I have a 2007 Mercedes Benz W204, C200 Kompressor that occasionally gets stuck in second gear. Whenever that occurs and the car has been parked, the gear shifts with a jerk or clunking sound when shifting to drive or reverse. The dashboard shows ABS light, ESP, and the run flat Indicator inoperative, constantly. I replaced the ABS sensor but the errors remained on the dashboard. The ECU returned the following errors after it was scanned.
D40A An implausible right front wheel speed signal was received
7266 Consequential fault
5110 Component ‘L6/2 (Right front axle rpm sensor)’ has an electrical fault.
5114 The signal of component ‘L6/2 (Right front axle rpm sensor)’ is implausible.
7271 Implausible values of rpm sensors:Speed at front axle
Based on the symptoms and error codes you’ve provided, it sounds like there is an issue with the right front wheel speed sensor (L6/2) on your W204 Mercedes-Benz C200 Kompressor. The wheel speed sensors are a critical part of the vehicle’s ABS, ESP (Electronic Stability Program), and run-flat indicator systems. They provide vital information about the rotational speed of each wheel to the car’s electronic control units (ECUs).
The error codes and symptoms indicate that the ABS ECU is not receiving plausible signals from the right front axle rpm sensor, which could cause the ABS light to illuminate and potentially trigger the ESP and run-flat warnings as well due to interconnected systems.
Here’s a breakdown of the issues related to the codes:
- D40A & 5114: Both these codes suggest that there is an implausible signal received from the right front axle rpm sensor. This could mean that the sensor is malfunctioning or that there is a wiring issue.
- 7266: This code indicates a consequential fault, which means it’s a fault that has occurred as a result of another problem. Given the context, it’s likely a result of the implausible signal from the wheel speed sensor.
- 5110: This indicates there is an electrical fault with the right front axle rpm sensor. This could mean there is a problem with the sensor itself, the wiring, or the connections.
- 7271: The implausible values from the rpm sensors at the front axle can cause the transmission control unit to have difficulty determining the correct gear to engage, especially if the vehicle relies on wheel speed for transmission shift points.
Here are steps you should take to address the problem:
- Inspect the Wheel Speed Sensor: Check the right front wheel speed sensor for any signs of damage or corrosion. The sensor can fail due to dirt build-up, metal shavings, or physical damage.
- Check the Wiring and Connectors: Inspect the wiring and connectors leading to the right front wheel speed sensor. Look for any signs of damage, corrosion, or loose connections that could cause an intermittent signal.
- Check the Sensor Gap: Ensure that the sensor is properly seated and the gap between the sensor and the reluctor ring is within specifications. An incorrect gap can lead to an implausible signal.
- Clear Codes and Test Drive: After the physical inspection and any necessary replacements or repairs, clear the error codes with a scan tool. Then, take the vehicle for a test drive to see if the codes reappear.
- Wheel Bearing Inspection: Sometimes a faulty wheel bearing can cause erratic signals if it allows too much play in the wheel hub, where the sensor reads the wheel speed.
- Further Diagnostics: If the problem persists, further diagnostics with a more advanced scan tool or oscilloscope may be necessary to monitor the live data from the wheel speed sensor.
- Transmission Connection: Given that there’s also a transmission symptom (getting stuck in second gear), it’s also possible that there’s an issue with how the transmission control module is interpreting the signals from the wheel speed sensors. A fault in the sensor or circuit could be affecting the transmission’s operation.
- Visit a Specialist: If the issue is not resolved with the above steps, it would be advisable to visit a Mercedes-Benz specialist or a workshop with the necessary expertise and equipment to diagnose and repair ABS, ESP, and transmission systems.
The interconnected nature of the ABS, ESP, and transmission systems means that a fault in one can affect the others, so it’s important to address these issues promptly to ensure the safety and proper functioning of your vehicle.
Thank you for your response. I forgot to mention one bit of very important information. When the car is parked, the scanner sees the right front wheel as having a different speed from the other three wheels.
Here’s a snapshot of what the scanner reports.
The first step may be to replace the sensor that is throwing incorrect readings. If that doesn’t fix it, the problem could be the ABS module itself.