harness connector. See Fig. 251-Fig. 255 . If IMRCM or SCVM PID voltage reading cycled from VREF
voltage to less than one volt, go to next step. If IMRCM or SCVM PID voltage reading does not change
from VREF voltage to less than one volt, go to step 36).
33) Check SIG RTN Or Chassis GND Circuit Continuity With PCM Connected
Turn ignition switch to OFF position. Reconnect PCM harness connector(s). Using a DVOM, measure
resistance between negative battery terminal and SIG RTN or GND circuit at IMRC or SCVM harness
connector. See Fig. 251-Fig. 255 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms
or more, go to step 35).
34) Check Monitor Circuit For Intermittent Open
Ensure ignition switch is turned to OFF position. Using a DVOM, measure resistance of IMRCM or
SCVM circuit between PCM harness connector and IMRC or SCVM harness connector. Wiggle and bend
wiring harness between IMRC or SCVM harness connector and PCM harness connector. A fault will be
indicated by a change in resistance measurement. If fault is indicated, isolate fault and repair as
necessary. After repairs, go to step 38). If no faults are indicated, replace IMRC or IMSC actuator. After
repairs, go to step 38).
35) Check SIG RTN Or Chassis GND Circuit Continuity With PCM Disconnected
Disconnect PCM connector(s). Using a DVOM, measure resistance of SIG RTN or chassis GND circuit
between IMRC or IMSC actuator harness connector and PCM harness connector. See Fig. 251-Fig. 255 .
If resistance is 5 ohms or more, repair open in SIG RTN or chassis GND circuit. After repairs, go to step
38). If resistance is less than 5 ohms, check for intermittent faults. Go to TEST Z, step 1). If no
intermittent faults are found, replace PCM. After repairs, go to step 38).
36) Check Monitor Circuit For Open In Harness
Turn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance
of IMRCM or SCVM circuit between PCM harness connector and IMRC or SCVM harness connector. If
resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in IMRCM or
SCVM circuit. After repairs, go to step 38).
37) Check Monitor Circuit For Intermittent Open
Ensure ignition switch is in OFF position. Using a DVOM, measure resistance of IMRCM or SCVM
circuit between PCM harness connector and IMRC or IMSC actuator harness connector while wiggling
wiring harness between IMRC or IMSC actuator connector and PCM harness connector. See Fig. 251-
Fig. 255 . A fault will be indicated by change in resistance measurement. If fault is indicated, isolate fault
and repair as necessary. After repairs, go to next step. If no faults are indicated, replace PCM. After
repairs, go to next step.
38) IMRC Or IMSC Repair Verification Drive Cycle
Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Perform PCM
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline