GM Lumina/Silhouette/Transport APVs 1990-1999 Repair Guide

Crankshaft Position Sensor

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The 3.1L Engine uses a Distributor.

OPERATION



3.8L Engine

The dual Hall-effect crank sensor is the most critical part of the ignition system. If the sensor is damaged so that the crank sensor pulses are not generated, the engine will not start. There are four circuit wires connecting the dual crankshaft position sensor to the ignition control module. If there is a problem with any of the four, the engine will not start (no spark and no injector pulses). The circuits are:



Source voltage (10 to 12 volts) operating power supply for the Hall-effect switches from the ignition control module.
 
18X sensor pulse signal to the ignition control module.
 
3X sensor pulse signal to the ignition control module.
 
Ground circuit for both Hall-effect switches. Equally important is the crankshaft reference (fuel control) signal generated by the ignition control module. If the PCM does not receive this signal, it will not pulse the injectors.
 

If the 3x crankshaft position sensor pulses stop while the engine is running, the engine will keep running. It will not restart after being shut "OFF".

If the 18X crankshaft position sensor pulses stop while the engine is running, the engine will stop running and will not restart.

Crankshaft Position (CKP) Sensor clearance is very important! The sensor must not contact the rotating interrupter rings at any time, or sensor damage will result.

Ignition timing is not adjustable.-The firing order is 1-6-5-4-3-2.

See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Crankshaft position sensor connector and cover shown



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Fig. Fig. 2: CMP and CKP Sensor locations for the 3.8L Engine



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Fig. Fig. 3: 18X and 3X Crank Sensor Pulses for one crankshaft revolution



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Fig. Fig. 4: Crankshaft Balancer with Interrupter Rings

3.4L Engine

3X reference PCM input

From the ignition control module, the PCM uses this signal to calculate engine Rpm and crankshaft position at engine speeds above 1200 RPM .The PCM also uses the pulses on this circuit to initiate injector pulses. If the PCM receives no pulses on this circuit, it will use the 24X reference signal circuit for fuel and ignition control. The engine will continue to start and run using the 24X reference signal only.

24X reference PCM input

From the ignition control module, the DPCM uses this signal to calculate engine RPM and crankshaft position at engine speeds below 1200 RPM. The PCM also uses the pulses on this circuit to initiate injector pulses. If the PCM receives no pulses on this circuit, the PCM will use the 3X reference signal circuit at all times for fuel and ignition control. The engine will continue to start and run using the 3X reference signal only.

7X Crankshaft Position (CKP) Sensor

The 7X crankshaft position sensor provides a signal used by the ignition control module to calculate ignition sequence. The ignition control module also uses the crankshaft position sensor signals to initiate 3X reference pulses that the PCM uses as reference to calculate RPM and crankshaft position.

Ignition timing is not adjustable.-The firing order is 1-2-3-4-5-6.

TESTING



3.4L Engine


Incorrect harness routing near secondary ignition components.
 
Ignition coil arcing to the wiring harness or to the Ignition Control Module. Check the ignition coils for cracks, carbon tracking, or other signs of damage.
 
Secondary ignition wire(s) arcing to the wiring harness.
 
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.
 
Check for a poor connection or damaged harness: Inspect the PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connections and damaged harnesses.
 
If harness appears to be OK, disconnect the PCM, turn the ignition ON and observe a voltmeter connected to the 24X reference circuit at the PCM harness connector while moving connectors and wiring harnesses related to the 24X Crankshaft Position Sensor and Camshaft Position Sensor. The 24X and Camshaft Position sensors share the same sensor feed from the PCM. A change in voltage will indicate the location of the fault.
 
If the 24X sensor feed is open, the tachometer on the dash (if vehicle is equipped) will not operate.
 

  1. If necessary to perform a test on the crankshaft sensor, use the diagnostic repair chart and the wire and connector diagram given here for the 3.4L Engine.
  2.  

See Figures 5, 6 and 7



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Fig. Fig. 5: Circuit Description for Crankshaft (CKP) and Camshaft (CMP) Sensors



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Fig. Fig. 6: CKP Sensor circuit performance testing-Page One



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Fig. Fig. 7: CKP Sensor circuit performance testing-Page Two

3.8L Engine

During cranking, the ignition control module monitors the crankshaft position sensor sync signal. The sync signal is used to determine the correct cylinder pair to spark first. After the sync signal has been processed by the ignition control module, it sends a reference pulse to the PCM. If there is an intermittent fault, a code may not set immediately or under all conditions. Certain symptoms experienced may help isolate the cause of the condition. A poor connection or fault in the camshaft position sensor circuits or a faulty camshaft position sensor may cause the PCM to re-initialize injector sequence when the fault occurs, causing a possible stumble or miss. A poor connection or fault in the fuel control circuit, crankshaft position sensor circuits, the 18X portion of the crankshaft position sensor or damaged vanes on the harmonic balancer interrupter rings will cause the PCM to stop pulsing the injectors when the fault occurs, causing an intermittent stumble or stall.

