 Scanner:
   • Plug the OBD2 scanner into the OBD2 port. Ensure it is securely connected.

E39 OBD2 Port Location

4. Turn on the Ignition:
   • Turn the ignition key to the “ON” position without starting the engine. This provides power to the vehicle’s computer systems.
5. Power on the Scanner:
   • The scanner should power on automatically once connected. If not, check the scanner’s power button.
6. Navigate the Scanner Menu:
   • Use the scanner’s menu to select the appropriate function. Common options include:
     • Read Codes: Retrieves diagnostic trouble codes (DTCs) stored in the vehicle’s computer.
     • Clear Codes: Erases DTCs and resets the check engine light.
     • Live Data: Displays real-time data from various sensors and systems.
     • Freeze Frame: Shows data captured when a DTC was first recorded.
7. Read Diagnostic Trouble Codes (DTCs):
   • Select the “Read Codes” option to retrieve any stored DTCs.
   • Record the codes and their descriptions. These codes will help you diagnose the issue.
8. Diagnose the Issue:
   • Use the DTCs to research the potential causes of the problem. Online resources, repair manuals, and technical forums can be helpful.
9. Perform Repairs:
   • Based on your diagnosis, perform the necessary repairs. This may involve replacing faulty sensors, repairing wiring, or addressing mechanical issues.
10. Clear the Codes:
    • After completing the repairs, select the “Clear Codes” option on the scanner.
    • This will erase the DTCs and reset the check engine light.
11. Verify the Repair:
    • Start the engine and monitor the vehicle to ensure the issue is resolved.
    • Use the scanner to monitor live data and confirm that all systems are functioning correctly.

3.2 Interpreting OBD2 Codes

Interpreting OBD2 codes involves understanding the standardized format and using resources to determine the specific issue. Each code consists of five characters: a letter followed by four numbers. The letter indicates the system (P for powertrain, B for body, C for chassis, and U for network). The numbers provide further detail about the fault.

• First Character:
  • P (Powertrain): Relates to the engine, transmission, and associated components.
  • B (Body): Concerns the body of the vehicle, including doors, seats, and airbags.
  • C (Chassis): Involves the chassis, such as brakes, suspension, and steering.
  • U (Network): Relates to the vehicle’s communication network.
• Second Character:
  • 0: Standardized (SAE) code
  • 1: Manufacturer-specific code
• Third Character:
  • Indicates the specific system area:
    • 1: Fuel and air metering
    • 2: Fuel and air metering (injector circuit)
    • 3: Ignition system or misfire
    • 4: Auxiliary emission controls
    • 5: Vehicle speed control and idle control system
    • 6: Computer output circuit
    • 7: Transmission
    • 8: Transmission
• Fourth and Fifth Characters:
  • Specific fault code number

3.3 Common OBD2 Codes for E39 BMWs

Here are some common OBD2 codes that may appear on an E39 BMW:

• P0170: Fuel Trim Malfunction (Bank 1)
  • Indicates that the engine’s air-fuel mixture is too lean or too rich.
  • Possible causes include vacuum leaks, faulty oxygen sensors, or issues with the fuel system.
• P0173: Fuel Trim Malfunction (Bank 2)
  • Similar to P0170 but applies to Bank 2 of the engine.
• P0300: Random Misfire Detected
  • Indicates that the engine is experiencing random misfires.
  • Possible causes include faulty spark plugs, ignition coils, or fuel injectors.
• P0301 – P0306: Misfire Detected in Cylinder (1-6)
  • Specifies which cylinder is experiencing a misfire.
  • Possible causes include faulty spark plugs, ignition coils, fuel injectors, or compression issues.
• P0420: Catalyst System Efficiency Below Threshold (Bank 1)
  • Indicates that the catalytic converter is not functioning efficiently.
  • Possible causes include a faulty catalytic converter, oxygen sensors, or exhaust leaks.
• P1624: DME EWS Manipulation
  • Indicates a problem with the communication between the DME (engine control module) and the EWS (immobilizer system).
  • Possible causes include a faulty EWS module, DME, or wiring issues.

