Central Control Module (CCM)

Circuit Description

The PASS-Key(R) detection circuit is completed by the PASS-Key(R) (with embedded resistor pellet) in the ignition lock cylinder. Contacts in the ignition lock cylinder mate with those on the pellet and the CCM compares the resistance value of the key pellet to the "valid" resistance programmed into the CCM at vehicle assembly.

Code 52 will set if the CCM detects a resistance of less than 50 ohms in the PASS-Key(R) detection circuit. The CCM will test the circuit 10 times in succession before setting the Code 52.

Test Description

Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test determines if the CCM is reading a short to ground condition.
2. This test is to determine if a problem lies in the lock cylinder or its harness.
3. This checks if there is a short to ground in CKT 1073.
4. This checks if there is a short between CKT 1073 and CKT 1074, which the CCM would interpret as a short to ground.
5. This test tries to induce an intermittent, checks the key itself for a shorted resistor pellet, and checks if the CCM is the cause of the fault. If' after clearing codes, the fault resets, the CCM must be faulty since the rest of the system has checked as

Diagnostic Aids

If the code is a history code, the problem may be intermittent. Try performing the tests shown while "wiggling" wiring and connectors; this can often cause the fault to appear. Check for poor connections at both the CCM and the ignition lock cylinder assembly; these could cause an open, short, incorrect PASS-Key(R) resistance, or an intermittent fault. Refer to "Intermittents/Poor Connections".

Make sure the key resistor contacts are clean and free of any grease, oil, etc. These substances could interfere with the key detection circuit and set a code.

If there is a short to ground in CKT 1073, the vehicle will exhibit a no-crank condition.