Diagnostic Procedure
CAUTION:
To prevent damage to scan tool, always turn the ignition off before connecting or disconnecting scan tool.
- Install scan tool. With gearshift lever in the "P" position, start the engine and run at idle. Using scan tool, monitor crankshaft position sensor. When the throttle is fully closed, the scan tool engine speed display should be 600-900 RPM. With the throttle fully opened, the scan tool engine speed display should increase according to engine speed. Is the sensor operating properly? If so, malfunction is intermittent. If not, go to next step.
- Using the oscilloscope, check the waveform at crankshaft position sensor harness connector. Do not disconnect harness connector. Connect an oscilloscope probe to crankshaft position sensor harness connector terminal No. 2 by backprobing. With the gearshift lever in the "P" position, start the engine and run at idle. Check the waveform. The waveform should show a pattern similar to the illustration. See Fig 1 . The waveform voltage value should be 0.6-4.8 volts. Turn ignition off. Is the waveform normal? If so, go to next step. If not, go to step 5 .
- Check crankshaft position sensor and PCM harness connectors for damage. Are the harness connectors in good condition? If so, go to next step. If not, repair or replace the defective harness connector(s).
- With gearshift lever in the "P" position, start the engine and run at idle. Using scan tool, monitor crankshaft position sensor. When the throttle is fully closed, the scan tool engine speed display should be 600-900 RPM. When the throttle is fully opened, the scan tool engine speed display should increase according to engine speed. Is the sensor operating properly? If so, malfunction is intermittent. If not, possible faulty PCM exists. Replace the PCM if necessary. See POWERTRAIN CONTROL MODULE under REMOVAL & INSTALLATION.
- Check crankshaft position sensor harness connector for damage. Is the harness connector in good condition? If so, go to next step. If not, repair or replace defective harness connector.
- Check the sensor output voltage at crankshaft position sensor harness connector. Disconnect crankshaft position sensor harness connector and measure at the harness side. Turn ignition on. Measure the voltage between crankshaft position sensor harness connector terminal No. 2 and ground. Voltage should be 4.9-5.1 volts. Turn ignition off. Is the voltage as specified? If so, go to step 11 . If not, go to next step.
- Check the crankshaft position sensor output voltage at PCM harness connector by backprobing. Do not disconnect PCM harness connector. Disconnect crankshaft position sensor harness connector. Turn ignition on. Measure the voltage between PCM harness connector terminal No. 45 and ground. Voltage should be 4.9-5.1 volts. Turn ignition off. Is the voltage as specified? If so, go to next step. If not, go to step 9 .
- Check PCM harness connectors for damage. Are the harness connectors in good condition? If so, repair open in wire harness between crankshaft position sensor harness connector terminal No. 2 and PCM harness connector terminal No. 45. If not, repair or replace defective harness connector(s).
- Check PCM harness connectors for damage. Are the harness connectors in good condition? If so, go to next step. If not, repair or replace defective harness connector(s).
- Check wire harness for short to ground between crankshaft position sensor harness connector terminal No. 2 and PCM harness connector terminal No. 45. Is the wire harness in good condition? If so, go to step 4 . If not, repair wire harness as necessary.
- Check the power supply voltage at crankshaft position sensor harness connector. Disconnect crankshaft position sensor harness connector and measure at the harness side. Turn ignition on. Measure voltage between crankshaft position sensor harness connector terminal No. 3 and ground. Battery voltage should exist. Turn ignition off. Is the voltage as specified? If so, go to step 13 . If not, go to next step.
- Check MFI relay harness connector in engine compartment relay box for damage. Is the harness connector in good condition? If so, repair open or short to ground between MFI relay connector terminal No. 1 and crankshaft position sensor harness connector terminal No. 3. If not, repair or replace MFI relay harness connector.
- Check resistance at crankshaft position sensor harness connector. Disconnect crankshaft position sensor harness connector and measure at the harness side. Measure resistance between crankshaft position sensor harness connector terminal No. 1 and ground. Resistance should be less than 2 ohms. Is the resistance as specified? If so, go to next step. If not, repair open or damage in wire harness between crankshaft position sensor harness connector terminal No. 1 and ground.
- Check PCM and MFI relay harness connectors for damage. Are the harness connectors in good condition? If so, go to next step. If not, repair or replace the defective harness connector(s).
- Check wire harness for damage between crankshaft position sensor harness connector terminal No. 2 and PCM harness connector terminal No. 45. Is the wire harness in good condition? If so, go to next step. If not, repair wire harness as necessary.
- Check wire harness for damage between MFI relay harness connector terminal No. 1 and crankshaft position sensor harness connector terminal No. 3. Is the wire harness in good condition? If so, go to next step. If not, repair wire harness as necessary.
- Check wire harness for damage between crankshaft position sensor harness connector terminal No. 1 and ground. Is the wire harness in good condition? If so, go to next step. If not, repair wire harness as necessary.
- Check the crankshaft position sensor vane. Is the vane in good condition? If so, replace crankshaft position sensor. If not, repair or replace crankshaft position sensor vane as necessary.