4. What Are Common E39 OBD2 Diagnostic Problems?

Common E39 OBD2 diagnostic problems include issues with the OBD2 port itself, communication errors, and inaccurate readings. Problems with the OBD2 port can be caused by physical damage or corrosion. Communication errors may occur due to faulty wiring or issues with the vehicle’s computer. Inaccurate readings can result from faulty sensors or outdated software in the scan tool. Understanding these common problems can help you troubleshoot diagnostic issues more effectively.

Common E39 OBD2 diagnostic problems include port issues, communication errors, and inaccurate readings. Identifying and addressing these problems can improve the accuracy and reliability of diagnostic results.

4.1 Issues with the OBD2 Port

The OBD2 port can sometimes be the source of diagnostic problems. Common issues include physical damage, corrosion, and loose connections.

• Physical Damage:
  • The OBD2 port can be damaged by repeated use or accidental impact.
  • Damaged pins can prevent the scanner from making a proper connection.
• Corrosion:
  • Moisture and environmental factors can cause corrosion on the OBD2 port’s pins.
  • Corrosion can disrupt the electrical connection and prevent communication with the scanner.
• Loose Connections:
  • Over time, the pins in the OBD2 port can become loose, leading to intermittent or no connection.
  • Loose connections can cause inaccurate readings or prevent the scanner from powering on.

4.2 Communication Errors

Communication errors between the OBD2 scanner and the vehicle’s computer can also cause diagnostic problems.

• Faulty Wiring:
  • Damaged or corroded wiring between the OBD2 port and the vehicle’s computer can disrupt communication.
  • Check the wiring for any signs of damage, such as cuts, abrasions, or corrosion.
• ECU Issues:
  • Problems with the vehicle’s engine control unit (ECU) can prevent communication with the scanner.
  • ECU issues may include software glitches, hardware failures, or corrupted data.
• Scanner Compatibility:
  • Some OBD2 scanners may not be fully compatible with all E39 models or specific systems.
  • Ensure that your scanner is compatible with your vehicle and supports the necessary diagnostic protocols.

4.3 Inaccurate Readings

Inaccurate readings from the OBD2 scanner can lead to misdiagnosis and unnecessary repairs.

• Faulty Sensors:
  • Faulty sensors can provide incorrect data to the vehicle’s computer, resulting in inaccurate readings on the scanner.
  • Common culprits include oxygen sensors, temperature sensors, and mass airflow sensors.
• Outdated Software:
  • Outdated software in the OBD2 scanner can cause inaccurate readings or prevent the scanner from recognizing certain codes.
  • Ensure that your scanner is updated with the latest software.
• Incorrect Configuration:
  • Incorrect configuration of the OBD2 scanner, such as selecting the wrong vehicle model or diagnostic protocol, can lead to inaccurate readings.

5. How to Troubleshoot E39 OBD2 Communication Problems?

Troubleshooting E39 OBD2 communication problems involves checking the OBD2 port, verifying the scanner’s compatibility, inspecting wiring, and testing the vehicle’s battery. Start by visually inspecting the OBD2 port for damage or corrosion. Ensure that your scanner is compatible with the E39 model and supports the correct diagnostic protocols. Inspect the wiring between the OBD2 port and the vehicle’s computer for any signs of damage. Test the vehicle’s battery to ensure it is providing sufficient power. If these steps do not resolve the issue, further diagnostics may be required.

To troubleshoot E39 OBD2 communication problems, inspect the port, verify scanner compatibility, check wiring, and test the battery. Systematic troubleshooting can help identify and resolve communication issues.

5.1 Checking the OBD2 Port for Damage or Corrosion

The first step in troubleshooting OBD2 communication problems is to inspect the port for any signs of damage or corrosion.

1. Visual Inspection:
   • Examine the OBD2 port for any physical damage, such as bent or broken pins.
   • Look for signs of corrosion, such as rust or green residue, on the pins or inside the connector.
2. Cleaning the Port:
   • If you find corrosion, use a small brush or contact cleaner to gently clean the pins.
   • Ensure that the port is completely dry before attempting to connect the scanner.
3. Testing the Connection:
   • Try connecting the OBD2 scanner to the port.
   • If the scanner does not power on or establish a connection, the port may be damaged and need replacement.

5.2 Verifying Scanner Compatibility

Ensure that your OBD2 scanner is compatible with the E39 BMW model and supports the correct diagnostic protocols.

1. Check the Scanner Manual:
   • Refer to the scanner’s manual or manufacturer’s website to verify compatibility with your vehicle.
   • Look for specific mention of E39 BMW models or the diagnostic protocols supported (e.g., ISO 9141-2, KWP2000).
2. Software Updates:
   • Ensure that the scanner has the latest software updates installed.
   • Outdated software may not support newer vehicle models or diagnostic protocols.
3. Try a Different Scanner:
   • If possible, try using a different OBD2 scanner to see if it can establish a connection.
   • This can help determine whether the issue is with the scanner or the vehicle.

5.3 Inspecting Wiring and Connections

Inspect the wiring and connections between the OBD2 port and the vehicle’s computer for any signs of damage or loose connections.

1. Locate Wiring Diagrams:
   • Obtain wiring diagrams for your E39 BMW to identify the specific wires connected to the OBD2 port.
   • These diagrams can be found in repair manuals or online resources.
2. Visual Inspection:
   • Carefully inspect the wiring for any signs of damage, such as cuts, abrasions, or corrosion.
   • Check the connectors for loose or corroded pins.
3. Testing Continuity:
   • Use a multimeter to test the continuity of the wires between the OBD2 port and the vehicle’s computer.
   • Ensure that there are no breaks or shorts in the wiring.
4. Repairing Wiring:
   • If you find any damaged wiring, repair it using appropriate techniques, such as soldering and heat-shrinking.
   • Replace any damaged connectors with new ones.

5.4 Testing the Vehicle’s Battery

A weak or failing battery can sometimes cause communication problems with the OBD2 system.

1. Check Battery Voltage:
   • Use a multimeter to check the battery voltage.
   • A fully charged battery should have a voltage of around 12.6 volts.
2. Load Test:
   • Perform a load test on the battery to check its ability to maintain voltage under load.
   • A load tester can be used to simulate the electrical load of the vehicle’s systems.
3. Clean Battery Terminals:
   • Clean the battery terminals and connectors to ensure a good electrical connection.
   • Use a wire brush and battery terminal cleaner to remove any corrosion.
4. Replace Battery:
   • If the battery is weak or failing, replace it with a new one.
   • Ensure that the new battery is properly installed and connected.

6. What Are Common E39 Sensor Issues Identified Through OBD2?

Common E39 sensor issues identified through OBD2 diagnostics include problems with oxygen sensors, mass airflow (MAF) sensors, and crankshaft position sensors. Faulty oxygen sensors can cause fuel trim issues and decreased fuel efficiency. MAF sensor problems can result in poor engine performance and incorrect air-fuel mixtures. Crankshaft position sensor failures can lead to starting problems and engine misfires. Identifying these sensor issues early can prevent more significant problems.

Common E39 sensor issues identified through OBD2 include oxygen sensor, MAF sensor, and crankshaft position sensor problems. Addressing these issues promptly can maintain optimal engine performance.

6.1 Oxygen Sensor Problems

Oxygen sensors are critical components of the engine management system, monitoring the oxygen content in the exhaust gases. Issues with oxygen sensors can lead to various problems.

