Engine Control System

DIAGNOSTIC CHART

Diagnostic Chart:

Diagnosis
Throttle position sensor signal is abnormal.
Sensor is installed incorrectly.
Harness connector between ECM and throttle position sensor is shorted or open.

Trouble Symptom
Engine stalls, poor idle quality, poor driveability.

CHECK INPUT SIGNAL FOR ECM

Harness Test:

1. Turn ignition ON.
2. Measure signal voltage between ECM and body while throttle valve is fully closed.

Connector & Terminal Voltage
(E30) 15 - body 4.4 - 5.5 V
(E30) 4 - body 0.4 - 0.5 V
(E30) 11 - body 0 V

3. Measure signal voltage between ECM and body while throttle valve is fully open.

Connector & Terminal Voltage
(E30) 15 - body 4.4 - 5.5 V
(E30) 4 - body 3.5 - 4.3 V
(E30) 11 - body 0 V

CHECK HARNESS CONNECTOR BETWEEN ECM AND THROTTLE POSITION SENSOR

Harness Test:

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

Connector & Terminal Resistance
(E30) 15 - (E10) 1 10 ohms max.
(E30) 4 - (E10) 2 10 ohms max.
(E30) 11 - (E10) 3 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) 15 - body 1 M ohm min.
(E30) 4 - body 1 M ohm min.
(E30) 11 - body 1 M ohm min.

CHECK AND ADJUST THROTTLE POSITION SENSOR

Measuring Voltage At ECM:

1. Plug in all connectors.
2. Loosen sensor mounting screws.
3. Adjust sensor while throttle valve is fully closed.
4. Using a voltmeter:
a. Turn ignition ON.
b. Loosen mounting screws and adjust sensor to specified voltage between ECM connector terminals.

Connector & Terminal Voltage
(E30) 15 - 4 0.45 - 0.55 V

c. Tighten mounting screws.

Select Monitor:

5. Using Select Monitor:
a. Attach Select Monitor.
b. Turn ignition ON.
c. Select mode F10.
d. Loosen mounting screws and adjust sensor to specified data.

Conditions Voltage
Throttle valve fully closed 0.50 V

d. Tighten sensor mounting screws.