Test KQ: Thermostat Heater Control: Testing

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2003 Mercury Sable, 2003 Mercury Mountaineer, 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Procedure starts from step 10). No test procedures have been omitted.

NOTE: For additional testing information, see DIAGNOSTIC AIDS .

10) For KOEO, KOER & Continuous Memory DTCs P0597 & P1432: Check VPWR To THTRC Harness Connector
DTC P0597 or P1432 is set when PCM detects THTRC circuit voltage below a calibrated limit for a calibrated time during Comprehensive Component Monitor (CCM). Possible causes are:
- THTRC Circuit Open Or Shorted To B+, GND Or VPWR
- VPWR Circuit Open
- Open Or Shorted Thermostat Assembly
- Faulty PCM
Turn ignition switch to OFF position. Disconnect THTRC connector. Turn ignition switch to ON position. Using a DVOM, measure voltage between chassis ground and VPWR circuit (Light Blue/Orange wire) at THTRC harness connector. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in Light Blue/Orange wire between THTRC and splice No. 153 at engine.

11) Check THTRC Resistance

Turn ignition switch to OFF position. Using a DVOM, measure resistance between THTRC connector terminals. Resistance should be 14-16 ohms. If resistance is within specification, go to next step. If resistance is not within specification, replace THTRC.

12) Check THTRC Circuit For Open In Harness

Ensure ignition switch is turned to OFF position. Disconnect PCM connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of THTRC circuit (Dark Blue wire) between THTRC harness connector and PCM harness connector. See PCM CONNECTOR IDENTIFICATION and Figure. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in THTRC circuit.

13) Check THTRC Circuit For Short To GND Or VPWR In Harness

Using a DVOM, measure resistance between THTRC circuit, and SIG RTN, PWR GND and VPWR circuits at PCM harness connector. If all resistance measurements are more than 10 k/ohms, go to TEST Z, step 1) (for Continuous Memory DTC P1432), or replace PCM (for KOEO or KOER DTC P1432). If any resistance measurement is 10 k/ohms or less, repair THTRC circuit for short to GND, SIG RTN or VPWR circuit.