Engine Control System Self-Diagnostics: Diagnosis Toyota RAV4 II

MALFUNCTION INDICATOR LIGHT INSPECTION

Note. Malfunction Indicator Light (MIL) may also be referred to as CHECK ENGINE light. Inspect MIL to ensure it is operational and will come on if a Diagnostic Trouble Code (DTC) is set.

1. Turn ignition on. Check that MIL comes on and remains on. MIL is displayed as an engine icon located just below engine coolant temperature gauge on instrument cluster on instrument panel. If MIL comes on and remains on, go to next step. If MIL does not come on, check bulb circuit on instrument cluster and Green/Red or White wire and electrical connectors between MIL and Engine Control Module (ECM). See WIRING DIAGRAMS article. There are 2 different wiring harnesses used and wire color varies according to wiring harness used. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2
2. Start engine and ensure MIL goes off. If MIL goes off, no malfunction is detected at this time. If MIL remains on or blinks with engine running, a malfunction is detected. Proceed to «TESTING PROCEDURE»(ref-91210-S04395390682001030500000).

TESTING PROCEDURE

To ensure correct diagnosis and repair, testing should be done in the following sequence

1. Record Customer Complaint Ensure all customer complaints or observations are recorded. Test drive vehicle with customer when necessary for malfunction verification.
2. Retrieve Diagnostic Trouble Codes Using Toyota hand-held tester or scan tool, retrieve Diagnostic Trouble Codes (DTC) from Engine Control Module (ECM) and record any freeze frame data (if applicable). See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-91210-S27026032392001030500000) .
3. Clear Diagnostic Trouble Codes Using Toyota hand-held tester or scan tool, clear DTCs and freeze frame data from ECM. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-91210-S03284523452001030500000) .
4. Visual Inspection Inspect all electrical connectors and wiring for suspected circuit or component. Ensure all electrical connections are clean and tight.
5. Confirm Symptoms & Diagnostic Trouble Codes Perform road test. Determine if original symptoms still exist. Using scan tool or Toyota hand-held tester, retrieve DTCs from ECM. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-91210-S27026032392001030500000) .
6. Diagnose & Repair Diagnostic Trouble Codes Perform appropriate DTC test listed under DIAGNOSTIC TESTS as necessary. For DTC descriptions, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-91210-S35593989792001030500000) table under DIAGNOSTIC TROUBLE CODE DEFINITIONS. If no DTCs are present and a no start condition exists, proceed to appropriate BASIC DIAGNOSTIC PROCEDURES article. If no DTCs are present and a driveability condition exists, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).
7. Verification Procedure After repairs have been completed, clear all DTCs from ECM. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-91210-S03284523452001030500000) . Perform road test. Ensure no DTCs exist and all symptoms and/or complaints have been repaired.

RETRIEVING DIAGNOSTIC TROUBLE CODES

Note. Diagnostic Trouble Codes (DTC) may be retrieved using Toyota hand-held tester or On-Board Diagnostic (OBD-II) scan tool that complies with SAE standard J-1978. Toyota hand-held tester or OBD-II scan tool may be operated in NORMAL mode when retrieving DTCs. Only Toyota hand-held tester may be used in CHECK mode when retrieving DTCs.

NORMAL mode is used to retrieve DTCs from Engine Control Module (ECM). CHECK mode is used to check for DTCs when operating vehicle to simulate conditions during which DTC was set. CHECK mode contains a higher sensing ability to detect malfunctions. CHECK mode helps determine malfunctions caused by poor electrical connections or intermittent problems which are difficult to determine using NORMAL mode.

Note. If using Toyota hand-held tester, when ignition switch is turned from ON to ACC or OFF position during CHECK mode, hand-held tester is switched from NORMAL mode to CHECK mode or from CHECK MODE to NORMAL mode, all DTCs and freeze frame data will be erased from ECM. DO NOT switch modes until all DTCs and freeze frame data have been recorded.

NORMAL Mode Diagnostic Trouble Code Retrieval

1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on with engine off. Turn hand-held tester or scan tool on. Using hand-held tester or scan tool manufacturer's instructions, check for DTCs and freeze frame data.
2. If hand-held tester or scan tool does not display UNABLE TO CONNECT TO VEHICLE, go to next step. If hand-held tester or scan tool displays UNABLE TO CONNECT TO VEHICLE, check DLC No. 3. See «DATA LINK CONNECTOR NO. 3 INSPECTION»(ref-91210-S14789613832001030500000) under SCAN TOOL PROBLEMS.
3. Record any DTCs and freeze frame data displayed for system diagnosis. If driveability problem exist and no DTCs are present, go to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom.
4. If any DTCs are present, perform appropriate DTC test under «DIAGNOSTIC TESTS»(ref-91210-S25433912062001030500000). For DTC descriptions, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-91210-S35593989792001030500000) table under DIAGNOSTIC TROUBLE CODE DEFINITIONS. For information on freeze frame data, see «FREEZE FRAME DATA»(ref-91210-S36467994772001030500000). For information on two-trip detection logic DTCs, see «TWO-TRIP DETECTION LOGIC»(ref-91210-S19405305212001030500000).
5. After repairs for DTC have been completed, DTC must be cleared from ECM. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-91210-S03284523452001030500000). Road test vehicle to ensure all symptoms and/or complaints have been repaired.

CHECK Mode Diagnostic Trouble Code Retrieval (Toyota Hand-Held Tester Only)

Note. If using Toyota hand-held tester, if ignition switch is turned from ON to ACC or OFF position during CHECK mode, all DTCs and freeze frame data will be erased from ECM. DO NOT switch from CHECK mode to NORMAL mode until all DTCs and freeze frame data are recorded.

1. Ensure vehicle battery is fully charged. Apply parking brake. Place transaxle in Park or Neutral. Ensure A/C and ignition are off. Check that throttle valve is fully closed. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on and then turn hand-held tester on.
2. Switch hand-held tester from NORMAL mode to CHECK mode. Ensure Malfunction Indicator Light (MIL) on instrument cluster flashes to indicate CHECK mode operation. Start engine. If no DTCs are present, MIL will turn off. Try to simulate conditions of driveability complaint described by customer.
3. Record any DTCs and freeze frame data displayed for system diagnosis. If driveability problem exist and no DTCs are present, go to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom.
4. If any DTCs are present, perform appropriate DTC test under «DIAGNOSTIC TESTS»(ref-91210-S25433912062001030500000). For DTC descriptions, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-91210-S35593989792001030500000) table under DIAGNOSTIC TROUBLE CODE DEFINITIONS. For information on freeze frame data, see «FREEZE FRAME DATA»(ref-91210-S36467994772001030500000). For information on two-trip detection logic DTCs, see «TWO-TRIP DETECTION LOGIC»(ref-91210-S19405305212001030500000).
5. After repairs for DTC have been completed, DTC must be cleared from ECM. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-91210-S03284523452001030500000). Road test vehicle to ensure all symptoms and/or complaints have been repaired.

