Electronic Ignition (EI) System Diagnosis with Special Tool
Circuit Description
Each ignition coil supplies secondary voltage to a pair of spark plugs. This is called a waste spark ignition system. The powertrain control module (PCM) supplies a signal on each of the ignition control (IC) timing control circuits to the ignition control module (ICM). The ICM fires the correct ignition coil at the correct time based on the signals. The ICM detects if cylinder 1 or cylinder 3 is on the compression stroke by sensing the secondary voltage and polarity of each side of the ignition coil. The ICM detects this voltage with sensing circuitry integrated into each ignition coil. The higher voltage is on the compressing cylinder. This is called compression sense ignition. The ICM provides a synthesized cam signal to the PCM based on these inputs. The PCM uses the cam signal to synchronize fuel injection.
This system consists of the following circuits:
| • | An ignition voltage circuit |
| • | A ground circuit |
| • | A camshaft position (CMP) sensor signal circuit |
| • | An IC timing control circuit for cylinders #1 and #4 |
| • | An IC timing control B circuit for cylinders #2 and #3 |
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||
2 |
Does the CKP Active Counter increment? | -- | Go to Step 3 | |||||||||
3 |
Does the spark tester spark on all cylinders? | -- | Go to Step 6 | Go to Step 4 | ||||||||
4 | Is the no spark condition only present on one cylinder? | Go to Step 16 | Go to Step 5 | |||||||||
5 | Is the no spark condition only present on companion cylinders 1-4 or 2-3? | -- | Go to Step 12 | Go to Step 8 | ||||||||
6 | Does the spark tester indicate a bright blue spark on all cylinders? | -- | Go to Step 7 | Go to Step 16 | ||||||||
7 |
Are the spark plugs in good condition? | -- | System OK | Go to Step 23 | ||||||||
8 |
Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 19 | ||||||||
9 | Connect a test lamp from the ignition voltage circuit to the ground circuit of the ICM. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 20 | ||||||||
10 |
Is the resistance less than the specified value? | 3 ohms | Go to Step 11 | Go to Step 21 | ||||||||
11 | Measure the resistance of the ground circuit of the ICM from the harness connector of the ICM to a good ground. Is the resistance less than the specified value? | 3 ohms | Go to Step 12 | Go to Step 22 | ||||||||
12 |
Do the 1-4 and 2-3 LEDs flash on the tester? | -- | Go to Step 16 | Go to Step 13 | ||||||||
13 | Does only one of the LEDs flash on the tester? | -- | Go to Step 14 | Go to Step 17 | ||||||||
14 |
Does the inoperative LED on the tester flash now? | -- | Go to Step 15 | Go to Step 17 | ||||||||
15 | Test the IC timing control circuit for the affected coil of the ICM for one of the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 18 | ||||||||
16 | Test for shorted terminals or a poor connection at the ignition coil housing. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 24 | ||||||||
17 | Test for shorted terminals or a poor connection at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 25 | ||||||||
18 | Test for shorted terminals or poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 26 | ||||||||
19 | Repair an open or short to ground in the ignition voltage circuit of the ICM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 27 | -- | ||||||||
20 | Repair an open in the ground circuit of the ICM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 27 | -- | ||||||||
21 | Repair the high resistance in the ignition voltage circuit of the ICM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 27 | -- | ||||||||
22 | Repair the high resistance in the ground circuit of the ICM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 27 | -- | ||||||||
23 | Replace the spark plugs. Refer to Spark Plug Replacement . Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
24 | Replace the ignition coil housing. Refer to Ignition Coil Housing Replacement . Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
25 | Replace the ICM. Refer to Ignition Control Module Replacement . Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
26 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
27 |
Does the vehicle operate normally? | -- | System OK | Go to Step 3 | ||||||||
Electronic Ignition (EI) System Diagnosis Without Special Tool
Circuit Description
Each ignition coil supplies secondary voltage to a pair of spark plugs. This is called a waste spark ignition system. The powertrain control module (PCM) supplies a signal on each of the ignition control (IC) timing control circuits to the ignition control module (ICM). The ICM fires the correct ignition coil at the correct time based on the signals. The ICM detects if cylinder 1 or cylinder 3 is on the compression stroke by sensing the secondary voltage and polarity of each side of the ignition coil. The ICM detects this voltage with sensing circuitry integrated into each ignition coil. The higher voltage is on the compressing cylinder. This is called compression sense ignition. The ICM provides a synthesized cam signal to the PCM based on these inputs. The PCM uses the cam signal to synchronize fuel injection.
This system consists of the following circuits:
| • | An ignition voltage circuit |
| • | A ground circuit |
| • | A camshaft position (CMP) sensor signal circuit |
| • | An IC timing control circuit for cylinders #1 and #4 |
| • | An IC timing control B circuit for cylinders #2 and #3 |
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||
2 |
Does the CKP Active Counter increment? | -- | Go to Step 3 | |||||||||
3 |
Does the spark tester spark on all cylinders? | -- | Go to Step 6 | Go to Step 4 | ||||||||
4 | Is the no spark condition only present on one cylinder? | Go to Step 16 | Go to Step 5 | |||||||||
5 | Is the no spark condition only present on companion cylinders 1-4 or 2-3? | -- | Go to Step 12 | Go to Step 8 | ||||||||
6 | Does the spark tester indicate a bright blue spark on all cylinders? | -- | Go to Step 7 | Go to Step 16 | ||||||||
7 |
Are the spark plugs in good condition? | -- | System OK | Go to Step 23 | ||||||||
8 |
Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 19 | ||||||||
9 | Connect a test lamp from the ignition voltage circuit to the ground circuit of the ICM. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 20 | ||||||||
10 |
Is the resistance less than the specified value? | 3 ohms | Go to Step 11 | Go to Step 21 | ||||||||
11 | Measure the resistance of the ground circuit of the ICM from the harness connector of the ICM to a good ground. Is the resistance less than the specified value? | 3 ohms | Go to Step 12 | Go to Step 22 | ||||||||
12 |
Important: If using a different test lamp, the bulb resistance needs to be 4 ohms or less. Does the test lamp illuminate? | -- | Go to Step 13 | Go to Step 17 | ||||||||
13 |
Does the test lamp flash? | -- | Go to Step 16 | Go to Step 14 | ||||||||
14 |
Does the test lamp flash? | -- | Go to Step 15 | Go to Step 17 | ||||||||
15 | Test the IC timing control circuit of the ICM for one of the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 18 | ||||||||
16 | Test for shorted terminals or a poor connection at the ignition coil housing. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 24 | ||||||||
17 | Test for shorted terminals or a poor connection at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 25 | ||||||||
18 | Test for shorted terminals or poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 26 | ||||||||
19 | Repair an open or short to ground in the ignition voltage circuit of the ICM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 27 | -- | ||||||||
20 | Repair an open in the ground circuit of the ICM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 27 | -- | ||||||||
21 | Repair the high resistance in the ignition voltage circuit of the ICM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 27 | -- | ||||||||
22 | Repair the high resistance in the ground circuit of the ICM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 27 | -- | ||||||||
23 | Replace the spark plugs. Refer to Spark Plug Replacement . Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
24 | Replace the ignition coil housing. Refer to Ignition Coil Housing Replacement . Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
25 | Replace the ICM. Refer to Ignition Control Module Replacement . Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
26 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
27 |
Does the vehicle operate normally? | -- | System OK | Go to Step 3 | ||||||||
