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.
VERIFICATION PROCEDURE
| CAUTION | This procedure requires the vehicle to be placed on rollers or raised and supported on sturdy jack stands to allow the free movement of both front and rear wheels. Ensure all safety precautions are exercised to ensure well being of technicians and equipment during this procedure. |
Subaru Select Monitor (SSM) Procedure
- Raise and suitably support vehicle, or place all wheels on rollers. Ensure vehicle is properly secured using 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 60)
- Connect SSM to data link connector (DLC) located under left side of dash. see scheme 1 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.
- 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.
- 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 60
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.