P0608 Control Module VSS Output A Malfunction
OBD-II Trouble Code Technical Description
Control Module VSS Output A Malfunction
What does that mean?
This generic powertrain diagnostic trouble code (DTC) typically applies to many OBD-II vehicles. That may include but is not limited to vehicles from Citroen, Chevy, Ford, Peugeot, GMC, Dodge, Ram, Ducati, etc.
The powertrain control module (PCM) has detected a malfunction in a particular vehicle speed sensor (VSS) output voltage signal when a code P0608 is stored.
In this case, a VSS output signal was expected to come from either the PCM itself or one of the many (other) on-board controllers. This particular VSS output circuit has been given the designation "A". Consult a source of reliable vehicle information for the specific function of this circuit as it pertains to the vehicle in question.
Vehicles which are equipped with OBD-II diagnostic systems may utilize as many as seventy on-board controllers. These controllers communicate via the controller area network (CAN).
The VSS is an electromagnetic sensor that is used to complete a circuit which provides one or more controllers with an accurate signal reflecting vehicle speed. The VSS is typically positioned near the output shaft of the transmission (or 4WD transfer case) or in the rear differential. A toothed, steel reluctor (permanently affixed to the output shaft or ring gear) passes within close proximity to the electromagnetic sensor and completes the circuit. The gaps between the teeth provide circuit interruptions. The PCM and other controllers receive these circuit completions and interruptions as a wave form pattern of voltage. The frequency of this wave form pattern is interpreted as vehicle speed.
The VSS signal is usually input to a primary controller, such as the PCM or transmission control module (TCM). Once the primary controller receives the VSS input, it is shared with other controllers via the CAN. If any of these secondary controllers fails to receive the VSS signal, or receives an inconsistent VSS signal, a code P0608 will be stored and a malfunction indicator lamp (MIL) may be illuminated.
Example photo of a VSS (Vehicle Speed Sensor):
What is the severity of this DTC?
VSS related codes may affect transmission shift strategy and engine drivability. A stored code P0608 should be classified as severe and diagnosed/repaired as quickly as possible.
What are some of the symptoms of the code?
Symptoms of a P0608 trouble code may include:
Erratic or incorrect speedometer/odometer Abnormal (automatic) transmission shifting Output shaft speed sensor codes Input speed sensor codes ABS or Traction Control System (TCS) codesWhat are some of the common causes of the code?
Causes for this code may include:
Defective PCM, TCM, or other controller Open or shorted circuits in the CAN Corroded, broken, or loose electrical connectors Controller programming errorWhat are some P0608 troubleshooting steps?
If other VSS related codes are stored, they will need to be diagnosed and repaired before attempting to diagnose the P0608.
A diagnostic scanner, a digital volt/ohmmeter, and a source of reliable vehicle information will be required to diagnose this code.
Use the vehicle information source to search technical service bulletins (TSB) that parallel the vehicle in question, as well as the code stored and the symptoms exhibited. If you find an applicable TSB, the likelihood that it will provide helpful diagnostic information is very great.
Utilize the vehicle information source for diagnostic flow charts, wiring diagrams, connector pin-out charts, connector face views, and component testing procedures/specifications. All this information will be required for a successful diagnosis.
After a visual inspection of controller conn
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