CLEARING DIAGNOSTIC TROUBLE CODES

1. After repairs for Diagnostic Trouble Codes (DTC) have been completed, DTCs and freeze frame data should be cleared from Engine Control Module (ECM) memory. Using scan tool or Toyota hand-held tester, follow the manufacturer's instructions and clear DTCs and freeze frame data from ECM.
2. DTCs and freeze frame data may also be cleared by removing EFI1 fuse (20-amp). EFI1 fuse is located in fuse/relay box at driver's side front corner of engine compartment. DTCs and freeze frame data may also be cleared by disconnecting negative battery cable. However, other various memory functions such as the clock, radio, alarm, seats, etc. will be cleared and must be reset.

TEST DRIVE CONFIRMATION

1. On certain Diagnostic Trouble Codes (DTC), once DTC has been cleared from Engine Control Module (ECM) memory, a test drive confirmation test can be performed to verify repairs are made and that DTC does not reset. Test drive confirmation test will duplicate conditions required to set specified DTCs.
2. Test drive confirmation test lists the procedure to be performed to check that DTC does not reset. Test drive confirmation tests apply only to specific DTCs. Test drive confirmation test will be included within proper DTC test under DIAGNOSTIC TESTS.

DATA LINK CONNECTOR NO. 3 INSPECTION

1. If Toyota hand-held tester or scan tool displays UNABLE TO CONNECT TO VEHICLE when hand-held tester or scan tool is connected to Data Link Connector (DLC) No. 3, try hand-held tester or scan tool on another vehicle. If hand-held tester or scan tool operates on another vehicle, go to next step. If hand-held tester or scan tool does not operate on another vehicle, problem is probably with hand-held tester or scan tool.
2. Check DLC No. 3 for loose or damaged terminals. Ensure DLC No. 3 terminals are in correct position in connector. See WIRING DIAGRAMS article. For full wiring diagram of DLC No. 3, it may be necessary to see DATA LINK CONNECTORS article in WIRING DIAGRAMS. If connector and terminals are okay, go to next step. If connector or terminals are defective, repair as necessary.
3. Check voltage and resistance between ground and specified terminal on DLC No. 3. See «DATA LINK CONNECTOR NO. 3 VOLTAGE & RESISTANCE SPECIFICATIONS»(ref-91210-S42185314062001030500000) table. (Scheme 297) If voltage or resistance readings are not within specification, check wiring circuit. See WIRING DIAGRAMS article.

DATA LINK CONNECTOR NO. 3 VOLTAGE & RESISTANCE SPECIFICATIONS

Scheme 297

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TESTS

Note. Before performing any diagnostic test, see SELF-DIAGNOSTIC SYSTEM for diagnostic system functions and system diagnostic procedures. Also check for any related Technical Service Bulletins (TSBs).

Note. When performing diagnostic tests, it may be necessary to identify Engine Control Module (ECM) electrical connector terminals which are referenced to in testing procedure. (Scheme 298) When wire color is called out at a specified terminal, there may be 2 different wire colors listed, as there are 2 different wiring harnesses used.

Scheme 298

Diagnosis & Repair

1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on and then turn hand-held tester or scan tool on. Start engine and allow engine to idle. Using hand-held tester or scan tool, monitor MAF meter air flow rate. If MAF meter air flow rate is 0.0 gm/sec., go to next step. If MAF meter air flow rate is 271 gm/sec. or more, go to step 5.
2. Turn ignition off. Disconnect electrical connector at MAF meter. MAF meter is bolted to upper cap on air cleaner assembly and contains a Black 5-pin electrical connector. Turn ignition on. Using voltmeter, check voltage between ground and terminal No. 1 (Black/Red wire) on MAF meter electrical connector. (Scheme 299) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, repair open in Black/Red wire between EFI main relay and MAF meter. See WIRING DIAGRAMS article. EFI main relay may also be referred to as EFI relay. EFI main relay is located in fuse/relay box at driver's side front corner of engine compartment.
3. Turn ignition off. Reinstall electrical connector at MAF meter. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Ensure A/C switch is in OFF position shift lever is in Neutral. Start engine and allow engine to idle. Using voltmeter, check voltage between body ground and terminal No. 12 (Blue/White wire) at ECM electrical connector E5. (Scheme 298) This is the VG terminal on ECM. Voltage should be 1.1-1.5 volts. If voltage is not within specification, go to next step. If voltage is within specification, replace ECM.
4. Check for open and short in Blue/White wire and electrical connectors between MAF meter and ECM. See WIRING DIAGRAMS article. If wiring harness and electrical connectors are okay, replace MAF meter. If wiring harness or electrical connector is defective, repair as necessary.
5. Turn ignition off. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Using ohmmeter, check resistance between body ground and terminal No. 21 (Blue wire) at ECM electrical connector E5. (Scheme 298) The is the E2G terminal on ECM. If resistance is one ohm or less, go to next step. If resistance is greater than one ohm, replace ECM.
6. Check for open in wiring harness and electrical connectors between MAF meter and ECM. See WIRING DIAGRAMS article. If wiring harness and electrical connectors are okay, replace MAF meter. If wiring harness or electrical connector is defective, repair as necessary.

Scheme 299

Circuit Description

Mass Airflow (MAF) meter uses a platinum hot wire which is maintained at a constant temperature by controlling the current flow through the hot wire. Current flow is then measured as an output voltage. MAF meter may also be referred to as airflow meter. DTC is set when ECM detects MAF meter output is greater than 2.2 volts with throttle valve closed for more than 10 seconds with engine speed of 900 RPM or less, or MAF meter output is less than 1.06 volts with Throttle Position (TP) sensor VTA circuit signal voltage of .63 volt or more for more than 10 seconds with engine speed of 1500 RPM or more. Possible cause is defective MAF meter.

Diagnostic Aids

Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

Using Toyota hand-held tester or scan tool, check for any other DTCs. If other DTCs exist, diagnose and repair those DTCs first and retest. If only DTC P0101 exists, replace MAF meter. MAF meter is bolted to upper cap on air cleaner assembly and contains a Black 5-pin electrical connector.

