Technical Description of OBD-II Trouble Code
Malfunction in Control Module VSS Output B
What does that signify?
This generic powertrain diagnostic trouble code (DTC) is applicable to various OBD-II vehicles, including but not limited to Citroen, Chevy, Ford, Peugeot, GMC, Dodge, Ram, Ducati, etc.
When a code P0609 is stored, it means that the powertrain control module (PCM) has detected a malfunction in a specific vehicle speed sensor (VSS) output voltage signal.
In this scenario, the PCM or one of the many other on-board controllers was expected to provide a VSS output signal. The particular VSS output circuit is designated as “B”. To understand the specific function of this circuit for the vehicle in question, consult a reliable source of vehicle information.
Vehicles equipped with OBD-II diagnostic systems may have up to seventy on-board controllers that communicate via the controller area network (CAN).
The VSS is an electromagnetic sensor positioned near the transmission output shaft or rear differential. It completes a circuit by interacting with a toothed, steel reluctor attached to the output shaft or ring gear. The PCM and other controllers interpret the circuit completions and interruptions as a voltage wave form pattern, which is then interpreted as vehicle speed.
The VSS signal is usually shared with other controllers via the CAN after being received by a primary controller such as the PCM or transmission control module (TCM). If any secondary controller fails to receive the VSS signal or receives an inconsistent signal, a code P0609 will be stored and the malfunction indicator lamp (MIL) may illuminate.
Example photo of a VSS (Vehicle Speed Sensor):
What is the severity of this DTC?
VSS related codes can impact transmission shift strategy and engine drivability. A stored code P0609 should be considered severe and diagnosed/repaired promptly.
What are some of the symptoms of the code?
Symptoms of a P0609 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some P0609 troubleshooting steps?
If there are other VSS related codes stored, they should be diagnosed and repaired before attempting to diagnose the P0609 code.
To diagnose this code, you will need a diagnostic scanner, a digital volt/ohmmeter, and a reliable source of vehicle information.
Use the vehicle information source to search for technical service bulletins (TSB) that match the vehicle, the stored code, and the exhibited symptoms. If you find a relevant TSB, it may provide helpful diagnostic information.
Refer to 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 is necessary for a successful diagnosis.
After visually inspecting controller connectors and visible CAN harnesses, connect the scanner to the vehicle diagnostic port and retrieve all stored codes. If freeze frame data is available, make note of it. Clear the codes and test drive the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode without any codes being stored, it indicates an intermittent code and the problem may need to worsen before an accurate diagnosis can be made.
If the code is reset, continue with the diagnosis.
Warning: Before using the DVOM to test circuit resistance and continuity, disconnect all related controllers to avoid controller damage.
With the key on and the engine off, use the DVOM to test individual VSS output circuits at the appropriate controller. Compare your findings with VSS signal data. If no acceptable output signal is detected, suspect controller failure.
If an acceptable VSS output signal is discovered at the controller, use the DVOM to test individual circuits between each of the related controllers. Repair or replace system circuits or components as required and retest the VSS signal.