• Symptoms:
  • Check engine light
  • Poor fuel economy
  • Rough idling
  • Failed emissions test
• Common OBD2 Codes:
  • P0130: O2 Sensor Circuit Malfunction (Bank 1, Sensor 1)
  • P0135: O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
  • P0170: Fuel Trim Malfunction (Bank 1)
• Troubleshooting:
  • Inspect the sensor for damage or contamination.
  • Check the wiring and connectors for corrosion or loose connections.
  • Use a multimeter to test the sensor’s resistance and voltage.
  • Replace the sensor if it is faulty.

6.2 Mass Airflow (MAF) Sensor Problems

The mass airflow (MAF) sensor measures the amount of air entering the engine, providing crucial data for fuel injection calculations.

• Symptoms:
  • Check engine light
  • Poor engine performance
  • Stalling
  • Rough idling
• Common OBD2 Codes:
  • P0100: Mass or Volume Air Flow Circuit Malfunction
  • P0102: Mass or Volume Air Flow Circuit Low Input
  • P0103: Mass or Volume Air Flow Circuit High Input
• Troubleshooting:
  • Inspect the sensor for damage or contamination.
  • Check the wiring and connectors for corrosion or loose connections.
  • Clean the sensor with MAF sensor cleaner.
  • Replace the sensor if it is faulty.

6.3 Crankshaft Position Sensor Problems

The crankshaft position sensor monitors the position and speed of the crankshaft, providing critical data for ignition and fuel injection timing.

• Symptoms:
  • Check engine light
  • Starting problems
  • Engine misfires
  • Stalling
• Common OBD2 Codes:
  • P0335: Crankshaft Position Sensor A Circuit Malfunction
  • P0336: Crankshaft Position Sensor A Circuit Range/Performance
• Troubleshooting:
  • Inspect the sensor for damage or contamination.
  • Check the wiring and connectors for corrosion or loose connections.
  • Use a multimeter to test the sensor’s resistance and voltage.
  • Replace the sensor if it is faulty.

7. Can E39 OBD2 Be Used to Diagnose Transmission Issues?

Yes, E39 OBD2 can be used to diagnose transmission issues. The transmission control module (TCM) stores diagnostic trouble codes (DTCs) related to transmission problems, which can be read using an OBD2 scanner. These codes can help identify issues such as slipping gears, incorrect gear ratios, and solenoid malfunctions. In addition to reading codes, some advanced scanners can monitor live transmission data, such as temperature and gear selection, providing further insight into potential problems.

E39 OBD2 can diagnose transmission issues by reading DTCs and monitoring live data. This capability is essential for identifying and addressing transmission-related problems.

7.1 Common Transmission Codes for E39 BMWs

Here are some common transmission codes that may appear on an E39 BMW:

• P0700: Transmission Control System Malfunction
  • Indicates a general problem with the transmission control system.
  • Further diagnosis is needed to pinpoint the specific issue.
• P0720: Output Speed Sensor Circuit Malfunction
  • Indicates a problem with the output speed sensor, which monitors the speed of the transmission’s output shaft.
  • Possible causes include a faulty sensor, wiring issues, or a problem with the transmission control module (TCM).
• P0730: Incorrect Gear Ratio
  • Indicates that the transmission is not shifting into the correct gear.
  • Possible causes include low transmission fluid, faulty solenoids, or mechanical issues within the transmission.
• P0740: Torque Converter Clutch Circuit Malfunction
  • Indicates a problem with the torque converter clutch, which locks the engine and transmission together for improved fuel economy.
  • Possible causes include a faulty solenoid, wiring issues, or a problem with the torque converter itself.
• P1740: Torque Converter Clutch PWM Solenoid Circuit Malfunction
  • Indicates a specific problem with the pulse width modulation (PWM) solenoid that controls the torque converter clutch.
  • Possible causes include a faulty solenoid, wiring issues, or a problem with the TCM.