1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on and then turn hand-held tester or scan tool on.
2. Using hand-held tester or scan tool, read engine coolant temperature for ECT sensor. If displayed engine coolant temperature is -40°F (-40°C), go to next step. If displayed engine coolant temperature is 284°F (140°C) or more, go to step 8. If displayed engine coolant temperature is same as actual engine coolant temperature, problem is intermittent. Check for defective connections or intermittent problem in wiring between ECT sensor and ECM. ECT sensor is located on coolant housing at flywheel end of cylinder head and contains Green 2-pin electrical connector with White and Brown wires. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2
3. Turn ignition off. Disconnect electrical connector at ECT sensor. ECT sensor is located on coolant housing at flywheel end of cylinder head and contains Green 2-pin electrical connector with White and Brown wires. Connect jumper wire between both terminals on electrical connector for ECT sensor. Turn ignition on.
4. Using hand-held tester or scan tool, read engine coolant temperature for ECT sensor. If displayed engine coolant temperature is less than 284°F (140°C), go to next step. If displayed engine coolant temperature is 284°F (140°C) or more, check for defective electrical connections at ECT sensor and electrical connector. If electrical connections are defective, repair as necessary. If electrical connections are okay, replace ECT sensor.
5. Turn ignition off. Remove jumper wire. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Ensure electrical connectors at ECM are securely installed so all terminals in electrical connectors are contacting terminals in ECM.
6. Ensure electrical connector at ECT sensor is still disconnected. Connect jumper wire between terminal No. 18 (Brown wire) at ECM electrical connector E5 and No. 22 (White wire) at ECM electrical connector E4 with all electrical connectors installed on ECM. (Scheme 298) This is the E2 and THW terminals on ECM.
7. Turn ignition on. Using hand-held tester or scan tool, read engine coolant temperature for ECT sensor. If displayed engine coolant temperature is 284°F (140°C) or more, repair open Brown wire or White wire between ECT sensor and ECM. See WIRING DIAGRAMS article. If displayed engine coolant temperature is not 284°F (140°C) or more, replace ECM.
8. Turn ignition off. Disconnect electrical connector at ECT sensor. ECT sensor is located on coolant housing at flywheel end of cylinder head and contains Green 2-pin electrical connector with White and Brown wires. Turn ignition on.
9. Using hand-held tester or scan tool, read engine coolant temperature for ECT sensor. If displayed engine coolant temperature is not -40°F (-40°C), go to next step. If displayed engine coolant temperature is -40°F (-40°C), replace ECT sensor.
10. Turn ignition off. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Disconnect ECM electrical connectors E4 and E5. (Scheme 298) Ensure electrical connector is still disconnected at ECT sensor.
11. Turn ignition on. Using hand-held tester or scan tool, read engine coolant temperature for ECT sensor. If displayed engine coolant temperature is -40°F (-40°C), repair short in wiring harness and electrical connectors between ECT sensor and ECM. See WIRING DIAGRAMS article. If displayed engine coolant temperature is not -40°F (-40°C), replace ECM.

1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0116 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
2. Remove and inspect cooling system thermostat for damage and proper operation. Thermostat is located behind thermostat housing which is located just behind the generator. If thermostat is defective, replace thermostat. If thermostat is okay, replace ECT sensor. ECT sensor is located on coolant housing at flywheel end of cylinder head and contains Green 2-pin electrical connector with White and Brown wires.

1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on and then turn hand-held tester or scan tool on.
2. Using hand-held tester or scan tool, read throttle valve opening percentages with throttle fully closed and fully open. Throttle valve opening percentage should be approximately 10 percent with throttle fully closed and approximately 70 percent with throttle fully open. If throttle valve opening percentages are not within specification, go to next step. If throttle valve opening percentages are within specification, problem is intermittent. Check for defective connections or intermittent problem in wiring between TP sensor and ECM. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2
3. Turn ignition off. Disconnect electrical connector at TP sensor. Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 1 (Yellow wire) at electrical connector for TP. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, go to step 6.
4. Check TP sensor. See THROTTLE POSITION SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If TP sensor is okay, go to next step. If TP sensor is defective, replace TP sensor.
5. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on. Using voltmeter, check voltage between terminals No. 18 (Brown wire) at ECM electrical connector E5 and No. 24 (Blue/Red wire) at ECM electrical connector E4 with all electrical connectors installed on ECM with throttle fully closed and fully open. (Scheme 298) This is the E2 and VTA terminals on ECM. Voltage should be.3-1.0 volt with throttle fully closed and 3.2-4.9 volts with throttle fully open. If voltages are within specification, replace ECM. If voltages are not within specification, repair open or short in Brown wire and/or Blue/Red wire and electrical connectors between TP sensor and ECM. See WIRING DIAGRAMS article.
6. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Ensure ignition is on. Using voltmeter, check voltage between terminals No. 2 (Yellow wire) and No. 18 (Brown wire) at ECM electrical connector E5 with all electrical connectors installed on ECM. (Scheme 298) This is the VC and E2 terminals on ECM. Voltage should be 4.5-5.5 volts. If voltage is not within specification, replace ECM. If voltage is within specification, repair open or short in Yellow wire and electrical connectors between TP sensor and ECM. See WIRING DIAGRAMS article.

Throttle Position (TP) sensor is a variable resistor located on throttle body which monitors throttle opening and delivers input signals to Engine Control Module (ECM). ECM uses input signals for determining vehicle driving conditions and adjusts air/fuel mixture accordingly. DTC is set after vehicle speed is more than 19 MPH once and TP sensor output voltage is out of range. Possible cause is defective TP sensor.

Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

Using Toyota hand-held tester or scan tool, check for any other DTCs. If other DTCs exist, diagnose and repair those DTCs first and retest. If only DTC P0121 exists, replace TP sensor.

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. If using Toyota hand-held tester, go to next step. If Toyota hand-held tester is not available, go to step 3.
2. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine. Allow engine to idle for at least 60 seconds.
4. Drive vehicle at 24 MPH or more for at least 40 seconds and then allow engine to idle for at least 10 seconds. Repeat this procedure 9 times and then check operation of Malfunction Indicator Light (MIL). If MIL illuminates, malfunction exists and DTC is set. If MIL does not illuminate, malfunction does not exist.

