Engine Control System

DIAGNOSTIC CHART

Diagnostic Chart:

Diagnosis
Oxygen sensor does not function.
Harness connector between ECM and oxygen sensor is shorted or open.

Trouble Symptom
Engine will not start, poor idling, poor driveability, engine stalls, idle mixture out of specification.

CHECK HARNESS CONNECTOR BETWEEN ECM AND OXYGEN SENSOR

Harness Test:

1. Unplug connectors from ECM and oxygen sensor.
2. Measure resistance of harness connector between ECM and oxygen sensor.

Connector & Terminal Resistance
(E30) 10 - (E23) 4 0 ohms

Harness Test:

3. Measure resistance of harness connector between oxygen sensor and body to ensure no short circuit.

Connector & Terminal Resistance
(E23) 4 - body 1 M ohms min.


CHECK OXYGEN SENSOR

Voltage Test:

1. Idle engine.
2. Unplug oxygen sensor connector.
3. Measure voltage between oxygen sensor terminal and body.

Connector & Terminal Voltage
No. 4 - body 0.1 - 1.0 V