BUS +/- Signals Open Or No Response From Sentry Key Immobilizer Module

Possible Causes:

Attempt to communicate with CTM.
Ground circuit open.
Fused Ignition Switch Output circuit open.
Fused B+ circuit open.
PCI Bus circuit open.
SKIM.

CAUTION: Always turn ignition off before disconnecting or connecting any control module connector. Failure to do so could result in damage to control module.

NOTE: Ensure vehicle being tested has a fully charged battery. If it does not, false symptoms may occur.

NOTE: For component location, see appropriate illustration under COMPONENT LOCATIONS . For terminal identification, see appropriate illustration under CONNECTOR IDENTIFICATION . For circuit and wire color identification, see WIRING DIAGRAMS . For component removal and installation procedures, see appropriate component under REMOVAL & INSTALLATION .

Testing:

Turn ignition off. Connect DRBIII(R) to DLC. Turn ignition on. Select BODY, then BODY COMPUTER. Is DRBIII(R) able to identify or communicate with CTM? If yes, go to next step. If no, see PCI BUS COMMUNICATION FAILURE .
Turn ignition off. Disconnect SKIM harness connector. Using a 12-volt test light connected to 12 volts, probe SKIM harness connector terminal No. 5. Does test light illuminate? If yes, go to next step. If no, repair open in Ground circuit. Perform SENTRY KEY IMMOBILIZER SYSTEM VERIFICATION TEST under VERIFICATION TESTS.
Turn ignition on. Using 12-volt test light connected to ground, probe SKIM harness connector terminal No. 4. Does test light illuminate? If yes, go to next step. If no, repair open in the Fused Ignition Switch Output circuit. Perform SENTRY KEY IMMOBILIZER SYSTEM VERIFICATION TEST under VERIFICATION TESTS.
Turn ignition off. Using 12-volt test light connected to ground, probe SKIM harness connector terminal No. 6. Does test light illuminate? If yes, go to next step. If no, repair open in Fused B+ circuit. Perform SENTRY KEY IMMOBILIZER SYSTEM VERIFICATION TEST under VERIFICATION TESTS.

NOTE: Ensure there is PCI Bus communication with other modules on the vehicle before proceeding. If not, see PCI BUS COMMUNICATION FAILURE .

Connect Scope Input Cable (CH7058) to channel one connector on DRBIII(R). Connect Cable-To-Probe Adapter (CH7062) and Black and Red test probes to scope input cable. Using the DRBIII(R), select PEP MODULE TOOLS, LAB SCOPE, LIVE DATA and 12 VOLT SQUARE WAVE. Press F2 for SCOPE. Press F2 and use DOWN arrow to set voltage scale to 20 volts. Set probe to x10. Press F2 again when complete. Connect Black test probe to ground. Connect Red test probe to SKIM harness connector terminal No. 2. Turn ignition on. Observe DRBIII(R) lab scope. Does voltage toggle from zero to approximately 7.5 volts? See Figure -Figure . If yes, go to next step. If no, repair open in PCI Bus circuit. Perform SENTRY KEY IMMOBILIZER SYSTEM VERIFICATION TEST under VERIFICATION TESTS.
If there are no possible causes remaining, replace SKIM. Perform SENTRY KEY IMMOBILIZER SYSTEM VERIFICATION TEST under VERIFICATION TESTS.