Circuit Description
The ignition control module (ICM) has independent power and ground circuits. The circuits between the ICM and the powertrain control module (PCM) consists of the following circuits:
| • | The ignition control (IC) timing signal |
| • | The IC timing control |
| • | The low resolution engine speed signal |
| • | The medium resolution engine signal |
| • | The camshaft position signal |
| • | The low reference |
The ICM sends 3X signals to the PCM, and controls the timing advance during engine cranking. The timing advance changes to PCM control after the following actions occur:
| • | The PCM receives the second 3X signal |
| • | The PCM applies 5 volts to the ignition control (IC) timing signal circuit. |
The ICM monitors the CKP sync signal when the engine is cranking. The CKP sync signal is passed from the CKP sensor to the ICM on the CKP sensor 2 signal circuit. The CKP sync signal is used to determine the correct cylinder pair and initiate the ignition coil firing sequence. The 18X reference pulses are passed from the CKP sensor to the ICM on the CKP sensor 1 circuit. The 18X reference pulses are used for fuel injection and ignition control. After the ICM receives both signals, the ICM passes the 18X and 3X reference signals to the PCM. The CMP and the CKP sensors share a 12 volt reference and low reference circuit. The CKP sensor consists of the following circuits:
| • | A 12 volt reference |
| • | A low reference |
| • | A CKP sensor 1 signal |
| • | A CKP sensor 2 signal |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Determines if the ignition control (IC) module is receiving the CKP sensor 1 signal. If the CKP sensor 1 signal to the ICM is not present, there will be no RPM, spark, or fuel injector pulses.
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Ensures that the IC module has the proper voltage supply and ground.
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Verifies that the IC module is supplying the 12-volt reference to the sensor.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | ||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||
2 |
Important: Before proceeding with this diagnostic table, verify that the vehicle's battery is fully charged. Inspect the fuses which supply ignition 1 voltage to the following components:
Are either of the fuses open? | -- | Go to Step 27 | Go to Step 3 | ||||
Does the scan tool display engine RPM? | -- | Go to Step 13 | Go to Step 4 | |||||
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 5 | |||||
5 |
Does the test lamp illuminate? | -- | Go to Step 28 | Go to Step 29 | ||||
Is the difference between the measured voltage and the system voltage more than the specified value? | 0.5 V | Go to Step 8 | Go to Step 7 | |||||
7 | Connect the DMM between the sensor 1 signal circuit of the CKP and the ground circuit of the CKP. Is the voltage within the specified range? | 6-8 V | Go to Step 16 | Go to Step 11 | ||||
8 | Connect the DMM between the CKP 12-volt reference circuit of the CKP and a good ground. Is the difference between the measured voltage and the system voltage more than the specified value? | 0.5 V | Go to Step 9 | Go to Step 10 | ||||
9 |
Did you find and correct the condition? | -- | Go to Step 33 | Go to Step 27 | ||||
10 |
Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 26 | ||||
11 |
Is the difference between the measured voltage and the system voltage more than the specified value? | 0.5 V | Go to Step 30 | Go to Step 12 | ||||
12 | Test the CKP sensor 1 signal circuit for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 26 | ||||
13 |
Do all of the cylinders have spark? | -- | Go to Step 23 | Go to Step 14 | ||||
14 | Do any of the cylinders have spark? | -- | Go to Step 19 | Go to Step 15 | ||||
15 |
Is the measured voltage within the specified range? | 6-8 V | Go to Step 16 | Go to Step 17 | ||||
16 | Test for intermittent and for a poor connection at the CKP sensor. 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 35 | Go to Step 32 | ||||
17 |
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 18 | ||||
18 | Test the CKP sensor 2 signal for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 26 | ||||
19 |
Important:: If carbon tracking is detected on any component, replace that component and the mate.
Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 20 | ||||
20 | Measure the secondary resistance of the ignition coils. Is the resistance within the specified value? | 5000-8000 ohms | Go to Step 21 | Go to Step 34 | ||||
21 | Measure the resistance of the ignition wires associated with the cylinders that did not have spark. Refer to Spark Plug Wire Inspection . Is the resistance more than the specified value? | 3000 ohms/ft | Go to Step 31 | Go to Step 22 | ||||
22 |
Does the test lamp flash continuously while the engine is being cranked? | -- | Go to Step 34 | Go to Step 33 | ||||
23 |
Are any of the spark plugs fouled? | -- | Go to Engine Compression Test in Engine Mechanical-3.8L | Go to Step 24 | ||||
24 | Test for a short between the CKP sensor 1 and CKP sensor 2 circuits of the ICM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 25 | ||||
25 | Test for a short between the medium resolution and low resolution speed signal circuits to the PCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Engine Compression Test in Engine Mechanical-3.8L | ||||
26 | Test for an intermittent and for 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 35 | Go to Step 33 | ||||
27 | Repair the short to ground in the affected circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 35 | -- | ||||
28 | Repair the open in the ICM ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 35 | -- | ||||
29 | Repair the open in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 35 | -- | ||||
30 | Repair the short to voltage in the CKP sensor 1 signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 35 | -- | ||||
31 | Replace the spark plug wires. Refer to Spark Plug Wire Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- | ||||
32 | Replace the CKP sensor. Refer to Crankshaft Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- | ||||
33 | Replace the ignition control module. Refer to Ignition Control Module Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- | ||||
34 | Replace the ignition coils associated with the cylinders that did not have spark. Refer to Ignition Coil Replacement . 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 2 | ||||
36 |
Are there any DTCs that have not been diagnosed? | -- | System OK | |||||
