Component Tests and General Diagnostics

VOLTAGE AND CONTINUITY TESTS AT DME CONNECTOR:

The following voltage and continuity tests can be used to help determine whether there are faults in the wiring and/or components that provide input information to the Motronic Control Unit. If all inputs are found to be correct and the system still does not perform as expected, the Motronic Control Unit may be defective.

As a general rule, a complete absence of the voltage or continuity specified in the tests suggests an open circuit in the wiring harness. Test results that differ from the specified values do not necessarily mean that components are faulty. Check carefully for connections that are loose, corroded or otherwise damaged.

NOTE: Before testing, disable the ignition system.

With the battery disconnected, remove the Motronic Control Unit connector. Use a multimeter to check for voltage or continuity at the connector terminals. Use care to avoid damaging the small connector terminals with the meter probes.

CAUTION: Use only a digital voltmeter-ohmmeter; or multimeter with high input impedance. The electrical characteristics of other types of test equipment may cause inaccurate results or damage to the electronic components. The ignition must be off before disconnecting or connecting any electrical connections.

NOTE: For accurate test results, battery voltage at the connector must be 12 to 13 volts. Charge the battery if necessary.

View - DME Connector:

Voltage Supply to Control Unit:
Test terminals: 18 and ground.
Test conditions: Ignition ON.
Test value: battery voltage (approx 12 VDC).

Test terminals: 35 and ground.
Test conditions: Ignition ON.
Test value: battery voltage (approx 12 VDC).

Main Grounds:
Test terminals: 5 and ground.
Test conditions: Ignition OFF.
Test value: continuity.

Test terminals: 16 and ground.
Test conditions: Ignition OFF.
Test value: continuity.

Test terminals: 17 and ground.
Test conditions: Ignition OFF.
Test value: continuity.

Test terminals: 19 and ground.
Test conditions: Ignition OFF.
Test value: continuity.

Fuel Pump Relay Control:
Test terminals: 20 and ground.
Test conditions: Ignition ON.
Test value: fuel pumps run (audibly) when terminal 20 is touched to ground.

Starter Input (terminal 50 on starter):
Test terminals: 4 and ground.
Test conditions: actuate starter.
Test value: 8 VDC (minimum).

Throttle Switch:
Test terminals: 2 and ground.
Test conditions: throttle closed.
Test value: continuity.

Test terminals: 2 and ground.
Test conditions: open throttle slowly to half-open position.
Test value: no continuity.

Test terminals: 3 and ground.
Test conditions: throttle fully open.
Test value: continuity.

Engine Speed Sensor:
Test terminals: 8 and 27.
Test conditions: Ignition OFF.
Test value: 960 +/- 96 ohms resistance.

Reference Sensor:
Test terminals: 25 and 26.
Test conditions: ignition OFF.
Test value: 960 +/- 96 ohms resistance.

Coolant Temperature Sensor:
Test terminals: 13 and ground.
Test conditions: Ignition OFF.
Test value: resistance varies with temperature:
14 +/- 2°F (-10 +/- 1°C) 7000-11600 ohms.
68 +/- 2°F (20 +/- 1°C) 2100-2900 ohms.
176 +/- 2°F (80 +/-1°C) 270-400 ohms.

Fuel Injector Control (injectors 1, 2, and 3):
Test terminals: 14 and ground.
Test conditions: Ignition ON.
Test value: fuel injectors (1, 2, and 3) click when terminal 14 is touched to ground.

Fuel Injector Control (injectors 4, 5, and 6):
Test terminals: 15 and ground.
Test conditions: Ignition ON.
Test value: fuel injectors (4, 5, and 6) click when terminal 15 is touched to ground.

Air Flow Sensor:
Test terminals: 7 and 9.
Test conditions: move sensor flap by hand or actuate starter.
Test value: resistance must fluctuate.

Oxygen Sensor:
Test terminals: 24 and ground.
Test conditions: separate oxygen sensor connector and connect green wire to ground.
Test value: continuity.

Evaporative Purge Valve Control:
Test terminals: 31 and ground.
Test conditions: Ignition ON.
Test value: purge valve clicks when terminal 31 is touched to ground.