Test Description
The numbers below refer to the step numbers in the diagnostic table.
The battery should be fully charged prior to any tests.
- 1. Perform the OBD system check before proceeding unless it was already performed.
- 2. Checks for proper output from the enhanced ignition system. The spark tester requires a minimum of 25,000 volts to operate. This check can be used in case of an ignition miss, because the system may provide enough voltage to run the engine but not enough to operate a spark plug under heavy load.
- 3. This test separates the distributor cap, rotor and ignition wires from the ignition coil in order to help identify a secondary ignition system problem.
- 5. This test checks the ignition control module, connections, and wiring.
- 12. This test begins to determine if the VCM is providing a signal to the ignition control module. If the VCM is not providing a signal to the ignition control module, the problem exists between the ignition control module and the VCM.
- 14. This test checks for a basic engine mechanical problem.
ENHANCED IGNITION SYSTEM DIAGNOSIS
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| 1 | Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame and Failure Records for reference. The control module's data is deleted once the clear info function is used. Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? |
-- | Go to Step 2 | Go to POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK |
| 2 | 1. Check the spark plug wires for open circuits, cracks or improper seating of terminals at the spark plugs, distributor and ignition coil before proceeding with the test. 2. Check spark at the plug with the J 26792 spark tester or equivalent while cranking. (If there is no spark on one wire, check a second wire). A few sparks then nothing is considered no spark. Is adequate spark present? |
-- | Go to SYMPTOMS | Go to Step 3 |
| 3 | 1. Remove the coil wire from the distributor cap. 2. Insert J 26792 spark tester into the coil wire and clamp the tester onto a ground. 3. Crank the engine. Is adequate spark present? |
-- | Go to Step 13 | Go to Step 4 |
| 4 | Measure the coil wire resistance using a J 39200 DMM. The resistance should be approximately the specified value. Is the resistance within the specified value? |
1000 ohms/inch | Go to Step 5 | Go to Step 32 |
| 5 | 1. Disconnect the ignition coil harness connector. 2. Probe the ignition coil connector terminal C with a test lamp connected to B+. 3. Crank the engine. Is the test lamp flashing while cranking the engine? |
-- | Go to Step 7 | Go to Step 6 |
| 6 | 1. Turn OFF the ignition. 2. Probe the ignition coil harness connector terminal C with a test lamp connected to B+. Is the test lamp ON? |
-- | Go to Step 28 | Go to Step 9 |
| 7 | Probe the ignition coil harness connector terminal B with a test lamp connected to B+. Is the test lamp ON? |
-- | Go to Step 29 | Go to Step 8 |
| 8 | 1. Turn ON the ignition leaving the engine OFF. 2. Measure the terminal A voltage with a J 39200 DMM connected to a ground. Does the voltage measure above the specified value? |
10.0 V | Go to Step 21 | Go to Step 18 |
| 9 | 1. Turn OFF the ignition. 2. Disconnect the ignition control module harness connector. 3. Check for an open circuit between the ignition coil harness connector terminal C and the ignition control module harness connector terminal D. Is the circuit open? |
-- | Go to Step 27 | Go to Step 10 |
| 10 | 1. Disconnect the ignition control module harness connector. 2. Turn ON the ignition leaving the engine OFF. 3. Measure the voltage on terminal A at the ignition control module harness connector with a J 39200 DMM connected to a ground. Does the voltage measure above the specified value? |
10.0 V | Go to Step 11 | Go to Step 19 |
| 11 | Probe the ignition control module harness connector terminal C with a test lamp connected to B+. Is the test lamp ON? |
-- | Go to Step 12 | Go to Step 23 |
| 12 | 1. Disconnect the ignition control module harness connector. 2. Probe the ignition control module harness connector terminal B with a J 39200 DMM set to the AC scale connected to a ground. 3. Crank the engine. 4. Observe the voltage while the engine is being cranked. Is the voltage between the specified values? |
