Chart C-16 PCM Controlled Warning Lamp Circuit

PCM Controlled Warning Lamp Circuit:

CIRCUIT DESCRIPTION
The "Temp" lamp or optional "Check Gauges" lamp, is connected to battery voltage through the ignition switch. The Powertrain Control Module (PCM) energizes the bulb by supplying a path to ground through the "Quad-Driver" module (QDSM).

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. With the ignition "ON" and engine "OFF," the PCM should be grounding CKT 35.
2. While the engine is running, the "Temp" lamp or optional "Check Gauges" lamp should be turned "ON" by the PCM only when the engine coolant temperature is above 123°C (253°F). The "Temp" lamp or "Check Gauges" lamp should be turned "OFF" when the engine is running and the engine coolant temperature goes lower than 120°C (249°F).

DIAGNOSTIC AIDS
^ The engine coolant temperature sensor, in rare cases, may fail to indicate the correct engine coolant temperature without setting a Diagnostic Trouble Code (DTC). This could result in turning "ON" the "Temp" lamp or optional "Check Gauges" lamp without having an overheating condition. It could also result in overheating without the "Temp/Check Gauges" lamp being turned "ON."
^ An intermittent problem may be caused by a poor or corroded connection, rubbed through wire connection, a wire that is broken inside the insulation, or a corroded wire.
^ Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections, corroded terminals and/or wiring, or physical damage to the wiring harness.