Central Control Module (CCM)

Circuit Description

The VATS (PASS-Key) fuel enable circuit is powered by 5 volts from the ECM, and is completed (grounded) by the CCM if all VATS (PASS-Key) requirements are met. When the ECM fuel enable signal input line senses that the CCM has grounded the circuit (senses a high-to-low transition), the ECM enables the fuel injectors so fuel can be delivered to the engine.

Code 54 will set if the fuel enable acknowledgment signal from the ECM (through serial data) indicates that the ECM has not detected the fuel enable signal when VATS (PASS-Key) is requesting fuel enable. Because the ECM sends serial data only with the ignition "ON," a Code 54 condition will only be recognized with the ignition "ON." Also, if serial data from the ECM is not being received by the CCM (Code 41), Code 54 will not set due to a lack of communications.

Test Description

Numbers below refer to circled numbers on the diagnostic chart.

1. This test checks to see if the ECM is putting out 5 volts up to the 10-way harness interconnect. If 5 volts is not found and the CKT 229 wiring and connectors are good, the ECM is faulty and should be replaced.
2. This test checks to see if the CCM is active on CKT 229 and if the wiring and connectors are good up to the 10-way harness interconnect.
3. This test checks to see if a fault indicated in Test 2 is in the wiring, connectors, VATS (PASS-Key), or the CCM.
4. This test checks to see if a fault indicated in Test 3 is due to VATS (PASS-Key), a poor connection at the CCM, or the CCM itself.

Diagnostic Aids

Check for poor connections at the CCM, the ECM, and at the 10-way I/P Harness-to-Engine Harness interconnect; these could cause an open or an intermittent fault.

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. Refer to "IntermittentslHistory Codes".

It is possible that a blown SIR fuse or a disconnected SIR harness could cause a Code 54. The ECM receives its power through the SIR fuse and SIR harness connection, so if the harness connector was disconnected or had poor connections, or the SIR fuse was blown, the ECM would not be able to send a "fuel enabled" signal to the CCM, causing a Code 54. A disconnected SIR harness or blown SIR fuse would also be indicated by all ECM functions being inoperative, since the ECM would have no power.

If there is a short to battery, a short to ground, or an open in CKT 229, the vehicle will exhibit a cranks-but-will-not-run condition.

If this code is set, it is very likely that ECM Code 46 will also be set.