Checking Components and Wiring
Check of components and wiring:
- Refer to wiring diagram as needed during tests.
Switch off the ignition:
- Remove panel in front of right front door (pass. side).
- Remove connector from the Engine Control Module (ECM).
- Push connector catch to the side and fold out ECM connector.
Remove connector cover:
CAUTION: Never check terminals from front. Experience has shown that the terminals are easily damaged causing further faults.
- Check terminals through the holes in side of connector. Do not use excessive force.
- Terminal (pin) numbers are stamped on the connector.
Check grounds:
- Connect ohmmeter between ground and terminal 11.
- Connect ohmmeter between ground and terminal 25.
- Resistance should be 0 ohms (no resistance) for both terminals.
- These wires are grounded at the intake manifold (arrows).
Check supply voltage:
- Switch on ignition.
- Connect voltmeter between ground and terminal 18.
- Voltmeter should show battery voltage.
- Switch off ignition.
Check shielding wires:
- Check that wires are twisted together and connected to terminal 5.
Check fuel pump relay:
- Switch on ignition.
- Ground terminal 17.
- Relay should switch on and fuel pumps start.
- Switch off ignition.
Check system relay:
- Connect voltmeter between ground and terminal 9.
- Ground terminal 21.
- Relay should switch on and meter show battery voltage.
Check air mass meter current supply and ground:
- Ground terminal 21.
- Peel back rubber boot from around air mass meter wiring connector.
- Connect voltmeter between terminal 9 and ground.
- Connect voltmeter between terminal 9 and terminal 36.
- Meter should show battery voltage in both cases. (Air mass meter terminal 36 is grounded at the intake manifold).
- Reposition rubber boot around wiring connector.
Check wiring from starter motor:
- Connect voltmeter between ground and terminal 4.
- Crank engine.
- Meter should show battery voltage.
Check wiring from ignition coil:
- Switch on ignition.
- Connect voltmeter between ground and terminal 1.
- Meter should deflect.
- Switch off ignition.
Check fuel injectors:
- Connect ohmmeter between fuel pump relay terminal 87 and ECM connector terminal 13.
- Correct resistance is approx. 4 ohms.
If meter shows:
approx. 5.3 ohms: either an injector or an injector wire is defective.
approx. 8 ohms: two injectors or injector wires are defective.
approx. 16 ohms: three injectors or injector wires are defective.
If reading other than 4 ohms is obtained:
- remove injector connectors and check each injector separately.
- Resistance for each injector should be 16 ohms.
Check coolant temperature sensor:
- Connect ohmmeter between ground and terminal 2.
- Resistance depends on temperature (see chart).
- Resistance at certain temperatures:
+80°C (175°F) = 290 - 364 ohms.
+20°C (68°F) = 2280 - 2720 ohms.
-10°C (14°F) = 8260 - 10560 ohms.
- Incorrect test values indicate the coolant temperature sensor is defective.
- Extremely high test values indicates an open circuit in coolant temperature sensor or wiring (check the temperature sensor ground at intake manifold).
- Zero resistance indicates a short circuit.
Check air mass meter:
- Connect ohmmeter between terminal 6 and terminal 7.
- Resistance should be 3.7 ohms.
- Connect ohmmeter between terminal 6 and terminal 14.
- Resistance should be between 0 - 1000 ohms (resistance varies depending on CO-adjustment screw position).
Check throttle valve switch:
- Connect ohmmeter between ground and terminal 3.
- Depress accelerator pedal.
- Meter should show 0 ohms (no resistance) in idle position and infinite resistance in all other positions.
- Connect ohmmeter between ground and terminal 12.
- Depress accelerator pedal.
- Meter should show 0 ohms (no resistance) in full throttle position and infinite resistance in all other positions.
- If incorrect, check throttle valve switch ground at intake manifold. If ground connection is OK replace throttle valve switch.
Check idle air control valve:
- Connect ohmmeter between fuel pump relay terminal 87 and ECM connector terminal 10.
- Resistance should be approx. 20 ohms.
- Connect ohmmeter between fuel pump relay terminal 87 and ECM connector terminal 23.
- Resistance should be approx. 20 ohms.
Check air conditioning micro-switch:
- Connect ohmmeter between ground and terminal 16.
- Turn knob on air conditioning control panel clock-wise.
- Resistance should decrease.
Reinstall engine control module (ECM) connector cover:
- Plug in ECM connector.
- Ignition should be switched off.