Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2007 Chevrolet Express 2500 V8-4.8LFACTORY OEM SERVICE PROCEDURE
Ignition System: Testing and Inspection
Electronic Ignition (EI) System Diagnosis
Circuit Description
The electronic ignition system uses an individual ignition coil for each cylinder. The powertrain control module (PCM) controls the ignition operation through 8 individual ignition control (IC) circuits. Each bank of four ignition coils is connected to the PCM, power, and ground by the following circuits:
* The low reference
* The ground
* The Ignition 1 voltage
* The appropriate IC circuit
The PCM triggers an ignition coil by grounding the appropriate IC control using information from the crankshaft position (CKP) and camshaft position (CMP) sensors.
Diagnostic Aids
Important: A missing CMP sensor signal may cause a long crank condition.
* The CKP signal must be available for the engine to start. The CMP signal is not needed to start and operate the engine. The PCM can determine when a cylinder is on either the firing or exhaust stroke by the 24X signal.
* Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
* For an intermittent condition, Refer to Testing for Intermittent Conditions and Poor Connections in Diagnostic Aids. Component Tests and General Diagnostics
Test Description
Step 1 - Step 11:
Step 12 - Step 23:
Step 24 - Step 35:
The number below refers to the step number on the diagnostic table.
4. Monitoring the misfire current counters determines if a fault is present.
Factory Service Tools
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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