Scheme 300

1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0125 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
2. With Toyota hand-held tester or scan tool still connected to DLC No. 3, start engine and maintain engine speed at 2500 RPM for about 90 seconds to fully warm the A/F sensor. Allow engine to idle.
3. Using hand-held tester or scan tool, monitor each A/F sensor output voltage with engine idling, engine racing and while driving vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. Ensure A/F sensor output voltage is within specification. See «AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS»(ref-91210-S24337057112001042700000) table. If A/F sensor output voltage is not within specification, go to next step. If A/F sensor output voltage is within specification, go to step 10. NOTE: If A/F sensor output voltage remains 3.30 volts (Toyota hand-held tester) or.66 volt (OBD-II scan tool) during all conditions, A/F sensor circuit may be open. If A/F sensor output voltage remains 3.80 volts or more (Toyota hand-held tester) or.76 volt or more (OBD-II scan tool) during all conditions, A/F sensor circuit may be shorted. If A/F sensor output voltage remains 2.80 volts or less (Toyota hand-held tester) or.56 volt or less (OBD-II scan tool) during all conditions, A/F sensor circuit may be shorted. During fuel enrichment, A/F sensor output voltage may be less than 2.8 volts (Toyota hand-held tester) or.56 volt (OBD-II scan tool) which is normal. During fuel cut, A/F sensor output voltage may be more than 3.8 volts (Toyota hand-held tester) or.76 volt (OBD-II scan tool) which is normal. AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS Application & Operating Condition Specification Using OBD-II Scan Tool Engine Idling, Engine Racing & Driving Vehicle (1) (2) Using Toyota Hand-Held Tester Engine Idling, Engine Racing & Driving Vehicle (1) (3) (1) Drive vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. (2) Voltage should not remain at.56 volt or less,.66 volt, or.76 volt or more. (3) Voltage should not remain at 2.80 volts or less, 3.30 volts, or 3.80 volts or more.
4. Check for open and short in wiring harness and electrical connectors between A/F sensors and ECM. See WIRING DIAGRAMS article. A/F sensors are located on exhaust manifold above catalytic converters. see scheme 7 A/F sensor for cylinders No. 1 and 4 is referred to as bank No. 1, sensor No. 1. A/F sensor for cylinders No. 2 and 3 is referred to as bank No. 2, sensor No. 1. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
5. Disconnect electrical connector for A/F sensor. Using ohmmeter, check resistance for heater on A/F sensor between +B and HT terminals on electrical connector for A/F sensor. (Scheme 300) Resistance should be.8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistance is within specification, go to next step. If resistance is not within specification, replace A/F sensor.
6. Ensure engine oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem does not exist, go to next step. If problem exists, repair as necessary.
7. Check fuel pressure. See FUEL PRESSURE under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ) with engine idling and should remain at least 21 psi (1.5 kg/cm 2 ) for a minimum of 5 minutes after engine is shut off. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, repair fuel system as necessary.
8. Check operation of fuel injectors. See FUEL CONTROL under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Fuel injector volume should be 53-65 cc (3.2-3.9 cu. in.) within 15 seconds and difference in volume between each fuel injector should be less than 6 cc (.4 cu. in.). Fuel injectors should not leak more than one drop every 12 minutes. If fuel injectors are okay, go to next step. If fuel injectors are defective, replace fuel injectors as necessary.
9. Check exhaust system for leaks. If no exhaust leak exists, replace A/F sensors. If exhaust leak exists, repair exhaust system as necessary.
10. Using Toyota hand-held tester or scan tool, clear DTCs from ECM. Perform test drive confirmation and then go to next step. See «TEST DRIVE CONFIRMATION»(ref-91210-S15875293492001042700000).
11. Recheck for DTCs. If DTC P0125 does not exist, go to next step. If DTC P0125 exists, replace ECM. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2
12. Verify if vehicle ran out of fuel. If vehicle ran out of fuel, DTC P0125 was caused by the vehicle running out of fuel. If vehicle did not run out of fuel, problem is intermittent. Check for defective connections or intermittent problem in wiring. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2

1. Remove and inspect cooling system thermostat for damage and proper operation. Thermostat is located behind thermostat housing which is located just behind the generator. If thermostat is okay, go to next step. If thermostat is defective, replace thermostat.
2. Using Toyota hand-held tester or scan tool, check for any other DTCs. If other DTCs exist, diagnose and repair those DTCs first and retest. If only DTC P0128 exists, replace ECM. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2

Heated oxygen sensors monitor exhaust gas oxygen content and deliver input signals to Engine Control Module (ECM). Heated oxygen sensors are located on exhaust manifold below catalytic converters. see scheme 7 Heated oxygen sensor for cylinders No. 1 and 4 is referred to as bank No. 1, sensor No. 2. ECM uses input signals to determine fuel injection system operation. DTC is set when heated oxygen sensor (bank No. 1, sensor No. 2) output voltage remains at.40 volt or more, or.50 volt or less when vehicle is driven at 25 MPH with engine at normal operating temperature. Possible causes are

1. Heated oxygen sensor (bank No. 1, sensor No. 2) circuit is open or shorted.
2. Defective heated oxygen sensor (bank No. 1, sensor No. 2).

Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. If using Toyota hand-held tester, go to next step. If Toyota hand-held tester is not available, go to step 3.
2. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine. Allow engine to idle for at least 60 seconds.
4. Drive vehicle at 24 MPH or more for at least 40 seconds and then allow engine to idle for at least 10 seconds. Repeat this procedure 9 times and then check operation of Malfunction Indicator Light (MIL). If MIL illuminates, malfunction exists and DTC is set. If MIL does not illuminate, malfunction does not exist.

1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0136 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
2. Check for open and short in wiring harness and electrical connectors between heated oxygen sensor (bank No. 1, sensor No. 2) and ECM. See WIRING DIAGRAMS article. Heated oxygen sensor (bank No. 1, sensor No. 2) is located on exhaust manifold below catalytic converters. see scheme 7 ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
3. With hand-held tester or scan tool still connected to DLC No. 3, start engine and warm engine to normal operating temperature. Monitor heated oxygen sensor (bank No. 1, sensor No. 2) output voltage while quickly accelerating engine to 4000 RPM for 3 times. Output voltage should fluctuate from.40 volt or less to.55 volt or more. If output voltage is not within specification, replace heated oxygen sensor (bank No. 1, sensor No. 2). If output voltage is within specification, problem is intermittent. Check for defective connections or intermittent problem in wiring between heated oxygen sensor (bank No. 1, sensor No. 2) and ECM.

1. Test drive confirmation may be performed to operate vehicle under the conditions which may cause DTC to be set. If using Toyota hand-held tester, go to next step. If Toyota hand-held tester is not available, go to step 3.
2. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine. Allow engine to idle for at least 60 seconds.
4. Drive vehicle at 24 MPH or more for at least 40 seconds and then allow engine to idle for at least 10 seconds. Repeat this procedure 9 times and then check operation of Malfunction Indicator Light (MIL). If MIL illuminates, malfunction exists and DTC is set. If MIL does not illuminate, malfunction does not exist.

1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0156 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
2. Check for open and short in wiring harness and electrical connectors between heated oxygen sensor (bank No. 2, sensor No. 2) and ECM. See WIRING DIAGRAMS article. Heated oxygen sensor (bank No. 2, sensor No. 2) is located on exhaust manifold. see scheme 7 ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
3. With hand-held tester or scan tool still connected to DLC No. 3, start engine and warm engine to normal operating temperature. Monitor heated oxygen sensor (bank No. 2, sensor No. 2) output voltage while quickly accelerating engine to 4000 RPM for 3 times. Output voltage should fluctuate from.40 volt or less to.55 volt or more. If output voltage is not within specification, replace heated oxygen sensor (bank No. 2, sensor No. 2). If output voltage is within specification, problem is intermittent. Check for defective connections or intermittent problem in wiring between heated oxygen sensor (bank No. 2, sensor No. 2) and ECM.

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. If using Toyota hand-held tester, go to next step. If Toyota hand-held tester is not available, go to step 3.
2. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine. Allow engine to idle for at least 60 seconds.
4. Drive vehicle at 24 MPH or more for at least 40 seconds and then allow engine to idle for at least 10 seconds. Repeat this procedure 9 times and then check operation of Malfunction Indicator Light (MIL). If MIL illuminates, malfunction exists and DTC is set. If MIL does not illuminate, malfunction does not exist.

