Crankshaft Position Sensor

CRANKSHAFT POSITION SENSOR





OPERATION
The crankshaft position sensor functions to detect the crank angle (position) of each cylinder, and to convert those data to pulse signals, which are then input to the engine control module. The engine control module, based upon those signals, calculates the engine rpm, and also regulates the fuel injection timing and the ignition timing.

The power for the crankshaft position sensor is supplied from the MFI relay and is grounded to the vehicle body. The crankshaft position sensor, by intermitting the flow (to ground) of the 5 V voltage applied from the engine control module, produces pulse signals.

TROUBLESHOOTING HINTS
Hint 1: If an impact is suddenly felt during driving or the engine suddenly stalls during idling, try shaking the crankshaft position sensor during idling. If the engine stalls, the cause is probably improper or incomplete contact of the crankshaft position sensor's connector.

Hint 2: If the crankshaft position sensor output rpm is 0 rpm during cranking when the engine cannot be started, the cause is probably a malfunction of the crankshaft position sensor or a broken timing belt.

Hint 3: If the indicated value of the crankshaft position sensor output rpm is 0 rpm during cranking when the engine cannot be started, the cause is probably a failure of the ignition coil's primary current to intermittently pulse correctly, so a malfunction of the ignition system circuitry, the ignition coil and/or the power transistor is the probable cause.

Hint 4: If idling is possible even though the crankshaft position sensor indicated rpm is outside the standard value, the cause is usually a malfunction of something other than the crankshaft position sensor.

Examples:
(1) Malfunction of engine coolant-temperature sensor
(2) Malfunction of idle air control motor
(3) Incorrect adjustment of the standard idling speed.


INSPECTION

Using Scan tool





Wave Pattern Inspection Using an Analyzer





Measurement Method
(1) Disconnect the distributor connector and connect the special tool (test harness: MB991 348) in between. (All terminals should be connected.)
(2) Connect the analyzer special patterns pickup to terminal (1) of the distributor connector. (When inspecting the camshaft position sensor signal wave pattern.)
(3) Connect the analyzer special patterns pickup to terminal (2) of the distributor connector. (When inspecting the crankshaft position sensor signal wave pattern.)

Alternative method (when test harness is not available)
(1) Connect the analyzer special patterns pickup to ECM terminal (68) for the camshaft position sensor.
(2) Connect the analyzer special patterns pickup to ECM terminal (69) for the crankshaft position sensor.






Wave pattern observation points
- Check that cycle time T becomes shorter and the frequency increases when the engine speed is increased.


Examples of abnormal wave patterns

- Example 1




Cause of problem
- Malfunction of sensor interface

Wave pattern characteristics
- Short wave pattern is output even when the engine is not started.


- Example 2




Cause of problem
- Loose timing belt
- Abnormality in sensor disk

Wave pattern characteristics
- Wave pattern is displaced to the left or right.



HARNESS INSPECTION