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Error Code P0501 is described as Vehicle Speed Sensor “A” Range/Performance. This means there’s an erratic signal output coming from the VSS (vehicle speed sensor) causing various problems to the engine such as erratic shifting, or too fast or too slow shifting.
This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II, especially vehicles made since 1996 up to present. Specifications on the definition, troubleshooting and repairs, vary from one make and/or model to another.
Error Code P0501 means the PCM (powertrain control module, also known as ECM or engine control module) has received an input coming from the VSS indicating the output of the system is out of range or erratic voltage output, which is unstable and smooth, and moves up or down.
This error code is related to:
- P0500 Vehicle Speed Sensor “A” Malfunction
- P0502 Vehicle Speed Sensor “A” Low Input
- P0503 Vehicle Speed Sensor “A” Intermittent/Erratic/High
As with other error codes, Error Code P0501 illuminates the Check Engine light. For other symptoms, the engine will experience drivability issues such as:
- Transmission shifting causing the engine to lose some power
- Speedometer works normally but may jump up and down and will read too low or too high than the actual road speed of the vehicle
- Transmission shifting may be too fast or too slow, depending whether the VSS signal output is too low or too high
There are a couple of possible causes for Error Code P0501, namely:
- VSS output voltage specifications is out of range as it jumps up or down faster than the PCM expects it
- VSS voltage output is lower than expected, causing a output speed lower than normal speed of the actual vehicle speed
How to Check
This error code is pretty easy to diagnose, first, technicians use their scanner to scan the codes and document information from the PCM.
Next, they monitor the signal from the VSS while driving at known speeds with the help of a GPS signal and other vehicle to see whether the speedometer is accurate and working within a few miles per hour.
Then, they check the VESS electrical connections for any corroded or loose connections.
Then, they remove the VSS and inspect the tip of the sensor for metal particles, which are known to cause a weak signal. They clean it and then retest the VSS proper its proper operation.
How to Fix
This error code is pretty easy to fix as well, and repairs are of course, derived from the diagnosis. Some of the most common repairs include:
- Repair of the wire connections in the VSS
- Replacing the VSS’s rear end or transmission
- Cleaning off metal particles, clearing the codes and taking the vehicle for a road test
One of the most common mistakes about this error code is not verifying that the output is bad due to old sensor before replacing VSS.
Many people also fail to remove and check the VSS for any metal particles that may be indicating a problem in the internal transaxle or rear axle components.
Error Code P0501 should definitely be solved as soon as possible, as it can cause serious damage to the transition due to erratic shifting. Also, Check Engine light almost always guarantees that the vehicle will fail emissions testing.