7.2 How to Diagnose Transmission Problems Using OBD2

To diagnose transmission problems using OBD2, follow these steps:

1. Connect the OBD2 Scanner:
   • Plug the OBD2 scanner into the OBD2 port.
   • Turn on the ignition without starting the engine.
2. Read Diagnostic Trouble Codes (DTCs):
   • Use the scanner to read any stored DTCs related to the transmission.
   • Record the codes and their descriptions.
3. Research the Codes:
   • Use online resources, repair manuals, or technical forums to research the potential causes of the DTCs.
   • Pay attention to any symptoms that accompany the codes.
4. Check Transmission Fluid Level and Condition:
   • Check the transmission fluid level using the dipstick (if equipped) or the fill plug.
   • The fluid should be at the correct level and have a clean, red color.
   • If the fluid is low, add the appropriate type of transmission fluid.
   • If the fluid is dark, burnt, or contains debris, the transmission may need to be serviced or rebuilt.
5. Monitor Live Data:
   • Use the scanner to monitor live transmission data, such as temperature, gear selection, and solenoid status.
   • This can help identify problems that are not indicated by DTCs.
6. Perform Bidirectional Tests (If Available):
   • Some advanced scanners can perform bidirectional tests on the transmission, such as activating solenoids or commanding gear changes.
   • This can help verify the functionality of specific components.

7.3 When to Seek Professional Help

While OBD2 diagnostics can help identify many transmission problems, some issues may require professional attention. Seek professional help if:

• You are not comfortable performing the necessary repairs.
• The transmission problems are complex or require specialized tools.
• You suspect internal damage to the transmission.
• The transmission continues to malfunction after performing basic troubleshooting steps.

8. What Role Does OBD2 Play in E39 Emissions Testing?

OBD2 plays a crucial role in E39 emissions testing by monitoring emissions-related components and systems. The OBD2 system continuously checks the performance of the catalytic converter, oxygen sensors, and other components to ensure they are functioning correctly. During emissions testing, the testing equipment connects to the OBD2 port to verify that all emissions-related systems are ready and that there are no active diagnostic trouble codes (DTCs) indicating a failure. If any problems are detected, the vehicle will fail the emissions test.

OBD2 plays a vital role in E39 emissions testing by monitoring emissions-related components and ensuring compliance with regulations. Successful completion of an emissions test is often required for vehicle registration and legal operation.

8.1 How OBD2 Monitors Emissions Systems

The OBD2 system continuously monitors various emissions-related components and systems to ensure they are functioning correctly. These components include:

• Catalytic Converter:
  • The catalytic converter reduces harmful pollutants in the exhaust gases.
  • The OBD2 system monitors the efficiency of the catalytic converter using oxygen sensors placed before and after the converter.
  • If the catalytic converter is not functioning efficiently, the OBD2 system will store a DTC.
• Oxygen Sensors:
  • Oxygen sensors measure the amount of oxygen in the exhaust gases, providing feedback to the engine control unit (ECU) for fuel injection adjustments.
  • The OBD2 system monitors the performance of the oxygen sensors to ensure they are providing accurate readings.
  • If an oxygen sensor is faulty, the OBD2 system will store a DTC.
• Evaporative Emission Control System (EVAP):
  • The EVAP system prevents fuel vapors from escaping into the atmosphere.
  • The OBD2 system monitors the EVAP system for leaks and other malfunctions.
  • If a leak or other problem is detected, the OBD2 system will store a DTC.
• Exhaust Gas Recirculation (EGR) System:
  • The EGR system reduces the formation of nitrogen oxides (NOx) by recirculating a portion of the exhaust gases back into the intake manifold.
  • The OBD2 system monitors the EGR system for proper operation.
  • If the EGR system is not functioning correctly, the OBD2 system will store a DTC.

8.2 Readiness Monitors and Their Importance

Readiness monitors are internal tests performed by the OBD2 system to verify the functionality of various emissions-related components and systems. These monitors must be completed before an emissions test can be performed.