1. Ensure engine oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem does not exist, go to next step. If problem exists, repair as necessary.
2. Check operation of fuel injectors. See FUEL CONTROL under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Fuel injector volume should be 53-65 cc (3.2-3.9 cu. in.) within 15 seconds and difference in volume between each fuel injector should be less than 6 cc (.4 cu. in.). Fuel injectors should not leak more than one drop every 12 minutes. If fuel injectors are okay, go to next step. If fuel injectors are defective, replace fuel injectors as necessary.
3. Check Mass Airflow (MAF) meter and Engine Coolant Temperature (ECT) sensor. MAF meter may also be referred to as airflow meter. See AIRFLOW METER and ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If MAF meter and ECT sensor are okay, go to next step. If MAF meter or ECT sensor is defective, replace components as necessary.
4. Check ignition system by performing spark test. See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If ignition system operates properly and spark exist, go to next step. If ignition system does not operate properly and spark does not exist, repair ignition system as necessary.
5. Check fuel pressure. See FUEL PRESSURE under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ) with engine idling and should remain at least 21 psi (1.5 kg/cm 2 ) for a minimum of 5 minutes after engine is shut off. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, repair fuel system as necessary.
6. Check exhaust system for leaks. If no exhaust leak exists, go to next step. If exhaust leak exists, repair exhaust system as necessary.
7. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Start engine and maintain engine speed at 2500 RPM for about 90 seconds to fully warm the A/F sensor. Allow engine to idle.
8. Using hand-held tester or scan tool, monitor A/F sensor (bank No. 1, sensor No. 1) output voltage with engine idling, engine racing and while driving vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. Ensure A/F sensor output voltage is as specified. See «AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS»(ref-91210-S14703999412001060800000) table. If A/F sensor output voltage is not within specification, go to next step. If A/F sensor output voltage is within specification, go to step 10. AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS Application & Operating Condition Specification Using OBD-II Scan Tool Engine Idling, Engine Racing & Driving Vehicle (1) (2) Using Toyota Hand-Held Tester Engine Idling, Engine Racing & Driving Vehicle (1) (3) (1) Drive vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. (2) Voltage should not remain at.56 volt or less,.66 volt, or.76 volt or more. (3) Voltage should not remain at 2.80 volts or less, 3.30 volts, or 3.80 volts or more.
9. Check for open and short in wiring harness and electrical connectors between A/F sensor (bank No. 1, sensor No. 1) and ECM. See WIRING DIAGRAMS article. A/F sensor (bank No. 1, sensor No. 1) is located on exhaust manifold above catalytic converters. see scheme 7 ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, replace A/F sensor (bank No. 1, sensor No. 1). If wiring harness or electrical connector is defective, repair as necessary.
10. Using Toyota hand-held tester or scan tool, clear DTCs from ECM. Perform test drive confirmation and then go to next step. See «TEST DRIVE CONFIRMATION»(ref-91210-S01602834182001042700000).
11. Recheck for DTCs. If DTC P0171 or P0172 does not exist, go to next step. If DTC P0171 and/or P0172 exist, replace ECM. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2
12. Verify if vehicle ran out of fuel. If vehicle ran out of fuel, DTC P0171 and/or P0172 was caused by the vehicle running out of fuel. If vehicle did not run out of fuel, problem is intermittent. Check for defective connections or intermittent problem in wiring. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. If using Toyota hand-held tester, go to next step. If Toyota hand-held tester is not available, go to step 3.
2. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine. Allow engine to idle for at least 60 seconds.
4. Drive vehicle at 24 MPH or more for at least 40 seconds and then allow engine to idle for at least 10 seconds. Repeat this procedure 9 times and then check operation of Malfunction Indicator Light (MIL). If MIL illuminates, malfunction exists and DTC is set. If MIL does not illuminate, malfunction does not exist.

1. Ensure engine oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem does not exist, go to next step. If problem exists, repair as necessary.
2. Check operation of fuel injectors. See FUEL CONTROL under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Fuel injector volume should be 53-65 cc (3.2-3.9 cu. in.) within 15 seconds and difference in volume between each fuel injector should be less than 6 cc (.4 cu. in.). Fuel injectors should not leak more than one drop every 12 minutes. If fuel injectors are okay, go to next step. If fuel injectors are defective, replace fuel injectors as necessary.
3. Check Mass Airflow (MAF) meter and Engine Coolant Temperature (ECT) sensor. MAF meter may also be referred to as airflow meter. See AIRFLOW METER and ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If MAF meter and ECT sensor are okay, go to next step. If MAF meter or ECT sensor is defective, replace components as necessary.
4. Check ignition system by performing spark test. See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If ignition system operates properly and spark exist, go to next step. If ignition system does not operate properly and spark does not exist, repair ignition system as necessary.
5. Check fuel pressure. See FUEL PRESSURE under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ) with engine idling and should remain at least 21 psi (1.5 kg/cm 2 ) for a minimum of 5 minutes after engine is shut off. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, repair fuel system as necessary.
6. Check exhaust system for leaks. If no exhaust leak exists, go to next step. If exhaust leak exists, repair exhaust system as necessary.
7. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Start engine and maintain engine speed at 2500 RPM for about 90 seconds to fully warm the A/F sensor. Allow engine to idle.
8. Using hand-held tester or scan tool, monitor A/F sensor (bank No. 2, sensor No. 1) output voltage with engine idling, engine racing and while driving vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. Ensure A/F sensor output voltage is as specified. See «AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS»(ref-91210-S10441497282001060800000) table. If A/F sensor output voltage is not within specification, go to next step. If A/F sensor output voltage is within specification, go to step 10. AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS Application & Operating Condition Specification Using OBD-II Scan Tool Engine Idling, Engine Racing & Driving Vehicle (1) (2) Using Toyota Hand-Held Tester Engine Idling, Engine Racing & Driving Vehicle (1) (3) (1) Drive vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. (2) Voltage should not remain at.56 volt or less,.66 volt, or.76 volt or more. (3) Voltage should not remain at 2.80 volts or less, 3.30 volts, or 3.80 volts or more.
9. Check for open and short in wiring harness and electrical connectors between A/F sensor (bank No. 2, sensor No. 1) and ECM. See WIRING DIAGRAMS article. A/F sensor (bank No. 2, sensor No. 1) is located on exhaust manifold above catalytic converters. see scheme 7 ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, replace A/F sensor (bank No. 2, sensor No. 1). If wiring harness or electrical connector is defective, repair as necessary.
10. Using Toyota hand-held tester or scan tool, clear DTCs from ECM. Perform test drive confirmation and then go to next step. See «TEST DRIVE CONFIRMATION»(ref-91210-S27493987712001060800000).
11. Recheck for DTCs. If DTC P0174 or P0175 does not exist, go to next step. If DTC P0174 and/or P0175 exist, replace ECM. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2
12. Verify if vehicle ran out of fuel. If vehicle ran out of fuel, DTC P0174 and/or P0175 was caused by the vehicle running out of fuel. If vehicle did not run out of fuel, problem is intermittent. Check for defective connections or intermittent problem in wiring. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2

