P0608 Control Module VSS Output “A” Malfunction P0609 Control Module VSS Output “B” Malfunction

P0608	Control Module VSS Output “A” Malfunction
P0609	Control Module VSS Output “B” Malfunction

The OBD-II trouble codes P0608 and P0609 both relate to malfunctions in the vehicle speed sensor (VSS) output signals in the engine control module (ECM) or powertrain control module (PCM).

P0608 - Control Module VSS Output “A” Malfunction: This code indicates that the ECM or PCM is not receiving the proper VSS signal from the VSS circuit "A". The VSS signal is used by the ECM or PCM to adjust various systems in the vehicle, such as the transmission, cruise control, and speedometer. A malfunction in this signal can cause a variety of drivability issues, such as harsh shifting, reduced fuel efficiency, or even stalling.

P0609 - Control Module VSS Output “B” Malfunction: This code indicates that the ECM or PCM is not receiving the proper VSS signal from the VSS circuit "B". This signal is used by the ECM or PCM to adjust the same systems as circuit "A". A malfunction in this signal can cause similar drivability issues as with P0608.

In order to diagnose and repair the issue, a qualified technician will need to use specialized diagnostic equipment to communicate with the ECM or PCM and identify the root cause of the VSS output malfunction. The technician may need to test the wiring and connectors associated with the VSS circuits, as well as perform tests on the VSS sensor itself.

Once the root cause of the issue is identified, the technician may need to repair or replace the VSS sensor, repair or replace the wiring and connectors associated with the VSS circuits, or replace the ECM or PCM if it is determined that the VSS output circuits in the control module are at fault.

It is important to address these issues promptly, as malfunctions in the VSS signal can cause a variety of drivability issues and may even cause the vehicle to stall or fail to start.