Circuit Description
The ignition control (IC) module has independent power and ground circuits. The circuits between the IC module and the powertrain control module (PCM) consist of the following:
| • | The low reference circuit |
| • | The CKP 7x Reference signal circuit |
| • | The two IC timing control signals |
| - | For cylinders 1 and 4 |
| - | For cylinders 2 and 3 |
The crankshaft position (CKP) 7x signal is derived from the CKP sensor, which is connected directly to the IC module. The IC module and PCM use the CKP 7x signal to control ignition operation.
The Alternative Fuels ECM monitors the CKP 7x signal in order to determine the engine RPM.
Diagnostic Aids
| • | If the misfire condition is only apparent when the vehicle is operating on gasoline, performing the fuel injector coil test may isolate the condition. Refer to Fuel Injector Solenoid Coil Test in Engine Controls-2.2L (LN2) in the J platform Service Manual. |
| • | If the misfire condition is only apparent when the vehicle is operating on CNG, inspect the secondary ignition system for signs of deterioration. Operating on CNG places a higher load on the ignition system components, due to the increased voltage requirements. |
| • | If you determine the condition is intermittent, wet down the secondary ignition system with water from a spray bottle. Look and listen for arcing or for an engine misfire as the water is applied. If this does not isolate a condition, refer to Intermittent Conditions . |
| • | A loose CKP sensor may cause an intermitted NO START by moving away from the reluctor wheel. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests the ignition voltage circuit to the ignition control module (ICM).
-
This step tests the ground circuit to the ICM.
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This step tests the continuity of the CKP sensor and related circuits.
-
This step tests the frequency output of the CKP sensor.
-
This step tests the CKP 7x reference circuit. The CKP active counter should increment as the circuit is probed with the test lamp.
-
This step tests the ignition coil. If the swapped coil sparks, then the ICM, PCM, and wiring are OK.
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This step tests the ignition control circuit, ignition module, and the ignition coil. If the spark tester sparks when the ignition control circuit is probed with the test lamp, inspect for a faulty connection at the PCM.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||
1 | Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Alternative Fuels (Engine Controls) | ||||||
2 |
Important: This diagnostic only diagnoses an engine no start and an engine misfire caused by the ignition system. This diagnostic assumes there are no diagnostic trouble codes (DTCs) set. Does the engine start and idle? | -- | Go to Step 3 | Go to Step 4 | ||||||
3 |
Are any of the Misfire Current Counters incrementing? | -- | Go to Step 10 | Go to Diagnostic Aids | ||||||
Does the DMM display a voltage at the specified value? | B+ | Go to Step 5 | Go to Step 23 | |||||||
Measure the voltage between the ignition voltage circuit and the ground circuit of the ICM, with a DMM. Does the DMM display a voltage at the specified value? | B+ | Go to Step 6 | Go to Step 24 | |||||||
Does the resistance measure within the specified range? | 700-1,350 ohms | Go to Step 7 | Go to Step 17 | |||||||
Does the DMM display a frequency within the specified value while cranking the engine? | 28-32 Hz | Go to Step 8 | Go to Step 26 | |||||||
Does the CKP Active Counter increment? | -- | Go to Step 21 | Go to Step 9 | |||||||
9 |
Does the CKP Active Counter increment? | -- | Go to Step 30 | Go to Step 19 | ||||||
10 | Does the engine misfire affect both cylinders 1 and 3, or 2 and 4? | -- | Go to Step 15 | Go to Step 11 | ||||||
11 |
Important: If the spark tester sparks once or twice and then quits, this is considered no spark. Does the J 26792 spark and is the spark consistent? | -- | Go to Step 14 | Go to Step 12 | ||||||
12 |
Is the resistance less than the specified value, but more than zero? | 1000 ohms Per 30 cm -- Per 1 Foot | Go to Step 13 | Go to Step 25 | ||||||
Does the J 26792 spark? | -- | Go to Step 28 | Go to Step 27 | |||||||
14 |
Important: If the spark plug is gas, coolant, or oil fouled, determine the cause of the fouling. Refer to Spark Plug Inspection in Engine Controls-2.2L (LN2) in the J Platform Service Manual for spark plugs that are gas fouled. Did you find and correct the condition? | -- | Go to Step 31 | Go to Symptoms - Engine Mechanical in Engine Mechanical-2.2L | ||||||
Important: The ignition control A circuit operates cylinders 1 and 4. The ignition control B circuit operates cylinders 2 and 3. Does the J 26792 spark? | -- | Go to Step 22 | Go to Step 16 | |||||||
16 | Test the isolated ignition control circuit for the following conditions:
Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 21 | ||||||
17 | Test the CKP sensor signal circuit for an open, or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 18 | ||||||
18 | Test the CKP sensor ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 20 | ||||||
19 | Test the CKP 7x reference circuit of the CKP sensor for the following conditions:
Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 22 | ||||||
20 | Inspect for faulty connections at the CKP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 26 | ||||||
21 | Inspect for faulty connections at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 27 | ||||||
22 | Inspect for faulty connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | -- | Go to Step 31 | Go to Step 29 | ||||||
23 | Repair the ignition voltage circuit of the ICM. Refer to Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you complete the repair? | -- | Go to Step 31 | -- | ||||||
24 | Repair the ground circuit of the ICM. Refer to Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you complete the repair? | -- | Go to Step 31 | -- | ||||||
25 | Replace the spark plug wire. Refer to Spark Plug Wire Replacement Did you complete the replacement? | -- | Go to Step 31 | -- | ||||||
26 | Replace the CKP sensor. Refer to Crankshaft Position Sensor Replacement in the J Platform Service Manual. Did you complete the replacement? | -- | Go to Step 31 | -- | ||||||
27 | Replace the ICM. Refer to Ignition Control Module Replacement in the J Platform Service Manual. Did you complete the replacement? | -- | Go to Step 31 | -- | ||||||
28 | Replace the affected ignition coil. Refer to Ignition Coil Replacement in the J Platform Service Manual. Did you complete the replacement? | -- | Go to Step 31 | -- | ||||||
29 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 31 | -- | ||||||
30 | Replace the alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 31 | -- | ||||||
31 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2 | ||||||