• Catalyst Monitor:
  • Verifies the efficiency of the catalytic converter.
• Oxygen Sensor Monitor:
  • Verifies the performance of the oxygen sensors.
• EVAP System Monitor:
  • Verifies the integrity of the EVAP system.
• EGR System Monitor:
  • Verifies the proper operation of the EGR system.
• Secondary Air System Monitor:
  • Verifies the functionality of the secondary air injection system (if equipped).
• Fuel System Monitor:
  • Verifies the proper operation of the fuel system.

8.3 What to Do if Your E39 Fails an Emissions Test

If your E39 fails an emissions test, follow these steps:

1. Obtain the Emissions Test Report:
   • The emissions test report will indicate the reason for the failure, such as a specific DTC or incomplete readiness monitors.
2. Diagnose the Problem:
   • Use an OBD2 scanner to read any stored DTCs and research the potential causes.
   • Inspect the emissions-related components and systems for any signs of damage or malfunction.
3. Perform Repairs:
   • Based on your diagnosis, perform the necessary repairs.
   • This may involve replacing faulty sensors, repairing wiring, or addressing mechanical issues.
4. Clear the Codes:
   • After completing the repairs, use the OBD2 scanner to clear the DTCs.
5. Drive the Vehicle:
   • Drive the vehicle for a period of time to allow the readiness monitors to complete.
   • The driving cycle may vary depending on the specific monitors.
6. Re-Test the Vehicle:
   • Take the vehicle back to the emissions testing facility for a re-test.
   • Ensure that all readiness monitors are complete before the re-test.

9. Can E39 OBD2 Unlock Hidden Features?

Yes, E39 OBD2 can be used to unlock hidden features, but this requires specialized software and coding knowledge. Some features, such as daytime running lights, one-touch window operation, and alarm system settings, can be activated or customized using coding tools connected through the OBD2 port. However, incorrect coding can cause serious problems, so it’s essential to proceed with caution and follow reliable guides or seek professional assistance.

E39 OBD2 can unlock hidden features, but requires specialized tools and expertise. Proper coding can enhance vehicle functionality, while incorrect coding can lead to issues.

9.1 Common Hidden Features That Can Be Unlocked

Here are some common hidden features that can be unlocked on an E39 BMW using OBD2 coding:

• Daytime Running Lights (DRL):
  • Enable or disable daytime running lights.
  • Customize the brightness and style of the DRLs.
• One-Touch Window Operation:
  • Enable one-touch operation for all windows, allowing them to be fully opened or closed with a single press of the button.
• Alarm System Settings:
  • Adjust the sensitivity of the alarm system.
  • Enable or disable the audible alarm confirmation.
• Remote Key Functions:
  • Customize the functions of the remote key, such as unlocking all doors with a single press or opening the trunk.
• Automatic Door Locking:
  • Enable automatic door locking when the vehicle reaches a certain speed.
• Welcome Lights:
  • Activate welcome lights that turn on when the vehicle is unlocked, illuminating the exterior.
• Cornering Lights:
  • Enable cornering lights that illuminate the direction of the turn when the turn signal is activated.

9.2 Tools and Software Required for Unlocking Features

Unlocking hidden features on an E39 BMW requires specialized tools and software, including:

• OBD2 Coding Interface:
  • A compatible OBD2 interface that allows communication between the vehicle’s computer and the coding software.
  • Examples include the BMW ENET cable or the BMW ICOM interface.
• Coding Software:
  • Coding software that allows you to read and modify the vehicle’s coding data.
  • Examples include BMW Coding Tool, NCS Expert, and E-Sys.
• Laptop:
  • A laptop with the necessary software installed and a stable internet connection.
• Battery Charger:
  • A battery charger to maintain a stable voltage during the coding process.

9.3 Risks and Precautions When Unlocking Hidden Features

Unlocking hidden features on an E39 BMW can be rewarding, but it also carries certain risks. It’s essential to