z
Open Or Shorted Thermostat Assembly
z
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 Fig. 354. 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.
TEST NB: MALFUNCTION INDICATOR LIGHT
Diagnostic Aids
This test is used to diagnose the following:
z
Malfunction Indicator Light (MIL) Bulb Or Socket
z
Wiring Harness Circuit; (MIL)
z
Faulty Powertrain Control Module (PCM)
Testing
NOTE:
Diagnostic procedures beginning with step 1) are performed when
directed here from an MIL concern under WARNING INDICATOR LIGHTS
under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline