Ground Circuits
- Turn ignition off. Using ohmmeter, backprobe each ECM ground terminal. (Terminal Nos. 17, 18, 19, 20, 42, 46, 69, 94, & 94). See appropriate «WIRING DIAGRAMS»(ref-26255) article. Resistance should be zero ohms. If resistance is not close to zero ohms, repair open to ground.
- Start engine. Using voltmeter, 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. See ECM POWER TERMINAL IDENTIFICATION table. 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 or fusible link is okay, check for an open in wire between fuse/fusible link and ECM. See WIRING DIAGRAMS article.
Power Circuits (Ignition On)
Turn ignition on. Check for battery voltage between ECM power terminals and ground. See ECM POWER TERMINAL IDENTIFICATION table. 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 DIAGRAMS article.
Power Circuits (Cranking)
- Using voltmeter, backprobe appropriate ECM terminal. See ECM POWER TERMINAL IDENTIFICATION table. 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. See «WIRING DIAGRAMS»(ref-26255) article.
| Application | Wire Color | |
|---|---|---|
| Ignition On | ||
| 1 | (1) | |
| 2 | (1) | |
| 39 (2) | (1) | |
| (1) See appropriate WIRING DIAGRAMS article. (2) Back-up power supply. Battery voltage at all times. | ||
| (1) | See appropriate WIRING DIAGRAMS article. |
| (2) | Back-up power supply. Battery voltage at all times. |
ECM POWER TERMINAL IDENTIFICATION
A/C SWITCH
See WIRING DIAGRAMS article. Test switch and circuits as necessary.
MASS AIRFLOW (MAF) SENSOR
For testing, see appropriate articles; BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES and WIRING DIAGRAMS .
CAMSHAFT POSITION (CMP) SENSOR
For testing information, see appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article.
CRANKSHAFT POSITION (CKP) SENSOR
For testing information, see appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article.
ENGINE COOLANT TEMPERATURE (ECT) SENSOR
Disconnect ECT sensor harness connector. Check resistance between ECT sensor terminals at temperatures specified. See ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE table.
| Application | Temperature °F (°C) | Ohms |
|---|---|---|
| Legacy | (1) | (1) |
| (1) See appropriate Diagnostic Trouble Code (DTC) in appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article. | ||
| (1) | See appropriate Diagnostic Trouble Code (DTC) in appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article. |
ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE
KNOCK SENSOR
For testing procedures, see appropriate DTC in appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article.
OXYGEN SENSOR (O2S)
For testing procedures, see appropriate DTC for rich or lean running, front or rear O2S. See appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES and WIRING DIAGRAMS articles.
P/N SWITCH
See appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES and WIRING DIAGRAMS articles. Test switch and circuits as necessary.
PRESSURE SENSOR
For testing, see appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES and WIRING DIAGRAMS articles.
THROTTLE POSITION (TP) SENSOR
For testing and adjustments, see ADJUSTMENTS and appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES articles.
VEHICLE SPEED SENSOR (VSS)
For testing, see appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES and WIRING DIAGRAMS articles.
Cooling Fan Relay
For testing procedures, see appropriate DTC in appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article.
Fuel Pump Relay
For testing procedures, see BASIC TESTING and WIRING DIAGRAMS articles.
Main Relay
For testing procedures, see BASIC TESTING and WIRING DIAGRAMS articles.
EGR Solenoid Valve
See EXHAUST GAS RECIRCULATION (EGR) under EMISSION SYSTEMS & SUB-SYSTEMS. See appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article for appropriate DTC.
Purge Control Solenoid Valve
See FUEL EVAPORATIVE SYSTEM (EVAP) under EMISSION SYSTEMS & SUB-SYSTEMS. See appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article for appropriate DTC.
FUEL DELIVERY
Note. For fuel system pressure testing, see BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article.
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. See INJECTOR RESISTANCE SPECIFICATIONS table. If resistance is not to specification, replace injector.
| Application | Ohms |
|---|---|
| Legacy | 5-20 |
INJECTOR RESISTANCE SPECIFICATIONS
BY-PASS AIR CONTROL VALVE
- Turn ignition off. Unplug by-pass air control valve harness connector. By-pass air control valve is located near throttle body. Check resistance between valve terminals No. 1 and No. 2. Resistance should be 9 ohms.
- Check resistance between control valve harness connector terminals No. 2 and No. 3. Resistance should be 9 ohms. If resistance is not as specified, replace by-pass air control valve. For more detailed test procedures, see appropriate «BASIC TESTING»(ref-26247) article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate «TESTS W/CODES»(ref-26249) article.
IDLE AIR CONTROL SOLENOID VALVE
For testing procedures, see appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article.
IGNITION SYSTEM
Note. For basic ignition checks (coil and wires), see appropriate BASIC TESTING article. For camshaft and crankshaft position sensor testing, see appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article.
Electronic Advance
For testing, see ADJUSTMENTS article.
For testing, see appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article. Also see WIRING DIAGRAMS article.
EGR Solenoid
Check continuity between solenoid terminals. If continuity does not exist, replace solenoid valve. Check solenoid valve winding for short to ground. Apply battery voltage to solenoid valve terminals. Verify passage opens and closes as voltage is applied and removed. Replace solenoid valve if winding is shorted, or if operation is not as specified.
EGR System
- Apply about 8 in. Hg vacuum to EGR valve with a hand-held vacuum pump. With engine warmed up, engine should stall or idle rough.
- If engine idle does not change, check EGR pipe and gas passages for clogging and leaks. Clean or replace if necessary. When cleaning, inspect exhaust gas inlet to intake manifold for presence of deposits. Inspect EGR inlet pipe for exhaust deposits.
EGR Valve
- Look through opening in EGR valve body. 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
- Disconnect vacuum hose from canister purge vent port. Blow air into canister purge vent port. Airflow will be blocked if valve is operating properly.
- Disconnect hoses from fuel tank port on canister. Blow air into port. Air should flow into canister. Blow into hose. Air should flow with a slight resistance.
EVAP Pressure Sensor
For testing see appropriate DTC in BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article.
Check self-diagnostic system for any DTCs. See appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article. 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.
2-Way Valve
Remove 2-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.
