Ground Circuits
- Turn ignition off. Using DVOM in ohmmeter mode, backprobe each ECU ground terminal. See ECU GROUND TERMINAL IDENTIFICATION table. Resistance should be zero ohms. If resistance is not close to zero ohms, repair open to ground.
- Start engine. With DVOM in voltmeter mode, 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.
| Application | Wire Color |
|---|---|
| 25 | Red/Yellow |
| 45 | Black/Red |
| 46 | Black/Red |
| 69 | Black |
| 70 | Black/White |
| 71 | Black/Yellow |
| 72 | Black/Yellow |
| 95 | Black/White |
| 96 | Black/White |
ECU GROUND TERMINAL IDENTIFICATION
Power Circuits (Ignition Off)
Turn ignition off. Check for battery voltage between ECU power terminals and ground. See ECU 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 ECU. See the WIRING DIAGRAMS article.
Power Circuits (Ignition On)
Turn ignition on. Check for battery voltage between ECU power terminals and ground. See ECU POWER TERMINAL IDENTIFICATION table. If battery voltage does not exist, check fuse. If fuse okay, check for an open in wire or defective ignition switch. See the WIRING DIAGRAMS article.
Power Circuits (Cranking)
- Using voltmeter, backprobe appropriate ECU terminal. See «ECU POWER TERMINAL IDENTIFICATION»(ref-26211-S01234612132001010500000) table. Hold ignition switch in START position. Battery voltage should exist between ECU 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 ECU terminal, or for defective ignition switch. See «WIRING DIAGRAMS»(ref-26155) article.
| Application | Wire Color | |
|---|---|---|
| Ignition Off | ||
| 42 | Red | |
| Ignition On | ||
| 15 | Yellow/Blue | |
| 16 | Yellow/Blue | |
| 79 | Yellow | |
| Cranking | ||
| 81 | Red/Yellow | |
ECU POWER TERMINAL IDENTIFICATION
A/C SWITCH
See WIRING DIAGRAMS article. Test switch and circuits as necessary.
MASS AIRFLOW SENSOR
For testing, see the TESTS W/CODES article and the WIRING DIAGRAMS article.
| Ign. Switch | Wire Colors | Readings |
|---|---|---|
| Key On | Red & Black/Red | 10-13 Volts |
| Key On | Black & Black/Red | 0-0.3 Volt |
| Key On | White & Black/Red | Zero Volts |
| Engine On | Red & Black/Red | 13-14 Volts |
| Engine On | Black & Black/Red | 0.8-1.2 Volts |
| Engine On | White & Black/Red | Zero Volts |
MAF SENSOR TEST SPECIFICATIONS
ENGINE COOLANT TEMPERATURE (ECT) SENSOR
Disconnect coolant temperature sensor connector. Measure resistance between sensor terminals at temperatures specified. See ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE table.
| Application | Temperature | Ohms |
|---|---|---|
| Legacy | 68°F (20°C) | 2000-3000 |
| Legacy | 176°F (80°C) | 300-400 |
ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE
CRANKSHAFT POSITION (CKP) SENSOR
For testing information, see TESTS W/CODES article.
OXYGEN SENSOR (O2S)
For testing procedures, see appropriate trouble codes for rich or lean running. See the TESTS W/CODES article and the WIRING DIAGRAMS article.
P/N SWITCH
See the TESTS W/CODES article and the WIRING DIAGRAMS article. Test switch and circuits as necessary.
THROTTLE POSITION SENSOR (OR SWITCH)
For testing and adjustments, see ON-VEHICLE ADJUSTMENTS and appropriate SELF-DIAGNOSTICS articles.
PRESSURE SENSOR
For testing, see the TESTS W/CODES article and the WIRING DIAGRAMS article.
VEHICLE SPEED SENSOR (VSS)
For testing, see the TESTS W/CODES article and the WIRING DIAGRAMS article.
Fuel Pump Relay
For testing procedures, see the BASIC TESTING and the WIRING DIAGRAMS articles.
Main Relay
For testing procedures, see the BASIC TESTING and the WIRING DIAGRAMS articles.
EGR Solenoid Valve
See EXHAUST GAS RECIRCULATION (EGR) under EMISSION SYSTEMS & SUB-SYSTEMS. See the TESTS W/CODES article for appropriate trouble codes.
Purge Control Solenoid Valve
See FUEL EVAPORATIVE SYSTEM (EVAP) under EMISSION SYSTEMS & SUB-SYSTEMS. See the TESTS W/CODES article for appropriate trouble codes.
FUEL DELIVERY
Note. For fuel system pressure testing, see the BASIC TESTING 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. Measure injector resistance. See INJECTOR RESISTANCE SPECIFICATIONS table. If resistance is not to specification, replace injector.
| Application | Ohms |
|---|---|
| Legacy | 5-20 |
INJECTOR RESISTANCE SPECIFICATIONS
IDLE AIR CONTROL SOLENOID VALVE
For testing, see the TESTS W/CODES article.
IGNITION SYSTEM
Note. For basic ignition checks (coil and wires), see the BASIC TESTING article. For camshaft and crankshaft position sensor testing, see the TESTS W/CODES article.
Electronic Advance
For testing, see ADJUSTMENTS article.
Knock Sensor
For testing, see the TESTS W/CODES article. Also see the WIRING DIAGRAMS article.
EGR Solenoid
Check continuity between terminals of solenoid. If continuity does not exist, replace solenoid valve. 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.
EGR System
- Apply about 8 in. Hg vacuum to EGR valve with hand vacuum pump. EGR valve is located between intake and exhaust manifolds. 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 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 (main purge vent on turbo). (Scheme 32) 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. On turbo models, remove secondary purge hose. Blow into hose. Air should flow with a slight resistance.
Scheme 32
2-Way Valve
Remove 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.
Check self-diagnostic system for any trouble codes. See the 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. (Scheme 33)
Scheme 33
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 valve from intake manifold. Place finger over valve. Vacuum should be present. Remove finger from PCV valve. Valve should snap back.