Engine Control Module (ECM) uses input signals provided by crankshaft and camshaft position sensors to monitor the changes in crankshaft rotation. If engine speed rate changes enough to equal a preset number, a misfire is detected and Malfunction Indicator Light (MIL) is illuminated. If misfire rate is great enough and driving conditions will cause catalytic converter damage or overheating, the MIL will blink when misfire is occurring. DTC is set when misfiring of random cylinders is detected during any particular 200 or 1000 revolutions. Possible causes are

1. Open or short in engine wiring harness.
2. Defective connections at ECM or component.
3. Disconnected, restricted or damaged vacuum hose(s).
4. Ignition system malfunction.
5. Defective fuel injector(s).
6. Improper fuel pressure.
7. Defective Mass Airflow (MAF) meter.
8. Defective Engine Coolant Temperature (ECT) sensor.
9. Improper engine compression.
10. Improper valve clearance.
11. Improper valve timing.

When 2 or more DTCs for misfiring cylinder are recorded repeatedly and DTC P0300 does not exist, it indicates misfires were detected and recorded at different times. If misfire cannot be reproduced, the reason may be because vehicle was driven with a lack of fuel, improper fuel, fouled spark plug or etc. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected. If COOLANT TEMP displayed in freeze frame data is less than 176°F (80°C), there is a possibility that misfire only exists during warm-up.

If oscilloscope is available, fuel injector operation on misfiring cylinder may be checked by reading fuel injector signal waveform pattern and fuel injector duration signal waveform pattern by connecting oscilloscope between terminal No. 21 (White/Black wire) at ECM electrical connector E4 and fuel injector driver terminal at ECM with engine idling. Terminal No. 21 is the E01 terminal at ECM. For ECM electrical connector terminal identification (Scheme 298) For fuel injector driver identification, see IDENTIFYING ECM FUEL INJECTOR DRIVER TERMINALS table. Fuel injector signal waveform pattern and fuel injector duration signal waveform pattern should be properly displayed within proper intervals. (Scheme 301)

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Check for any DTCs and read FREEZE FRAME data. Record DTCs and freeze frame data. If using hand-held tester, switch hand-held tester to CHECK mode.
2. Drive vehicle several times with engine speed, load and its surrounding range shown with ENGINE SPD, CALC LOAD in freeze frame data or MISFIRE RPM and MISFIRE LOAD in the data list on hand-held tester or scan tool.
3. Allow engine to idle for at least 5 3/4 minutes and then drive vehicle at specified engine speeds for specified amount of time. See «DRIVING PATTERN»(ref-91210-S28664948992001042700000) table. If using scan tool, turn ignition off after symptom is simulated the first time, then repeat test drive again. If using hand-held tester or scan tool, if a misfire is detected, a DTC will set and misfire will be indicated in freeze frame data. Turn ignition off and wait a minimum of 5 seconds. DRIVING PATTERN RPM Specified Time 1000 4 Minutes Or More 2000 2 1/2 Minutes Or More 3000 1 1/2 Minute Or More

Scheme 301

1. Check vacuum hoses for leaks, restrictions and proper routing. See VACUUM DIAGRAMS article for proper vacuum hose routing. Also, check engine wiring harness and electrical connectors for damage or poor connections. If no problems exist, go to next step. If problem exists, repair as necessary and perform «TEST DRIVE CONFIRMATION»(ref-91210-S21009361712001042700000).
2. Remove spark plug for misfiring cylinder. Ensure no carbon deposits exist, spark plug is not fouled and spark plug gap is.039-.047" (1.00-1.20 mm). Check ignition system by performing spark test. See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If ignition system operates properly and spark exist, go to next step. If ignition system does not operate properly and spark does not exist, repair ignition system as necessary.
3. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on. Using voltmeter, check voltage between body ground and fuel injector driver terminal for misfiring cylinder at appropriate ECM electrical connector. See «IDENTIFYING ECM FUEL INJECTOR DRIVER TERMINALS»(ref-91210-S37664789092001060800000) table. For ECM electrical connector terminal identification (Scheme 298) If voltage is not 9-14 volts at fuel injector driver terminal, go to next step. If voltage is 9-14 volts at fuel injector driver terminal, go to step 6. IDENTIFYING ECM FUEL INJECTOR DRIVER TERMINALS Fuel Injector No. (1) ECM Electrical Connector & Terminal Wire Color 1 E4 Terminal No. 1 Black/Red 2 E4 Terminal No. 2 Black 3 E4 Terminal No. 3 White 4 E4 Terminal No. 4 Red (1) For ECM electrical connector terminal identification (Scheme 298)
4. Disconnect electrical connector at fuel injector on misfiring cylinder. Using ohmmeter, check resistance between electrical terminals on fuel injector. Resistance should be 13.40-14.20 ohms at 68°F (20°C). If resistance is within specification, go to next step. If resistance is not within specification, replace fuel injector.
5. Check for open and short in wiring harness and electrical connectors between fuel injector on misfiring cylinder and ECM. See WIRING DIAGRAMS article. If wiring harness or electrical connector is defective, repair as necessary. If wiring harness and electrical connectors are okay, it may be necessary to check for open and short in wiring harness and electrical connectors in fuel injector power supply circuit. See WIRING DIAGRAMS article.
6. Check fuel pressure. See FUEL PRESSURE under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ) with engine idling and should remain at least 21 psi (1.5 kg/cm 2 ) for a minimum of 5 minutes after engine is shut off. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, repair fuel system as necessary.
7. Check operation of fuel injector on misfiring cylinder. See FUEL CONTROL under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Fuel injector volume should be 53-65 cc (3.2-3.9 cu. in.) within 15 seconds and difference in volume between each fuel injector should be less than 6 cc (.4 cu. in.). Fuel injectors should not leak more than one drop every 12 minutes. If fuel injectors are okay, go to next step. If fuel injectors are defective, replace fuel injectors as necessary.
8. Check Mass Airflow (MAF) meter and Engine Coolant Temperature (ECT) sensor. MAF meter may also be referred to as airflow meter. See AIRFLOW METER and ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If MAF meter and ECT sensor are okay, go to next step. If MAF meter or ECT sensor is defective, replace components as necessary.
9. Check engine compression on misfiring cylinder. See MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Check valve clearance on misfiring cylinder. See VALVE CLEARANCE under ENGINE MECHANICAL in ON-VEHICLE ADJUSTMENTS - 4-CYLINDER article. Check valve timing. See appropriate article in ENGINES. Repair engine as necessary.

