A Charts

Fig. 010 - WIRING DIAGRAM for Chart A-1 CEL Malfunction. VIN N, VIN T:

CHART A-1

CEL ("SERVICE ENGINE SOON" LIGHT) MALFUNCTION

4.3L VIN "T"

5.7L VIN "N"

The "SERVICE ENGINE SOON" light (CEL) is used to indicate that the ECM has recognized a fault, and to aid in diagnosis of that fault by displaying codes. It is supplied 12V by the gages fuse, and the ground is completed by the ECM to turn the light "ON". The light should normally be "ON" with the key "ON", and should go "OFF" when engine speed exceeds 400 RPM.

Fig. 009 - Chart A-1 CEL Malfunction.:

1. If CEL (SERVICE ENGINE SOON Light) is off, CEL system problem is indicated.
2. CEL should light when ECM terminal "E" is grounded. If it does not, an open in CEL circuit indicated.
3. Checks for an open circuit to ECM. Normal voltage to ECM at Terminal "E" should be battery voltage. (10 volts or over)
4. Determines if problem is faulty ECM, connections or poor ground.
5. If CEL does not flash when ALCL "Test Terminal" is grounded, the ECM's memory cannot be accessed for fault codes.
6. Determines if fault is grounded CEL circuit, open ALCL Test Terminal Circuit or faulty ECM.
7. Fault is either grounded ALCL Test Terminal circuit or faulty ECM.