1.0-4.0 V | Go to Step 20 | Go to Step 15 |
| 13 | 1. Remove the distributor cap. 2. Check the cap for the following conditions: * Cracks * Moisture * Carbon tracks * Physical damage Are any of these conditions present? |
-- | Go to Step 34 | Go to Step 14 |
| 14 | 1. Crank the engine. 2. Observe the distributor rotor while the engine is being cranked. Did the distributor rotor turn? |
-- | Go to Step 33 | Go to SYMPTOMS |
| 15 | 1. Turn OFF the ignition. 2. Disconnect the VCM C3 connector. 3. Check the ignition timing signal circuit for an open between the VCM C3 harness connector and the ignition control module harness connector terminal B. Is the circuit open? |
-- | Go to Step 24 | Go to Step 16 |
| 16 | Probe the ignition control (IC) circuit at the VCM C3 connector with a test lamp connected to B+. Is the test lamp ON? |
-- | Go to Step 25 | Go to Step 17 |
| 17 | 1. Turn ON the ignition leaving the engine OFF. 2. Probe the ignition control (IC) circuit at the VCM C3 connector with a test lamp connected to a ground. Is the test lamp ON? |
-- | Go to Step 26 | Go to Step 22 |
| 18 | Check for an open or shorted to ground ignition positive voltage circuit at terminal A of the ignition coil. Repair as necessary. Is the action complete? |
-- | Go to Step 37 | -- |
| 19 | Check for an open or shorted to ground ignition positive voltage circuit at terminal A of the ignition control module. Repair as necessary. Is the action complete? |
-- | Go to Step 37 | -- |
| 20 | Check for a poor ignition control module connection. Did you find a problem? |
-- | Go to Step 30 | Go to Step 35 |
| 21 | Check for a poor coil connection . Did you find a problem? |
-- | Go to Step 30 | Go to Step 31 |
| 22 | Check for a poor VCM connection. Did you find a problem? |
-- | Go to Step 30 | Go to Step 36 |
| 23 | Repair the open ignition control module ground circuit. Is the action complete? |
-- | Go to Step 37 | -- |
| 24 | Repair the open IC circuit between the VCM and the ignition control module. Is the action complete? |
-- | Go to Step 37 | -- |
| 25 | Repair the grounded IC circuit between the VCM and the ignition control module. Is the action complete? |
-- | Go to Step 37 | -- |
| 26 | Repair short to voltage in the IC circuit between the VCM and the ignition control module. Is the action complete? |
-- | Go to Step 37 | -- |
| 27 | Repair the open in the tachometer signal circuit between the ignition coil and the ignition control module. Is the action complete? |
-- | Go to Step 37 | -- |
| 28 | Repair the short to ground in the tachometer signal circuit between the ignition coil and the ignition control module. Is the action complete? |
-- | Go to Step 37 | -- |
| 29 | Repair the short to ground in the tachometer input circuit between the ignition coil and the instrument cluster. Is the action complete? |
-- | Go to Step 37 | -- |
| 30 | Repair the circuit as necessary. Is the action complete? |
-- | Go to Step 37 | -- |
| 31 | Replace the ignition coil. Refer to IGNITION COIL & ICM REPLACEMENT (HVS) Is the action complete? |
-- | Go to Step 37 | -- |
| 32 | Replace the coil wire.IGNITION COIL & ICM REPLACEMENT (HVS) Is the action complete? |
-- | Go to Step 37 | -- |
| 33 | Replace the distributor rotor. Is the action complete? |
-- | Go to Step 37 | -- |
| 34 | Replace the distributor cap. Is the action complete? |
-- | Go to Step 37 | -- |
| 35 | Replace the ignition control module. Refer to IGNITION COIL & ICM REPLACEMENT (HVS)
. Is the action complete? |
-- | Go to Step 37 | -- |
| 36 | 1. Replace the VCM. 2. Program the new VCM. Refer to ELECTRONICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) PROGRAMMING (4.3L, 5.0L & 5.7L) 3. Perform the VTD Password Learn Procedure. Refer to PASSWORD LEARN PROCEDURE FOR ANTI-THEFT SYSTEM (4.3L, 5.0L, 5.7L & 7.4L) . 4. Perform the CKP System Variation Learn Procedure. Refer to CRANKSHAFT POSITION (CKP) SENSOR VARIATION LEARN PROCEDURE (4.3L, 5.0L, 5.7L & 7.4L ) Is the action complete? |
-- | Go to Step 37 | -- |
| 37 | Operate the vehicle within the conditions under which the original symptom was noted. Does the system now operate properly? |
-- | System OK | Go to Step 1 |