Fault code P0608 is called “Control Module VSS Output “A” Malfunction” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P0608
Error code P0608 indicates that the powertrain control module (PCM) has detected a fault in a specific voltage output signal. It refers to the vehicle speed sensor (VSS) output “A”. This fault code is generic and applies to all computer-controlled vehicles.
The VSS output was expected to come either from the PCM itself or from one of the other on-board modules. Vehicles equipped with OBD-II diagnostic systems can use up to seventy onboard modules. They communicate with each other via the Controller Area Network (CAN).
The vehicle speed sensor (VSS) is electromagnetic and is used to close a circuit. Which provides one or more modules with an accurate signal reflecting the speed of the vehicle.
The VSS is usually located near the transmission output shaft, transfer case in 4WD, or in the rear differential. A toothed steel ring attached to the output shaft runs in close proximity to the electromagnetic sensor and closes the circuit.
The gaps between the teeth provide an interruption to the circuit. The PCM and other controllers receive these circuit interrupts as a voltage waveform. The frequency of this waveform is interpreted as the speed of the vehicle.
The VSS signal usually goes to the primary PCM or transmission control module (TCM). Once the primary module receives VSS data, it is transmitted to other controllers via the CAN controller network.
If any of these secondary modules cannot receive the VSS signal or receives an inconsistent VSS signal. Code P0608 will be stored, and the Malfunction Indicator Light (MIL) may illuminate.
Symptoms of vehicle malfunctions
The main signal that an error P0608 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
- The ABS and Traction Control System (TCS) light may illuminate.
- Output shaft speed sensor codes may appear.
- Input speed sensor codes may occur.
- Transmission light illuminated (transmission may not shift properly).
- Incorrect speedometer or odometer readings.
- Problems with a particular system, indicating a possible loss of communication in that area.
Codes related to VSS may affect shift strategy and engine controllability. Stored code P0608 is serious and should be corrected as soon as possible.
Factors that can cause this error code
The error code P0608 can mean that one or more of the following problems have occurred:
- PCM, TCM, or other electronic control unit has failed.
- Low battery voltage.
- Open or short circuit in the wiring harness related to the control module.
- Loose or damaged connectors.
- Poor grounding is a common cause.
- CAN bus may be faulty and have a short to ground or wire breakage.
- Control module programming error.
How to fix or reset OBD-2 code P0608
Some suggested steps for troubleshooting and fix the error code P0608:
- Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances error P0608 appeared.
- Clear the error codes from the computer memory and test-drive the vehicle to find out if the malfunction appears again.
- If the error code appears again, visually inspect the electrical wires and control module connector.
- Measure the battery voltage and compare it to the value specified in the manufacturer’s specifications.
- Check the integrity of the control module’s power and ground circuits with a multimeter.
- Evaluate control module operation following the vehicle manufacturer’s procedure.
- Clear the error code from the computer memory again, and test drive the vehicle to see if the problem is resolved.
Diagnose and repair of problems
In some vehicles, a memory saver must be installed before the battery is disconnected in order to retain the memory of the engine-ECU. If the engine-ECU loses its memory due to lack of power, the vehicle will not start until it is reprogrammed by your dealer.
Wiring checks should be performed systematically using the wiring diagram and pin values. If you check the wrong terminal, the ECM or associated module may fail.
With the key on and the engine off, use a multimeter to check the individual VSS output circuits on the associated controller. Compare your results with the VSS signal data. If an acceptable output signal is not detected, there is most likely a controller failure.
If a normal VSS output signal is detected on the controller, use a multimeter to test the individual circuits between each of the linked controllers. Repair or replace system circuits or components as necessary and recheck the VSS signal.
In most cases, controller failure is unlikely. In the case of error P0608 it is more likely that a programming error problem may be the cause.
On which vehicles does this problem occur most frequently
Fault code P0608 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Chevrolet (Silverado)
- Citroen
- Dodge (RAM)
- Ford (Focus)
- GMC
- Nissan
- Peugeot (206, 207, 406)
- Ssangyong (Kyron)
- GAZelle
- UAZ (Patriot)
Fault code P0608 can sometimes be found with other errors. The most common are the following: P0600, P0601, P0602, P0603, P0604, P0605, P0606, P0607, P0609.
