Central Control Module (CCM)

Circuit Description

The PASS-Key(R) detection circuit is completed by the PASS-Key(R) (with embedded resistor pellet) into 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 53 will set if the CCM detects a resistance of greater than 20,000 ohms or a short to battery voltage in the PASS-Key(R) detection circuit. The CCM will test the circuit 10 times in succession before setting the Code 53.

Test Description

Number(s) below refer to circled number(s) on the diagnostic chart.

1. This test determines if the CCM is reading an open circuit condition.
2. This test determines if the CCM output to the ignition lock cylinder and CKT 1073's wiring and connectors are good.
3. This test checks for a short to B+ in CKT 1074.
4. This test determines if the CCM return path wiring, connectors, and CCM internal ground are good. If all are good, the ignition lock cylinder is faulty and should be replaced.

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, incorrect PASS-Key(R) resistance, or an intermittent fault. Refer to "Intermittents/Poor Connections".

Many other CCM-controlled circuits use the internal CCM ground mentioned in Test Description 4. Other inoperative or malfunctioning circuits, such as fuel gage, DIC switches, ambient light sensor, dimming potentiometer, etc., may indicate that the CCM internal ground is bad.

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 an open in CKT 1073 or CKT 1074, the vehicle will exhibit a no-crank condition. If there is a short to B+ in CKT 1073, there will also be a no-crank condition.