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

ON-BOARD DIAGNOSTICS

Engine Control Module (ECM) monitors engine operation and contains a self-diagnostic system which stores Diagnostic Trouble Codes (DTCs) and complies with On-Board Diagnostics Generation II (OBD-II) standards.

Self-diagnostic system is used to provide vehicle with an on-board diagnostic system which is capable of continuously monitoring efficiency of emission control system, and improving diagnosis and repair when system failures occur.

Federal Test Procedure (FTP) sets maximum allowable emission standards. Malfunction Indicator Light (MIL) must illuminate if a system or component either fails or deteriorates to a point where the vehicle emissions could increase to more than 1 1/2 times FTP standards.

If malfunction does not recur in 3 ignition cycles, MIL goes off, but DTCs remain recorded in ECM memory. DTCs may only be retrieved using an On-Board Diagnostic-II (OBD-II) scan tool that complies with SAE standard J-1978 or Subaru Select Monitor connected to Data Link Connector (DLC). Scan tool also provides freeze-frame data and can be used to clear codes.

MALFUNCTION INDICATOR LIGHT (MIL) INSPECTION

Note. The MIL, also referred to as Check Engine light, is a warning light on the instrument cluster.

DIAGNOSTIC PROCEDURE

Diagnosis of computerized engine control system should be performed in the following order

1. Ensure all engine systems not related to computer system are operating properly. DO NOT proceed with testing unless all other problems have been repaired. Basic diagnostic procedure must be performed before using specific DTC testing procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) .
2. If DTCs were displayed, determine whether codes are hard or intermittent. Hard codes will cause MIL to illuminate continuously while engine is running. See «HARD FAILURES»(ref-157722-S41544166792003082200000) and «INTERMITTENT FAILURES»(ref-157722-S16341832812003082200000) . For diagnosing hard codes, proceed to appropriate DTC test. See «DIAGNOSTIC TESTS»(ref-157722-S07760409382003082200000) . For diagnosing intermittent codes, see «TROUBLE SHOOTING - NO CODES»(ref-157458) article.
3. If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in «TROUBLE SHOOTING - NO CODES»(ref-157458) article. Doing so will help identify proper system or component to check in «SYSTEM & COMPONENT TESTING»(ref-157568) article.
4. After necessary repairs are made, clear DTCs, and perform verification of repair to ensure DTC does not reset.

BASIC DIAGNOSTIC PROCEDURE

Note. Subaru Select Monitor (SSM) or OBD-II generic scan tool must be used to perform basic diagnostic procedure. Follow scan tool manufacturer's instructions for proper operation. Communication with vehicle's on-board computer is through the OBD-II Data Link Connector (DLC). (Scheme 27)or (Scheme 28).

After performing procedures in PRELIMINARY INSPECTION & ADJUSTMENTS, BASIC FUEL SYSTEM CHECKS and BASIC IGNITION SYSTEM CHECKS in BASIC DIAGNOSTIC PROCEDURES article, this is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in the basic diagnostic procedure, if no codes are indicated and driveability problems still exist, see MALFUNCTION INDICATOR LIGHT DIAGNOSIS in TROUBLE SHOOTING - NO CODES article. Scan tool functions consist of

1. MODE $01 Current powertrain diagnostic data.
2. MODE $02 Powertrain freeze frame data.
3. MODE $03 Emission-related powertrain DTCs.
4. MODE $04 Clear/reset emission-related diagnostic information.

Scheme 27

Scheme 28

Note. Check for applicable Technical Service Bulletins (TSBs) before proceeding. DO NOT perform the following procedure if driveability conditions are not present. DO NOT turn ignition off during the following procedure or clear DTCs unless instructed to do so.

1. Verify customer complaint and conditions under which fault appears. Attempt to start engine. If engine starts, go to next step. If engine does not start, proceed to «TROUBLE SHOOTING - NO CODES»(ref-157458) article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).
2. Check to see if MIL (CHECK ENGINE) light on instrument cluster illuminates, indicating a system fault. If MIL (CHECK ENGINE) light illuminates, go to next step. If MIL (CHECK ENGINE) light does not illuminate, go to MALFUNCTION INDICATOR LIGHT DIAGNOSIS in «TROUBLE SHOOTING - NO CODES»(ref-157458) article.
3. Turn ignition off. Prepare Subaru Select Monitor (SSM) by inserting appropriate diagnostic cartridge and connecting diagnostic cable. Connect SSM or OBD-II generic scan tool to data link connector (DLC). Turn ignition and scan tool on. Retrieve diagnostic trouble codes (DTCs). If any DTCs are stored, save freeze frame data using scan tool MODE $02, then go to next step. If no DTCs are stored, although MIL (CHECK ENGINE) light is illuminated, go to MALFUNCTION INDICATOR LIGHT DIAGNOSIS in «TROUBLE SHOOTING - NO CODES»(ref-157458) article.
4. Perform required repair by using procedure associated with DTC retrieved. See «SUBARU DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION CHART»(ref-157722-S34010126652003082200000) . If an automatic transaxle DTC is set with other codes, perform basic A/T checks and repair other DTCs first. Basic A/T checks consist of transaxle fluid level, differential fluid level, transaxle fluid leak, differential fluid leak, stall test, line pressure test, transfer clutch pressure test, time lag test, road test and shift characteristics only. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.
5. After repair, perform clear memory function. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) . After clearing DTCs, verify effectiveness of repair. See «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) . If repair addresses all issues and no DTCs exist, turn ignition off. Turn scan tool off. Disconnect test mode connector under driver's side of instrument panel. Disconnect scan tool from DLC.

CLEARING DIAGNOSTIC TROUBLE CODES

Clear DTC(s) using scan tool (MODE $04). Refer to scan tool manufacturer's instruction. After clearing memory, initialize idle speed control (ISC) motor. See ISC INITIALIZATION under PROGRAMMING.

OBD-II Generic Scan Tool Procedure

1. Turn ignition off. Connect test mode connector leads together under left side of instrument panel. see scheme 8and see scheme 7. Connect scan tool to DLC. On A/T vehicles, ensure selector lever is in "P" position. On M/T vehicles, depress clutch pedal. On all vehicles, start engine.
2. Using selector (A/T) or shift (M/T) lever, turn "P" and "N" position switches on. Depress brake pedal on A/T vehicles to turn brake switch on. On all vehicles, maintain engine speed at 2500-3000 RPM for 40 seconds. On vehicles not equipped with a tachometer, use a secondary pick-up type tachometer to monitor engine speed.
3. Place transaxle in "D" position (A/T) or first gear (M/T) and drive vehicle at 3-6 MPH. On all-wheel drive vehicles, release parking brake. On all vehicles, DTCs will be displayed if problems are still present. Record codes as required. 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.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

SUBARU DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION CHART

DIAGNOSTIC TESTS

Note. Subaru Select Monitor (SSM) or OBD-II generic scan tool must be used to perform diagnostic tests. Values and procedures given in tests are based on the use of SSM scan tool. Follow scan tool manufacturer's instructions. After repair or replacement of faulty parts, clear memory and perform verification of repair. For ECM terminal identification, see PIN VOLTAGE CHARTS article. If backprobing ECM connector is required, use ECM terminal identification illustration or reverse image of (Scheme 29). For circuit identification and wire colors, see ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

Scheme 29

1. Start engine and bring to operating temperature. Turn ignition switch to off position. Disconnect ECM and front oxygen sensor harness connectors. Measure resistance between ECM harness connector B136, terminal No. 6 and front oxygen sensor harness connector B18, terminal No. 3. (Scheme 29)and (Scheme 30). Also measure resistance between ECM harness connector B136, terminal No. 17 and front oxygen sensor harness connector B18, terminal No. 3. If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open in appropriate wire and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Ensure ignition switch is in off position. Measure resistance between ECM harness connector B136, terminal No. 22 and front oxygen sensor harness connector B18, terminal No. 2. (Scheme 29)and (Scheme 30). Also measure resistance between ECM harness connector B136, terminal No. 13 and front oxygen sensor harness connector B18, terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open in appropriate wire and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
3. Ensure ignition switch is in the off position. Measure resistance between front oxygen harness connector B18, terminal No. 4 and main relay harness connector B47, terminal No. 4. If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open in wire between front oxygen sensor harness connector and main relay harness connector. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
4. Ensure ignition switch is in the off position. Measure resistance between front oxygen sensor harness connector B18 terminals No. 3 and No. 4. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, replace front oxygen sensor and test system operation.
5. Check the ECM and front oxygen sensor harness connectors for poor contact. If poor contact is found, repair as necessary and test system operation. If poor contact is not found, replace front oxygen sensor and test system operation.

1. Start engine and bring to operating temperature. Turn ignition switch to off position. Disconnect ECM and front oxygen sensor harness connectors. Measure resistance between ECM harness connector B136, terminal No. 6 and front oxygen sensor harness connector B262, terminal No. 3. (Scheme 29)and (Scheme 30). Also measure resistance between ECM harness connector B136, terminal No. 17 and front oxygen sensor harness connector B262, terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open in appropriate wire and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Ensure ignition switch is in off position. Measure resistance between ECM harness connector B136, terminal No. 22 and front oxygen sensor harness connector B262, terminal No. 2. Also measure resistance between ECM harness connector B136, terminal No. 13 and front oxygen sensor harness connector B262, terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open in appropriate wire and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
3. Ensure ignition switch is in the off position. Measure resistance between front oxygen harness connector B262, terminal No. 4 and main relay harness connector B47, terminal No. 4. If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open in wire between front oxygen sensor harness connector and main relay harness connector. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
4. Ensure ignition switch is in the off position. Measure resistance between front oxygen sensor harness connector B262 terminals No. 1 and No. 2, and No. 3 and No. 4. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, replace front oxygen sensor and test system operation.
5. Check the ECM and front oxygen sensor harness connectors for poor contact. If poor contact is found, repair as necessary and test system operation. If poor contact is not found, replace front oxygen sensor and test system operation.

Scheme 30

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). On Forester and Impreza, if DTCs P0031 and P0037 exist at the same time, go to next step. On Forester and Impreza, if DTCs P0031 and P0037 are not present at the same time, go to step 4. On Baja, Legacy and Outback, if DTCs P0141 and P1132 exist at the same time go to next step. On Baja, Legacy and Outback, if DTCs P0141 and P1132 are not present at the same time, go to step 4.
2. Turn ignition off. Disconnect front HO2S connector. Turn ignition on. Using DVOM connected to ground, measure voltage at front HO2S connector terminal No. 2. (Scheme 30) If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, locate and repair open circuit in wiring and check for proper terminal contact in connectors between front HO2S and main relay. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
3. Turn ignition off. Using an ohmmeter connected to ground, backprobe ECM connector B136 (26-pin connector) terminals No. 5 and No. 16. (Scheme 29) If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring and check for proper terminal contact in connectors between ECM and chassis ground point.
4. Start engine. Using scan tool, observe front HO2S heater current value. If current draw is more than 0.2 amp, check for poor contact at ECM and HO2S connectors. If current draw is not more than 0.2 amp, go to next step.
5. With engine idling, measure voltage between ground and ECM connector B136 (26-pin connector) terminals No. 6 and No. 17. (Scheme 29) If voltage is less than one volt, go to step 7. If voltage is not less than one volt, go to next step.
6. Measure voltage between ground and ECM connector B136 (26-pin connector) terminals No. 6 and No. 17 while wiggling harness and ECM connector. If voltage changes less than one volt while wiggling harness and connector, check for poor terminal contact at ECM connector. If voltage does not change less than one volt while wiggling harness and connector, go to next step.
7. Turn ignition off. Measure resistance between front HO2S connector terminals No. 3 and No. 4. (Scheme 30) If resistance is less than 10 ohms, locate and repair open or short to ground in wiring and check for proper terminal contact in connectors between ECM and front HO2S. If resistance is not less than 10 ohms, replace front HO2S. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition on. Using a DVOM connected to ground, backprobe ECM connector B136 (26-pin connector) terminals No. 6 and No. 17. (Scheme 29) If voltage is more than 8 volts, go to step 3. If voltage is not more than 8 volts, go to next step.
2. Start engine. Using scan tool, observe front HO2S heater current value. If value is more than 2.3 amp, replace ECM. If value is not more than 2.3 amp, system has returned to normal. Check for poor terminal contact in connectors.
3. Measure voltage between ground and ECM connector B136 (26-pin connector) terminals No. 6 and No. 17 while wiggling harness and ECM connector. (Scheme 29) If voltage changes to more than 8 volts while wiggling harness and connector, locate and repair short to voltage in wiring between ECM and front HO2S. If voltage does not change to more than 8 volts while wiggling harness and connector, system has returned to normal. Check for poor terminal contact in connectors. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Disconnect ECM connector B136 (26-pin connector). Using an ohmmeter connected to ground, measure resistance at ECM connector B136 (26-pin connector) terminals No. 5 and No. 16. (Scheme 29) If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, repair open in appropriate wire between ECM and engine ground terminal. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Start engine. Using scan tool, observe rear HO2S heater current value. If current draw is not more than 0.2 amp, go to next step. If current draw is more than 0.2 amp, check for poor terminal contact in connectors between ECM and rear oxygen sensor.
3. Start and idle engine. Using a DVOM connected to ground, measure voltage at ECM connector B136 (26-pin connector), terminal No. 4. (Scheme 29) If voltage is less than one volt, go to step 6. If voltage is not less than one volt, go to next step.
4. Measure voltage between ECM connector B136 (26-pin connector), terminal No. 4 and ground while wiggling harness and ECM connector. If voltage changes to less than one volt while wiggling harness and connector, repair poor terminal contact in connectors. If voltage does not change to less than one volt while wiggling harness and connector, go to next step.
5. Turn ignition off. Disconnect electrical connector from rear oxygen sensor. Turn ignition on. Using a DVOM connected to ground, measure voltage at ECM connector B136 (26-pin connector), terminal No. 4. (Scheme 29) If voltage is less than one volt, replace ECM. If voltage is not less than one volt, locate and repair short circuit in wiring between ECM and rear oxygen sensor. After repair, replace ECM.
6. With electrical connector disconnected from rear oxygen sensor, measure voltage between rear HO2S connector terminal No. 2 and ground. (Scheme 30) If voltage is more than 10 volts, go to next step. 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 rear oxygen sensor.
7. Turn ignition off. Measure resistance across rear oxygen sensor connector terminals No. 1 and No. 2. If resistance is less than 30 ohms, locate and repair open circuit in wiring between ECM and rear oxygen sensor and check for poor terminal contact in connectors. If resistance is not less than 30 ohms, replace rear oxygen sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Using a DVOM connected to ground, backprobe ECM connector B136 (26-pin connector), terminal No. 4. (Scheme 29) If voltage is more than 8 volts, go to next step. If voltage is not more than 8 volts, go to step 2.
2. Turn ignition on. Using scan tool, observe rear HO2S heater current value. If current draw is more than 7 amps, replace ECM. If current draw is not more than 7 amps, system has returned to normal. Check for poor terminal contact in connectors.
3. Check for poor terminal contact in connectors between ECM and rear HO2S. If poor contact is not located, system has returned to normal. Check for intermittent conditions. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If DTC P0065 is only DTC set, go to next step. If any other DTCs exist, diagnose and repair those DTCs. Do not diagnose DTC P0065.
2. Turn ignition off. Connect test mode connector. see scheme 8 Turn ignition on. While using scan tool to command air assist injector solenoid valve on and off, listen for clicking sound from valve. If clicking sound is heard while valve is being commanded on and off, go to next step. If no clicking sound is heard while valve is being commanded on and off, replace air assist injector solenoid valve.
3. Remove air by-pass hose and blow through hose. If air by-pass hose is clogged or damaged, replace hose. If air by-pass hose is not clogged or damaged, go to next step.
4. Turn ignition off. Remove injectors and check for clogged fuel injectors. Replace any clogged or faulty injectors. If no clogged or faulty injectors are present, replace air assist injector solenoid valve. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition on. Using a DVOM connected to ground, backprobe ECM connector B137 (35-pin connector), terminal No. 12. (Scheme 29) If voltage is more than 10 volts, repair poor terminal contact in ECM connector. If voltage is not more than 10 volts, go to next step.
2. Turn ignition off. Disconnect electrical connector from air assist injector solenoid valve. Turn ignition on. Using a DVOM connected to ground, measure voltage at air assist injector connector terminal No. 2. If voltage is more than 10 volts, go to next step. 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 air assist injector solenoid valve.
3. Turn ignition off. On Baja, Legacy and Outback, disconnect ECM connector B134 (35-pin connector). On Forester and Impreza, disconnect ECM connector B137 (35-pin connector). With electrical connector disconnected from air assist injector solenoid valve, use an ohmmeter to measure resistance between ECM connector terminal No. 12 and air assist injector solenoid valve terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and air assist injector solenoid valve.
4. Using an ohmmeter connected to ground, measure resistance at ECM connector terminal No. 12. (Scheme 29) If resistance is less than 1 megohm, locate and repair short to ground in wiring between ECM and air assist injector solenoid valve. If resistance is greater than 1 megohm, go to next step.
5. Check for poor terminal contact in connectors between ECM and air assist injector solenoid valve. Repair poor contact as required. If poor contact is not located, replace air assist injector solenoid valve. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Scheme 31

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition on. Using a DVOM connected to ground, backprobe ECM connector B134 (35-pin connector), terminal No. 12 on Baja, Legacy and Outback or ECM connector B137 (35-pin connector), terminal No. 12 on Forester and Impreza. (Scheme 29) If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, go to step 3.
2. Turn ignition off. Disconnect electrical connector from air assist injector solenoid valve. Turn ignition on. Using a DVOM connected to ground, backprobe ECM connector terminal No. 12. If voltage is more than 10 volts, locate and repair short to voltage in wiring between ECM and air assist injector solenoid valve. After repair, replace ECM. If voltage is not more than 10 volts, replace air assist injector solenoid valve.
3. Using a DVOM connected to ground, backprobe ECM connector terminal No. 12 while wiggling harness and ECM connector. If voltage changes to more than 10 volts while wiggling harness and connector, locate and repair short to voltage in wiring between ECM and air assist injector solenoid valve. After repair, replace ECM. If voltage does not change to more than 10 volts while wiggling harness and connector, contact authorized Subaru dealership because probable cause is deterioration of multiple parts. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If DTC P0068 is only DTC set, go to next step. If any other DTCs exist, diagnose and repair those DTCs. Do not diagnose DTC P0068.
2. Inspect air intake system hoses for holes, cracks or loose bolts and connections. If any problems are found with air intake system, repair as necessary. If no problems are found with air intake system, go to next step.
3. Start engine and bring to operating temperature. Turn ignition off. Turn ignition on. Ensure A/C and all accessories are turned off. Using scan tool, monitor intake manifold pressure sensor signal. Reading should be 21.65-31.50 in. HG. Start engine and let idle. Using scan tool, monitor intake manifold pressure sensor signal. Reading should be 5.91-13.78 in. HG. If readings are as specified, go to next step. If readings are not as specified, replace intake manifold pressure sensor.
4. Turn ignition off. Turn ignition on. Using scan tool, monitor the throttle position (TP) sensor while throttle is fully closed. If reading is less than 5 percent, go to next step. If reading is greater than 5 percent, adjust TP sensor. See «ON-VEHICLE ADJUSTMENTS»(ref-157280) .
5. Using scan tool, monitor the TP sensor reading while throttle is fully open. If reading is greater than 85 percent, replace then intake manifold pressure sensor. If reading is less than 85 percent, replace the TP sensor.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine. Using scan tool, observe intake manifold absolute pressure. If pressure reads less than 3.94 in. Hg, go to step 3. If pressure does not read less than 3.94 in. Hg, go to next step.
2. Check for poor terminal contact at ECM and intake manifold pressure sensor connectors. Repair as required. If terminal contact is okay, circuit has returned to normal.
3. Using a DVOM connected to ground, backprobe ECM connector B135 (28-pin connector), terminal No. 3. (Scheme 29) If voltage is more than 4.5 volts, go to step 5. If voltage is not more than 4.5 volts, go to next step.
4. Measure voltage between ground and ECM connector B135 (28-pin connector), terminal No. 3 while wiggling harness and ECM connector. If voltage changes more than 4.5 volts while wiggling harness and ECM connector, repair poor terminal contact in ECM connector. If voltage does not change more than 4.5 volts while wiggling harness and ECM connector, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
5. Measure voltage between ECM connector B135 (28-pin connector), terminal No. 15 and ground. If voltage is less than 0.2 volt, go to step 7. If voltage is not less than 0.2 volt, go to next step.
6. Using scan tool, observe atmospheric absolute pressure signal while wiggling harness and ECM connector. If pressure changes to more than 3.94 in. Hg while wiggling harness and ECM connector, repair poor terminal contact in ECM connector. If pressure does not change to more than 3.94 in. Hg while wiggling harness and ECM connector, go to next step.
7. Turn ignition off. Disconnect intake manifold pressure sensor connector. Turn ignition on. Using a DVOM connected to ground, measure voltage at intake manifold pressure sensor connector terminal No. 3. (Scheme 32) If voltage is more than 4.5 volts, go to next step. If voltage is not more than 4.5 volts, locate and repair open circuit in wiring between ECM and intake manifold pressure sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
8. Turn ignition off. Disconnect ECM connector B135 (28-pin connector). Using a DVOM, measure resistance between ECM connector B135 (28-pin connector), terminal No. 3 and intake manifold pressure sensor connector terminal No. 1. (Scheme 29) If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring between ECM and intake manifold pressure sensor.
9. Measure resistance between ground and intake manifold pressure sensor connector terminal No. 1. (Scheme 32) If resistance is more than 500 k/ohms, go to next step. If resistance is not more than 500 k/ohms, locate and repair short to ground in wiring between ECM and intake manifold pressure sensor.
10. Check intake manifold pressure sensor connector for poor terminal contact. Repair as necessary. If terminal contact is okay, replace intake manifold pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine. Using scan tool, observe intake manifold absolute pressure reading. If pressure is less than 3.94 in. Hg, go to step 3. If pressure is not less than 3.94 in. Hg, go to next step.
2. Check for poor terminal contact at ECM and intake air temperature and pressure sensor connectors. Repair as required. If terminal contact is okay, system has returned to normal.
3. Using a DVOM connected to ground, backprobe ECM connector B134 (28-pin connector), terminal No. 3. (Scheme 29) If voltage is more than 4.5 volts, go to step 5. If voltage is not more than 4.5 volts, go to next step.
4. Measure voltage between ground and ECM connector B134 (28-pin connector), terminal No. 3 while wiggling harness and ECM connector. If voltage changes more than 4.5 volts, repair poor terminal contact in ECM connector. If voltage does not change more than 4.5 volts, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
5. Measure voltage between ground and ECM connector B134 (28-pin connector), terminal No. 15. If voltage is less than 0.2 volt, go to step 7. If voltage is not less than 0.2 volt, go to next step.
6. Using scan tool, observe absolute pressure signal while wiggling ECM connector. If pressure changes to more than 3.94 in. Hg, repair poor terminal contact at ECM connector. If pressure does not change to more than 3.94 in. Hg, go to next step.
7. Turn ignition off. Disconnect intake air temperature and pressure sensor connector. Turn ignition on. Using a DVOM connected to ground, measure voltage at intake air temperature and pressure sensor connector terminal No. 3. (Scheme 32) If voltage is more than 4.5 volts, go to next step. If voltage is not more than 4.5 volts, locate and repair open circuit in wiring between ECM and intake air temperature and pressure sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
8. Turn ignition off. Disconnect ECM connector B134 (28-pin connector). Measure resistance between ECM connector B134 (28-pin connector), terminal No. 19 and intake air temperature and pressure sensor connector terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring between ECM and intake air temperature and pressure sensor.
9. Check intake air temperature and pressure sensor connector for poor terminal contact. Repair as necessary. If connector is okay, replace intake air temperature and pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Scheme 32

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine. Using scan tool, observe intake manifold absolute pressure. If pressure reads more than 35.29 in. Hg, go to step 9. If pressure does not read more than 35.29 in. Hg, go to next step.
2. Using DVOM connected to ground, backprobe ECM connector B135 (28-pin connector), terminal No. 3. (Scheme 29) If voltage is more than 4.5 volts, go to step 4. If voltage is not more than 4.5 volts, go to next step.
3. Measure voltage between ground and ECM connector B135 (28-pin connector), terminal No. 3 while wiggling harness and ECM connector. If voltage changes more than 4.5 volts, repair poor terminal contact in ECM connector. If voltage does not change more than 4.5 volts while wiggling harness and ECM connector, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
4. Using DVOM connected to ground, backprobe ECM connector B135 (28-pin connector), terminal No. 15. If voltage is less than 0.2 volt, go to step 6. If voltage is not less than 0.2 volt, go to next step.
5. Using scan tool, observe atmospheric absolute pressure while wiggling harness and ECM connector. If reading changes more than 3.94 in. Hg while wiggling harness and ECM connector, repair poor terminal contact at ECM connector. If reading does not change more than 3.94 in. Hg while wiggling harness and ECM connector, go to next step.
6. Turn ignition off. Disconnect intake manifold pressure sensor connector. Turn ignition on. Measure voltage between ground and intake manifold pressure sensor connector terminal No. 3. (Scheme 32) If voltage is more than 4.5 volts, go to next step. If voltage is not more than 4.5 volts, locate and repair open circuit in wiring between ECM and intake manifold pressure sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
7. Turn ignition off. Disconnect ECM connector B135 (28-pin connector). Measure resistance between ECM connector B135 (28-pin connector), terminal No. 15 and intake manifold pressure sensor connector terminal No. 2. (Scheme 29)and (Scheme 32). Also measure resistance between ECM connector B135 (28-pin connector), terminal No. 1 and intake manifold pressure sensor terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring between ECM and intake manifold pressure sensor.
8. Check intake manifold pressure sensor connector for poor terminal contact. Repair as necessary. If connector is okay, replace intake manifold pressure sensor.
9. Turn ignition and scan tool off. Disconnect intake manifold pressure sensor connector. Turn ignition and scan tool on. Using scan tool, observe intake manifold absolute pressure. If pressure is more than 35.29 in. Hg, locate and repair short to voltage in wiring between ECM and intake manifold pressure sensor. If pressure is not more than 35.29 in. Hg, replace intake manifold pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine. Using scan tool, observe intake manifold absolute pressure. If pressure is more than 35.29 in. Hg, go to step 10. If pressure is not more than 35.29 in. Hg, go to next step.
2. Using DVOM connected to ground, backprobe ECM connector B134 (28-pin connector), terminal No. 3. (Scheme 29) If voltage is more than 4.5 volts, go to step 4. If voltage is not more than 4.5 volts, go to next step.
3. Measure voltage between ground and ECM connector B134 (28-pin connector), terminal No. 3 while wiggling harness and ECM connector. If voltage changes more than 4.5 volts while wiggling harness and ECM connector, repair poor contact in ECM connector. If voltage does not change more than 4.5 volts while wiggling harness and ECM connector, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
4. Using DVOM connected to ground, backprobe ECM connector B134 (28-pin connector), terminal No. 15. If voltage is less than 0.2 volt, go to step 6. If voltage is not less than 0.2 volt, go to next step.
5. Using scan tool, observe atmospheric absolute pressure signal while wiggling harness and ECM connector. If reading changes more than 3.94 in. Hg while wiggling harness and ECM connector, repair poor terminal contact at ECM. If reading does not change more than 3.94 in. Hg while wiggling harness and ECM connector, go to next step.
6. Turn ignition off. Disconnect intake air temperature and pressure sensor connector. Turn ignition on. Measure voltage between ground and intake air temperature and pressure sensor connector terminal No. 3. (Scheme 32) If voltage is more than 4.5 volts, go to next step. If voltage is not more than 4.5 volts, locate and repair open circuit in wiring between ECM and intake air temperature and pressure sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
7. Turn ignition off. Disconnect ECM connector B134 (28-pin connector). Measure resistance between ECM connector B134 (28-pin connector), terminal No. 15 and intake air temperature and pressure sensor connector terminal No. 2. (Scheme 29)and (Scheme 32). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring between ECM and intake air temperature and pressure sensor.
8. Measure resistance between ECM connector B134 (30-pin connector), terminal No. 19 and intake air temperature and pressure sensor connector terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring between ECM and intake air temperature and pressure sensor.
9. Check intake air temperature and pressure sensor connector for poor terminal contact. Repair as necessary. If connector is okay, replace intake air temperature and pressure sensor.
10. Turn ignition and scan tool off. Disconnect intake air temperature and pressure sensor connector. Turn ignition and scan tool on. Using scan tool, observe intake manifold absolute pressure signal. If pressure is more than 35.29 in. Hg, locate and repair short to voltage in wiring between ECM and intake air temperature and pressure sensor. If pressure is not more than 35.29 in. Hg, replace intake air temperature and pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P0111 exist, diagnose and repair those DTCs. Do not diagnose DTC P0111. If DTC P0111 is only DTC set, go to next step.
2. Start engine and warm to normal operating temperature. Using scan tool, observe engine coolant temperature. If temperature is between 167°F (75°C) and 203°F (95°C), replace intake air temperature sensor. If temperature is not between 167°F (75°C) and 203°F (95°C), check for code P0125. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . Start engine. Using scan tool, observe intake air temperature signal. If temperature is more than 248°F (120°C), go to next step. If temperature is not more than 248°F (120°C), repair poor terminal contact in connectors between ECM and intake air temperature and pressure sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Turn ignition off. Disconnect intake air temperature and pressure sensor connector. Turn ignition on. Using scan tool, observe intake air temperature signal. If temperature is less than -40°F (-40°C), replace intake air temperature and pressure sensor. If temperature is not less than -40°F (-40°C), locate and repair short to ground in wiring between ECM and intake air temperature and pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine. Using scan tool, observe intake air temperature signal. If temperature is less than -40°F (-40°C), go to next step. If temperature is not less than -40°F (-40°C), repair poor terminal contact in connectors between ECM and intake air temperature and pressure sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Turn ignition off. Disconnect intake air temperature and pressure sensor connector. Using a DVOM connected to ground, measure voltage at intake air temperature and pressure sensor connector terminal No. 1. (Scheme 32) If voltage is more than 10 volts, locate and repair short to voltage in wiring between ECM and intake air temperature and pressure sensor. If voltage is not more than 10 volts, go to next step.
3. Turn ignition on. Using a DVOM connected to ground, measure voltage at intake air temperature and pressure sensor connector terminal No. 1. If voltage is more than 10 volts, locate and repair short to voltage in wiring between ECM and intake air temperature and pressure sensor. If voltage is not more than 10 volts, go to next step.
4. Using a DVOM connected to ground, measure voltage at intake air temperature and pressure sensor connector terminal No. 1. If voltage is more than 3 volts, go to next step. If voltage is not more than 3 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and intake air temperature and pressure sensor.
5. Turn ignition off. Measure resistance between ground and intake air temperature and pressure sensor connector terminal No. 2. If resistance is less than 5 ohms, replace intake air temperature and pressure sensor. If resistance is not less than 5 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and intake air temperature and pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . Start engine. Using scan tool, observe coolant temperature. If temperature is more than 302°F (150°C) on Forester and Impreza 2.5L or more than 248°F (120°C) on all others, go to next step. If temperature is not more than 302°F (150°C) on Forester and Impreza 2.5L or 248°F (120°C) on all others, repair poor terminal contact in connectors between ECM and ECT sensor.
2. Turn ignition off. Disconnect ECT sensor connector. Turn ignition on. Using scan tool, observe coolant temperature. If temperature is less than -40°F (-40°C), replace ECT sensor. If temperature is not less than -40°F (-40°C), locate and repair short to ground in wiring between ECT sensor and ECM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine. Using scan tool, observe engine coolant temperature. If temperature is less than -40°F (-40°C), go to next step. If temperature is not less than -40°F (-40°C), check for poor terminal contact in connectors between ECM and ECT sensor.
2. Turn ignition off. Disconnect ECT sensor connector. Using a DVOM connected to ground, measure voltage at ECT sensor connector terminal No. 1. (Scheme 33) If voltage is more than 10 volts, locate and repair short to voltage in wiring between ECM and ECT sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If voltage is not more than 10 volts, go to next step.
3. Turn ignition on. Using a DVOM connected to ground, measure voltage at ECT sensor connector terminal No. 1. If voltage is more than 10 volts, locate and repair short to voltage in wiring between ECM and ECT sensor. If voltage is not more than 10 volts, go to next step.
4. Using a DVOM connected to ground, measure voltage at ECT sensor connector terminal No. 1. If voltage is more than 4 volts, go to next step. If voltage is not more than 4 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and ECT sensor.
5. Turn ignition off. Using an ohmmeter, measure resistance between ground and ECT sensor connector terminal No. 2. If resistance is less than 5 ohms, replace ECT sensor. If resistance is not less than 5 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and ECT sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Scheme 33

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P0121 exist, diagnose those DTCs. Do not diagnose DTC P0121. If DTC P0121 is only DTC set, replace throttle position sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . If DTC P0122 and/or P0123 exist, diagnose and repair those DTCs. Do not diagnose DTC P0121. If DTC P0121 is only DTC set, replace TP sensor. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .

Scheme 34

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine. Using scan tool, observe TP sensor signal. If voltage is less than 0.1 volt, go to next step. If voltage is not less than 0.1 volt, system has returned to normal. Check for poor terminal contact in connectors between ECM and TP sensor.
2. Ensure throttle valve is fully closed. Using DVOM connected to ground, backprobe ECM 28-pin connector B134 (Forester and Impreza) or B135 (Baja, Legacy and Outback), terminal No. 3. (Scheme 29) If voltage is more than 4.5 volts, go to step 4. If voltage is not more than 4.5 volts, go to next step.
3. Observe DVOM while wiggling harness and ECM connector. If voltage changes to more than 4.5 volts while wiggling harness and ECM connector, check for poor terminal contact at ECM connector. If voltage does not change to more than 4.5 volts while wiggling harness and ECM connector, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
4. Using DVOM connected to ground, backprobe ECM 28-pin connector B134 (Forester and Impreza) or B135 (Baja, Legacy and Outback), terminal No. 13. If voltage is less than 0.1 volt, go to step 6. If voltage is not less than 0.1 volt, go to next step.
5. Observe DVOM while wiggling harness and ECM connector. If voltage changes more than 0.1 volt while wiggling harness and ECM connector, repair poor terminal contact at ECM connector. If voltage does not change more than 0.1 volt while wiggling harness and ECM connector, go to next step.
6. Turn ignition off. Disconnect TP sensor connector. Turn ignition on. Using a DVOM connected to ground, measure voltage at TP sensor connector terminal No. 4. (Scheme 34) If voltage is more than 4.5 volts, go to next step. If voltage is not more than 4.5 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and TP sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
7. Turn ignition off. Measure resistance between ECM 28-pin connector B134 (Forester and Impreza) or B135 (Baja, Legacy and Outback), terminal No. 13 and TP sensor connector terminal No. 3. (Scheme 29)and (Scheme 34). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and TP sensor.
8. Measure resistance between ground and TP sensor connector terminal No. 3. (Scheme 34) If resistance is less than 1 megohms, locate and repair short to ground in wiring between ECM and TP sensor. If resistance is not less than 1 megohms, go to next step.
9. Check for poor terminal contact in TP sensor connector. Repair TP sensor connector as necessary. If connector is okay, replace TP sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine. Using scan tool, observe TP sensor signal. If voltage is more than 4.9 volts, go to next step. If voltage is not more than 4.9 volts, system has returned to normal. Check for poor terminal contact in connectors between ECM and TP sensor.
2. Turn ignition off. Disconnect TP sensor connector. Using an ohmmeter, measure resistance between ground and TP sensor connector terminal No. 2. (Scheme 34) If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open in wiring and check for poor terminal contact in connectors between ECM and TP sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
3. Turn ignition on. Using a DVOM connected to ground, measure voltage at TP sensor connector terminal No. 3. If voltage is more than 4.9 volts, locate and repair short to voltage in wiring between ECM and TP sensor. After repair, replace ECM. If voltage is not more than 4.9 volts, replace TP sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P0125 exist, diagnose and repair those DTCs. Do not diagnose DTC P0125. If DTC P0125 is only DTC set, go to next step.
2. Check operation of thermostat. If thermostat stays open, replace thermostat. If thermostat does not stay open, replace ECT sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If vehicle has been idling for an extended period or operated with engine partly submerged in water, clear codes and allow engine temperature to stabilize. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) . Road test vehicle. Using scan tool, retrieve DTCs. If any DTCs other than P0128 are all displayed, diagnose those DTCs first. Do not diagnose P0128. If DTC P0128 is the only DTC set, go to next step.
2. Check coolant level and antifreeze solution mixture ratio. Drain and refill coolant as required. If coolant level and solution mixture are correct, start engine and check cooling fan operation. If cooling fan runs continuously for more than 3 minutes with engine at idle, repair cooling fan circuit. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If cooling fan does not run continuously for more than 3 minutes with engine at idle, replace thermostat. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . Using scan tool, retrieve DTCs. If DTC P0129 is the only DTC retrieved, replace ECM. If any DTC other than P0129 is retrieved, diagnose those DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any DTCs other than P0130 exist, diagnose and repair those DTCs. If only DTC P0130 exists, go to next step.
2. Start engine and warm to more than 160°F (70°C). Operate engine at idle for one minute. Using scan tool, observe front HO2S signal. If voltage is.85-1.15 volt at idle, go to next step. If voltage is not.85-1.15 volt at idle, go to step 4.
3. Slowly accelerate engine (five seconds) from idle to 5,000 RPM a total of 5 times. If voltage is more than 1.1 volt for more than a moment, go to step 6. If voltage is not more than 1.1 volt for more than a moment, go to next step.
4. Turn ignition off. Disconnect front HO2S connector and ECM connector B136 (26-pin connector). Measure resistance between ECM terminals and HO2S connector terminals. See «ECM-TO-FRONT HO2S CONNECTOR IDENTIFICATION»(ref-157722-S06926653892003082200000) table. (Scheme 29)and (Scheme 30). If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and front HO2S. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. ECM-TO-FRONT HO2S CONNECTOR IDENTIFICATION ECM B136 (30-Pin Connector) Terminal No. Front HO2S Connector Terminal No. 13 1 22 2
5. With DVOM connected to ground, measure resistance between ECM connector B136 (26-pin connector) terminals No. 13 and 22. (Scheme 29) If resistance is more than 1 megohm, go to next step. If resistance is not more than 1 megohm, locate and repair short to ground in wiring between front HO2S and ECM.
6. Check for faulty exhaust system components, cracks and/or leaks. Check electrical connectors between front HO2S sensor and ECM. Repair and/or replace components as necessary. If exhaust system is okay, replace front HO2S. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Turn ignition switch to off position. Disconnect ECM and HO2S harness connectors. Measure resistance between ground ECM harness connector B136 terminals No. 13 and No. 22. If resistance is greater than 1 megohm, replace front HO2S and test system operation. If resistance is less than 1 megohm, repair short to ground between ECM harness connector and front HO2S. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .

Turn ignition switch to on position. Disconnect front HO2S harness connector. Measure voltage between ground and ECM harness connector B136 terminals No. 13 and No. 22. If voltage is greater than 8 volts, repair short to voltage between ECM and front HO2S harness connector. If voltage is less than 8 volts, replace front HO2S and test system operation.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P0133 exist, diagnose and repair those DTCs. Do not diagnose DTC P0133. If DTC P0133 is only DTC set, go to next step.
2. Check exhaust system components for damage, holes, leaks, or loose components. Repair or replace exhaust system components as necessary. If exhaust system is okay, replace front HO2S. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

1. Turn ignition switch to off position. Disconnect ECM and front HO2S harness connectors. Measure resistance between ECM harness connector B136 (26-pin connector), terminal No. 13 and front HO2S harness connector terminal No. 1. (Scheme 29)and (Scheme 30). Also measure resistance between ECM harness connector B136 (26-pin connector), terminal No. 22 and front HO2S harness connector terminal No. 2. If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open in appropriate wire between ECM and front HO2S harness connectors.
2. Check front HO2S harness connector for poor contact. If poor contact is found, repair as necessary. If contact is okay, replace front HO2S and test system operation.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any DTCs other than P0137 exist, diagnose and repair those DTCs. Do not diagnose DTC P0137. If DTC P0137 is only DTC set, go to next step.
2. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine and bring to operating temperature. Using scan tool, observe rear HO2S signal. If reading is 490 mV, go to step 5. If reading is not 490 mV, go to next step.
3. Turn ignition switch to off position. Disconnect ECM 28-pin harness connector B134 (Forester and Impreza) or B135 (Baja, Legacy and Outback) and rear HO2S harness connector. Measure resistance between ECM harness connector terminal No. 14 and rear HO2S terminal No. 4. (Scheme 29)and (Scheme 30). Also measure resistance between ECM harness connector terminal No. 19 and rear HO2S terminal No. 3. If resistance is greater than 3 ohms, repair open in appropriate wire and test system operation. If resistance is less than 3 ohms, go to next step.
4. Ensure ignition switch is in the off position. Disconnect rear HO2S harness connector. Turn ignition switch to on position. Measure voltage between ground and rear HO2S harness connector terminal No. 4. (Scheme 30) If voltage is 0.2-0.5 volts, replace rear HO2S sensor. If voltage is not 0.2-0.5 volts, repair open between rear HO2S and ECM harness connector.
5. Check exhaust system components for damage, holes, leaks, or loose components. Repair or replace exhaust system components as necessary. If exhaust system is okay, replace rear HO2S. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any DTCs other than P0137 exist, diagnose and repair those DTCs. Do not diagnose DTC P0137. If DTC P0137 is only DTC set, go to next step.
2. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine and bring to operating temperature. Using scan tool, observe rear HO2S signal. If reading is 250 mV, go to step 5. If reading is not 250 mV, go to next step.
3. Turn ignition switch to off position. Disconnect ECM 28-pin harness connector B134 (Forester and Impreza) or B135 (Baja, Legacy and Outback) and rear HO2S harness connector. Measure resistance between ECM harness connector terminal No. 14 and rear HO2S terminal No. 4. (Scheme 29)and (Scheme 30). Also measure resistance between ECM harness connector terminal No. 19 and rear HO2S terminal No. 3. If resistance is greater than 3 ohms, repair open in appropriate wire and test system operation. If resistance is less than 3 ohms, go to next step.
4. Ensure ignition switch is in the off position. Disconnect rear HO2S harness connector. Turn ignition switch to on position. Measure voltage between ground and rear HO2S harness connector terminal No. 4. (Scheme 30) If voltage is 0.2-0.5 volts, replace rear HO2S sensor. If voltage is not 0.2-0.5 volts, repair open between rear HO2S and ECM harness connector.
5. Check exhaust system components for damage, holes, leaks, or loose components. Repair or replace exhaust system components as necessary. If exhaust system is okay, replace rear HO2S. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . If any DTCs other than P0139 exist, diagnose and repair those DTCs first. Further inspection of DTC P0139 is not necessary. If DTC P0139 is only DTC set, replace rear HO2S. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .

Note. For diagnosis of DTC P0171, see DTC P0172: FUEL TRIM MALFUNCTION (TOO RICH) - BAJA, LEGACY & OUTBACK

Note. For diagnosis of DTC P0171, see DTC P0172: FUEL TRIM MALFUNCTION (TOO RICH) - FORESTER & IMPREZA

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P0171 and P0172 exist, diagnose and repair those DTCs. Do not diagnose DTCs P0171 and P0172. If DTCs P0171 and P0172 are only DTCs set, go to next step.
2. Check for loose bolts and/or holes in exhaust system. Repair as required. If exhaust system is sealed and has no loose components, go to next step.
3. Check EGR valve. If EGR valve is clogged, stuck or dirty, replace EGR valve. If EGR system is okay, go to next step.
4. Check for holes, loose bolts and/or disconnected hoses in air intake system. Repair as required. If air intake system is sealed and has no loose or disconnected components, go to next step.
5. Check purge control solenoid valve for problems. If purge control solenoid valve is okay, go to next step. If purge control solenoid valve is not okay, repair as required.
6. Check PCV valve. If PCV valve is clogged, replace PCV valve. If PCV valve is okay, go to next step.
7. Disconnect fuel delivery hose from fuel filter and connect a fuel pressure gauge between filter and delivery hose. Install fuel filler cap. Start engine and idle with transaxle in Neutral. Check fuel pressure with pressure regulator hose disconnected from intake manifold. See «FUEL SYSTEM»(ref-157258-S10921948112003080700000) in SERVICE & ADJUSTMENT SPECIFICATIONS article. If fuel pressure is within specifications, go to next step. If fuel pressure is too high, check for blocked fuel return line or bent hose. If fuel pressure is too low, check for improper fuel pump discharge or blocked fuel supply line.
8. Check fuel pressure with pressure regulator vacuum hose connected. See «FUEL SYSTEM»(ref-157258-S10921948112003080700000) in SERVICE & ADJUSTMENT SPECIFICATIONS article. If fuel pressure is within specifications, go to next step. If fuel pressure is too high, check for faulty pressure regulator, blocked fuel return line or bent hose. If fuel pressure is too low, check for faulty pressure regulator, improper fuel pump discharge or blocked fuel supply line. WARNING: Release fuel pressure before removing fuel pressure test gauge. On Forester models, see «FUEL SYSTEM PRESSURE RELEASE»(ref-161274-S08519937592004033100000) in REMOVAL & INSTALLATION - FORESTER article. On Impreza and Outback Sport models, see «FUEL SYSTEM PRESSURE RELEASE»(ref-161281-S01635209422004033100000) in REMOVAL & INSTALLATION - IMPREZA & OUTBACK SPORT article.
9. Remove fuel pressure test gauge and reconnect fuel delivery hose. Start engine. Check for leaks. Turn ignition off. Start and warm engine to normal operating temperature. Using scan tool, observe coolant temperature. If coolant temperature is 158°F -212°F (70°C -100°C), go to next step. If coolant temperature is not 158°F -212°F (70°C -100°C), replace engine coolant temperature sensor.
10. Start engine. Operate engine until coolant temperature is greater than 140°F (60°C). Place transaxle in Neutral. Ensure all accessories and A/C are off. Using scan tool, read intake manifold absolute pressure. If pressure is 7.09-12.20 in. Hg with engine idling and 21.65-31.50 in. Hg with ignition on (engine off), contact authorized Subaru dealership because probable cause is deterioration of multiple parts. If pressure is not 7.09-12.20 in. Hg with engine idling and 21.65-31.50 in. Hg with ignition on (engine off), replace intake manifold pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . Check for loose bolts and/or holes in exhaust system. Repair as required. If exhaust system is sealed and has no loose components, go to next step.
2. Check for holes, loose bolts and/or disconnected hoses in air intake system. Repair as required. If air intake system is sealed and has no loose or disconnected components, go to next step.
3. Check purge control solenoid valve for problems. If purge control solenoid valve is okay, go to next step. If purge control solenoid valve is not okay, repair as required.
4. Disconnect fuel delivery hose from fuel filter and connect a fuel pressure gauge between filter and delivery hose. Install fuel filler cap. Start engine and idle with transaxle in Neutral. Check fuel pressure with pressure regulator hose disconnected from intake manifold. See «FUEL SYSTEM»(ref-157258-S10921948112003080700000) in SERVICE & ADJUSTMENT SPECIFICATIONS article. If fuel pressure is within specifications, go to next step. If fuel pressure is too high, check for blocked fuel return line or bent hose. If fuel pressure is too low, check for improper fuel pump discharge or blocked fuel supply line.
5. Check fuel pressure with pressure regulator vacuum hose connected. See «FUEL SYSTEM»(ref-157258-S10921948112003080700000) in SERVICE & ADJUSTMENT SPECIFICATIONS article. If fuel pressure is within specifications, go to next step. If fuel pressure is too high, check for faulty pressure regulator, blocked fuel return line or bent hose. If fuel pressure is too low, check for faulty pressure regulator, improper fuel pump discharge or blocked fuel supply line. WARNING: Release fuel pressure before removing fuel pressure test gauge. On Forester models, see «FUEL SYSTEM PRESSURE RELEASE»(ref-161274-S08519937592004033100000) in REMOVAL & INSTALLATION - FORESTER article. On Impreza and Outback Sport models, see «FUEL SYSTEM PRESSURE RELEASE»(ref-161281-S01635209422004033100000) in REMOVAL & INSTALLATION - IMPREZA & OUTBACK SPORT article.
6. Remove fuel pressure test gauge and reconnect fuel delivery hose. Start engine. Check for leaks. Turn ignition off. Start and warm engine to normal operating temperature. Using scan tool, observe coolant temperature. If coolant temperature is 158-212°F (70°-100°C), go to next step. If coolant temperature is not 158°F -212°F (70°C -100°C), replace engine coolant temperature sensor.
7. Start engine. Operate engine until coolant temperature is greater than 140°F (60°C). Place transaxle in Neutral. Ensure all accessories and A/C are off. Using scan tool, read intake manifold absolute pressure. If pressure is 7.09-12.20 in. Hg with engine idling and 21.65-31.50 in. Hg with ignition on (engine off), contact authorized Subaru dealership because probable cause is deterioration of multiple parts. If pressure is not 7.09-12.20 in. Hg with engine idling and 21.65-31.50 in. Hg with ignition on (engine off), replace intake manifold pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . If any DTCs other than P0181 exist, diagnose and repair those DTCs first. Do not diagnose DTC P0181. If DTC P0181 is only DTC set, replace fuel temperature sensor. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . Start engine. Using scan tool, observe fuel temperature sensor signal. If temperature is more than 302°F (150°C), go to next step. If temperature is not more than 302°F (150°C), system has returned to normal. Check for poor connections or intermittent open in wiring. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Turn ignition off. Remove fuel pump access cover located in right rear of trunk floor (sedan), or luggage compartment floor (wagon). Disconnect 6-pin fuel pump connector. Turn ignition on. Using scan tool, observe fuel temperature sensor signal. If temperature is less than -40°F (-40°C), replace fuel temperature sensor. If temperature is not less than -40°F (-40°C), locate and repair short to ground in wiring between fuel pump and ECM. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Start engine. Using scan tool, observe fuel temperature sensor signal. If temperature is less than -40°F (-40°C), go to next step. If temperature is not less than -40°F (-40°C), locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and fuel pump. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Turn ignition off. Remove fuel pump access cover located in right rear of trunk floor (sedan), or luggage compartment floor (wagon). Disconnect 6-pin fuel pump connector. Using a DVOM connected to ground, measure voltage at fuel pump connector terminal No. 5 (Baja, Legacy and Outback) or terminal No. 6 (Forester and Impreza). (Scheme 35)or (Scheme 36). If voltage is more than 10 volts, locate and repair short to voltage in wiring between ECM and fuel pump. If voltage is not more than 10 volts, leave voltmeter connected and go to next step.
3. Turn ignition on and recheck voltage. If voltage is more than 10 volts, locate and repair short to voltage in wiring between fuel pump and ECM. If voltage is not more than 10 volts, go to next step.
4. Recheck voltage. If voltage is more than 4 volts, go to next step. If voltage is not more than 4 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and fuel pump. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
5. Turn ignition off. For Forester and Impreza, using an ohmmeter, measure resistance between ECM harness connector B134 (28-pin connector) and fuel pump connector terminal No. 5. (Scheme 29)and (Scheme 35). If resistance is less than 1 ohms, replace fuel temperature sensor. If resistance is not less than 5 ohms, locate and repair open circuit and check for poor terminal contact in connectors between fuel pump and ECM. For Baja, Legacy and Outback, measure resistance between ground and fuel pump connector terminal No. 4. (Scheme 36) If resistance is less than 5 ohms, replace fuel temperature sensor. If resistance is greater than 5 ohms, repair open between fuel pump and ECM harness connectors. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Scheme 35

Scheme 36

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Disconnect ECM 28-pin connector B134 (Forester and Impreza) or B135 (Baja, Legacy and Outback). Using an ohmmeter, measure resistance between ground and ECM 28-pin connector, terminal No. 16. (Scheme 29) If resistance is more than 700 k/ohms, go to next step. If resistance is not more than 700 k/ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between KS and ECM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Turn ignition off. Reconnect ECM connector. Disconnect electrical connector from KS. Using an ohmmeter, measure resistance between ground and KS harness terminal No. 2. (Scheme 31) If resistance is more than 700 k/ohms, go to next step. If resistance is not more than 700 k/ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between KS and ECM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
3. Check KS installation bolt for tightness. If bolt is tight, replace KS. If bolt is not tight, tighten bolt. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Disconnect ECM 28-pin connector B134 (Forester and Impreza) or B135 (Baja, Legacy and Outback). Using an ohmmeter, measure resistance between ground and ECM connector B136 (30-pin connector), terminal No. 16. (Scheme 29) If resistance is less than 400 k/ohms, go to next step. If resistance is not less than 400 k/ohms, go to step 3.
2. Turn ignition off. Reconnect ECM connector. Disconnect electrical connector from KS. Using an ohmmeter, measure resistance between ground and KS harness terminal No. 2. (Scheme 31) If resistance is less than 400 k/ohms, replace KS. If resistance is not less than 400 k/ohms, locate and repair short to ground in wiring between KS and ECM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Note that wiring between both connectors is shielded. Repair circuit in wiring together with shield.
3. Turn ignition off. Ensure ECM and KS connectors are properly connected at component. Turn ignition on. Using DVOM connected to ground, backprobe ECM connector, terminal No. 16. If voltage is more than 2 volts, circuit has returned to normal. Check for poor terminal contact in connectors between ECM and KS. If voltage is not more than 2 volts, repair poor terminal contact in ECM connector. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Note. Wiring between both connectors is shielded. Repair circuit in wiring together with shield.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Disconnect CKP sensor connector. Using an ohmmeter, measure resistance between ground and CKP sensor connector terminal No. 1. (Scheme 31) If resistance is not more than 100 k/ohms, go to next step. If resistance is more than 100 k/ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and CKP sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Measure resistance between CKP sensor connector terminal No. 1 and ground. If resistance is less than 10 ohms, locate and repair short to ground in wiring between CKP sensor and ECM connector. If resistance is not less than 10 ohms, go to next step.
3. Measure resistance between CKP sensor connector terminal No. 2 and ground. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and CKP sensor.
4. Ensure CKP sensor bolt is tightened securely. Tighten bolt as necessary. If CKP sensor bolt is tight, go to next step.
5. Remove CKP sensor. Measure resistance across CKP sensor terminals. If resistance is 1000-4000 ohms, repair poor terminal contact in CKP sensor connector. If resistance is not 1000-4000 ohms, replace CKP sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If DTC P0335 exists, diagnose and repair that DTC first. If DTC P0336 is only DTC set, go to next step.
2. Turn ignition off. Ensure CKP sensor bolt is tightened securely. Tighten bolt as required. If CKP sensor and mounting bolt are properly installed, go to next step.
3. Remove front timing belt cover and inspect crankshaft sprocket for damage. Replace crankshaft sprocket, if necessary. If crankshaft sprocket is okay, go to next step.
4. Check installation of timing belt. see scheme 19 Repair/replace timing belt and adjust as necessary. If timing belt is properly installed, replace CKP sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Note. Wiring between both connectors is shielded. Repair circuit in wiring together with shield.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Disconnect CMP sensor connector. Using an ohmmeter, measure resistance between CMP sensor connector terminal No. 1 and ground. (Scheme 31) If resistance is not more than 100 k/ohms, leave ohmmeter connected and go to next step. If resistance is more than 100 k/ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and CMP sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Measure resistance between CMP sensor connector terminal No. 1 and ground. If resistance is less than 10 ohms, locate and repair short to ground in wiring between CMP sensor and ECM. If resistance is not less than 10 ohms, go to next step.
3. Measure resistance between CMP sensor connector terminal No. 2 and ground. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and CMP sensor.
4. Ensure CMP sensor bolt is tightened securely. Tighten bolt as required. If bolt is tight, remove CMP sensor and measure resistance across CMP sensor terminals. If resistance is 1000-4000 ohms, repair poor terminal contact in CMP sensor connector. If resistance is not 1000-4000 ohms, replace CMP sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Note. Wiring between both connectors is shielded. Repair circuit in wiring together with shield.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any DTC other than P0341 exists, diagnose and repair that DTC first. If DTC P0341 is only DTC set, go to next step.
2. Turn ignition off. Disconnect CMP sensor connector. Using an ohmmeter, measure resistance between CMP sensor connector terminal No. 1 and ground. (Scheme 31) If resistance is not more than 100 k/ohms, go to next step. If resistance is more than 100 k/ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and CMP sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
3. Measure resistance between CMP sensor connector terminal No. 1 and ground. If resistance is less than 10 ohms, locate and repair short to ground in wiring between ECM and CMP sensor. If resistance is not less than 10 ohms, go to next step.
4. Measure resistance between CMP sensor connector terminal No. 2 and ground. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and CMP sensor.
5. Ensure CMP sensor bolt is tightened securely. Tighten bolt as required. If CMP sensor is securely installed, go to next step.
6. Turn ignition off and remove CMP sensor. Using an ohmmeter, measure resistance between CMP sensor connector terminals No. 1 and No. 2. If resistance is between 1000-4000 ohms, go to next step. If resistance is not between 1000-4000 ohms, replace CMP sensor.
7. Turn ignition off. Ensure CMP sensor bolt is tightened securely. Tighten bolt as required. If CMP sensor is securely installed, go to next step.
8. Remove front timing belt cover and inspect camshaft sprocket for damage. Replace camshaft sprocket, if necessary. If camshaft sprocket is okay, go to next step.
9. Check installation of timing belt. see scheme 19 Repair/replace timing belt and adjust as necessary. If timing belt is properly installed, replace CMP sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any DTCs other than P0400 exist, diagnose and repair those DTCs. Do not diagnose DTC P0400. If DTC P0400 is only DTC set, go to next step.
2. Start engine. Using scan tool, observe intake manifold pressure sensor signal. If reading is more than 15.75 in. Hg, check for proper installation of EGR valve, intake manifold pressure sensor and TP sensor. If reading is less than 15.75, go to next step.
3. Disconnect EGR valve harness connector. Turn ignition switch to on position. Measure voltage between ground and EGR valve harness connector terminals No. 2 and No. 5. (Scheme 35) If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open between main relay and EGR valve harness connector.
4. Measure resistance between EGR valve terminals No. 1 and No. 2, No. 2 and No. 3, No. 4 and No. 5, and No. 5 and No. 6. If resistance is 20-30 ohms, go to next step. If resistance is not 20-30 ohms, replace EGR valve and test system operation.
5. Turn ignition to off position. Reconnect EGR harness connector. Turn ignition switch to on position. Measure voltage between ground and ECM harness connector B134 terminals No. 15, No. 16, No. 17 and No. 18. If voltage changes between 0 and 10 volts, repair poor contact in ECM connectors. If voltage does not change between 0 and 10 volts, go to next step.
6. Turn ignition switch to off position. Disconnect EGR and ECM harness connectors. Measure resistance between ECM harness connector B134 and terminals and EGR valve harness connector terminals. See «EGR VALVE CIRCUIT IDENTIFICATION»(ref-157722-S31742091522003082700000) table. (Scheme 29)and (Scheme 35). If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, open in appropriate wire between EGR valve and ECM harness connectors. EGR VALVE CIRCUIT IDENTIFICATION ECM Harness Connector B134 Terminal No. EGR Valve Harness Connector Terminal No. 15 3 16 4 17 1 18 6
7. Ensure ignition switch is in the off position. Measure resistance between ground and ECM harness connector B134 terminals No. 13, No. 14, No. 25 and No. 26. (Scheme 29) If resistance is greater than 1 megohm, go to next step. If resistance is less than 1 megohm, repair short to ground in appropriate wire and test system operation.
8. Check for poor contact at ECM and EGR valve harness connectors. If poor contact is found, repair as necessary. If poor contact is not found, system has returned to normal condition at this time.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If DTC P0420 is only DTC set, go to next step. If any DTCs other than P0420 are present, diagnose and repair those DTCs first. Do not diagnose DTC P0420.
2. Check for exhaust leaks or air suction caused by loose or missing nuts and bolts, or damage to exhaust system. Check especially between cylinder head and front exhaust pipe, between front exhaust pipe and front catalytic converter, and between front and rear catalytic converters. If damage is found, repair or replace exhaust system. If no damage is found, go to next step.
3. Separate rear catalytic converter from exhaust pipe. If there is damage at catalytic converter, replace front converter. If there is no damage to catalytic converter, go to next step.
4. Disconnect rear HO2S harness connector. Measure resistance between ECM harness connector B135, terminal No. 19 and rear HO2S harness connector terminal No. 3. (Scheme 29)and (Scheme 30). If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open between ECM and rear HO2S harness connectors.
5. Check sealed wire. If sealed wire is not properly connected, repair sealed wire and test system operation. If sealed wire is properly connected, contact authorized Subaru dealership because probable cause is deterioration of multiple parts. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any other DTCs are set, diagnose and repair those DTCs first. If DTC P0442 is only DTC set, turn ignition off. Check fuel filler cap for tightness. Ensure that fuel filler cap is OEM part. Check for damaged or broken seal in fuel filler cap. Replace fuel filler cap or repair seal as necessary. If fuel filler cap is okay, go to next step.
2. Turn ignition off. Connect test mode connector under left side of dash. see scheme 8and see scheme 7. Turn ignition on. Using scan tool, activate drain valve and listen for operating sound from drain valve (underneath right rear corner of vehicle). If operating sound is heard, go to next step. If operating sound is not heard, replace drain valve.
3. Using scan tool, activate purge control solenoid valve and listen for operating sound from purge control solenoid valve. If operating sound is heard, go to next step. If operating sound is not heard, replace purge control solenoid valve.
4. Using scan tool, activate pressure control solenoid valve and listen for operating sound from pressure control solenoid valve. If operating sound is heard, go to next step. If operating sound is not heard, replace pressure control solenoid valve.
5. Turn ignition off. Check for any leaks, holes larger than.02" (0.5 mm), damage, or clogged fuel lines, fuel tank, evaporative canister and evaporative system hoses. Repair or replace defective component as necessary. If there is no damage found, contact authorized Subaru dealership because probable cause is deterioration of multiple parts. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition on. Using voltmeter connected to ground, backprobe ECM 35-pin connector B134 (Baja, Legacy and Outback) or B137 (Forester and Impreza), terminal No. 3. (Scheme 29) If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, go to step 3.
2. Check for poor connection at ECM connector. If connection is okay, circuit has returned to normal. If connection is poor, repair as necessary.
3. Turn ignition off. Disconnect drain valve connector and ECM 35-pin connector. Using an ohmmeter connected to ground, measure resistance at drain valve connector terminal No. 2. (Scheme 31) If resistance is not less than 1 megohm, go to next step. If resistance is less than 1 megohms, locate and repair short to ground in wiring between ECM and drain valve connectors. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
4. Using an ohmmeter, measure resistance between drain valve connector terminal No. 2 and ECM 35-pin connector, terminal No. 3. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and drain valve.
5. Turn ignition off. Disconnect harness connector from drain valve. Using an ohmmeter, measure resistance across drain valve terminals. If resistance is between 10 and 100 ohms, go to next step. If resistance is not between 10 and 100 ohms, replace drain valve.
6. Turn ignition on. Using DVOM connected to ground, measure voltage at drain valve terminal No. 1. If voltage is more than 10 volts, go to next step. 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 drain valve.
7. Check for poor contact at drain valve connector. Repair connector as required. If connection is okay, contact authorized Subaru dealership because probable cause is deterioration of multiple parts. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Connect test mode connector under left side of dash. see scheme 8and see scheme 7. Turn ignition on. Using scan tool, activate drain valve. While activating drain valve, use DVOM connected to ground and backprobe ECM 35-pin connector B134 (Baja, Legacy and Outback) or B137 (Forester and Impreza), terminal No. 3. (Scheme 29) If voltage switches between zero and 10 volts while drain valve is being commanded on and off, go to next step. If voltage does not switch between zero and 10 volts while drain valve is being commanded on and off, circuit has returned to normal. Check for poor terminal contact in ECM connector.
2. Turn ignition on. Using DVOM connected to ground, backprobe ECM 35-pin connector, terminal No. 3. (Scheme 29) If voltage is more than 10 volts, go to step 4. If voltage is not more than 10 volts, go to next step.
3. Check for poor contact at ECM connector. Repair connector as required. If connection is okay, replace ECM.
4. Turn ignition off. Disconnect electrical harness from drain valve. Turn ignition on. Using a DVOM connected to ground, backprobe ECM 35-pin connector, terminal No. 3. (Scheme 29) If voltage is more than 10 volts, locate and repair short to voltage in wiring between ECM and drain valve. After repair, replace ECM. If voltage is not more than 10 volts, go to next step.
5. Turn ignition off. Measure resistance across drain valve terminals. If drain valve resistance is less than one ohm, replace drain valve and ECM. If drain valve resistance is not less than one ohm, go to next step.
6. Check for poor contact at ECM connector. Repair connector as required. If connector is okay, replace ECM. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . If any other DTCs are set, diagnose and repair those DTCs first. If DTC P0451 is only DTC set, turn ignition off. Check fuel filler cap for tightness. Check for disconnected, leaking or plugged vacuum hoses and pipes between fuel tank and fuel tank pressure sensor. Check for disconnected, leaking or plugged air ventilation hoses and pipes between fuel tank and fuel filler pipe. Repair or replace components as necessary. If all components are okay, replace fuel tank pressure sensor. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .

Scheme 37

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Remove and reinstall fuel filler cap. Turn ignition on. Using scan tool, observe fuel tank pressure. If pressure is less than -0.83 in. Hg, go to next step. If pressure is not less than -0.83 in. Hg, system has returned to normal. Check for intermittent open or short in wiring or poor terminal contact in connectors between fuel tank pressure sensor and ECM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Using a DVOM connected to ground, backprobe ECM 28-pin connector B135 (Baja, Legacy and Outback) or B134 (Forester and Impreza), terminal No. 3. (Scheme 29) If voltage is more than 4.5 volts, go to step 4. If voltage is not more than 4.5 volts, go to next step.
3. Using a DVOM connected to ground, backprobe ECM 28-pin connector, terminal No. 3 and wiggle harness and ECM connector. If voltage changes more than 4.5 volts while wiggling harness and ECM connector, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and fuel tank pressure sensor. If voltage does not change more than 4.5 volts while wiggling harness and ECM connector, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
4. Using a DVOM connected to ground, backprobe ECM 28-pin connector, terminal No. 26. If voltage is less than 0.2 volt, go to step 6. If voltage is not less than 0.2 volt, go to next step.
5. Using scan tool, observe fuel tank pressure while wiggling harness and ECM connector. If pressure changes more than -0.83 in. Hg while wiggling harness and ECM connector, check for poor terminal contact at ECM connector. If pressure does not change more than -0.83 in. Hg while wiggling harness and ECM connector, go to next step.
6. Turn ignition off. On wagon models, move rear seat cushion. On all other models, remove rear seat cushion. Disconnect in-line connector located between rear harness and fuel tank harness. Turn ignition on. Measure voltage between ground and ECM-side of in-line connector terminal No. 5 (Baja, Legacy and Outback) or terminal No. 12 (Forester and Impreza). (Scheme 35)or (Scheme 37). If voltage is more than 4.5 volts, go to next step. If voltage is not more than 4.5 volts, locate and repair an open circuit in wiring and check for poor terminal contact in connectors between ECM and 12-pin in-line connector. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
7. Turn ignition off. Disconnect ECM 28-pin connector. Using an ohmmeter, measure resistance between ECM 28-pin connector, terminal No. 19 and ECM-side of in-line connector terminal No. 3 (Baja, Legacy and Outback) or terminal No. 14 (Forester and Impreza). (Scheme 29)and (Scheme 35) or (Scheme 37). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and in-line connector. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
8. Measure resistance between ground and ECM-side of in-line connector terminal No. 3 (Baja, Legacy and Outback) or terminal No. 14 (Forester and Impreza). (Scheme 35)or (Scheme 37). If resistance is more than 500 k/ohms, go to next step. If resistance is not more than 500 k/ohms, locate and repair short to ground in wiring between ECM and in-line connector.
9. Disconnect fuel tank pressure sensor connector. Measure resistance between fuel tank pressure sensor harness connector terminal No. 3 and fuel-pump side of in-line connector terminal No. 5 (Baja, Legacy and Outback) or terminal No. 12 (Forester and Impreza). (Scheme 32), (Scheme 35) and (Scheme 37). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in fuel tank harness.
10. Measure resistance between fuel tank pressure sensor harness connector, terminal No. 1 and fuel-pump side of in-line connector terminal No. 3 (Baja, Legacy and Outback) or terminal No. 2 and No. 14 (Forester and Impreza). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in fuel tank harness.
11. Measure resistance between ground and fuel tank pressure sensor harness connector terminal No. 2 (Baja, Legacy and Outback) or terminal No. 1 (Forester and Impreza). If resistance is more than 500 k/ohms, go to next step. If resistance is not more than 500 k/ohms, locate and repair short to ground in fuel tank harness.
12. Check for poor terminal contact at fuel tank pressure sensor connector. If terminal contact is okay, replace fuel tank pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Remove and reinstall fuel filler cap. Using scan tool, observe fuel tank pressure. If pressure is more than 0.83 in. Hg, go to step 12. If pressure is not more than 0.83 in. Hg, go to next step.
2. Using a DVOM connected to ground, backprobe ECM connector B135 (28-pin connector), terminal No. 3. (Scheme 29) If voltage is more than 4.5 volts, go to step 4. If voltage is not more than 4.5 volts, go to next step.
3. Using DVOM connected to ground, backprobe ECM connector terminal No. 3 while wiggling harness and ECM connector. If voltage changes more than 4.5 volts while wiggling harness and ECM connector, locate and repair poor terminal contact in ECM connector. If voltage does not change more than 4.5 volts while wiggling harness and ECM connector, replace ECM.
4. Using DVOM connected to ground, backprobe ECM connector terminal No. 26. If voltage is less than 0.2 volt, go to step 6. If voltage is not less than 0.2 volt, go to next step.
5. Using scan tool, observe fuel tank pressure while wiggling harness and ECM connector. If pressure changes more than -0.83 in. Hg while wiggling harness and ECM connector, locate and repair poor terminal contact in ECM connector. If pressure does not change more than -0.83 in. Hg while wiggling harness and ECM connector, go to next step.
6. Turn ignition off. Disconnect 6-pin in-line connector located between rear harness and fuel tank harness (under rear seat), nearest fuel tank. Turn ignition on. Measure voltage between ground and ECM-side of 6-pin in-line connector terminal No. 5. (Scheme 35) If voltage is more than 4.5 volts, go to next step. If voltage is not more than 4.5 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and 6-pin in-line connector. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
7. Turn ignition off. Disconnect ECM connector B136. Using an ohmmeter, measure resistance between ECM connector terminal No. 26 and ECM-side of 6-pin in-line connector terminal No. 6. (Scheme 29)and (Scheme 35). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and 6-pin in-line connector.
8. Measure resistance between ECM connector terminal No. 19 and ECM-side of 6-pin in-line connector terminal No. 3. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, located and repair short to ground in wiring between ECM and 6-pin in-line connector.
9. Disconnect fuel tank pressure sensor connector. Measure resistance between fuel tank pressure sensor harness connector terminal No. 2 and fuel-pump side of 6-pin in-line connector terminal No. 6. (Scheme 32)and (Scheme 35). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in fuel tank harness.
10. Measure resistance between fuel tank pressure sensor connector terminal No. 1 and fuel-pump side of 6-pin in-line connector terminal No. 3. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in fuel tank harness.
11. Check for poor terminal contact at fuel tank pressure sensor connector. Repair connector as required. If terminal contact is okay, replace fuel tank pressure sensor.
12. Turn ignition off. Disconnect fuel tank pressure sensor connector. Turn ignition on. Using scan tool, observe fuel tank pressure. If pressure is more than.83 in. Hg, locate and repair short to power in wiring between ECM and fuel tank pressure sensor. If value is not more than.83 in. Hg, replace fuel tank pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Remove and reinstall fuel filler cap. Turn ignition on. Observe fuel tank pressure sensor signal. If pressure is more than 0.83 in. Hg, go to step 12. If pressure is not more than 0.83 in. Hg, go to next step.
2. Turn ignition on. Using DVOM connected to ground, backprobe ECM 28-pin connector B134, terminal No. 3. (Scheme 29) If voltage is more than 4.5 volts, go to step 4. If voltage is not more than 4.5 volts, go to next step.
3. Measure voltage between ground and ECM 28-pin connector, terminal No. 3 while wiggling harness and ECM connector. If voltage changes more than 4.5 volts while wiggling harness and ECM connector, check for poor terminal contact at ECM connector. If voltage does not change more than 4.5 volts while wiggling harness and ECM connector, replace ECM.
4. Using DVOM connected to ground, backprobe ECM 28-pin connector, terminal No. 26. If voltage is less than 0.2 volt, go to step 6. If voltage is not less than 0.2 volt, go to next step.
5. Using scan tool, observe fuel tank pressure while wiggling harness and ECM connector. If pressure changes to more than -0.83 in. Hg while wiggling harness and ECM connector, check for poor contact at ECM connector. If pressure does not change to more than -0.83 in. Hg while wiggling harness and ECM connector, go to next step.
6. Turn ignition off. Disconnect in-line connector located between rear harness and fuel tank harness (under rear seat). Turn ignition on. Using DVOM connected to ground, measure voltage at ECM-side of in-line connector terminal No. 12. (Scheme 37) If voltage is more than 4.5 volts, go to next step. If voltage is not more than 4.5 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and in-line connector. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
7. Turn ignition off. Disconnect ECM 28-pin connector. Using an ohmmeter, measure resistance between ECM connector terminal No. 19 and ECM-side of in-line connector terminal No. 14. (Scheme 29)and (Scheme 37). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and in-line connector.
8. Measure resistance between ECM connector terminal No. 26 and ECM-side of in-line connector terminal No. 13. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, located and repair short in wiring between ECM and in-line connector.
9. Disconnect fuel tank pressure sensor connector. Measure resistance between fuel tank pressure sensor harness connector terminal No. 1 and fuel-pump side of in-line connector terminal No. 13. (Scheme 32)and (Scheme 37). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, located and repair open circuit in fuel tank harness.
10. Measure resistance between fuel tank pressure sensor harness connector terminal No. 2 and fuel-pump side of in-line connector terminal No. 14. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, located and repair open circuit in fuel tank harness.
11. Check for poor terminal contact at fuel tank pressure sensor connector. Repair terminal contact as required. If terminal contact is okay, replace fuel tank pressure sensor.
12. Turn ignition off. Disconnect fuel tank pressure sensor connector. Turn ignition on. Using scan tool, read fuel tank pressure. If pressure is more than.83 in. Hg, locate and repair short to voltage in wiring between ECM and fuel tank pressure sensor. If pressure is not more than.83 in. Hg, replace fuel tank pressure sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any other DTCs are set, diagnose and repair those DTCs first. If DTC P0456 is only DTC set, go to next step.
2. Turn ignition off. Check fuel filler cap for tightness. Tighten or replace as necessary and go to next step.
3. Check for damaged or broken seal between fuel filler cap and fuel filler pipe. Replace fuel filler cap and/or filler pipe as necessary. If seal is okay, go to next step.
4. Turn ignition off. Connect test mode connector under left side of dash. see scheme 8and see scheme 7. Turn ignition on. Using scan tool, activate drain valve and listen for clicking sound as valve is turned on and off. If clicking sound is heard while commanding drain valve on and off, go to next step. If clicking sound is not heard while commanding drain valve on and off, replace drain valve.
5. Using scan tool, activate purge control solenoid valve and listen for clicking sound as valve is turned on and off. If clicking sound is heard while commanding purge control solenoid valve on and off, go to next step. If clicking sound is not heard while commanding purge control solenoid valve on and off, replace purge control solenoid valve.
6. Using scan tool, activate pressure control solenoid valve and listen for clicking sound as valve is turned on and off. If clicking sound is heard while commanding pressure control solenoid valve on and off, go to next step. If clicking sound is not heard while commanding pressure control solenoid valve on and off, replace pressure control solenoid valve.
7. Turn ignition off. Disconnect test mode connector under left side of dash. Check for any leaks, holes larger than.02" (0.5 mm), damage, or clogs in fuel lines, fuel tank, evaporative canister and evaporative system hoses. Repair or replace defective component as necessary. If there is no damage found, contact authorized Subaru dealership because probable cause is deterioration of multiple parts. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any other DTCs are set, diagnose and repair those DTCs first. If DTC P0457 is only DTC set, go to next step.
2. Turn ignition off. Check fuel filler cap for tightness. Tighten or replace as necessary and go to next step.
3. Check for damaged or broken seal between fuel filler cap and fuel filler pipe. Replace fuel filler cap and/or filler pipe as necessary. If seal is okay, go to next step.
4. Turn ignition off. Connect test mode connector under left side of dash. see scheme 8and see scheme 7. Turn ignition on. Using scan tool, activate drain valve and listen for clicking sound as valve is turned on and off. If clicking sound is heard while commanding drain valve on and off, go to next step. If clicking sound is not heard while commanding drain valve on and off, replace drain valve.
5. Using scan tool, activate purge control solenoid valve and listen for clicking sound as valve is turned on and off. If clicking sound is heard while commanding purge control solenoid valve on and off, go to next step. If clicking sound is not heard while commanding purge control solenoid valve on and off, replace purge control solenoid valve.
6. Using scan tool, activate pressure control solenoid valve and listen for clicking sound as valve is turned on and off. If clicking sound is heard while commanding pressure control solenoid valve on and off, go to next step. If clicking sound is not heard while commanding pressure control solenoid valve on and off, replace pressure control solenoid valve.
7. Turn ignition off. Disconnect test mode connector under left side of dash. Check for any leaks, holes larger than.02" (0.5 mm), damage, or clogs in fuel lines, fuel tank, evaporative canister and evaporative system hoses. Repair or replace defective component as necessary. If there is no damage found, contact authorized Subaru dealership because probable cause is deterioration of multiple parts. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Turn ignition switch to the on position. Using a DVOM connected to ground, measure voltage between ECM 35-pin harness connector, terminal No. 29 by backprobing ECM harness connector. (Scheme 29) If voltage is greater than 10 volts, system has returned to normal at this time. If voltage is less than 10 volts, go to next step.
2. Turn ignition switch to off position. Disconnect ECM and purge control solenoid valve harness connectors. Measure resistance between ground and purge control solenoid valve harness connector terminal No. 2. (Scheme 31) If resistance is less than 1 megohm, go to next step. If resistance is greater than 1 megohm, repair short to ground and test system operation.
3. Measure resistance between ECM harness connector terminal No. 29 and purge control solenoid valve harness connector terminal No. 2. If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit between ECM and purge control solenoid harness connectors.
4. Remove the purge control solenoid valve. Measure resistance between purge control solenoid valve terminals No. 1 and No. 2. If resistance is 10-100 ohms, go to next step. If resistance is not 10-100 ohms, replace purge control solenoid valve.
5. Turn ignition switch to on position. Measure voltage between ground and purge control solenoid valve terminal No. 1. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open circuit between main relay and purge control solenoid valve.
6. Check for poor contact at purge control solenoid valve harness connector. If poor contact is found, repair as necessary. If poor contact is not found, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.

1. Turn ignition switch to off position. Connect test mode connector on lower portion of instrument panel on driver's side. see scheme 8and see scheme 7. Turn ignition switch to on position. Operate the purge control solenoid on. Measure voltage between ground and ECM harness 35-pin harness connector B134 (Baja, Legacy and Outback) or B137 (Forester and Impreza), terminal No. 29 by backprobing ECM harness connector. If voltage changes from zero to 10 volts while purge control solenoid is commanded on, system has returned to normal at this time. If voltage does not change from zero to 10 volts while purge control solenoid is commanded on, go to next step.
2. Turn ignition switch to on position. Measure voltage between ground and ECM harness 35-pin harness connector, terminal No. 29. (Scheme 29) If voltage is greater than 10 volts, go to step 4. If voltage is less than 10 volts, go to next step.
3. Check for poor contact in ECM harness connector. If poor contact is found, repair as necessary. If poor contact is not found, replace ECM.
4. Turn ignition switch to off position. Disconnect purge control solenoid valve harness connector. Turn ignition switch to on position. Measure voltage between ground and ECM harness 35-pin harness connector, terminal No. 29. (Scheme 29) If voltage is more than 10 volts, repair short to voltage between ECM and purge control solenoid valve harness connectors. After repair, replace the ECM. If voltage is less than 10 volts, go to next step.
5. Turn ignition switch to off position. Measure resistance between purge control solenoid valve terminals. If resistance is less than one ohm, replace purge control solenoid valve. If resistance is greater than one ohm, go to next step.
6. Check for poor contact in ECM connector. If poor contact is found, repair as necessary. If poor contact is not found, replace the ECM.

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . If DTC P0461 is only DTC set, replace fuel sending unit and fuel sub level sensor assembly. If any DTCs other than P0461 also exist, diagnose and repair those codes first. Do not diagnose DTC P0461. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Check speedometer and tachometer operation. If speedometer and tachometer operate normally, go to next step. If speedometer and tachometer do not operate normally, repair or replace instrument cluster.
2. Turn ignition on. Using DVOM connected to ground, backprobe ECM 28-pin connector B135, terminal No. 25. (Scheme 29) If voltage is not less than 0.12 volt, go to next step. If voltage is less than 0.12 volt, go to step 4.
3. Using scan tool, read fuel level sensor signal while wiggling harness and ECM connector. If voltage changes to more than 0.12 volt while wiggling harness and ECM connector, repair poor terminal contact in ECM connector. If voltage does not change to more than 0.12 volt while wiggling harness and ECM connector, circuit has returned to normal. Check for poor terminal contact in connectors between instrument cluster and ECM.
4. Turn ignition off. Remove service hole cover located in left rear of trunk floor (sedan), or luggage compartment floor (wagon). Disconnect 6-pin in-line connector located between rear harness and fuel tank harness (nearest fuel tank). Turn ignition on. Using DVOM connected to ground, backprobe ECM 28-pin connector, terminal No. 25. (Scheme 29) If voltage is not less than 0.12 volt, go to step 6. If voltage is less than 0.12 volt, go to next step.
5. Turn ignition off. Disconnect ECM connector B135 (28-pin connector) and 30-pin instrument panel electrical harness connector. (Scheme 39) Using an ohmmeter connected to ground, backprobe ECM connector B134 (28-pin connector), terminal No. 25. (Scheme 29) If resistance is more than one megohm, go to next step. If resistance is not more than one megohm, locate and repair short to ground in wiring between ECM and instrument cluster. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
6. Measure resistance between ECM connector B134 (28-pin connector), terminal No. 25 and instrument cluster connector, terminal No. 3. If resistance is not less than 10 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and instrument cluster. If resistance is less than 10 ohms, repair or replace instrument cluster.
7. Turn ignition off. Disconnect fuel sub level sensor 2-pin connector. Measure resistance between ground and fuel sub level sensor connector, terminal No. 1. (Scheme 31) If resistance is more than one megohm, go to next step. If resistance is not more than one megohm, locate and repair short to ground in fuel tank harness.
8. Disconnect electrical connector at fuel pump. With fuel sub level sensor 2-pin connector still disconnected, use ohmmeter to measure resistance between ground and fuel sub level sensor connector, terminal No. 2. If resistance is not more than one megohm, locate and repair short to ground in fuel tank harness. If resistance is more than one megohm, go to next step.
9. Remove fuel pump assembly from fuel tank. With fuel level sensor float set to full position, measure resistance between terminals No. 3 and No. 6 of fuel level sensor. If resistance is between 0.5 and 2.5 ohms, go to next step. If resistance is not between 0.5 and 2.5 ohms, replace fuel level sensor.
10. Remove fuel sub level sensor. With fuel sub level sensor float set to full position, measure resistance between terminals of fuel sub level sensor. If resistance is between 0.5 and 2.5 ohms, repair poor terminal contact in connectors between ECM and instrument cluster. If resistance is not between 0.5 and 2.5 ohms, replace fuel sub level sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Check speedometer and tachometer operation. If speedometer and tachometer operate normally, go to next step. If speedometer and tachometer do not operate normally, repair or replace instrument cluster.
2. Turn ignition on. Using DVOM connected to ground, backprobe ECM 28-pin connector B134, terminal No. 25. (Scheme 29) If voltage is not less than 0.12 volt, go to next step. If voltage is less than 0.12 volt, go to step 4.
3. Using scan tool, read fuel level sensor signal while wiggling harness and ECM connector. If voltage changes to more than 0.12 volt while wiggling harness and ECM connector, repair poor terminal contact in ECM connector. If voltage does not change to more than 0.12 volt while wiggling harness and ECM connector, circuit has returned to normal. Check for poor terminal contact in connectors between instrument cluster and ECM.
4. Turn ignition off. Remove service hole cover located in left rear of trunk floor (sedan), or luggage compartment floor (wagon). Disconnect 12-pin in-line connector located between rear harness and fuel tank harness (nearest fuel tank). Turn ignition on. Using DVOM connected to ground, backprobe ECM 28-pin connector, terminal No. 25. (Scheme 29) If voltage is not less than 0.12 volt, go to step 6. If voltage is less than 0.12 volt, go to next step.
5. Turn ignition off. Disconnect ECM connector B134 (28-pin connector) and 14-pin instrument panel electrical harness connector (30-pin on Impreza and Outback Sport). (Scheme 38)and (Scheme 39). Using an ohmmeter connected to ground, backprobe ECM connector B134 (28-pin connector), terminal No. 25. If resistance is more than one megohm, go to next step. If resistance is not more than one megohm, locate and repair short to ground in wiring between ECM and instrument cluster. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
6. Measure resistance between ECM connector B134 (28-pin connector), terminal No. 25 and instrument cluster connector, terminal No. 3 (No. 2 on Impreza and Outback Sport). (Scheme 29)and (Scheme 38) or (Scheme 39). If resistance is not less than 10 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and instrument cluster. If resistance is less than 10 ohms, repair or replace instrument cluster.
7. Turn ignition off. Disconnect fuel sub level sensor 2-pin connector. Measure resistance between ground and fuel sub level sensor connector, terminal No. 1. (Scheme 31) If resistance is more than one megohm, go to next step. If resistance is not more than one megohm, locate and repair short to ground in fuel tank harness.
8. Disconnect electrical connector at fuel pump. With fuel sub level sensor 2-pin connector still disconnected, use ohmmeter to measure resistance between ground and fuel sub level sensor connector terminal No. 2. If resistance is not more than one megohm, locate and repair short to ground in fuel tank harness. If resistance is more than one megohm, go to next step.
9. Remove fuel pump assembly from fuel tank. With fuel level sensor float set to full position, measure resistance between terminals No. 2 and No. 3 of fuel level sensor. If resistance is between 0.5 and 2.5 ohms, go to next step. If resistance is not between 0.5 and 2.5 ohms, replace fuel level sensor.
10. Remove fuel sub level sensor. With fuel sub level sensor float set to full position, measure resistance between terminals of fuel sub level sensor. If resistance is between 0.5 and 2.5 ohms, repair poor terminal contact in connectors between ECM and instrument cluster. If resistance is not between 0.5 and 2.5 ohms, replace fuel sub level sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Scheme 38

Scheme 39

Scheme 40

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Check speedometer and tachometer operation. If speedometer and tachometer operate normally, go to next step. If speedometer and tachometer do not operate normally, repair or replace instrument cluster.
2. Turn ignition on. Using DVOM connected to ground, backprobe ECM connector B135 (28-pin connector), terminal No. 25. (Scheme 29) If voltage is more than 4.75 volts, go to next step. If voltage is not more than 4.75 volts, system has returned to normal. Check for poor terminal contact in connectors between fuel pump, ECM and instrument cluster.
3. Turn ignition off. Disconnect 30-pin instrument panel electrical harness connector and ECM connector B135 (28-pin connector). (Scheme 29)and (Scheme 39). Using DVOM connected to ground, backprobe ECM connector B135 (28-pin connector), terminal No. 25. If voltage is more than 4.75 volts, go to next step. If voltage is not more than 4.75 volts, locate and repair short in wiring between ECM and instrument cluster. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
4. Turn ignition off. Remove service hole cover located in left rear of trunk floor (sedan), or luggage compartment floor (wagon). Disconnect 6-pin in-line connector located between rear harness and fuel tank harness (nearest fuel tank). Measure resistance between ECM connector B135 (28-pin connector), terminal No. 25 and ECM-side 6-pin in-line connector, terminal No. 7. (Scheme 29)and (Scheme 40). If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring between ECM and fuel tank.
5. Measure resistance between ground and ECM-side of 6-pin in-line connector terminal No. 5. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between fuel tank and ground.
6. Disconnect 6-pin electrical connector from fuel level sensor. Using an ohmmeter, measure resistance between fuel level sensor terminal No. 3 and fuel pump-side 6-pin in-line connector terminal No. 5. (Scheme 36)and (Scheme 40). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring and check for poor terminal contact in connectors between in-line harness connector and fuel level sensor.
7. Turn ignition off. Disconnect 2-pin connector from fuel sub level sensor. Using an ohmmeter, measure resistance between 6-pin fuel level sensor harness connector terminal No. 6 and fuel sub level sensor connector terminal No. 2. (Scheme 31)and (Scheme 36). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring between fuel level sensor and fuel sub level sensor.
8. Measure resistance between 2-pin fuel sub level sensor harness connector terminal No. 1 and fuel pump-side of 6-pin in-line connector terminal No. 6. (Scheme 31)and (Scheme 36). If resistance is less than 10 ohms, go to next step. If resistance is not less than 10 ohms, locate and repair open circuit in wiring between fuel tank harness and fuel sub level sensor.
9. Remove fuel pump assembly from fuel tank. While moving fuel level sensor float up and down, measure resistance across terminals No. 3 and No. 6 of fuel level sensor. If resistance is more than 54.5 ohms, replace fuel level sensor. If resistance is not more than 54.5 ohms, go to next step.
10. Remove fuel sub level sensor. While moving fuel sub level sensor float up and down, measure resistance across fuel sub level sensor terminals. If resistance is more than 41.5 ohms, replace fuel sub level sensor. If resistance is not more than 41.5 ohms, replace instrument cluster. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Check speedometer and tachometer operation. If speedometer and tachometer operate normally, go to next step. If speedometer and tachometer do not operate normally, repair or replace instrument cluster.
2. Turn ignition on. Using DVOM connected to ground, backprobe ECM connector B134 (28-pin connector), terminal No. 25. (Scheme 29) If voltage is more than 4.75 volts, go to next step. If voltage is not more than 4.75 volts, system has returned to normal. Check for poor terminal contact in connectors between fuel pump, ECM and instrument cluster.
3. Turn ignition off. Disconnect 14-pin instrument panel electrical harness connector and ECM connector B134 (28-pin connector). (Scheme 29)and (Scheme 38). Using DVOM connected to ground, backprobe ECM connector B134 (28-pin connector), terminal No. 25. If voltage is more than 4.75 volts, go to next step. If voltage is not more than 4.75 volts, locate and repair short in wiring between ECM and instrument cluster. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
4. Turn ignition off. Remove service hole cover located in left rear of trunk floor (sedan), or luggage compartment floor (wagon). Disconnect 16-pin in-line connector located between rear harness and fuel tank harness (nearest fuel tank). Measure resistance between ECM connector B134 (28-pin connector), terminal No. 25 and ECM-side 16-pin in-line connector terminal No. 7. (Scheme 29)and (Scheme 37). If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring between ECM and fuel tank.
5. Measure resistance between ground and ECM-side of 16-pin in-line connector terminal No. 16 (No. 11 on Impreza and Outback Sport). If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between fuel tank and ground.
6. Disconnect 6-pin electrical connector from fuel level sensor. Using an ohmmeter, measure resistance between fuel level sensor terminal No. 6 (No. 2 on Impreza and Outback Sport) and fuel pump-side 16-pin in-line connector terminal No. 16 (No. 11 on Impreza and Outback Sport). (Scheme 35)and (Scheme 37). If resistance is less than 10 ohms, go to next step. If resistance is not less than 10 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between in-line harness connector and fuel level sensor.
7. Turn ignition off. Disconnect 2-pin connector from fuel sub level sensor. Using an ohmmeter, measure resistance between 6-pin fuel level sensor harness connector terminal No. 1 (No. 3 on Impreza and Outback Sport) and fuel sub level sensor connector terminal No. 2. (Scheme 31)and (Scheme 35). If resistance is less than 10 ohms, go to next step. If resistance is not less than 10 ohms, locate and repair open circuit in wiring between fuel level sensor and fuel sub level sensor.
8. Measure resistance between 2-pin fuel sub level sensor harness connector terminal No. 1 and fuel pump-side of 16-pin in-line connector terminal No. 7. (Scheme 31)and (Scheme 37). If resistance is less than 10 ohms, go to next step. If resistance is not less than 10 ohms, locate and repair open circuit in wiring between fuel tank harness and fuel sub level sensor.
9. Remove fuel pump assembly from fuel tank. While moving fuel level sensor float up and down, measure resistance across terminals No. 3 and No. 2 of fuel level sensor. If resistance is more than 54.5 ohms, replace fuel level sensor. If resistance is not more than 54.5 ohms, go to next step.
10. Remove fuel sub level sensor. While moving fuel sub level sensor float up and down, measure resistance across fuel sub level sensor terminals. If resistance is more than 41.5 ohms, replace fuel sub level sensor. If resistance is not more than 41.5 ohms, replace instrument cluster. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If DTC P0464 is only DTC set, go to next step. If DTC P0462 or P0463 also exist, diagnose and repair those codes first.
2. Remove fuel pump assembly from fuel tank. While moving fuel level sensor float up and down, measure resistance across terminals No. 3 and No. 6 (No. 2 and No. 3 on Forester, Impreza and Outback Sport) of fuel level sensor (component side). If resistance changes smoothly, go to next step. If resistance does not change smoothly, replace fuel level sensor.
3. Remove fuel pump assembly from fuel tank. While moving fuel sub level sensor float up and down, measure resistance across terminals No. 1 and No. 2 of fuel sub level sensor (component side). If resistance changes smoothly, repair poor terminal contact in connectors between ECM and instrument cluster. If resistance does not change smoothly, replace fuel sub level sensor. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

Note. To prevent abnormal cooling operation, ensure vehicle has not been placed close to a wall or another vehicle with engine idling. The OBD system may detect this as a malfunction.

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . If any other DTCs exist, repair those first. If DTC P0483 is only DTC set, check cooling system fan and fan motor operation and repair as necessary. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .

Note. For diagnostics of DTC P0502, see DTC P0503: VEHICLE SPEED SENSOR INTERMITTENT/ERRATIC/HIGH .

1. Check if vehicle is equipped with A/T. If vehicle is equipped with A/T, go to next step. If vehicle is not equipped with A/T, go to step 3.
2. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If DTC P0720 exists, check front speed sensor circuit. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If DTC P0720 is not set, go to next step.
3. Check speedometer for proper operation. If speedometer operates properly, go to next step. If speedometer does not operate properly, check front vehicle speed sensor and speedometer. See appropriate GAUGES & INSTRUMENT PANELS article in ELECTRICAL.
4. Turn ignition switch to off position. Disconnect instrument cluster 30-pin harness connector. Measure resistance between ECM harness 20-pin connector B137, terminal No. 10 and instrument cluster 30-pin harness connector, terminal No. 13. (Scheme 29)and (Scheme 39). If resistance is less than 10 ohms, repair poor contact in ECM harness connector. If resistance is greater than 10 ohms, repair open between ECM harness connector and instrument cluster harness connector.

1. Check if vehicle is equipped with A/T. If vehicle is equipped with A/T, go to next step. If vehicle is not equipped with A/T, go to step 3.
2. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If DTC P0720 exists, check front speed sensor circuit. See appropriate AUTOMATIC TRANSMISSIONS article. If DTC P0720 is not set, go to next step.
3. Check speedometer for proper operation. If speedometer operates properly, go to next step. If speedometer does not operate properly, check front vehicle speed sensor and speedometer. See appropriate article in AUTOMATIC TRANSMISSIONS.
4. Turn ignition switch to off position. Disconnect instrument cluster 10-pin harness connector (30-pin on Forester). Measure resistance between ECM harness 28-pin connector B135, terminal No. 24 and instrument cluster 10-pin harness connector, terminal No. 2 (terminals No. 10 and No. 2 on Forester). (Scheme 29)and 4 or (Scheme 39). If resistance is less than 10 ohms, repair poor contact in ECM harness connector. If resistance is greater than 10 ohms, repair open between ECM harness connector and instrument cluster harness connector.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P0506 exist, diagnose and repair those DTCs. Do not diagnose DTC P0506. If DTC P0506 is only DTC set, go to next step.
2. Turn ignition off. Remove IAC solenoid valve from throttle body. Remove throttle body from intake manifold. Using an air gun, force air into IAC solenoid valve installation area. Ensure air escapes from interior of throttle body. If air escapes from interior of throttle body, replace IAC solenoid valve. If air does not escape from interior of throttle body, replace throttle body. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P0507 are present, diagnose and repair those DTCs. Do not diagnose DTC P0507. If DTC P0507 is only DTC set, go to next step.
2. Start engine and allow to idle. Check intake manifold, idle air control (IAC) solenoid valve and throttle body for loose installation or defective gaskets. Check by-pass hoses for loose connection or cracking and vacuum hoses for disconnection or cracking. Repair as necessary and go to next step. If no damage is noted, go to next step.
3. Turn ignition off. Check throttle cable play and adjust as necessary. See «ON-VEHICLE ADJUSTMENTS»(ref-157280) article. Remove IAC solenoid valve from throttle body. Check for foreign particles in by-pass air line. Remove foreign particles as necessary. If no foreign particles are present, replace IAC solenoid valve. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

Note. On M/T vehicles, depress and release clutch pedal while turning ignition to on position.

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . Place inhibitor switch in each position and attempt to start engine. If starter operates in each inhibitor switch position, repair short to power in starter circuit. If starter does not operate in each inhibitor switch position, check starter circuit. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P0519 exist, diagnose and repair those DTCs. Do not diagnose DTC P0519. If DTC P0519 is only DTC set, go to next step.
2. Turn ignition switch to on position. Start engine and allow to idle. Check intake manifold, idle air control (IAC) solenoid valve and throttle body for loose installation or defective gaskets. Check by-pass hoses for loose connection or cracking and vacuum hoses for disconnection or cracking. Repair as necessary. If no problems were found, go to next step.
3. Turn ignition off. Check throttle cable play and adjust as necessary. See «ON-VEHICLE ADJUSTMENTS»(ref-157280) article. Remove IAC solenoid valve from throttle body. Check for foreign particles in by-pass air line. Remove foreign particles as necessary. If no foreign particles are present, replace IAC solenoid valve. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000) .

1. Turn ignition switch to off position. Disconnect TCM and cruise control module harness connectors. Measure resistance between TCM harness 24-pin connector B55, terminal No. 22 (with sport shift) or B54, terminal No. 11 (without sport shift) and cruise control module 20-pin harness connector, terminal No. 3. (Scheme 41) If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit between TCM and cruise control module. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Ensure ignition is in the off position. Measure resistance between ground and TCM 24-pin harness connector B54, terminal No. 11 (without sport shift) or B55, terminal No. 22 (with sport shift). If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground between TCM and cruise control module.
3. Reconnect TCM and cruise control module harness connectors. Raise and suitably support vehicle or set the vehicle on free rollers. Start engine and turn on main cruise control switch. Place vehicle in drive and slowly increase vehicle speed to 31 MPH. Turn cruise control command switch to on. Measure voltage between ground and TCM 24-pin harness connector B54, terminal No. 11 (without sport shift) or B55, terminal No. 22 (with sport shift) by backprobing TCM connector. If voltage is less 1 volt, go to next step. If voltage is greater than 1 volt, check cruise control circuit. See appropriate CRUISE CONTROL article in ACCESSORIES & EQUIPMENT.
4. Check for poor contact in TCM harness connector. If poor contact is found, repair as necessary. If poor contact is not found, replace TCM and test system operation. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Turn ignition switch to off position. Disconnect TCM and cruise control module harness connectors. Measure resistance between TCM harness 24-pin connector terminal No. 11 and cruise control module 20-pin harness connector terminal No. 3. (Scheme 41) If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit between TCM and cruise control module. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Ensure ignition is in the off position. Measure resistance between ground and TCM 24-pin harness connector terminal No. 11. If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground between TCM and cruise control module.
3. Reconnect TCM and cruise control module harness connectors. Raise and suitably support vehicle or set the vehicle on free rollers. Start engine and turn on main cruise control switch. Place vehicle in drive and slowly increase vehicle speed to 31 MPH. Turn cruise control command switch to on. Measure voltage between ground and TCM 24-pin harness connector terminal No. 11 by backprobing TCM connector. If voltage is less 1 volt, go to next step. If voltage is greater than 1 volt, check cruise control circuit. See appropriate CRUISE CONTROL article in ACCESSORIES & EQUIPMENT.
4. Check for poor contact in TCM harness connector. If poor contact is found, repair as necessary. If poor contact is not found, replace TCM and test system operation. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Scheme 41

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . If any DTCs other than P0604 exist, repair those DTCs first. Do not diagnose DTC P0604. If only DTC P0604 exists, check for poor contact at ECM harness connectors. Repair as necessary. If contact at ECM harness connectors is okay, replace ECM. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .

1. Turn ignition switch to off position. Connect the test mode connectors at lower instrument panel on drivers side. see scheme 7and see scheme 8. Turn ignition switch to on position. Using scan tool, operate radiator fan relay on. Measure voltage between ground and ECM 35-pin harness connector terminal No. 14 by backprobing ECM connector. If voltage changes from zero to 10 volts while fan relay is turned on, repair poor contact in ECM connector. If voltage does not change from zero to 10 volts while fan relay is turned on, go to next step.
2. Turn ignition switch to off position. Disconnect ECM harness connectors. Measure resistance between ground and ECM 35-pin harness connector B134, terminal No. 14. If resistance is less than 1 megohm, repair short to ground and test system operation. If resistance is greater than 1 megohm, go to next step.
3. Remove main fan relay from A/C relay holder. Turn ignition switch to on position. Measure voltage between relay cavity terminal No. 5 and ground. (Scheme 42) If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open circuit between ignition switch and relay cavity terminal No. 5.
4. Turn ignition switch to off position. Measure resistance of relay terminals No. 5 and No. 7. If resistance is 87-107 ohms, go to step next step. If resistance is not 87-107, replace main fan relay and test system operation.
5. Ensure ignition switch is in the off position. Measure resistance between ECM 35-pin harness connector terminal No. 14 and relay cavity terminal No. 7. (Scheme 29)and (Scheme 42). If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit between ECM and main relay harness connector.
6. Check for poor contact in ECM and main fan relay connectors. If poor contact is found, repair as necessary. If poor contact is not found, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.

Scheme 42

1. Turn ignition switch to off position. Connect the test mode connectors at lower instrument panel on drivers side. see scheme 8and see scheme 7. Turn ignition switch to on position. Using scan tool, operate radiator fan relay on. Measure voltage between ground and ECM 35-pin harness connector terminal No. 14 by backprobing ECM connector. If voltage changes from zero to 10 volts while fan relay is turned on, repair poor contact in ECM connector. If voltage does not change from zero to 10 volts while fan relay is turned on, go to next step.
2. Turn ignition switch to off position. Disconnect ECM harness connectors. Measure resistance between ground and ECM 35-pin harness connector B137, terminal No. 14. (Scheme 29) If resistance is less than 10 ohms, repair short to ground and test system operation. If resistance is greater than 10 ohms, go to next step.
3. Remove main fan relay from A/C relay holder. Turn ignition switch to on position. Measure voltage between relay cavity terminal No. 34 and ground. (Scheme 43) If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open circuit between ignition switch and relay cavity terminal No. 34.
4. Turn ignition switch to off position. Measure resistance of cavity terminals No. 32 and No. 34. If resistance is 87-107 ohms, go to step next step. If resistance is not 87-107, replace main fan relay and test system operation.
5. Ensure ignition switch is in the off position. Measure resistance between ECM 35-pin harness connector terminal No. 14 and relay cavity terminal No. 32. See and (Scheme 43). If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit between ECM and main relay harness connector.
6. Check for poor contact in ECM and main fan relay connectors. If poor contact is found, repair as necessary. If poor contact is not found, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.

Scheme 43

1. Turn the ignition switch to off position. Connect the test mode connectors at lower instrument panel on driver's side. see scheme 7 Turn ignition switch to on position. Using scan tool operate the radiator fan relay. Measure the voltage between ground and ECM 35-pin harness connector B134, terminal No. 14. (Scheme 29) If voltage changes from zero to 10 volts while relay is operated on, system has returned to normal condition at this time. If voltage does not change from zero to 10 volts while relay is operated on, go to next step.
2. Turn the ignition switch to off position. Remove the main fan relay. On vehicles with A/C, remove the sub fan relay. Disconnect test mode connectors. Turn ignition switch to on position. Measure voltage between ground and ECM 35-pin harness connector terminal No. 14. (Scheme 29) If voltage is greater than 10 volts, repair short to power in appropriate wire and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If voltage is less than 10 volts, go to next step.
3. Ensure the ignition switch is in the off position. Measure resistance between main relay terminals No. 5 and No. 7. (Scheme 42) If resistance is less than one ohm, replace main relay. If resistance is greater than one ohm, go to next step.
4. Measure resistance between sub relay terminals No. 22 and No. 24. If resistance is less than one ohm, replace sub fan relay. If resistance is greater than one ohm, go to next step.
5. Check for poor contact in ECM connector. If poor contact is found, repair as necessary. If contact is okay, replace ECM. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Turn the ignition switch to off position. Connect the test mode connectors at lower instrument panel on driver's side. see scheme 8 Turn ignition switch to on position. Using scan tool operate the radiator fan relay. Measure the voltage between ground and ECM 35-pin harness connector B137 terminals No. 13 and No. 14. (Scheme 29) If voltage changes from zero to 10 volts while relay is operated on, system has returned to normal condition at this time. If voltage does not change from zero to 10 volts while relay is operated on, go to next step.
2. Turn the ignition switch to off position. Remove the main fan relay. On vehicles with A/C, remove the sub fan relay. Disconnect test mode connectors. Turn ignition switch to on position. Measure voltage between ground and ECM 35-pin harness connector terminals No. 13 and No. 14. If voltage is greater than 10 volts, repair short to power in appropriate wire and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If voltage is less than 10 volts, go to next step.
3. Ensure the ignition switch is in the off position. Measure resistance between main relay terminals No. 30 and No. 31 (Forester) or terminals No. 25 and No. 26 (Impreza and Outback Sport). (Scheme 43) If resistance is less than one ohm, replace main relay. If resistance is greater than one ohm, go to next step.
4. Measure resistance between sub relay terminals No. 28 and No. 29 (Forester) or terminals No. 17 and No. 18 (Impreza and Outback Sport). (Scheme 43) If resistance is less than one ohm, replace sub fan relay. If resistance is greater than one ohm, go to next step.
5. Check for poor contact in ECM connector. If poor contact is found, repair as necessary. If contact is okay, replace ECM. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Press brake pedal and verify the brake lights are working properly. If brake lights are working properly, go to next step. If brake lights are not working properly, repair brake light circuit. See EXTERIOR LIGHTS article in SYSTEM WIRING DIAGRAMS.
2. Disconnect brake light switch and TCM 24-pin harness connector. On Forester, Impreza and Outback Sport, measure resistance between TCM 24-pin harness connector terminal No. 24 and brake light switch 2-pin harness connector terminal No. 1 (without cruise control) or TCM 24-pin harness connector terminal No. 24 and brake light switch 4-pin harness connector terminal No. 3 (with cruise control). On Baja, Legacy and Outback, measure resistance between TCM 24-pin harness connector terminal No. 24 and brake light switch 2-pin harness connector terminal No. 2 (without cruise control) or TCM 24-pin harness connector terminal No. 24 and brake light switch 4-pin harness connector terminal No. 3 (with cruise control). (Scheme 30), (Scheme 31) and (Scheme 41). If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit between TCM and brake light switch connector.
3. Measure resistance between ground and TCM 24-pin harness connector terminal No. 24. (Scheme 41) If resistance is greater than 1 megohm, go to next step. If resistance is less than 1 megohm, repair short to ground and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
4. Reconnect TCM and brake light switch harness connectors. Measure voltage between ground and TCM 24-pin harness connector terminal No. 24 by backprobing terminal No. 24 at TCM. If voltage is less than one volt, go to next step. If voltage is greater than one volt, adjust or replace brake light switch as necessary and test system operation.
5. Measure voltage between ground and TCM 24-pin harness connector terminal No. 24 by backprobing terminal No. 24 at TCM. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, adjust or replace brake light switch and test system operation.
6. Check for poor contact in TCM harness connector. If poor contact is found, repair as necessary. If contact is okay, replace TCM.

Note. For DTC P0731 diagnosis, see DTC P0734: GEAR 4 INCORRECT RATIO (A/T) .

Note. For DTC P0732 diagnosis, see DTC P0734: GEAR 4 INCORRECT RATIO (A/T) .

Note. For DTC P0733 diagnosis, see DTC P0734: GEAR 4 INCORRECT RATIO (A/T) .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P0731, P0732, P0733 or P0734 are present, diagnose those DTCs first. If no other DTCs are present, go to next step.
2. Check the TP sensor circuit. Perform test for DTC 31 in appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If a problem is found, repair as necessary. If no problem is found, go to next step.
3. Check the front vehicle speed sensor circuit. Perform test for DTC 33 in appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If a problem is found, repair as necessary. If no problem is found, go to next step.
4. Check the torque converter turbine speed sensor circuit. Perform test for DTC 36 in appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If a problem is found, repair as necessary. If no problem is found, go to next step.
5. Check for poor contact in TCM harness connector. If poor contact is found, repair as necessary. If contact is okay, go to next step.
6. Check automatic transmission for internal mechanical failures. If mechanical failures are found, repair automatic transmission as necessary. If no mechanical failures are found, replace TCM and test system operation.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P0741 is present, diagnose those DTCs first. If no other DTCs are present, go to next step.
2. Check the lock-up duty solenoid circuit. Perform test for DTC 77 in appropriate AUTOMATIC TRANSMISSION article. If a problem is found, repair as necessary. If no problem is found, go to next step.
3. Check the TP sensor circuit. Perform test for DTC 31 in appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If a problem is found, repair as necessary. If no problem is found, go to next step.
4. Check the torque converter turbine speed sensor circuit. Perform test for DTC 36 in appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If a problem is found, repair as necessary. If no problem is found, go to next step.
5. Check the engine speed input circuit. Perform test for DTC 11 in appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If a problem is found, repair as necessary. If no problem is found, go to next step.
6. Check inhibitor switch circuit. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If problem is found, repair as necessary. If no problem is found, go to next step.
7. Check brake light switch circuit. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If problem is found, repair as necessary. If no problem is found, go to next step.
8. Check Automatic Transmission Fluid (ATF) temperature sensor circuit. Perform test for DTC 27 in appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If a problem is found, repair as necessary. If no problem is found, go to next step.
9. Check for poor contact in TCM harness connector. If poor contact is found, repair as necessary. If contact is okay, go to next step.
10. Check automatic transmission for internal mechanical failures. If mechanical failures are found, repair automatic transmission as necessary. If no mechanical failures are found, replace TCM and test system operation.

Scheme 44

Scheme 45

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any DTCs other than P0851 is present, diagnose those DTCs first. If no other DTCs are present, go to next step.
2. Turn ignition switch to on position. Place the gearshift lever in any position other than "P" or "N". Measure voltage between ground and ECM harness connector B136, terminal No. 21 by backprobing terminal at ECM harness connector. (Scheme 29) If voltage is 4.5-5.5 volts, the system has returned to normal at this time. If voltage is not 4.5-5.5 volts, go to next step.
3. Turn ignition switch to off position. Disconnect ECM 26-pin harness connector and TCM 12-pin harness connector B136 and transmission harness connector T3. Measure resistance between ground and ECM 26-pin harness connector B136 terminal No. 21. If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
4. Disconnect Transmission harness connector T7 from inhibitor switch. Measure resistance between ground and Transmission harness connector T7 12-pin harness connector terminal No. 12. (Scheme 44) If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
5. Ensure the ignition switch is in the off position and gearshift lever is in any position other than "P" or "N". Measure resistance at inhibitor switch terminals No. 7 and No. 12 (component side). (Scheme 45) If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, replace inhibitor switch.
6. Check transmission cable connection to inhibitor switch. If any problem is found with transmission selector cable, repair as necessary. If no problem is found with transmission cable connection, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.

1. Turn ignition switch to on position. Place gearshift lever in Neutral. Measure voltage between ground and ECM 26-pin harness connector terminal No. 21. (Scheme 29) If voltage is greater than 10 volts (5 volts on Baja, Legacy and Outback), go to next step. If voltage is less than 10 volts (5 volts on Baja, Legacy and Outback), go to step 4.
2. Place gearshift lever in any position other than Neutral. Measure voltage between ground and ECM 26-pin harness connector terminal No. 21. If voltage is less than one volt, go to next step. If voltage is greater than one volt, go to step 4.
3. Check for poor contact in ECM harness connector. If poor contact is found, repair as necessary. If contact is okay, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
4. Turn ignition switch to off position. Disconnect transmission 2-pin harness connector. Place gearshift lever in Neutral. Measure resistance between transmission 2-pin connector terminals (component side) and between transmission 2-pin harness connector terminals No. 1 and No. 2. If resistance is greater than 1 megohm, go to next step. If resistance is less than one megohm, repair short circuit or replace neutral switch. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
5. Place gearshift lever in any position other than Neutral. Measure resistance between transmission 2-pin harness connector terminals. If resistance is greater than one ohm, go to next step (on Baja, Legacy and Outback, go to step 9 ). If resistance is greater than one ohm, repair short to ground or replace neutral switch. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
6. Ensure ignition switch is in the off position. Measure resistance between ground and ECM 26-pin harness connector terminal No. 21. (Scheme 29) If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground between ECM and transmission harness connectors. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
7. Disconnect ECM 26-pin harness connector. Measure resistance between ECM 26-pin harness connector terminal No. 21 and neutral switch 2-pin connector terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit between ECM and transmission harness connectors.
8. Measure resistance between ground and transmission 2-pin harness connector terminal No. 2. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit between transmission harness connector and engine ground terminal.
9. Check for poor contact in transmission harness connector. If poor contact is found, repair as necessary. If contact is okay, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any DTCs other than P0852 is present, diagnose those DTCs first. If no other DTCs are present, go to next step.
2. Turn ignition switch to on position. Measure voltage between ground and ECM 26-pin harness connector terminal No. 21. (Scheme 29) If voltage is less than one volt, go to next step. If voltage is greater than one volt, go to step 5.
3. Measure voltage between ground and ECM 26-pin harness connector terminal No. 21. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, go to step 5.
4. Check for poor contact in ECM harness connector. If poor contact is found, repair as necessary. If contact is okay, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
5. Measure voltage between ground and ECM 26-pin harness connector terminal No. 21. (Scheme 29) If voltage is greater than 10 volts, repair short to voltage between ECM and inhibitor switch connector. If voltage is less than 10 volts, go to next step.
6. Turn ignition switch to off position. Disconnect ECM and inhibitor switch harness connectors. Measure resistance between ECM 26-pin harness connector terminal No. 21 and inhibitor switch 12-pin harness connector terminal No. 12. (Scheme 29)and (Scheme 44). If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit in between ECM and inhibitor switch harness connectors.
7. Ensure ignition switch is in the off position. Measure resistance between ground and inhibitor switch 12-pin harness connector terminal No. 7. (Scheme 44) If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open between inhibitor switch and starter ground line.
8. Ensure gear shift lever is in any position other than "P" or "N". Measure resistance between inhibitor switch connector terminals No. 7 and No. 12 (component side). If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, replace inhibitor switch and test system operation.
9. Check transmission shift cable connections to inhibitor switch. If any problems are found, repair as necessary. If no problems are found, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.

1. Turn ignition switch to on position. Ensure transmission is in Neutral. Measure voltage between ground and ECM 26-pin harness connector terminal No. 21. (Scheme 29) If voltage is less than 5 volts, go to step 4. If voltage is greater than 5 volts, go to next step.
2. Place transmission in any position other than Neutral. Measure voltage between ground and ECM 26-pin harness connector terminal No. 21. If voltage is less than one volt, go to next step. If voltage is greater than one volt, go to step 5.
3. Check for poor contact in ECM harness connector. If poor contact is found, repair as necessary. If contact is okay, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
4. Ensure transmission is in any position other than Neutral. Measure resistance between transmission 2-pin harness connector terminals No. 1 and No. 2 (component side). If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit or replace neutral switch.
5. Disconnect ECM 26-pin harness connector. Measure resistance of harness between ECM 26-pin harness connector terminal No. 21 and transmission 2-pin harness connector terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit between ECM and transmission harness connector. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
6. Measure resistance of harness between ground and transmission 2-pin harness connector terminal No. 2. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open between transmission 2-pin harness connector and engine ground. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
7. Check for poor contact in transmission harness connector. If poor contact is found, repair as necessary. If contact is okay, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.

1. Start and warm-up engine until the radiator the radiator fan turns on. Drive vehicle and verify the automatic transmission shift control is operating properly. If shift control is operating properly, go to next step. If shift control does not operate properly, replace the TCM and test system operation.
2. Check vehicle for aftermarket accessories such as a car phone or CB radio. If aftermarket accessories are found, verify proper installation of aftermarket components and their grounding lines. If no aftermarket accessories are found, replace TCM and test system operation.

1. Turn ignition switch to on position. Measure the voltage between ground and ECM 20-pin harness connector terminal No. 19. (Scheme 29) If voltage is less than 1 volt, go to next step. If voltage is greater than one volt, system has returned to normal at this time.
2. Turn ignition to off position. Disconnect the ECM and TCM harness connectors. Measure resistance between ground and ECM 20-pin harness connector terminal No. 19. If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground between ECM and TCM harness connectors.
3. Reconnect ECM harness connector. Turn ignition switch to on position. Measure voltage between ground and ECM 20-pin harness connector terminal No. 19. If voltage is greater than 5 volts, go to next step. If voltage is less than 5 volts, repair poor contact in ECM harness connector.
4. Read automatic transmission DTCs. See appropriate AUTOMATIC TRANSMISSION article. If an automatic transmission DTCs are found, repair as necessary. See appropriate AUTOMATIC TRANSMISSION article. If no automatic transmission DTCs are found, replace TCM and test system operation.

1. Turn ignition switch to on position. Measure the voltage between ground and ECM 28-pin harness connector terminal No. 19 (Impreza and Outback Sport) or ECM 35-pin harness connector terminal No. 10 (Forester). (Scheme 29) If voltage is less than 1 volt, go to next step. If voltage is greater than one volt, system has returned to normal at this time.
2. Turn ignition to off position. Disconnect the ECM and TCM harness connectors. Measure resistance between ground and ECM 28-pin harness connector terminal No. 19 (Impreza and Outback Sport) or ECM 35-pin harness connector terminal No. 10 (Forester). (Scheme 29) If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground between ECM and TCM harness connectors.
3. Reconnect ECM harness connector. Turn ignition switch to on position. Measure voltage between ground and ECM 28-pin harness connector terminal No. 19 (Impreza and Outback Sport) or ECM 35-pin harness connector terminal No. 10 (Forester). If voltage is greater than 5 volts, go to next step. If voltage is less than 5 volts, repair poor contact in ECM harness connector.
4. Read automatic transmission DTCs. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If an automatic transmission DTCs are found, repair as necessary. If no automatic transmission DTCs are found, replace TCM and test system operation.

1. Turn ignition switch to on position. Measure voltage between ground and ECM 20-pin harness connector terminal No. 19. (Scheme 29) If voltage is greater than 10 volts, repair short to voltage between ECM and TCM harness connectors. If voltage is less than 10 volts, go to next step.
2. Measure voltage between ECM 20-pin harness connector terminal No. 19. If voltage is greater than 4 volts go to step 5. If voltage is less than 4 volts, go to next step.
3. Measure voltage between ECM 20-pin harness connector terminal No. 19. If voltage is less than one volt, repair poor contact in ECM harness connector. If voltage is greater than one volt, go to next step.
4. Measure voltage between ECM 20-pin harness connector terminal No. 19. If voltage is 1-4 volts, the system has returned to normal at this time. If voltage is not 1-4 volts, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
5. Measure voltage between ground and TCM 24-pin harness connector terminal No. 10. (Scheme 41) If voltage is greater than 4 volts, go to next step. If voltage is less than 4 volts, repair open circuit between TCM and ECM harness connectors.
6. Check for poor contact in TCM harness connector. If poor contact is found, repair as necessary. If contact is okay, check TCM power supply and ground lines. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

1. Turn ignition switch to on position. Measure voltage between ground and ECM 28-pin harness connector terminal No. 19 (Impreza and Outback Sport) or ECM 35-pin harness connector terminal No. 10 (Forester). (Scheme 29) If voltage is greater than 10 volts, repair short to voltage between ECM and TCM harness connectors. If voltage is less than 10 volts, go to next step.
2. Measure voltage between ECM 28-pin harness connector terminal No. 19 (Impreza and Outback Sport) or ECM 35-pin harness connector terminal No. 10 (Forester). If voltage is greater than 4 volts go to step 5. If voltage is less than 4 volts, go to next step.
3. Measure voltage between ECM 28-pin harness connector terminal No. 19 (Impreza and Outback Sport) or ECM 35-pin harness connector terminal No. 10 (Forester). (Scheme 29) If voltage is less than one volt, repair poor contact in ECM harness connector. If voltage is greater than one volt, go to next step.
4. Measure voltage between ECM 28-pin harness connector terminal No. 19 (Impreza and Outback Sport) or ECM 35-pin harness connector terminal No. 10 (Forester). (Scheme 29) If voltage is 1-4 volts, the system has returned to normal at this time. If voltage is not 1-4 volts, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
5. Measure voltage between ground and TCM 24-pin harness connector terminal No. 4. (Scheme 41) If voltage is greater than 4 volts, go to next step. If voltage is less than 4 volts, repair open circuit between TCM and ECM harness connectors.
6. Check for poor contact in TCM harness connector. If poor contact is found, repair as necessary. If contact is okay, check TCM power supply and ground lines. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . If any DTCs other than P1110 are present, diagnose those DTCs first. Do not diagnose DTC P1110. If only DTC P1110 is present, replace ECM and test system operation.

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . If any DTCs other than P1111 are present, diagnose those DTCs first. Do not diagnose DTC P1111. If only DTC P1111 is present, replace ECM and test system operation.

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . If any DTCs other than P1134 are present, diagnose those DTCs first. Do not diagnose DTC P1134. If only DTC P1134 is present, replace ECM and test system operation.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any DTCs other than P1137 exist, repair those DTCs first. If only DTC P1137 exists, go to next step.
2. Start and ensure engine operating temperature is more than 160°F (70°C). If engine is already warmed up, operate engine at idle for one minute. Using scan tool, observe front HO2S output signal. If voltage is.85-1.15 volt during idle, go to next step. If voltage is not.85-1.15 volt, go to step 4.
3. Slowly accelerate engine (five seconds) from idle to 5,000 RPM a total of 5 times while using scan tool to monitor front HO2S output signal. If voltage is more than 1.1 volts for a moment, go to step 6. If voltage is not more than 1.1 volts for a moment, go to next step.
4. Turn ignition off. Disconnect ECM connector B136 (26-pin connector) and front HO2S connector. Using ohmmeter, measure resistance between ECM 26-pin harness connector terminal No. 13 and front HO2S 4-pin harness connector terminal No. 1. (Scheme 29)and (Scheme 30). Also measure resistance between ECM 26-pin harness connector terminal No. 22 and front HO2S 4-pin harness connector terminal No. 2. If resistance is less than 5 ohms at all points, go to next step. If resistance is not less than 5 ohms at all points, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and front HO2S. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
5. Using an ohmmeter, measure resistance between ECM connector B136 (26-pin connector) terminals No. 13 and 22 and chassis ground. (Scheme 29) If resistance is more than one megohm, go to next step. If resistance is not more than one megohm, locate and repair short to ground in wiring between ECM and front HO2S. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
6. Check exhaust system for damage or loose components, poor HO2S installation, exhaust system leaks ahead of HO2S or loose HO2S. Repair or replace exhaust system components as necessary. If exhaust system is okay, replace front HO2S. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition on. Using DVOM connected to ground, backprobe ECM 35-pin connector terminal No. 4. (Scheme 29) If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, go to step 3.
2. Check ECM connector for poor terminal contact. Repair connector as needed. If poor terminal contact is not present, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
3. Turn ignition off. Disconnect fuel tank pressure control solenoid valve connector and ECM 35-pin connector. Using an ohmmeter, measure resistance between fuel tank pressure control solenoid valve connector terminal No. 2 and chassis ground. (Scheme 31) If resistance is less than 10 ohms, locate and repair short to ground in wiring between ECM and fuel tank pressure control solenoid valve. 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 fuel tank pressure control solenoid valve connector terminal No. 2 and ECM 35-pin connector, terminal No. 4. (Scheme 29)and (Scheme 31). If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and fuel tank pressure control solenoid valve.
5. Measure resistance across both terminals of fuel tank pressure control solenoid valve. (Scheme 31) If resistance is not 10-100 ohms, replace fuel tank pressure control solenoid valve. If resistance is 10-100 ohms, go to next step.
6. Turn ignition on. Measure voltage between fuel tank pressure control solenoid valve terminal No. 1 and chassis ground. If voltage is more than 10 volts, go to next step. 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 tank pressure control solenoid valve.
7. Check for poor terminal contact in fuel tank pressure control solenoid valve connector. Repair connector as necessary. If poor contact is not present, contact authorized Subaru dealership because probable cause is deterioration of multiple parts. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Connect test mode connector. see scheme 8and see scheme 7. Turn ignition on. While using scan tool to command fuel tank pressure control solenoid valve on and off, use DVOM connected to ground to backprobe ECM 35-pin connector, terminal No. 4. (Scheme 29) If voltage switches between zero and 10 volts when solenoid is commanded on and off, go to next step. If voltage does not switch between zero and 10 volts when solenoid is commanded on and off, circuit has returned to normal. Repair poor terminal contact in ECM connector.
2. Using DVOM connected to ground, measure voltage at ECM 35-pin connector, terminal No. 4. If voltage is more than 10 volts, go to step 4. If voltage is not more than 10 volts, go to next step.
3. Check for poor terminal contact in ECM connector. Repair ECM connector as necessary. If ECM connector is okay, replace ECM.
4. Turn ignition off. Disconnect fuel tank pressure control solenoid valve connector. Turn ignition on. Measure voltage between ECM 35-pin connector, terminal No. 4 and chassis ground. (Scheme 29) If voltage is more than 10 volts, locate and repair short to voltage in wiring between ECM and fuel tank pressure control solenoid valve. After repair, replace ECM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If voltage is not more than 10 volts, go to next step.
5. Turn ignition off. Measure resistance across both terminals of fuel tank pressure control solenoid valve. (Scheme 31) If resistance is less than one ohm, replace fuel tank pressure control solenoid valve and ECM. If resistance is not less than one ohm on, go to next step.
6. Check for poor terminal contact in ECM connector. Repair ECM connector as required. If ECM connector is okay, replace ECM. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Scheme 46

Scheme 47

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any DTCs other than P1443 exist, repair those DTCs first. If DTC P1443 is only DTC set, check the following: Blockage of drain filter. Blockage of junction pipe. Blockage of vent hoses between drain filter and junction pipe. Blockage of vent hose between drain valve and drain filter. Blockage of vent hoses between canister and drain valve. (Scheme 46)and (Scheme 47). Repair as necessary. If no problem was found, go to next step.
2. Turn ignition off. Connect test mode connector. see scheme 7and see scheme 8. Connect scan tool to DLC. Turn ignition on. While using scan tool to command drain valve on and off, listen for clicking sound from valve. If clicking sound was heard, contact authorized Subaru dealership because probable cause is deterioration of multiple parts. If no clicking sound was heard, replace drain valve. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Turn ignition switch to on position. Measure voltage between ground and ECM 35-pin harness connector, terminal No. 1 by backprobing ECM harness connector. (Scheme 29) If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, go to step 3.
2. Check for poor contact in ECM harness connector. If poor contact is found, repair as necessary. If contact is okay, the system has returned to normal at this time.
3. Turn ignition switch to off position. Disconnect ECM and fuel tank sensor control valve harness connectors. Measure resistance between ground and fuel tank sensor control valve 2-pin harness connector, terminal No. 2. (Scheme 31) If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
4. Ensure ignition switch is in the off position. Measure resistance between ECM 35-pin harness connector, terminal No. 1 and fuel tank sensor control valve 2-pin harness connector, terminal No. 2. (Scheme 29)and (Scheme 31). If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit between ECM and fuel tank sensor control valve harness connectors. See WIRING DIAGRAMS under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
5. Ensure ignition switch is in the off position. Measure resistance between fuel tank sensor control valve 2-pin harness connector terminals No. 1 and No. 2. (Scheme 31) If resistance is 10-100 ohms, go to next step. If resistance is not 10-100 ohms, replace fuel tank sensor control valve.
6. Turn ignition switch to on position. Measure voltage between ground and fuel tank sensor control valve 2-pin harness connector, terminal No. 1. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open circuit between main relay and fuel tank sensor control valve. See WIRING DIAGRAMS under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
7. Check for poor contact in fuel tank sensor control valve. If poor contact is found, repair as necessary. If contact is okay, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.

1. Turn ignition switch to on position. Measure the voltage between ground and ECM 35-pin harness connector, terminal No. 1 by backprobing ECM harness connector. (Scheme 29) If voltage is greater than 10 volts, go to step 3. If voltage is less than 10 volts, go to next step.
2. Check for poor contact in ECM harness connector. If poor contact is found, repair as necessary. If contact is okay, replace ECM and test system operation.
3. Turn ignition switch to off position. Disconnect fuel tank sensor control valve 2-pin harness connector. Turn ignition switch to on position. Measure voltage between ground and ECM 35-pin harness connector terminal No. 1. (Scheme 29) If voltage is greater than 10 volts, repair short to voltage between ECM and fuel tank pressure sensor control. See WIRING DIAGRAMS under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If voltage is less than 10 volts, go to next step.
4. Check for poor contact in ECM harness connector. If poor contact is found, repair as necessary. If contact is okay, replace ECM and test system operation.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000) . If any DTCs other than P1448 is present, diagnose those DTCs first. If no other DTCs are present, go to next step.
2. Turn ignition switch to off position. Check the fuel cap. Ensure fuel cap in securely tightened. If fuel cap is okay, go to next step. If fuel cap is not okay, secure fuel cap properly and test system operation.
3. Check EVAP system for problems. Check for disconnection, blockage or leakage in hoses and pipes between fuel filler pipe and fuel tank. If EVAP system is okay, replace fuel tank pressure sensor. If EVAP system is not okay, repair as necessary and test system operation.

Note. For diagnosis of DTC P1492, see DTC P1498: EGR SOLENOID VALVE SIGNAL 4 CIRCUIT LOW INPUT .

Note. For diagnosis of DTC P1493, see DTC P1499: EGR SOLENOID VALVE SIGNAL 4 CIRCUIT HIGH INPUT .

Note. For diagnosis of DTC P1494, see DTC P1498: EGR SOLENOID VALVE SIGNAL 4 CIRCUIT LOW INPUT .

Note. For diagnosis of DTC P1495, see DTC P1499: EGR SOLENOID VALVE SIGNAL 4 CIRCUIT HIGH INPUT .

Note. For diagnosis of DTC P1496, see DTC P1498: EGR SOLENOID VALVE SIGNAL 4 CIRCUIT LOW INPUT .

Note. For diagnosis of DTC P1497, see DTC P1499: EGR SOLENOID VALVE SIGNAL 4 CIRCUIT HIGH INPUT .

1. Turn ignition switch to off position. Disconnect EGR solenoid valve harness connector. Turn ignition switch to on position. Measure voltage between ground and EGR solenoid valve harness connector terminals No. 2 and No. 5. (Scheme 35) If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open circuit between EGR solenoid valve and main relay.
2. Turn ignition switch to off position. Measure resistance between ECM 35-pin harness connector and EGR 6-pin harness connector terminals for appropriate DTC. See «ECM & EGR SOLENOID VALVE CIRCUIT IDENTIFICATION»(ref-157722-S37766384362003090300000) table. (Scheme 29)and (Scheme 35). If resistance is less than one ohm, go to next step. If resistance is greater than one ohm, repair open circuit between ECM and EGR harness connectors. ECM & EGR SOLENOID VALVE CIRCUIT IDENTIFICATION DTC ECM Harness Connector Terminal No. EGR Solenoid Valve Harness Connector Terminal No. P1492 18 8 P1494 17 1 P1496 16 4 P1498 15 3
3. Disconnect ECM 35-pin harness connector. Measure resistance between ground and ECM 35-pin harness connector terminals for appropriate DTC. See «DTC CIRCUIT IDENTIFICATION»(ref-157722-S10613170592003090300000) table. (Scheme 29) If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground in appropriate wire and test system operation. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. DTC CIRCUIT IDENTIFICATION DTC ECM Harness Connector Terminal No. P1492 18 P1494 17 P1496 16 P1498 15
4. Check for poor contact in ECM and EGR solenoid valve harness connectors. If poor contact is found, repair as necessary. If contact is okay, replace EGR solenoid valve and test system operation.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If any DTCs other than P1493, P1495, P1497 or P1499 are present, go to next step. If no other DTCs are present, go to step 3.
2. Turn ignition switch to off position. Measure resistance between ground and ECM 35-pin harness connector terminals No. 7, No. 14 and No. 21. (Scheme 29) If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open between ECM 35-pin harness connector and engine ground.
3. Ensure ignition switch is in the off position. Disconnect EGR solenoid valve harness connector. Turn ignition switch to on position. Measure voltage between ground and ECM 35-pin harness connectors for appropriate DTC. See table. If voltage is greater than 10 volts, repair short to ground between ECM and EGR solenoid valve harness connectors. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair, replace ECM. If voltage is less than 10 volts, replace ECM and test system operation.

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Disconnect IAC solenoid valve connector. Turn ignition on. Using DVOM connected to ground, measure voltage at IAC solenoid valve connector terminals No. 2 and No. 5. (Scheme 35) If voltage is greater than 10 volts at each terminal, go to next step. If voltage is less than 10 volts at each terminal, locate and repair open in wiring and check for poor terminal contact in connectors between main relay and IAC solenoid valve. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Turn ignition off. Using an ohmmeter, measure resistance between specified ECM 35-pin harness connector and IAC 6-pin harness connector terminals for related DTC. (Scheme 29)and (Scheme 35). See «ECM & IAC SOLENOID VALVE CIRCUIT IDENTIFICATION»(ref-157722-S30638938322003082200000) table. If resistance is less than one ohm on all circuits, go to next step. If resistance is greater than one ohm on any circuit, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and IAC solenoid valve. ECM & IAC SOLENOID VALVE CIRCUIT IDENTIFICATION DTC ECM 35-Pin Connector Terminal No. IAC Solenoid Valve 6-Pin Connector Terminal No. P1510 20 4 P1512 6 1 P1514 5 6 P1516 19 3
3. Ensure ignition is off. Disconnect ECM 35-pin connector. Measure resistance between ECM 35-pin connector terminals No. 5, 6, 19 and 20 and chassis ground for applicable DTC. See «ECM & IAC SOLENOID VALVE CIRCUIT IDENTIFICATION»(ref-157722-S30638938322003082200000) table. (Scheme 29) If resistance is less than one megohm on any circuit, locate and repair short to ground in wiring between ECM and IAC solenoid valve. If resistance is greater than one megohm on all circuits, go to next step.
4. Check for poor contact at ECM and IAC solenoid valve connectors. Repair connectors as necessary. If connectors are okay, replace IAC solenoid valve. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). If DTCs P1511, P1513, P1515 and P1517 exist at the same time, go to next step. If DTCs P1511, P1513, P1515 and P1517 do not exist at the same time, go to step 3.
2. Turn ignition off. On all models, using an ohmmeter connected to ground, backprobe ECM 35-pin connector, terminal No. 7. (Scheme 29) On Forester, Impreza and Outback Sport, measure resistance between ground and ECM 20-pin harness connector, terminal No. 14 and ECM 28-pin harness connector, terminal No. 21. If all resistances are less than 5 ohms, go to next step. If resistances are not less than 5 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and IAC solenoid valve. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
3. Turn ignition off. Disconnect IAC solenoid valve connector. Turn ignition on. Using DVOM connected to ground, measure voltage between ECM 35-pin harness connector terminals No. 5, No. 6, No. 19 and No. 20. (Scheme 29) If voltage is more than 10 volts, locate and repair short to voltage in wiring between ECM and IAC solenoid valve. After repair, replace ECM. If voltage is not more than 10 volts, replace ECM. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

Note. On A/T vehicles, place transmission in "P" or "N". On M/T vehicles, depress clutch pedal.

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . Attempt to start engine. If starter operates in START position, locate and repair short to ground or open in wiring between ECM and starter. If starter does not operate in START position, check starter circuit. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .

1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-157722-S13148851682003082200000). Turn ignition off. Using DVOM connected to ground, backprobe ECM 28-pin harness connector, terminal No. 9. (Scheme 29) If voltage is greater than 10 volts, repair poor terminal contact in ECM connector. If voltage is less than 10 volts, go to next step.
2. Turn ignition off. Disconnect ECM 28-pin connector. Using an ohmmeter connected to ground, measure resistance at ECM 28-pin connector, terminal No. 9. If resistance is less than 10 ohms, locate and repair short to ground in wiring between ECM and battery. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If resistance is greater than 10 ohms, go to next step.
3. Check condition of fuse SBF-5 (30-amp) in main fuse box, located in left side of engine compartment. Replace fuse if open. If fuse is okay, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and battery. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-157722-S39072035892003082200000) and «VERIFICATION PROCEDURE»(ref-157722-S12187126812003082200000).

1. Start and warm engine to normal operating temperature. Turn ignition switch to off position. Turn ignition switch to on position. Measure voltage between ground and ECM 26-pin harness connector, terminal No. 15 by backprobing ECM harness connector. (Scheme 29) If voltage is greater than 3 volts, repair poor connection in ECM connector. If voltage is less than 3 volts, go to next step.
2. Turn ignition switch to off position. Disconnect ECM 26-pin harness connector. Measure resistance between ground and ECM 26-pin harness connector, terminal No. 15. If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground between ECM and TCM harness connectors.
3. Ensure ignition switch is in the off position. Measure between ECM 26-pin harness connector, terminal No. 15 and TCM 24-pin harness connector, terminal No. 2 (Forester, Impreza and Outback Sport) or terminal No. 2 without sport shift and No. 10 with sport shift (Baja, Legacy and Outback). (Scheme 29)and (Scheme 41). If resistance is less than one ohm, repair poor contact in ECM or TCM connector. If resistance is greater than one ohm, repair open circuit between ECM and TCM harness connectors.

1. Start engine and warm to operating temperature. Turn ignition switch to off position. Disconnect TCM harness connector. Turn ignition switch to on position. Measure voltage between ground and ECM 26-pin harness connector, terminal No. 15 by backprobing ECM harness connector. (Scheme 29) If voltage is less than 3 volts, go to next step. If voltage is greater than 3 volts, repair short to voltage between ECM and TCM. After repair, replace ECM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. Turn ignition switch to off position. Measure voltage between ground and ECM 26-pin harness connector terminal No. 15 by backprobing ECM harness connector. Shake and wiggle the ECM harness and connector. If voltage is greater than 10 volts while shaking and wiggling harness and connector, locate and repair short to voltage between ECM and TCM harness connectors. If voltage remains less than 10 volts while shaking and wiggling harness and connector, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.

1. Turn ignition switch to on position. Measure voltage between ground and ECM 26-pin harness connector, terminal No. 1 by backprobing ECM harness connector. (Scheme 29) If voltage is greater than 4.5 volts, go to next step. If voltage is less than 4.5 volts, go to step 4.
2. Measure voltage between ground and ECM 26-pin harness connector, terminal No. 1 by backprobing ECM harness connector. If voltage is greater than 10 volts, repair short to voltage between ECM and TCM harness connectors. If voltage is less than 10 volts, go to next step.
3. Check for poor contact in ECM harness connector. If poor contact is found, repair as necessary. If contact is okay, replace ECM and test system operation.
4. Turn ignition switch to off position. Disconnect ECM 36-pin and TCM 24-pin harness connectors. On Forester, Impreza and Outback Sport, measure resistance between ECM 26-pin harness connector, terminal No. 1 and TCM 24-pin harness connector, terminal No. 13. On Baja, Legacy and Outback, measure resistance between ECM 26-pin harness connector, terminal No. 1 and TCM 24-pin harness connector B56, terminal No. 5 with sport shift or TCM harness connector B54, terminal No. 13 without sport shift. (Scheme 29)and (Scheme 41). If resistance is greater than one ohm, repair open circuit between ECM and TCM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If resistance is less than one ohm, go to next step.
5. Ensure ignition switch is in the off position. Measure resistance between ground and ECM 26-pin harness connector, terminal No. 1. (Scheme 29) If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground between ECM and TCM harness connectors.
6. Check for poor contact in TCM harness connector. If poor contact is found, repair as necessary. If contact is okay, replace TCM and test system operation.

1. Turn ignition switch to on position. Measure voltage between ground and ECM 26-pin harness connector, terminal No. 18 by backprobing ECM harness connector. (Scheme 29) If voltage is greater than 4.5 volts, go to next step. If voltage is less than 4.5 volts, go to step 4.
2. Measure voltage between ground and ECM 26-pin harness connector, terminal No. 18 by backprobing ECM harness connector. If voltage is greater than 10 volts, repair short to voltage between ECM and TCM harness connectors. If voltage is less than 10 volts, go to next step.
3. Check for poor contact in ECM harness connector. If poor contact is found, repair as necessary. If contact is okay, replace ECM and test system operation.
4. Turn ignition switch to off position. Disconnect ECM 36-pin and TCM 24-pin harness connectors. On Forester, Impreza and Outback Sport, measure resistance between ECM 26-pin harness connector, terminal No. 18 and TCM 24-pin harness connector, terminal No. 21. On Baja, Legacy and Outback, measure resistance between ECM 26-pin harness connector, terminal No. 18 and TCM 24-pin harness connector B56, terminal No. 14 with sport shift or TCM harness connector B54, terminal No. 21 without sport shift. (Scheme 29)and (Scheme 41). If resistance is greater than one ohm, repair open circuit between ECM and TCM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If resistance is less than one ohm, go to next step.
5. Ensure ignition switch is in the off position. Measure resistance between ground and ECM 26-pin harness connector, terminal No. 18. (Scheme 29) If resistance is greater than one megohm, go to next step. If resistance is less than one megohm, repair short to ground between ECM and TCM harness connectors.
6. Check for poor contact in TCM harness connector. If poor contact is found, repair as necessary. If contact is okay, replace TCM and test system operation.