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Home >> Pontiac >> 2007 >> Grand Prix GXP >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Engine Controls & Fuel - 3.8L - Diagnosis & Troubleshooting) >> Crankshaft Position Sensor System Diagnosis >> Circuit Description

Circuit Description

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The ignition control module (ICM) monitors the crankshaft position (CKP) sensor 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 signal 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 powertrain control module (PCM). The camshaft position sensor and the CKP sensor share a 12-volt reference and a low reference circuit. The CKP sensor consists of the following circuits:

Crankshaft Position Sensor System Diagnosis

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2 Attempt to start the engine.
Does the engine start and run?		 - Go to Testing for Intermittent Conditions and Poor Connections Go to Step 3 
3
  1. Crank the engine.
  2. Observe the Engine Speed parameter with a scan tool.
Does the scan tool display engine RPM?		 - Go to Step 12  Go to Step 4 
4
  1. Turn OFF the ignition.
  2. Disconnect the ignition control module (ICM).
  3. Turn ON the ignition.
  4. Measure the voltage from the ignition 1 voltage circuit of the ICM to a good ground with a DMM. Refer to Circuit Testing .
Is the voltage equal to the specified value?		 B+ Go to Step 5  Go to Step 14 
5 Test the ignition 1 voltage circuit of the ICM for high resistance. Refer to Circuit Testing and Wiring Repairs .
Is the resistance greater than the specified value?		 1 Ω Go to Step 26  Go to Step 6 
6 Measure the voltage between the ignition 1 voltage circuit and the ground circuit of the ICM with a DMM. Refer to Circuit Testing .
Is the voltage within the specified value?		 B+ Go to Step 7  Go to Step 15 
7
  1. Turn OFF the ignition.
  2. Connect the ICM.
  3. Disconnect the crankshaft position (CKP) sensor.
  4. Turn ON the ignition.
  5. Measure the voltage from the 12-volt reference circuit of the CKP sensor to a good ground with a DMM. Refer to Circuit Testing .
Is the difference between the measured voltage and the system voltage more than the specified value?		 1 V Go to Step 16  Go to Step 8 
8 Measure the voltage between the 12-volt reference circuit and the low reference circuit of the CKP sensor with a DMM. Refer to Circuit Testing .
Is the difference between the measured voltage and the system voltage more than the specified value?		 1 V Go to Step 17  Go to Step 9 
9 Test for high resistance in the 12-volt reference circuit and the low reference circuit of the CKP sensor. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 10 
10 Measure the voltage between the CKP sensor 1 signal circuit and the low reference circuit of the CKP sensor with a DMM. Refer to Circuit Testing .
Is the voltage within the specified range?		 4-8 V Go to Step 23  Go to Step 11 
11 Is the voltage more than the specified range? 4-8 V Go to Step 18  Go to Step 19 
12
  1. Disconnect the CKP sensor.
  2. Turn ON the ignition.
  3. Measure the voltage between the CKP sensor 2 signal circuit and the low reference circuit of the CKP sensor with a DMM. Refer to Circuit Testing .
Is the voltage within the specified range?		 4-8 V Go to Step 22  Go to Step 13 
13 Is the voltage more than the specified range? 4-8 V Go to Step 20  Go to Step 21 
14 Test for an open or short to ground in the ignition 1 voltage circuit. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 25 
15 Repair the open or high resistance in the ground circuit. Refer to Circuit Testing and Wiring Repairs .
Did you complete the repair?		 - Go to Step 31  -
16 Test the 12-volt reference circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 25 
17 Test the low reference circuit for an open and for high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 25 
18 Test the CKP sensor 1 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 25 
19 Test the CKP sensor 1 signal circuit for an open and for a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 25 
20 Test the CKP sensor 2 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 25 
21 Test the CKP sensor 2 signal circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 25 
22 Test the CKP sensor 2 signal circuit for high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 24 
23 Test the CKP sensor 1 signal circuit for high resistance, and for the CKP sensor signal 1 circuit shorted to the CKP sensor signal 2 circuit. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 24 
24 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 31  Go to Step 27 
25 Test for shorted terminals and for a poor connection at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 30 
26 Repair the high resistance in the ignition 1 voltage circuit. Refer to Wiring Repairs .
Did you complete the repair?		 - Go to Step 31  -
27
  1. Remove the CKP sensor. Refer to Crankshaft Position Sensor Replacement .
  2. Visually inspect the CKP sensor for the following conditions:
    • Physical damage
    • Excessive play or looseness
    • Improper installation
    • Foreign material passing between the CKP sensor and the reluctor wheel
    • Excessive air gap between the CKP sensor and the reluctor wheel
    • Electromagnetic interference (EMI) in the CKP sensor circuits
Did you find and correct the condition?		 - Go to Step 31  Go to Step 28 
28 Inspect the crankshaft reluctor wheel for the following conditions:
  • Physical damage
  • Excessive end play or looseness
  • Improper installation

Refer to Crankshaft and Bearings Cleaning and Inspection .
Did you find and correct the condition?		 - Go to Step 31  Go to Step 29 
29 Replace the CKP sensor. Refer to Crankshaft Position Sensor Replacement .
Did you complete the replacement?		 - Go to Step 31  -
30 Replace the ICM. Refer to Ignition Control Module Replacement .
Did you complete the replacement?		 - Go to Step 31  -
31
  1. Turn the ignition OFF for 30 seconds.
  2. Start the engine and operate the vehicle.
  3. Observe the vehicle performance and driveability.
Does the vehicle operate normally?		 - System OK Go to Step 2 
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