## Multiplex Control System

#### Troubleshooting (cont'd)

22-274

8. About 1 second after you go into self-diagnosis mode 1, the ceiling light will indicate the DTC and repeat it every 3 seconds. If there is more than one DTC, the system will indicate them in ascending order, beginning from the DTC with the lowest numerical value. Troubleshoot the DTCs as indicated below:

- DTC 1, 2, and 3 (ECM/PCM P0600) simultaneously: Check for a short to body ground in the YEL wire between multiplex control unit terminal E10 and ECM/PCM terminal E24 and in the WHT/GRN wire between multiplex control unit terminal K10 and gauge assembly terminal A2. If both wires are OK, substitute a known-good multiplex control unit, gauge assembly and ECM/PCM one at a time, in that order and recheck for the DTCs after each substitution.
- DTC 2 and 5 simultaneously: Check for an open in the YEL wire between multiplex control unit terminal E10 and ECM/PCM terminal E24, If the wire is OK, substitute a known-good multiplex control unit, gauge assembly and ECM/PCM one at a time, in that order and recheck for the DTC's after each substitution.
- DTC 1, and 6 simultaneously: Check for an open in the WHT/GRN wire between multiplex control unit terminal K10 and gauge assembly terminal A2, If the wire is OK, substitute a known-good multiplex control unit, gauge assembly and ECM/PCM one at a time, in that order and recheck for the DTC's after each substitution.
- DTC 1 only (no other DTC's present): Substitute a known-good multiplex control unit and a gauge assembly one at a time, in that order and recheck for the DTC's after each substitution.
- DTC 2 only (no other DTC's present): Substitute a known-good multiplex control unit and a ECM/PCM one at a time, in that order and recheck for the DTCs after each substitution.
- DTC 3 only (no other DTC's present): Substitute a known-good multiplex control unit and recheck for the DTC.
- DTC 5 only (no other DTC's present): Substitute a known-good gauge assembly and recheck for the DTC.

- DTC 6 only (no other DTC's present): Substitute a known-good ECM/PCM and recheck for the DTC.

DTC | Cause
1 | The multiplex control unit cannot receive signals from the gauge assembly.
2 | The multiplex control unit cannot receive signals from the ECM/PCM.
3 | The multiplex control unit cannot receive signals from itself.
4 | The gauge assembly cannot receive signals from multiplex control unit and the ECM/PCM.
5 | The ECM/PCM cannot receive signals from multiplex control unit and the gauge assembly.