Troubleshooting Multiple Indicator Lights

TROUBLESHOOTING MULTIPLE INDICATOR LIGHTS

The ABS/TCS and ATTS control units communicate with the ECM/PCM. If a DTC causes a loss of communication between two or more of these control units, the loss can cause multiple indicator lights to come on. For instance, when the ABS/TCS control unit stops getting data from the ECM/PCM, it sets a communication DTC such as TCS DTC 31 [engine retard command (PFINH) signal]. This DTC doesn't mean there's a circuit or control unit failure. It just means the flow of data between the ABS/TCS control unit and the ECM/PCM has stopped. If you troubleshoot the PGM-FI system or the ABS/TCS first, and clear the DTCs, you'll most likely fix the problem.

As a general rule, troubleshoot DTCs that aren't related to communication first.

For example, if DTC P1676 (FPTDR signal line failure) is set, and the ABS/TCS control unit has set a TCS DTC 24 thru 27 (TCS solenoid), troubleshoot the TCS DTC problem first.

A second example: If the ECM/PCM sets a DTC P1498 (EGR valve position sensor circuit voltage high), and the ABS/TCS control unit sets a TCS DTC 31, you need to troubleshoot the DTC P1498 problem first.