Engine Controls - Self-Diagnostics - 2.5L: Other Subaru Forester SG

TWO-TRIP DETECTION LOGIC

Note. When road testing vehicle in OBD mode (Subaru Select Monitor tester only), Two-Trip Detection Logic will not function. Also, MIL will illuminate first time a malfunction is detected.

When a malfunction initially occurs, Diagnostic Trouble Code (DTC) will be temporarily stored in ECM memory, but MIL on instrument panel will not illuminate. The second time malfunction is detected, MIL on instrument panel will illuminate, provided ignition is turned off and then back on after first malfunction was detected. This is referred to as "Two-Trip Detection Logic" and only applies to specific DTCs.

FREEZE-FRAME DATA

OBD-II or Subaru Select Monitor tester can by used to check freeze-frame data. ECM records engine operating condition when a misfire, fuel trim (mixture) malfunction or other malfunction (fuel system, calculated load, coolant temperature, fuel trim (mixture), engine speed, vehicle speed, etc.) exists. If more than one fault is detected, only data from the first malfunction is recorded. Recorded data is useful for determining conditions during which the malfunction occurred.

Hard Failures

Hard failures cause MIL to illuminate and remain on until problem is repaired. If MIL comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using Diagnostic Trouble Code (DTC) charts. If a sensor fails, control unit will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, vehicle runs but driveability will not be optimum.

Intermittent Failures

Intermittent failures may cause MIL to flicker or illuminate then go out after intermittent fault goes away. However, a corresponding DTC will be retained in ECM memory. If related fault does not reoccur within a certain time frame, related DTC will be erased from ECM memory. Intermittent failures may be caused by sensor, connector or wiring related problems. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.

Scheme 49

Scheme 50

Scheme 51

Scheme 52

1. Turn ignition on. Using a DVOM connected to ground, backprobe ECM harness connector B137 terminal No. 28. (Scheme 49) If voltage is less than one volt, go to step 3. If voltage is not less than one volt, wiggle and tug ECM harness and connector. If MIL illuminates, repair poor contact in ECM harness connector. If MIL does not illuminate while wiggling harness and connector, go to next step.
2. Check ECM harness connectors for correct connection. If connectors are not properly connected, repair ECM connector as necessary. If connectors are properly connected, check for proper contact. If contact at connector is good, replace ECM.
3. Turn ignition off and remove instrument cluster. Disconnect ECM harness connector B137 and instrument cluster 14-pin harness connector. Using a DVOM, measure resistance between ECM harness connector B137 terminal No. 28 and instrument cluster 14-pin harness connector terminal No. 1 on Forester, terminal No. 6 on Impreza and Outback Sport. (Scheme 51) If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, repair open circuit in harness or poor contact in harness connectors between ECM and instrument cluster.
4. Check contact of instrument panel harness connector. Repair harness connector contact if necessary and go to next step.
5. Reconnect ECM harness connector. Turn ignition on. Disconnect instrument panel 10-pin harness connector. Using a DVOM connected to ground, measure voltage at instrument panel 10-pin harness connector terminal No. 9 on Forester, terminal No. 7 on Impreza and Outback Sport. (Scheme 52) If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, check condition of fuse No. 5 (No. 13 on Impreza and Outback Sport), check for open or short in power supply circuit between battery and instrument panel harness connector, and check for poor contact in all harness connectors between battery, ignition switch and instrument panel. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as required and retest system.
6. Remove MIL bulb from instrument panel. Replace bulb if faulty. Repair instrument cluster connector if bulb is not faulty and retest system.

Legacy & Outback

1. Turn ignition on. Using a DVOM connected to ground, backprobe ECM harness connector B134 terminal No. 28. If voltage is less than one volt, go to step 3. If voltage is not less than one volt, wiggle and tug ECM harness and connector. If MIL illuminates, repair poor contact in ECM harness connector. If MIL does not illuminate while wiggling harness and connector, go to next step.
2. Check ECM harness connectors for correct connection. If harness connectors are not properly connected, repair ECM connector as necessary. If harness connectors are properly connected, check for proper contact. If contact at harness connector is good, replace ECM.
3. Turn ignition off and remove instrument cluster. Disconnect ECM harness connector B134 and instrument cluster 14-pin harness connector. (Scheme 49), (Scheme 50) and (Scheme 51). Using a DVOM measure resistance between ECM harness connector B134 terminal No. 28 and instrument cluster 14-pin harness connector terminal No. 12. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, repair open circuit in harness or poor contact in harness connectors between ECM and instrument cluster.
4. Check contact of instrument panel harness connector. Repair connector contact if necessary and go to next step.
5. Turn ignition on. Using a DVOM, measure voltage between instrument panel 14-pin harness connector terminal No. 3 and ground. If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, check condition of fuse No. 5, check for open or short in power supply circuit between battery and instrument panel harness connector and check for poor contact in all harness connectors between battery, ignition switch and instrument panel. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary.
6. Remove MIL bulb from instrument panel. Replace bulb if faulty. Repair instrument cluster connector if bulb is not faulty and retest system.

