Circuit Description
The electronic ignition system uses an individual ignition coil for each cylinder. The engine control module (ECM) controls the ignition operation through eight individual ignition control (IC) circuits. Each bank of four ignition coils is connected to the ECM, power, or ground by the following circuits:
| • | A low reference circuit |
| • | A chassis ground circuit |
| • | An ignition 1 voltage circuit |
| • | The appropriate IC circuit |
The ECM triggers an ignition coil by grounding the appropriate IC circuit 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 ECM can determine when a cylinder is on either the firing or the exhaust stroke by the 24X signal. Remove any debris from the ECM connector surfaces before servicing the ECM. Inspect the ECM connector gaskets when diagnosing or replacing the ECM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the ECM.For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Monitoring the misfire current counters determines if a fault is present.
-
A good indication that the fuse is open is all off the misfire current counters are incrementing on one side of the engine. Inspect the ignition positive voltage circuit for a grounded circuit. If the fuse is open and the ignition coil circuits are OK, inspect the injector circuits for being grounded.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 | Attempt to start the engine. Does the engine start and run? | -- | Go to Step 5 | Go to Step 3 |
3 |
Does the scan tool indicate RPM is present? | -- | Go to Step 7 | Go to Step 4 |
4 | Is DTC P0335, P0336, or P0351-P0358 also set? | -- | Go to Step 16 | |
Does the scan tool display any misfire current counters incrementing? | -- | Go to Step 6 | Go to Diagnostic Aids | |
6 | Do the misfire current counters increment for most cylinders on one bank of the engine? | -- | Go to Step 12 | Go to Step 7 |
7 |
Is adequate spark present? | -- | Go to Step 33 | Go to Step 8 |
8 | Measure the spark plug wire resistance. Refer to Spark Plug Wire Inspection . Does the resistance measure within the specified range? | 188-312 ohms | Go to Step 9 | Go to Step 32 |
9 |
Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 13 |
10 | Probe the ignition 1 voltage circuit at the ignition coil with a test lamp connected to the ground circuit of the ignition coil. Refer to Probing Electrical Connectors . Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 14 |
11 | Probe the ignition 1 voltage circuit at the ignition coil with a test lamp connected to the low reference circuit of the ignition coil. Refer to Probing Electrical Connectors . Does the test lamp illuminate? | -- | Go to Step 20 | Go to Step 15 |
Inspect for an open INJ A fuse or INJ B fuse. Is the fuse open? | -- | Go to Step 29 | Go to Step 23 | |
13 |
Does the test lamp illuminate? | -- | Go to Step 24 | Go to Step 23 |
14 |
Does the test lamp illuminate? | -- | Go to Step 18 | Go to Step 26 |
15 |
Does the test lamp illuminate? | -- | Go to Step 19 | Go to Step 28 |
16 |
Is the difference in the voltage more than the specified value? | 0.5 V | Go to Step 17 | Go to Step 30 |
17 | Test for a short to ground in the CKP 12-volt reference circuit or the camshaft position (CMP) sensor 12-volt reference circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 22 |
18 | Test for an intermittent and for a poor connection at the ignition coil 8-way connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 25 |
19 | Test for an intermittent and for a poor connection at the ignition coil 8-way connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 27 |
20 | Test for an intermittent and for a poor connection at the ignition coil. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 31 |
21 | Test for an intermittent and for a poor connection at the CKP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 30 |
22 | Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 34 |
23 | Repair the open or high resistance in the ignition 1 voltage circuit between the fuse block and the splice. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 35 | -- |
24 | Repair the open or high resistance in the ignition 1 voltage circuit between the splice and the ignition coil connector. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 35 | -- |
25 | Repair the open in the ground circuit between the main 8-way connector and the ignition coil. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 35 | -- |
26 | Repair the open in the ground circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 35 | -- |
27 | Repair the open in the low reference circuit between the main 8-way connector and the ignition coil. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 35 | -- |
28 | Repair the open in the low reference circuit between the ECM and the splice. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 35 | -- |
29 |
Did you complete the repair? | -- | Go to Step 35 | -- |
30 | Replace the CKP sensor. Refer to Crankshaft Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- |
31 | Replace the ignition coil. Refer to Ignition Coil Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- |
32 | Replace the spark plug wire. Refer to Spark Plug Wire Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- |
33 | Replace the spark plug. Refer to Spark Plug Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- |
34 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 35 | -- |
35 | Attempt to start the engine. Does the engine start and continue to run? | -- | Go to Step 36 | Go to Step 3 |
36 |
Are there any DTCs that have not been diagnosed? | -- | System OK | |