Engine Control Module (ECM) uses input signals provided by crankshaft and camshaft position sensors to monitor the changes in crankshaft rotation. If engine speed rate changes enough to equal a preset number, a misfire is detected and Malfunction Indicator Light (MIL) is illuminated. If misfire rate is great enough and driving conditions will cause catalytic converter damage or overheating, the MIL will blink when misfire is occurring. DTC is set when misfiring cylinders is detected during any particular 200 or 1000 revolutions. Possible causes are

1. Open or short in engine wiring harness.
2. Defective connections at ECM or component.
3. Disconnected, restricted or damaged vacuum hose(s).
4. Ignition system malfunction.
5. Defective fuel injector(s).
6. Improper fuel pressure.
7. Defective Mass Airflow (MAF) meter.
8. Defective Engine Coolant Temperature (ECT) sensor.
9. Improper engine compression.
10. Improper valve clearance.
11. Improper valve timing.

If misfire cannot be reproduced, reason may be because of driving with lack of fuel, improper fuel, fouled spark plug, etc. Using Toyota hand-held tester or scan tool, read freeze frame data. Freeze frame data records engine conditions when malfunction is detected.

For diagnosis and repair procedure, see DTC P0300: RANDOM MISFIRE DETECTED .

1. Disconnect electrical connector at camshaft position sensor. Camshaft position sensor is located on end of cylinder head at flywheel end of engine and contains a Black 2-pin electrical connector with Yellow and Blue wires.
2. Using ohmmeter, check resistance between electrical terminals on camshaft position sensor. Resistance should be 835-1400 ohms with sensor temperature of 14-122°F (-10-50°C) and 1060-1645 ohms with sensor temperature of 122-212°F (50-100°C). If resistance is within specification, go to next step. If resistance is not within specification, replace camshaft position sensor. See CAMSHAFT POSITION SENSOR under IGNITION SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
3. Check for open and short in wiring harness and electrical connectors between camshaft position sensor and ECM. See WIRING DIAGRAMS article. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
4. Remove camshaft position sensor. See CAMSHAFT POSITION SENSOR under IGNITION SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article. Inspect camshaft position sensor and teeth of signal plate on outer circumference of intake camshaft. If camshaft position sensor or signal plate is damaged, replace components as necessary. If camshaft position sensor and signal plate are okay, replace ECM.

Engine Control Module (ECM) compares waveform pattern of Air/Fuel (A/F) sensor (bank No. 1, sensor No. 1) with waveform pattern of heated oxygen sensor (bank No. 1, sensor No. 2) below catalytic converter to determine if catalytic converter performance has deteriorated. A/F sensor and heated oxygen sensor are located on exhaust manifold above catalytic converter. see scheme 7 Air/fuel ratio compensation keeps the waveform pattern of A/F sensor repeatedly switching back and forth from rich to lean. If catalytic converter is functioning properly, the waveform pattern for heated oxygen sensor (bank No. 1, sensor No. 2) should switch back and forth from rich to lean more slowly than A/F sensor (bank No. 1, sensor No. 1). If both waveform patterns switch at a similar rate, catalytic converter performance has deteriorated. DTC is set when A/F sensor (bank No. 1, sensor No. 1) and heated oxygen sensor (bank No. 1, sensor No. 2) have nearly the same waveform pattern after engine and catalytic converter are at normal operating temperature and vehicle is driven. Possible causes are

1. Exhaust system leak.
2. Defective A/F sensor.
3. Defective heated oxygen sensor.
4. Defective catalytic converter.

Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

If oscilloscope is available, switching rate of heated oxygen sensor (bank No. 1, sensor No. 2) may compared to that of the A/F sensor (bank No. 1, sensor No. 1) by reading the waveform pattern to determine if malfunction exists. To check heated oxygen sensor waveform pattern, the A/F sensor (bank No. 1, sensor No. 1) must first be checked.

Connect oscilloscope between terminals No. 14 (Green wire) and No. 17 (Brown wire) at ECM electrical connector E5. This is the AF1A+ terminal at ECM for A/F sensor (bank No. 1 sensor No. 1) and E1 terminal on ECM. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 For ECM electrical connector terminal identification (Scheme 298)

Start engine and warm engine to normal operating temperature. Ensure all accessories are off. Increase engine speed to 2500-3000 RPM for 3 minutes. Confirm that waveform pattern for A/F sensor (bank No. 1, sensor No. 1) oscillates at about.5 volt during feedback to ECM. (Scheme 302) Disconnect oscilloscope and reconnect between terminals No. 11 (Black wire) and No. 17 (Brown wire) at ECM electrical connector E5. This is the OX1B terminal for heated oxygen sensor (bank No. 1, sensor No. 2) and E1 terminal on ECM. Read heated oxygen sensor (bank No. 1, sensor No. 2) waveform pattern. If malfunction exists, the heated oxygen sensor waveform pattern will be almost the same as that for the A/F sensor. (Scheme 302)

Scheme 302

1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0420 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and then retest.
2. Check exhaust system for leaks. If no exhaust leak exists, go to next step. If exhaust leak exists, repair exhaust system as necessary.
3. Disconnect electrical connector for A/F sensor (bank No. 1, sensor No. 1) located on exhaust manifold above catalytic converter. see scheme 7 Using ohmmeter, check resistance for heater on A/F sensor between +B and HT terminals on electrical connector for A/F sensor. (Scheme 300) Resistance should be.8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistance is within specification, go to next step. If resistance is not within specification, replace A/F sensor (bank No. 1, sensor No. 1).
4. Disconnect electrical connector for heated oxygen sensor (bank No. 1, sensor No. 2) located on exhaust manifold below catalytic converter. see scheme 7 Using ohmmeter, check resistance between +B and HT terminals on electrical connector for heater on heated oxygen sensor (bank No. 1, sensor No. 2). see scheme 9 Resistance should be 11-16 ohms at 68°F (20°C) and 23-32 ohms at 1472°F (800°C). If resistance is within specification, replace catalytic converters along with exhaust manifold. If resistance is not within specification, replace heated oxygen sensor (bank No. 1, sensor No. 2).

Engine Control Module (ECM) compares waveform pattern of Air/Fuel (A/F) sensor (bank No. 2, sensor No. 1) with waveform pattern of heated oxygen sensor (bank No. 2, sensor No. 2) below catalytic converter to determine if catalytic converter performance has deteriorated. A/F sensor and heated oxygen sensor are located on exhaust manifold above catalytic converter. see scheme 7 Air/fuel ratio compensation keeps the waveform pattern of A/F sensor repeatedly switching back and forth from rich to lean. If catalytic converter is functioning properly, the waveform pattern for heated oxygen sensor (bank No. 2, sensor No. 2) should switch back and forth from rich to lean more slowly than A/F sensor (bank No. 2, sensor No. 1). If both waveform patterns switch at a similar rate, catalytic converter performance has deteriorated. DTC is set when A/F sensor (bank No. 2, sensor No. 1) and heated oxygen sensor (bank No. 2, sensor No. 2) have nearly the same waveform pattern after engine and catalytic converter are at normal operating temperature and vehicle is driven. Possible causes are

1. Exhaust system leak.
2. Defective A/F sensor.
3. Defective heated oxygen sensor.
4. Defective catalytic converter.

Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

If oscilloscope is available, switching rate of heated oxygen sensor (bank No. 2, sensor No. 2) may compared to that of the A/F sensor (bank No. 2, sensor No. 1) by reading the waveform pattern to determine if malfunction exists. To check heated oxygen sensor waveform pattern, the A/F sensor (bank No. 2, sensor No. 1) must first be checked.

