Ignition System - Electrical Diagnostics: Overview Jeep Commander I

Theory Of Operation

The (F942) Fused Ignition Switch Output circuit supplies the FCM with battery power. The FCM processes the input and sends it out as the (F1) Fused Ignition Switch Output circuit to the Shift Lever assembly (3.7L) or the PCM (except 3.7L).

Scheme 1

Scheme 2

Scheme 3

Scheme 4

1. 1) CHECK FOR ACTIVE DTC With the scan tool, read the active DTC's. Cycle the ignition switch from off to on, leaving the ignition on for a minimum of 10 seconds. With the scan tool, read the active DTC's. Does the scan tool display this DTC as active? Yes Go to 2) . No If the DTC is stored, check for an intermittent condition. Using the wiring diagram/schematic as a guide, visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.
2. 2) DETERMINE ENGINE SIZE Is this vehicle equipped with a 3.7L engine? Yes Go to 3) . No Go to 6) .
3. 3) SHIFT LEVER ASSEMBLY With the scan tool, erase the FCM DTC's. Turn the ignition off. Disconnect the Shift Lever Assembly harness connector. Cycle the ignition switch from off to on, leaving the ignition on for a minimum of 10 seconds. With the scan tool, read the active FCM DTC's. Does the scan tool display this DTC as active? Yes Go to 4) . No Replace the Shift Lever Assembly in accordance with the service information. Perform «BODY VERIFICATION TEST»(ref-288232-S30638820392008062000000) .
4. 4) (F1) FUSED IGNITION SWITCH OUTPUT WIRE SHORT TO GROUND Turn the ignition off. Disconnect the Integrated Power Module C1 harness connector. Measure the resistance between ground and the (F1) Fused Ignition Switch Output circuit in the IPM C1 connector. Is the resistance below 1000.0 ohms? No Go to 5) . Yes Repair the (F1) Fused Ignition Switch Output circuit for a short to ground. Perform «BODY VERIFICATION TEST»(ref-288232-S30638820392008062000000) .
5. 5) INTEGRATED POWER MODULE SHORTED Remove the FCM from the Integrated Power Module. Measure the resistance between ground and the (F1) Fused Ignition Switch Output circuit in the Front Control Module IPM connector. Is the resistance below 1000.0 ohms? Yes Replace the Integrated Power Module in accordance with service information. Perform «BODY VERIFICATION TEST»(ref-288232-S30638820392008062000000) . No Replace and program the Front Control Module in accordance with the service information. Perform «BODY VERIFICATION TEST»(ref-288232-S30638820392008062000000) .
6. 6) POWERTRAIN CONTROL MODULE With the scan tool, erase the FCM DTC's. Turn the ignition off. Disconnect the Powertrain Control Module C1 connector. Cycle the ignition switch from off to on, leaving the ignition on for a minimum of 10 seconds. With the scan tool, read the active FCM DTC's. Does the scan tool display this DTC as active? Yes Go to 7) . No Replace the Powertrain Control Module in accordance with the service information. Perform «BODY VERIFICATION TEST»(ref-288232-S30638820392008062000000) .
7. 7) (F1) FUSED IGNITION SWITCH OUTPUT WIRE SHORT TO GROUND Turn the ignition off. Disconnect the Integrated Power Module C1 harness connector. Measure the resistance between ground and the (F1) Fused Ignition Switch Output circuit in the IPM C1 connector. Is the resistance below 1000.0 ohms? No Go to 5) . Yes Repair the (F1) Fused Ignition Switch Output circuit for a short to ground. Perform «BODY VERIFICATION TEST»(ref-288232-S30638820392008062000000) .