Scan Tool Does Not Communicate With Pcm
- Perform DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM.
- Turn ignition RUN. If ABS indicator lights, go to next step. If ABS indicator does not light, perform ABS diagnostic system test. See DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING in ANTI-LOCK - 4WAL - RWD TRUCKS - EXCEPT 1999 SIERRA & SILVERADO article in BRAKES.
- Select "chassis diagnostics" on scan tool main menu. If scan tool can communicate with EBCM, go to next step. If scan tool cannot communicate with EBCM, perform DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM.
- Select "powertrain diagnostics" on scan tool main menu. If scan tool cannot communicate with PCM, go to next step. If scan tool can communicate with PCM, perform DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM.
- Turn ignition OFF. Disconnect connector C3 from PCM. Check for continuity with DVOM between PCM connector terminal C8 and splice S150. If there is continuity, go to next step. If there is no continuity, go to step 7.
- Replace PCM. See REMOVAL, OVERHAUL & INSTALLATION - TRUCKS article in ENGINE PERFORMANCE article. Perform DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM.
- Repair open or resistance in Purple 1807 circuit wiring between EBCM and S107. Perform DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM.