Engine Controls - Basic Testing: Other Subaru Legacy BD/BG/BK

Compression

Check engine mechanical condition using a compression gauge, vacuum gauge or engine analyzer. See engine analyzer manual for specific instructions.

Exhaust System Backpressure

1. The exhaust system can be checked with a vacuum or pressure gauge. Remove HO2S sensor or air injection check valve (if equipped).
2. Connect a 1-10 psi pressure gauge and operate engine at 2500 RPM. If exhaust system backpressure is greater than 1 3/4 - 2 psi, exhaust system or catalytic converter is plugged.
3. If a vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold it steady. If vacuum gauge reading slowly drops after stabilizing, check exhaust system for restriction.

FUEL PRESSURE

Basic diagnosis of fuel system should begin by determining fuel system pressure. If fuel pump is inoperative, see appropriate test under FUEL PUMP CIRCUIT TESTS .

Relieving Fuel Pressure

1. Disconnect fuel pump connector. Crank engine for at least 5 seconds. If engine starts, let it run until it stops. Disconnect fuel hose at pressure regulator and install fuel pressure gauge using "T" connector.
2. Start engine and check fuel pressure at idle. See the «REGULATED FUEL PRESSURE»(ref-26162-S13861822372001010500000) table. Verify fuel pressure increases as engine speed increases.

REGULATED FUEL PRESSURE

IGNITION CHECKS

Note. Also see appropriate test under IGNITION CONTROL SYSTEM TESTS.

SPARK

Check for spark at spark plug wires using a spark tester. Check resistance of each spark plug wire. Replace wire if resistance is not within specification. See HIGH TENSION WIRE RESISTANCE table.

HIGH TENSION WIRE RESISTANCE

IGNITION COIL RESISTANCE

1. Disconnect 3-wire connector from ignition coil assembly. Using an ohmmeter, check primary resistance between terminals No. 1 and 2 for one coil. (Scheme 29)
2. Check primary resistance between terminals No. 2 and 3 for remaining coil. Resistance should be as specified. See the «IGNITION COIL RESISTANCE»(ref-26162-S41923722602001010500000) table. If resistance is not as specified for each coil, replace ignition coil assembly.
3. To test secondary resistance, connect one ohmmeter lead to tower at one end of coil. Connect remaining ohmmeter lead to tower at opposite end of same coil.
4. Repeat test for other coils. If resistance of each coil is not as specified, replace ignition coil assembly.

Scheme 29

IGNITION COIL RESISTANCE - OHMS @ 68°F (20°C)

CRANKSHAFT POSITION SENSOR & TDC SENSOR SIGNALS

Note. For crankshaft position and TDC sensor signal testing, see the TESTS W/CODES article.

IDLE SPEED & IGNITION TIMING

Verify idle speed and ignition timing are set to specification. See IDLE SPEED SPECIFICATIONS and IGNITION TIMING tables. For adjustment procedures, see the ADJUSTMENTS article.

IDLE SPEED SPECIFICATIONS

IGNITION TIMING (Degrees BTDC @ RPM)

ECU POWER SUPPLY & GROUND TESTS

1. Check Main Relay - Turn ignition off and remove main relay. Connect battery voltage to main relay terminals No. 1 (Black Wire) and 2 (Light Green wire). Ensure there is less than 10 ohms resistance between main relay terminals No. 3 (Yellow wire) and 5 (Red wire), and between terminals No. 4 (Yellow/Red wire) and 6 (Red wire). If resistance is less than 10 ohms, go to next step. If resistance is more than 10 ohms, replace main relay.
2. Check ECU Power Supply Circuit - Install main relay. Disconnect connectors from ECU. Turn ignition on. Ensure there is at least 10 volts between ECU connector terminal No. 15 (Yellow/Blue wire) and ground, between terminal No. 16 (Yellow/Blue wire) and ground, and between terminal No. 42 (Red wire) and ground. If at least 10 volts are present, go to next step. If at least 10 volts are not present, repair harness or connectors as necessary.
3. Check ECU Ground Circuit - Turn ignition off. Ensure there is less than 10 ohms harness resistance between ECU connector terminals No. 25 (Red/Yellow wire) and ground, No. 45 (Brown wire) and ground, No. 46 (Brown wire) and ground, No. 69 (Black wire) and ground, No. 71 (Black/Yellow wire) and ground, No. 72 (Black/Yellow wire) and ground, No. 95 (Black/White wire) and ground, and No. 96 (Black/White wire) and ground. If resistance is less than 10 ohms, see «IGNITION CONTROL SYSTEM TESTS»(ref-26162-S34773067022001010500000) . If resistance is more than 5 ohms, repair harness or connectors as necessary.

IGNITION CONTROL SYSTEM TESTS

1. Check Ignition System For Proper Spark - Remove injector sub-harness and plug wire cap from each spark plug. Install a known good spark plug to plug wire and position spark plug so it is grounded to engine. Ensure each spark plug has a spark as engine is cranked. If a spark does not occur at each spark plug, connect injector sub-harness and plug wires and go to next step. If a spark does occur at each spark plug, see «FUEL PUMP CIRCUIT TESTS»(ref-26162-S12570681432001010500000).
2. Check Voltage At Ignition Coil Positive Terminal - Turn ignition on. Ensure there is at least 10 volts between ignition coil 3-pin connector terminal No. 2 (Yellow/Red wire) and ground. If voltage is as specified, go to next step. If voltage is not as specified, repair harness or connectors as necessary.
3. Check Ignition Coil - Remove ignition coil connector and remove ignition coil. Measure resistance of ignition coil primary and secondary windings. If resistance is as specified, go to next step. If resistance is not as specified, replace coil. On primary side, verify.7 ohm resistance between 3-pin connector terminal No. 2 (Yellow/Red wire) and plug wire coil tower No. 1 or 3 (closest to 3-pin connector). On Hitachi coil secondary side, verify 13,800 ohms resistance between plug wire coil towers No. 1 and 2, and No. 3 and 4. On Diamond coil secondary side, verify 21,000 ohms resistance between plug wire coil towers No. 1 and 2, and No. 3 and 4. (Scheme 29)
4. Check Ignitor Output Signal - Connect all connectors. Measure voltage between ignitor output connector terminal No. 1 (Yellow/Blue wire) and ground, and terminal No. 2 (Green/White wire) and ground while cranking engine. If at least.1 volt is present, go to next step. If at least.1 volt is not present, replace ignitor.
5. Check Harness Between ECU & Ignitor - Turn ignition off and disconnect ECU and ignitor connectors. Ensure there is zero ohms between ECU connector terminal No. 13 (Yellow/Violet wire) and ignitor terminal No. 2, ECU connector terminal No. 10 (Yellow/Blue wire) and ignitor terminal No. 1, ECU connector terminal No. 15 (Black wire) and ignitor terminal No. 3 (Black wire) and ground. Ensure there is no continuity between ignitor terminal No. 1 (Yellow/Blue wire) and ground, and between ignitor terminal No. 2 (Green/White wire) and ground. If resistance is as specified, inspect ECU connector and repair as necessary. If ECU connector is okay, replace ECU. If resistance is not as specified, repair harness or connectors as necessary.

FUEL PUMP CIRCUIT TESTS

1. Check Fuel Pump Operation In D-Check Mode - Connect test mode connector and turn ignition on. Ensure fuel pump operates for 2 sec. after ignition on. If fuel pump operates for 2 sec., check fuel injector circuit. See «FUEL INJECTOR CIRCUIT TESTS»(ref-26162-S09134505742001010500000). If fuel pump does not operate, go to next step.
2. Check Fuel Pump Relay - Disconnect fuel pump relay connector and remove fuel pump relay from bracket. Ensure there is 70 ohms of resistance between fuel pump relay terminals No. 1 and 3. (Scheme 30) Replace fuel pump re lay if resistance is not as specified. If resistance is okay, connect positive battery lead to terminal No. 1 and negative lead to terminal No. 3. If fuel pump relay does not click, replace it. If fuel pump relay clicks, verify zero ohms resistance between terminals No. 2 and 4. If resistance is as specified, go to next step. If resistance is not as specified, replace fuel pump relay.
3. Check Voltage Between Fuel Pump Relay & Ground - Turn ignition off. Remove fuel pump relay without disconnecting connector. Ensure there is at least 10 volts between fuel pump relay connector terminal No. 1 (Yellow wire) and ground. If at least 10 volts are present, go to next step. If at least 10 volts are not present, repair harness or connector.
4. Check Voltage Between ECU & Ground - Turn ignition on. Ensure there is at least 10 volts when ignition is on and zero volts while cranking engine. Measure voltage between ECU 26-pin connector terminal No. 23 (Light Green/Blue wire) and ground. If voltage is as specified, go to next step. If voltage is not as specified, repair faulty connector or ground circuit. If connector and ground are okay, replace ECU.
5. Check Fuel Pump Terminal Voltage - Remove fuel pump access cover located in trunk area and remove fuel pump connector. Ensure there is at least 10 volts between 5-pin fuel pump connector terminal No. 1 (Brown wire) and ground. If at least 10 volts are present, go to next step. If at least 10 volts are not present, repair harness or connectors between fuel pump and fuel pump relay as necessary.
6. Check Fuel Pump Operation - Disconnect fuel pump connector. Connect positive battery lead to terminal No. 1 and negative lead to terminal No. 3. If fuel pump operates, repair fuel pump grounding circuit. If fuel pump does not operate, replace fuel pump.

Scheme 30

FUEL INJECTOR CIRCUIT TESTS

1. Check Fuel Injector Operation - Using a stethoscope, ensure there are injector operating sounds while engine is cranking. If operating sounds are not heard, go to next step. If operating sounds are heard, verify fuel pressure. See «FUEL PRESSURE»(ref-26162-S26350607912001010500000) under FUEL SYSTEM.
2. Check Fuel Injector Power Circuit - Turn ignition off and disconnect each fuel injector connector. Ensure there is at least 10 volts between each injector terminal No. 2 (Yellow wire) and ground. If at least 10 volts are present, go to next step. If at least 10 volts are not present, repair harness or connectors as necessary.
3. Check Fuel Injector Resistance - Disconnect each injector connector. Ensure there is 11-12 ohms resistance between injector terminals No. 1 and 2. If specified resistance is present, go to next step. If specified resistance is not present, replace fuel injector(s).
4. Check Voltage At Each ECU Terminal - Ensure there are at least 10 volts between ground and ECU 26-pin connector terminals No. 11 (Blue/White wire), No. 12 (Light Green wire), No. 13 (Brown wire), and No. 26 (Blue wire). If at least 10 volts are present, go to next step. If at least 10 volts are not present, repair harness or connectors as necessary.
5. Check Harness Connector Between ECU & Ground - Turn ignition off. Disconnect ECU 26-pin connector. Ensure there is zero ohms resistance between connector terminal No. 24 (Black/Yellow wire) and ground, and between terminal No. 25 (Black/Yellow wire) and ground. If specified resistance is not present, repair harness or connectors as necessary. If specified resistance is present, inspect and repair ECU connector. If ECU connector is okay, replace ECU.

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to the TESTS W/CODES article. If no hard codes are found in self-diagnostics, go to the TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.