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DTC 21

CODE NO.21: CRANKSHAFT POSITION SENSOR SYSTEM





CIRCUIT OPERATION
- The crankshaft position sensor power is supplied from the MFI relay (terminal 3), and the ground (terminal 1) is provided on the vehicle body. The PCM supplies a 5-volt voltage to crankshaft position sensor output terminal (terminal 2). The crankshaft position sensor generates a pulse signal when the output terminal is opened and then grounded. The sensor is opened and closed as the blade on the crankshaft passes by.

DTC CONDITIONS
- If no output pulse is detected from the crankshaft position sensor for 5 seconds or more while driving at 25 km/h (16 mph) or more, there is an open circuit in the crankshaft position sensor and diagnostic trouble code number "21" is sent.

TROUBLESHOOTING HINTS
The most likely causes for this code to be set:
- Malfunction of the crankshaft position sensor circuit
- Damaged harness, connector
- Malfunction of the PCM

DIAGNOSIS

STEP 1. Check The Crankshaft Position Sensor In One Of The Following Two Ways.
1. If scan tool MB991502 is used, go to Step 2.
2. If an oscilloscope is used, go to Step 3.

Required Special Tool: MB991502: Scan Tool (MUT-II)

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.


STEP 2. Using Scan Tool MB991502, Check Data List Item 21: Crankshaft Position Sensor.





1. Connect scan tool MB991502 to the data link connector.
2. With the gear selector lever in the "N" position, start the engine and run it at idle.
3. Set scan tool MB991502 to the data reading mode for item 21, Crankshaft position sensor.
4. When the accelerator pedal is not depressed (throttle valve is fully closed) the display should be 600 to 900 r/min.
5. With the accelerator pedal depressed, the engine speed reading should increase according to engine speed.
If the crankshaft position sensor is operating properly, this malfunction is intermittent. Refer to Diagnostic Strategies; General Electrical Troubleshooting.
If the crankshaft position sensor is not operating properly, go to Step 4.


STEP 3. Using An Oscilloscope, Check The Crankshaft Position Sensor.





Required Special Tool: MD998478: Test harness

1. Disconnect crankshaft position sensor connector B-20, and connect special tool MD998478 in between.
2. Connect the clip of special tool MB998478 (for terminal 2 of connector B-20) to an oscilloscope probe.
3. Start the engine and run at idle.





4. Check the wave form.
The wave form should slow normal pattern as shown in the illustration.
5. Turn off the engine.
If the wave form shows a normal pattern, this malfunction is intermittent. Refer to Diagnostic Strategies; General Electrical Troubleshooting.
If the wave form does not show a normal pattern, go to Step 4.


STEP 4. Check The Power Supply Circuit At The Crankshaft Position Sensor Connector.
1. Disconnect harness connector B-20 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.





3. Measure the voltage between terminal 3 and ground.
- Voltage should be battery positive voltage.
If battery positive voltage, go to Step 5.
If not battery positive voltage, repair the harness wire between the MFI relay and the crankshaft position sensor connector B-20.


STEP 5. Check The Power Supply Circuit At The Crankshaft Position Sensor Connector.
1. Disconnect harness connector B-20 and measure at the harness side.
2. Turn the ignition switch to the "LOCK" (OFF) position.





3. Check for continuity between terminal 1 and ground.
- Should be less than 2 ohms.
If less than 2 ohm, go to Step 6.
If open circuit, any harness wire between crankshaft position sensor connector B-20 and ground is damaged, repair it. Refer to Diagnostic Strategies; General Electrical Troubleshooting.
Then check the malfunction.


STEP 6. Check The Signal Circuit At The Crankshaft Position Sensor Connector.
1. Disconnect harness connector B-20 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.





3. Measure the voltage between terminal 2 and ground.
- Voltage should be approximately 5 volts.
If 5 volts, go to Step 7.
If not 5 volts, go to Step 8.


STEP 7. Check Harness Connector B-20 At The Crankshaft Position Sensor For Damage.





If harness connector B-20 is damaged, repair or replace it. Refer to Diagnostic Strategies; General Electrical Troubleshooting. Recheck for DTCs.
If harness connector B-20 is in good condition, replace the crankshaft position sensor.


STEP 8. Check Harness Connector C-40 At The PCM For Damage.





If any harness connector C-40 is damaged, repair or replace it. Refer to Diagnostic Strategies; General Electrical Troubleshooting. Recheck for DTCs.
If harness connector C-40 is in good condition, go to Step 9.


STEP 9. Check The Harness Wire Between PCM Connector C-40 And Crankshaft Position Sensor Connector B-20.








If any harness wire between the PCM connector C-40 and the crankshaft position sensor connector B-20 is damaged, repair it. Refer to Diagnostic Strategies; General Electrical Troubleshooting. Recheck for DTCs.
If the harness wire is in good condition, recheck for DTCs.
If the malfunction is not eliminated, replace the PCM. On 2000 models, the immobilizer-ECU should be replaced together with it. Refer to Ignition Switch and Immobilizer System.
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