Engine Control System

DIAGNOSTIC CHART

Diagnostic Chart:

Diagnosis
No signal entered from crankshaft position sensor, but signal entered from camshaft position sensor.
Harness connector between ECM and crankshaft position sensor is shorted or open.

Trouble Symptom
Engine stalls, restarting impossible.

CHECK INPUT SIGNAL FOR ECM

Input Signal:

1. Set the positive probe and earth lead of oscilloscope at ECM connector terminals (E30) No. 6 - (E30) No. 7.

Oscilloscope Pattern:

2. Measure signal voltage indicated on oscilloscope while cranking engine.

CHECK HARNESS CONNECTOR BETWEEN ECM AND CRANKSHAFT POSITION SENSOR

Harness Test:

1. Turn ignition OFF.
2. Unplug connectors from ECM and crank position sensor.
3. Measure resistance of harness connector between ECM and crank position sensor.

Connector & Terminal Resistance
(E30) 6 - (E14) 1 10 ohms max.
(E30) 7 - (E14) 2 10 ohms max.

Harness Test:

4. Measure resistance of harness connector between ECM and body to make sure there is not a short.

Connector & Terminal Resistance
(E30) 6 - body 1 M ohm min.
(E30) 7 - body 1 M ohm min.
(E30) 11 - body 1 M ohm min.

CHECK CRANKSHAFT POSITION SENSOR

Sensor Test:

1. Remove crankshaft position sensor.
2. Set the positive probe at sensor connector terminal No. 1 and set the earth lead at terminal No. 2.
3. Check that a wave profile appears crossing a magnet near the pick-up coil of the crankshaft position sensor.