P0491 Mercedes-Benz Auto Trouble Code

P0491 Mercedes-Benz OBD2 reports a sensor fault, replacement of the sensor is unlikely to resolve the underlying problem. The fault is most likely to be caused by the systems that the sensor is monitoring, but might even be caused by the wiring to the sensor itself.

Accelerator Pedal Position Sensor 1 Circuit Low and P2127 - Accelerator Pedal Position Sensor 2 Circuit Low would lead you to suspect a defective accelerator pedal position sensor.

P0491 Mercedes-Benz Possible Solution:

Vehicle Speed Sensor (VSS) Out of Self Test Range Indicates the VSS input signal is out of Self Test range. If the PCM detects a VSS input signal any time during Self Test, a DTC P1501 will be set and the test will abort. Noisy VSS input signal from Radio Frequency Interference/ Electro-Magnetic Interference (RFI/EMI) external sources such as ignition wires, charging circuit or after market equipment. Check for VSS input to be 0 mph when vehicle transmission is in Park.

P0491 Mercedes-Benz Description For All Models :

P0491 Mercedes-Benz Trouble Repair :

The sensors receive a 5 volt reference signal from the PCM. As pressure readings change, the sensor varies the voltage and the computer reads that to determine input. In the case of a broken wire, the sensor never sees the voltage and the computer assumes a major fault. So if you get this P0491 Mercedes-Benz code, first check to make sure you're getting a good 5 volt reference signal at the sensor.

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