If the CKP sensor is suspect, use the accompanying charts to help diagnose the problem.

See Figures 8 and 9

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Fig. Fig. 8: 3.8L engine CKP/CMP connector and wiring diagram



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Fig. Fig. 9: CKP/CMP Diagnostic Tree Chart

REMOVAL AND INSTALLATION



3.4L Engine

See Figure 10

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Fig. Fig. 10:

7X CKP SENSOR
  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle securely on jackstands.
  4.  
  5. Remove the intermediate exhaust pipe.
  6.  
  7. Remove the rack and pinion heat shield.
  8.  
  9. Disconnect the electrical connector.
  10.  
  11. Remove the crankshaft Position sensor shield retaining nut.
  12.  
  13. Extract the 7X CKP sensor from the block.
  14.  

To install:

Before installing the new crankshaft sensor, lubricate new O-ring with clean oil.

  1. Install the crankshaft sensor in the block.
  2.  
  3. Install the sensor retainer and bolt. Tighten the bolt to 8N.m (70 inch lbs.).
  4.  
  5. Install the rack and pinion heat shield.
  6.  
  7. Install the intermediate exhaust pipe.
  8.  
  9. Lower the vehicle.
  10.  
  11. Connect the negative battery cable.
  12.  

24x CKP SENSOR

See Figure 11

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Fig. Fig. 11:

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the serpentine engine belt form the crankshaft pulley.
  4.  
  5. Raise and safely support the vehicle securely on jackstands.
  6.  
  7. Remove the right front tire and wheel assembly.
  8.  
  9. Remove the right inner fender access cover.
  10.  
  11. Remove the crankshaft harmonic balancer retaining bolt and harmonic balancer using a suitable tool.
  12.  
  13. Remove the CKP sensor harness clip, the electrical connector, and remove the sensor from the block face.
  14.  

To install:
  1. Install the sensor to the block, connect the electrical connector, and install the sensor harness clip.
  2.  
  3. Torque the sensor mounting bolts to 10Nm (8 lb. ft)
  4.  
  5. Apply sealer to the keyway of the balancer.
  6.  
  7. Install the balancer onto the crankshaft.
  8.  
  9. Apply thread sealer to the threads of the crankshaft balancer bolt and tighten to 107Nm (79 lb. ft)
  10.  
  11. Install the serpentine engine belts.
  12.  
  13. Install the right inner fender access cover.
  14.  
  15. Install the right side tire and wheel assembly.
  16.  
  17. Lower the vehicle.
  18.  
  19. Connect the negative battery cable.
  20.  

3.8L Engine

See Figure 12



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Fig. Fig. 12: Crankshaft Position Sensor Shield

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the serpentine engine belt from the crank pulley.
  4.  
  5. Raise and safely support the vehicle securely on jackstands.
  6.  
  7. Remove the right front tire and wheel assembly.
  8.  
  9. Right inner fender access cover.
  10.  
  11. Remove crankshaft harmonic balancer retaining bolt, and harmonic balancer using a suitable puller.
  12.  
  13. Remove the CKP sensor shield, do not use a pry bar.
  14.  
  15. Disconnect the electrical connector.
  16.  
  17. Remove the sensor and pedestal from the block face.
  18.  
  19. Remove the sensor from the pedestal.
  20.  

See Figures 13 and 14

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Fig. Fig. 13: Crankshaft Sensor Tool to Harmonic Balancer Alignment



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Fig. Fig. 14: Crankshaft Sensor Tool to Crankshaft Alignment

To install:
  1. Loosely install the CKP sensor on the pedestal.
  2.  
  3. Position the sensor with pedestal attached using the appropriate tool.
  4.  
  5. Position the special tool onto the crankshaft and install the bolts to hold the pedestal to the block face. Torque to 20-40 N.m (14-28 ft. lbs.). Torque the pedestal pinch bolt to 4-4.5 Nm (36-40 inch lbs.).
  6.  
  7. Remove the special tool.
  8.  
  9. Replace the crankcase position shield.
  10.  
  11. Connect the electrical connector.
  12.  
  13. Place the tool on the harmonic balancer and turn. If any vane of the harmonic balancer touches the tool, replace the balancer assembly.
  14.  
  15. Install the balancer to the crankshaft, apply sealer to the threads, and torque the crankshaft bolt to 150Nm (110 ft. lbs.) + 76°.
  16.  
  17. Install the inner fender shield, and the tire and wheel assembly.
  18.  
  19. Lower the vehicle, and install the serpentine belt.
  20.  
  21. Connect the negative battery cable.
  22.  

 
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