The P0501 code means: Vehicle Speed Sensor “A” Range/Performance. It is a generic code that can be present in any car model of any brand, with more or less similar definitions.
A weak signal output from the VSS (vehicle speed sensor) is the cause of many engine difficulties, such as erratic gear changes or excessively fast or slow shifting.
This is a general OBD-II fault code, which applies to all OBD-II equipped vehicles, particularly those manufactured after 1996. It is important to note that the definition, diagnosis and repair specifications differ from model to model. other.
VSS Sensor Operation
In most cases, the VSS employs a rotating reluctor ring to complete an input circuit to the PCM, which is typically an electromagnetic sensor.
The VSS is installed in the gearbox housing so that the reluctor ring can pass through it; It is quite close to the reluctor ring.
There is an output shaft connected to the reluctor ring that rotates with the transmission. The notches and grooves in the reluctor ring fill in and break the circuit quickly as it passes the electromagnetic tip of the VSS.
The PCM recognizes these circuit changes as transmission output speed or vehicle speed, processing these signals and acting accordingly.
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What is the P0501 code?
Fault code P0501 OBD2 indicates that the vehicle speed read by the vehicle speed sensor (VSS) is outside the expected range. For example, it is too high or too low.
The VSS (Vehicle Speed) sensor is responsible for transmitting this information to the ECM module which, in turn, sends this information to the speedometer and odometer.
The primary function of the vehicle speed sensor (VSS) is to send data to the vehicle’s PCM (powertrain control module) about how fast the car is traveling. The speedometer displays this information in kilometers per hour (km/h).
It does this by providing a 4-pulse signal for each revolution of the rotor shaft, which rotates the output shaft through a driven gear. Typically, the VSS is an electromagnetic sensor that uses rotation to send a signal to the ECM.
The VSS It is mounted on the gearbox housing in a position where pulses from the gearbox can pass very close to it. When the box emits pulses, they will pass through the tip of the VSS solenoid.
These signals are recognized by the PCM module as the transmission output speed or the vehicle speed. Which allows us to see the usual speed display on the speedometer.
Additionally, the PCM uses this information to control the timing of other signals.
Symptoms of Code P0501
The vehicle speed sensor changes too quickly or is not synchronized with WSS; therefore, a DTC code P0501 is issued if the signal does not fall within the expected range or changes too quickly.
For example, the vehicle speed sensor drops instantly and then rises to 50 kph while the cruise control remains constant.
Faulty circuits or sensors and mechanical system failures can affect the functionality and range of the vehicle speed sensor.
The main sign that a P0501 error has occurred is the Malfunction Indicator Lamp (MIL), also known as Check Engine.
You may also see the following symptoms to a greater or lesser extent:
- The vehicle’s anti-lock braking system (ABS) and traction control system (TCS) are disabled.
- The ABS warning lights activate on the dashboard.
- The speedometer does not work.
- The vehicle’s rev limiter may be lower than normal.
- The automatic transmission may have trouble shifting gears.
- You will see the check engine light come on.
Under certain circumstances, the driver may not detect any adverse conditions, and may only notice the Check Engine light on the dashboard.
What Are the Probable Causes of Code P0501?
Depending on the year of manufacture and model, DTC code P0501 may be caused by several factors. Here are some of the most common ones.
- The most common causes of VSS failure are age and mileage. The VSS sensor can usually be ruled out as the source of the problem after performing circuit tests and getting no results.
- Like crankshaft position sensors, some VSSs produce their signal through the use of a ring. Metal flakes can build up on the electromagnetic tip of the VSS and affect the signal.
- The clarity of the VSS signal is usually restored after a thorough cleaning, although closer examination may be necessary to find the metal particles causing it.
- The VSS voltage output is lower than expected, resulting in an output speed lower than the actual vehicle speed.
- The transmission or differential gears feed the VSS. An irregular VSS signal can be the result of broken teeth in any of the gears. VSS replacement or transmission repair may be necessary.
