HARD FAILURES
Hard failures cause Malfunction Indicator Light (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 the TESTS W/O CODES article.
SUMMARY
If no hard fault codes (or only pass codes) are present, driveability symptoms exist or intermittent codes exist, proceed to the TESTS W/O CODES article for diagnosis by symptom (ie, ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.
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Note. Before starting any testing, connect Subaru Select Monitor (SSM) or OBD-II general scan tool see scheme 2, and read data. For operational details of OBD-II scan tester, refer to manufacturers instruction manual.
| CAUTION | After repair or replacement of faulty parts, clear memory and reset codes. |
Condition
Following conditions continue with engine speed at idle
- Uneven idle
- Engine stalls
- Poor driveability
"a" - Only One Cylinder
Check following items for that cylinder
- Spark plug
- Spark plug wire
- Fuel injector
- Compression
"b" - Group Of Cylinders No. 1 And 2
Check following items for cylinders No. 1 and 2
- Spark plugs
- Fuel injectors
- Igniters, coils, etc.
"c" - Group Of Cylinders No. 3 And 4
Check following items for cylinders No. 3 and 4
- Spark plugs
- Fuel injectors
- Igniters, coils, etc.
"d" - Group Of Cylinders No. 1 And 3
Check following items for cylinders No. 1 and 3
- Spark plugs
- Fuel injectors
- Skipped timing belt teeth
"e" - Group Of Cylinders No. 2 And 4
Check following items for cylinders No. 2 and 4
- Spark plugs
- Fuel injectors
- Skipped timing belt teeth
"f" - Cylinder At Random
If engine idle is not rough, go to DTC P0170 . If engine idle is rough on A/T vehicles, note the differential between maximum EGR system pressure (function mode F37) and minimum EGR pressure (function mode F38) observed in step 2). If differential is less than 0.39 in. Hg, replace EGR valve. If differential is more than 0.39 in. Hg, go to DTC P0170 and retest.
"a"
Conduct CLEAR MEMORY and INSPECTION MODES.
"b"
Connect SSM to data link connector.
Start and warm engine until radiator fan completes one cycle (all accessories OFF).
Turn SSM to ON and select function mode FA4.
Drive vehicle at 52-58 MPH (83-93 km/h) until LED No. 5 is turned ON.
Note. Keep throttle valve opening steady. Diagnosis will be interrupted if opening varies. Diagnosis starts in 190 seconds after starting engine and requires 4 seconds to run. Transmission should be in "D" range for diagnosis.
"f"
On SSM, select function code FB0. Confirm "No Trouble" indication on SSM.