Ground Circuits
- Turn ignition off. Using ohmmeter connected to ground, backprobe each ECM ground terminal. For ECM ground terminal identification, see appropriate pin voltage chart in PIN VOLTAGE CHART S article in this section. Resistance should be zero ohms. If resistance is not close to zero ohms, repair open to ground.
- Start engine. Using voltmeter connected to ground, backprobe each ground terminal. Voltage should be less than one volt. If voltage is greater than one volt, check for open, corrosion, or loose connection on ground lead.
Power Circuits (Ignition Off)
Turn ignition off. Check for battery voltage between ECM power terminals and ground. For ECM power terminal identification, see appropriate pin voltage chart in PIN VOLTAGE CHART S article in this section. If battery voltage does not exist, check fuse or fusible link. Fuses are located under instrument panel. On some models, an auxiliary fuse panel is located in engine compartment. Fusible links are in engine compartment. If fuse and fusible link are okay, check for an open in wire between fuse/fusible link and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
Power Circuits (Ignition On)
Turn ignition on. Check for battery voltage between ECM power terminals and ground. For ECM power terminal identification, see appropriate pin voltage chart in PIN VOLTAGE CHART S article in this section. If battery voltage does not exist, check fuse. If fuse is okay, check for an open in wire or a defective ignition switch. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
Power Circuits (Cranking)
- Using voltmeter, backprobe ECM connector crank signal terminal. See appropriate wiring diagram in WIRING DIAGRAMS article in this section. Hold ignition switch in START position. Battery voltage should exist between ECM terminal and ground only when ignition switch is in START position.
- If battery voltage does not exist, check fusible link. Fusible links are in engine compartment. If fusible link is okay, check for open wire between fusible link and ECM terminal, or for defective ignition switch.
A/C SWITCH
Test switch and circuits as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
CAMSHAFT POSITION (CMP) SENSOR
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
CRANKSHAFT POSITION (CKP) SENSOR
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
ENGINE COOLANT TEMPERATURE (ECT) SENSOR
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
FUEL LEVEL SENSOR
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
FUEL TEMPERATURE SENSOR
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
KNOCK SENSOR
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
MASS AIRFLOW (MAF) SENSOR
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
OXYGEN SENSOR (O2S)
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
PARK/NEUTRAL POSITION (PSP) SWITCH
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
PRESSURE SENSOR
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
THROTTLE POSITION (TP) SENSOR
For adjustments, see ADJUSTMENTS article in this section. For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
VEHICLE SPEED SENSOR (VSS)
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
Cooling Fan Relay
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
Fuel Pump Relay
For testing procedures, see BASIC TESTING article in this section.
Main Relay
For testing procedures, see BASIC TESTING article in this section.
EGR Solenoid Valve
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
Purge Control Solenoid Valve
See FUEL EVAPORATIVE SYSTEM (EVAP) under EMISSION SYSTEMS & SUB-SYSTEMS .
FUEL DELIVERY
Note. For fuel system pressure testing, see BASIC TESTING article in this section.
Feedback System
Manufacturer recommends performing complete inspection of self-diagnostic system. This includes checking mechanical condition of engine, available fuel to injectors, and ignition. Repair or replace components as required, and test drive vehicle.
Fuel Injector(s)
- Connect tachometer to engine. Start and idle engine. Unplug harness connector from injectors one at a time. Engine idle speed should drop 100-300 RPM as each injector is disconnected. If engine idle speed does not drop, check wiring connector, injector resistance, and injection signal from computer.
- Turn ignition off. Unplug connector from each injector. Check injector resistance. Resistance should be 5-20 ohms. If resistance is not to specification, replace injector.
IDLE AIR CONTROL SOLENOID VALVE
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
* PLEASE READ FIRST *
Note. For basic ignition checks (coil and wires), see BASIC TESTING article in this section. For camshaft and crankshaft position sensor testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
Electronic Advance
For testing procedures, see ADJUSTMENTS article in this section.
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
Secondary Air Injection System
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
EGR Solenoid
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
EGR System
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
EGR Valve
- Look through opening in EGR valve body and observe valve shaft. Warm engine to normal operating temperature. Increase engine speed and check whether valve shaft moves when engine reaches 3500-4000 RPM under no-load condition.
- If shaft does not move, remove valve and manually check valve movement. If valve appears okay, check vacuum lines for leaks. Clean or replace valve if it does not operate properly. NOTE: When cleaning EGR valve, DO NOT wash in solvent or degreaser, or permanent damage to valve diaphragm will result.
- Press valve diaphragm and inspect valve seat area. Inspect valve inlet and outlet for deposits. Clean as necessary. Blow clean with compressed air. Recheck valve operation by applying 8 in. Hg vacuum with hand-held vacuum pump.
FUEL EVAPORATIVE SYSTEM (EVAP)
| WARNING | DO NOT inhale fuel vapor when blowing into fuel evaporative hoses. |
Charcoal Canister
Inspect for visual damage. For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
EVAP Pressure Sensor
For testing procedures, see appropriate DTC in TESTS W/CODES article in this section.
Check self-diagnostic system for any DTCs. see appropriate DTC in TESTS W/CODES article in this section. Check valve winding for short to ground. Apply battery voltage to valve terminals. Verify passage opens and closes as voltage is applied and removed. Replace valve if winding is shorted, or if operation is not as specified.
Two-Way Valve
Remove two-way valve. Valve is located near fuel tank. Mark hoses for reinstallation. Blow air into each valve port. Air should flow through valve with light resistance. Visually inspect valve for cracks.
POSITIVE CRANKCASE VENTILATION (PCV)
With engine idling, disconnect ventilation hose from PCV valve. If hissing noise and strong vacuum are not present at hose end, check hose and hose connections for leaks and obstructions. Repair or replace as necessary. Connect hose to PCV valve. Remove PCV valve from intake manifold. Place finger over PCV valve. Vacuum should be present. Remove finger from PCV valve. Valve should snap back.