- The wire going to the vehicle speed sensor is broken or frayed.
- Connection problems in the VSS sensor circuit.
- Change in the size of the car’s wheels, without the proper configuration in the PCM.
- The engine control module (ECM) may be defective.
How to Diagnose a P0501 Code?
This trouble code is easy to identify as it is unique to this code and its control system.
1. Connect the scanner and check the code
- First, you must scan the codes and record the information using an OBD2 scanner.
- Then clear the error codes and test drive the vehicle to see if there are any problems.
- After this, if the code returns, check the vehicle speed sensor and all relevant wires for wear or damage.
2. Check the wiring
- Visually inspect all wiring and connectors going to the speed sensor. Look carefully for abrasions, frayed wires, or broken wires. Also, look for melted or damaged areas. Repair if necessary.
3. Check the VSS sensor
- The location of the sensors varies depending on the make and model of the vehicle. Rear axle components, wheel hubs, and transmission sensors are all possibilities for where the sensor will be located.
4. Check the VSS sensor with a multimeter
- When the cable and connectors have been checked and are in good condition, check the VSS signal output. Again, the particular process depends on the model and brand of the car.
- It also checks with the scanner if there is a signal from the speed sensor when the car is running.
- The ECM-VSS input circuit should be checked first. The resistance between the ECM memory and the VSS should be 0 ohms and more than 10 thousand ohms for power or ground. When the ignition is turned on, the VSS should have a reference voltage of 5V and a solid ground connection.
- The VSS can be checked by detecting the DC pulse on the signal cable and spinning the wheels with a multimeter when the wheels are not touching the ground.
- It is possible to detect a two-wire VSS by detecting an increase in AC voltage and increasing the speed of the moving wheels.
5. Disassemble the VSS sensor and clean it
- The VSS electrical connection is inspected for loose or corroded connections.
- Remove the VSS and inspect the sensor tip for any metal particles that are causing the weak signal. Clean and retest to make it work properly.
6. Change the VSS sensor
- If cleaning the sensor does not work, it is because the sensor has a problem. You must exchange it for an original part.
- The location of the sensor depends on your vehicle, it is not always installed in the box. It may be on the rear transmission axle or wheel hub (brake) assembly.
Possible Repairs With Code P0501
- An engine control module (ECM) problem can cause the P0501 code. Therefore, it is highly recommended to replace the engine control module if any problem is detected.
- When it comes to the safety of your car, you cannot afford to overlook the ABS system. The P0501 code may start flashing if there is something wrong with it.
- If your tachometer is damaged or broken, you will see intermittent signals, although this does not mean you have problems with the sensor. You should check the tachometer if you think it is failing.
- The most common cause of the P0501 error code is a faulty wiring harness. Therefore, you should perform a thorough check of this harness before deciding to change the sensor.
Common Errors When Diagnosing and Repairing Code P0501
As in most repair tasks carried out on the car, a good diagnosis is a fundamental part of doing the job well.
The most common error with this code is to go directly to change the sensor without checking the status of the system.
The VSS is not replaced before validating that the sensor output is defective. You should also check the wiring harness.
Another common mistake happens when the VSS is not removed and checked for excess metal particles. This error is solved by cleaning the sensor.
Is Code P0501 Serious?
Fault code P0501 It is of medium severity. Indicates that the vehicle speed sensor is not working correctly. Its severity will depend on how much it affects other systems in the car.
The automatic transmission, ABS, traction control, and power steering can use this data. Therefore, these systems can be affected by this failure, even disabling the car.
One of the most common locations for the vehicle speed sensor is the rear differential or a gearbox output shaft, although it may also be located near a tire and coupled to a speedometer.
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Error code P0501 It definitely needs to be resolved as soon as possible as it can cause serious damage due to erratic transmission shifting. Additionally, the Check Engine light almost always guarantees that the vehicle will fail the emissions test.
If you want to know other articles similar to Code P0501. Vehicle Speed Sensor “A” Range/Performance you can visit the category Fault Codes.