- Truck Engines:
- With ADEM II and ADEM 2000 Engine Control Modules
If the 84-02 diagnostic fault code is active in an ECM, do not replace the ECM. The diagnostic fault code may be present due to an intermittent connection in the vehicle speed sensor or the diagnostic fault code may be present due to another problem in the circuit for the vehicle speed signal. Once the 84-02 diagnostic fault code is triggered, this code will stay active in the ECM for one hour of normal engine operation after the code occurs. After one hour of normal engine operation, the active 84-02 diagnostic fault code will be cleared. The 84-02 diagnostic fault code does not affect engine performance. Follow the normal troubleshooting procedures for the vehicle speed sensor if the 84-02 diagnostic fault code has not been cleared after one hour of normal engine operation, but stop short of replacing the ECM.