VERIFICATION PROCEDURE

Subaru Select Monitor (SSM) Procedure

1. Raise and suitably support vehicle, or place all wheels on rollers. Ensure vehicle is properly secured using the front and rear towing/tie-down hooks. Prepare Subaru Select Monitor by inserting appropriate diagnostic cartridge and connecting diagnostic cable. Turn ignition off. Connect test mode connector leads together under left side of instrument panel. (Scheme 53)and (Scheme 54).
2. Connect SSM to data link connector (DLC) located under left side of dash. see scheme 6 Turn ignition switch and SSM on. On main menu display screen, select 2. EACH SYSTEM CHECK and press YES key. On system selection menu display screen, select ENGINE CONTROL SYSTEM and press YES key.
3. After engine type information is displayed, press YES key. On engine diagnosis display screen, select DEALER CHECK MODE PROCEDURE and press YES key. When PERFORM INSPECTION (DEALER CHECK) MODE? is shown on display screen, press YES key. Follow all instructions on display screen.
4. If problems are still present, DTCs will be displayed. Record codes as required. After codes have been displayed, release parking brake. This verification procedure may cause ABS warning light to illuminate due to speed variations between front and rear wheels. Clear ABS memory. See appropriate ANTI-LOCK article in BRAKES.

Scheme 53

Scheme 54

ISC INITIALIZATION

The idle speed control (ISC) motor must be initialized whenever ECM memory is cleared. To initialize ISC, turn ignition switch on. Wait 3 seconds before starting engine.

SUMMARY

If no hard fault codes are present, driveability symptoms exist or intermittent codes exist, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

CODE DEFINITION

1. DTC P0301: Cylinders No. 1 Misfire Detected
2. DTC P0302: Cylinders No. 2 Misfire Detected
3. DTC P0303: Cylinders No. 3 Misfire Detected
4. DTC P0304: Cylinders No. 4 Misfire Detected

Scheme 55

Scheme 56

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If no other DTCs exist, go to next step. If any DTCs other than P0301, P0302, P0303 or P0304 exist, diagnose and repair those DTCs first. Do not diagnose DTCs P0301, P0302, P0303 or P0304.
2. Turn ignition on. Using DVOM connected to ground, measure voltage at ECM 35-pin connector terminals No. 8, 22, 23 and 34. see scheme 10 If voltage is more than 10 volts at all test points, go to step 7. If voltage is not more than 10 volts at all test points, go to next step.
3. Turn ignition off. Disconnect fuel injector electrical connector at suspect cylinder. With an ohmmeter connected to ground, measure resistance at terminal No. 1 of suspect fuel injector wiring harness. (Scheme 55) If resistance is less than 10 ohms, locate and repair short to ground in wiring between injector and ECM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If resistance is not less than 10 ohms, go to next step.
4. Measure resistance between ECM 35-pin connector terminals No. 34 (injector No. 1), No. 23 (injector No. 2), No. 22 (injector No. 3) and No. 8 (injector No. 4) and corresponding fuel injector(s) connector terminal No. 1. If resistance is less than one ohm at each test point, go to next step. If resistance is not less than one ohm at each test point, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and fuel injector(s).
5. Turn ignition off. Disconnect electrical connector from suspect fuel injector(s). Using an ohmmeter, measure resistance between terminals of fuel injector(s). If resistance is between 5 and 20 ohms, go to next step. If resistance is not between 5 and 20 ohms, replace faulty injector(s).
6. Turn ignition on. With DVOM connected to ground, measure voltage at terminal No. 2 of suspect fuel injector(s) harness connector. If voltage is more than 10 volts, repair poor terminal contact in connectors of suspect fuel injector(s) circuit. If voltage is not more than 10 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between main relay and fuel injectors.
7. Turn ignition off. Disconnect electrical harness connector from suspect fuel injector(s). Turn ignition on. With DVOM connected to ground, backprobe ECM 35-pin connector terminals No. 34 (injector No. 1), No. 23 (injector No. 2), No. 22 (injector No. 3) and No. 8 (injector No. 4). If voltage is more than 10 volts at any test point, locate and repair short to voltage in wiring between ECM and fuel injector. After repair, replace ECM. If voltage is not more than 10 volts at any test point, go to next step.
8. Turn ignition off. Disconnect electrical connector from suspect fuel injector(s). Using an ohmmeter, measure fuel injector resistance. If resistance is less than one ohm, replace faulty injector(s). If resistance is not less than one ohm, go to next step.
9. Check camshaft position and crankshaft position sensors for proper installation of mounting bolts. Tighten bolts as required. If mounting bolts are properly installed and tightened, go to next step.
10. Remove timing belt cover and check crankshaft sprocket for rust, broken teeth or other damage. Replace crankshaft sprocket as needed. If crankshaft sprocket is okay, go to next step.
11. With timing belt cover removed, use Crankshaft Socket (ST499987500) to turn crankshaft. Align crankshaft sprocket timing mark with cylinder block timing mark. In this position, ensure right-side camshaft sprocket timing mark, cam cap and right-side cylinder head matching surface and/or left-side camshaft sprocket timing mark and left-side timing belt cover notch are aligned. (Scheme 56) Repair/replace timing belt and adjust as necessary. Go to next step.
12. Ensure fuel level is above the lowest limit. Add fuel as necessary. If fuel level is okay, go to next step.
13. Using scan tool, clear ECM memory. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000). Start engine and drive vehicle for more than 10 minutes. If the MIL comes on or is blinking, go to step 15. If MIL does not come on or blink, go to next step.
14. Was cause of misfire diagnosed while engine was running? If misfire fault was corrected while engine was running, finish diagnostics and go to step 26. If cause of misfire was not corrected while engine was running, check for poor terminal contact in connectors at ignitor, ignition coil, fuel injector and ECM. Ensure all connectors in harness are properly connected. Repair as necessary and go to next step.
15. Inspect air intake system for air leaks, holes or air suction caused by loose or missing nuts or bolts. Check for cracks or loose connections of any hoses in system and repair as necessary. If no leaks are found, go to next step.
16. Turn ignition on. Using scan tool, retrieve DTCs. If only one DTC (P0301, P0302, P0303 or P0304) is present, go to step 21. If more than one DTC is present, go to next step.
17. If DTCs P0301 and P0302 are present, go to step 22. If DTCs P0301 and P0302 are not present, go to next step.
18. If DTCs P0303 and P0304 are present, go to step 23. If DTCs P0303 and P0304 are not present, go to next step.
19. If DTCs P0301 and P0303 are present, go to step 24. If DTCs P0301 and P0303 are not present, go to next step.
20. If DTCs P0302 and P0304 are present, go to step 25. If DTCs P0302 and P0304 are not present, go to step 26.
21. If only one DTC was displayed, check spark plug, spark plug wire, ignition coil, fuel injector and compression ratio for that cylinder. Repair as required. If no faults are located, go to «DTC P0172»(ref-157722-S27516950022003082200000).
22. If DTCs P0301 and P0302 are present, check spark plug, spark plug wire, ignition coil, fuel injector and compression ratio for cylinders No. 1 (P0301) and No. 2 (P0302). Repair as required. If no faults are located, check ignition control system. See «IGNITION SYSTEM»(ref-157568-S27004678412003081800000) in SYSTEM & COMPONENT TESTING article. If no faults are found with ignition control system and cylinders No. 1 and No. 2, go to «DTC P0172»(ref-157722-S27516950022003082200000).
23. If DTCs P0303 and P0304 are present, check spark plug, spark plug wire, ignition coil, fuel injector and compression ratio for cylinders No. 3 (P0303) and No. 4 (P0304). Repair as necessary. If no faults are located, check ignition control system. See «IGNITION SYSTEM»(ref-157568-S27004678412003081800000) in SYSTEM & COMPONENT TESTING article. If no faults are found with ignition control system and cylinders No. 3 and No. 4, go to «DTC P0172»(ref-157722-S27516950022003082200000).
24. If DTCs P0301 and P0303 are present, check spark plug, spark plug wire, ignition coil, fuel injector, timing belt and compression ratio for cylinders No. 1 (P0301) and No. 3 (P0303). Repair as necessary. If no faults are located, go to «DTC P0172»(ref-157722-S27516950022003082200000).
25. If DTCs P0302 and P0304 are present, check spark plug, spark plug wire, ignition coil, fuel injector, timing belt and compression ratio for cylinders No. 2 (P0302) and No. 4 (P0304). Repair as necessary. If no faults are located, go to «DTC P0172»(ref-157722-S27516950022003082200000).
26. If engine idle is rough, go to «DTC P0172»(ref-157722-S27516950022003082200000). If engine idle is not rough, check spark plugs, fuel injectors and compression ratio. Repair as necessary. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. DTC P1510: Idle Air Control (IAC) Solenoid Valve Signal No. 1 Circuit Low Input
2. DTC P1512: Idle Air Control (IAC) Solenoid Valve Signal No. 2 Circuit Low Input
3. DTC P1514: Idle Air Control (IAC) Solenoid Valve Signal No. 3 Circuit Low Input
4. DTC P1516: Idle Air Control (IAC) Solenoid Valve Signal No. 4 Circuit Low Input

1. DTC P1511: Idle Air Control (IAC) Solenoid Valve Signal No. 1 Circuit High Input
2. DTC P1513: Idle Air Control (IAC) Solenoid Valve Signal No. 2 Circuit High Input
3. DTC P1515: Idle Air Control (IAC) Solenoid Valve Signal No. 3 Circuit High Input
4. DTC P1517: Idle Air Control (IAC) Solenoid Valve Signal No. 4 Circuit High Input