Connect oscilloscope between terminals No. 13 (White wire) and No. 17 (Brown wire) at ECM electrical connector E5. This is the AF2A+ terminal at ECM for A/F sensor (bank No. 2, sensor No. 1) and E1 terminal on ECM. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 For ECM electrical connector terminal identification (Scheme 298)

Start engine and warm engine to normal operating temperature. Ensure all accessories are off. Increase engine speed to 2500-3000 RPM for 3 minutes. Confirm that waveform pattern for A/F sensor (bank No. 2, sensor No. 1) oscillates at about.5 volt during feedback to ECM. (Scheme 302) Disconnect oscilloscope and reconnect between terminals No. 15 (White wire) and No. 17 (Brown wire) at ECM electrical connector E5. This is the OX2B terminal for heated oxygen sensor (bank No. 2, sensor No. 2) and E1 terminal on ECM. Read heated oxygen sensor (bank No. 2, sensor No. 2) waveform pattern. If malfunction exists, the heated oxygen sensor waveform pattern will be almost the same as that for the A/F sensor. (Scheme 302)

1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0430 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and then retest.
2. Check exhaust system for leaks. If no exhaust leak exists, go to next step. If exhaust leak exists, repair exhaust system as necessary.
3. Disconnect electrical connector for A/F sensor (bank No. 2, sensor No. 1) located on exhaust manifold above catalytic converter. see scheme 7 Using ohmmeter, check resistance for heater on A/F sensor between +B and HT terminals on electrical connector for A/F sensor. (Scheme 300) Resistance should be.8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistance is within specification, go to next step. If resistance is not within specification, replace A/F sensor (bank No. 2, sensor No. 1).
4. Disconnect electrical connector for heated oxygen sensor (bank No. 2, sensor No. 2) located on exhaust manifold below catalytic converter. see scheme 7 Using ohmmeter, check resistance between +B and HT terminals on electrical connector for heater on heated oxygen sensor (bank No. 2, sensor No. 2). see scheme 10 Resistance should be 11-16 ohms at 68°F (20°C) and 23-32 ohms at 1472°F (800°C). If resistance is within specification, replace catalytic converters along with exhaust manifold. If resistance is not within specification, replace heated oxygen sensor (bank No. 2, sensor No. 2).

1. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on. Using voltmeter, check voltage between terminals No. 2 (Yellow wire) and No. 18 (Brown wire) at ECM electrical connector E5. (Scheme 298) This is the VC and E2 terminals on ECM. Voltage should be 4.5-5.5 volts. If voltage is within specification, go to next step. If voltage is not within specification, replace ECM.
2. Turn ignition off. Connect voltmeter between terminals No. 18 (Brown wire) at ECM electrical connector E5 and No. 21 (Blue/Black or White wire) at ECM electrical connector E7. (Scheme 298) This is the E2 and PTNK terminals on ECM. There are 2 different wiring harnesses used and wire color varies according to wiring harness used. Remove fuel tank cap. Turn ignition on and note voltage. Voltage should be 3.0-3.6 volts. If voltage is not within specification, go to next step. If voltage is within specification, replace ECM.
3. Check for open and short in wiring harness and electrical connectors between vapor pressure sensor and ECM. See WIRING DIAGRAMS article. Vapor pressure sensor is located on top of fuel tank. see scheme 16 If wiring harness and electrical connectors are okay, replace vapor pressure sensor. See VAPOR PRESSURE SENSOR under EMISSION SYSTEMS & SUB-SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article. If wiring harness or electrical connector is defective, repair as necessary.

1. Test drive vehicle and check operation of speedometer. If speedometer operates properly, go to next step. If speedometer does not operate properly, repair speedometer as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Speedometer may not operate, as input signal from vehicle speed sensor may not be input to instrument cluster.
2. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Using ohmmeter, check for continuity between body ground and terminal No. 22 (Violet/White or White wire) at ECM electrical connector E7. (Scheme 298) This is the SPD terminal on ECM. There are 2 different wiring harnesses used and wire color varies according to wiring harness used. If no continuity exist, go to next step. If continuity exist, repair short to ground in Violet/White or White and electrical connectors between ECM and instrument cluster. See WIRING DIAGRAMS article.
3. Raise and support vehicle so front wheels may be rotated. Place transaxle in Neutral. Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 22 (Violet/White or White wire) at ECM electrical connector E7 while slowly rotating front wheel. (Scheme 298) This is the SPD terminal on ECM. Voltage should pulse between 0-5.0 volts. If voltage is within specification, replace ECM. If voltage is not within specification, repair open in Violet/White or White wire and electrical connectors between ECM and instrument cluster. See WIRING DIAGRAMS article.

1. Start engine and warm to engine to normal operating temperature. Ensure A/C and all accessories are off. Apply parking brake. Place transaxle in Neutral. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Note engine speed in less than 5 seconds and at more than 5 seconds. If difference in engine speed is 100 RPM or less, shut engine off. Go to next step. If difference in engine speed is more than 100 RPM, shut engine off. Go to step 7.
2. Ensure ignition is off. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Disconnect ECM electrical connector E4. (Scheme 298)
3. Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 18 (Black/Blue wire) at ECM electrical connector E4. (Scheme 298) This is the RSD terminal on ECM. Voltage should be 9-14 volts.
4. If voltage is within specification, go to next step. If voltage is not within specification, check IAC valve operation. See IDLE AIR CONTROL VALVE under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If IAC valve is defective, replace IAC valve. If IAC valve is okay, check for open and short in wiring harness and electrical connectors between IAC valve and ECM. See WIRING DIAGRAMS article. Repair wiring as necessary.
5. Check IAC valve operation. See IDLE AIR CONTROL VALVE under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If IAC valve is okay, go to next step. If IAC valve is defective, replace IAC valve.
6. Remove IAC valve from throttle body. Inspect IAC valve and passages for carbon build-up and blockage. If a problem exist, repair as necessary. If problem does not exist, replace ECM.
7. Ensure engine oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, an open or short in A/C switch signal circuit may exist. Check A/C amplifier. See appropriate MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Repair as necessary.

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. If using Toyota hand-held tester, go to next step. If Toyota hand-held tester is not available, go to step 3.
2. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine. Allow engine to idle for at least 60 seconds.
4. Drive vehicle at 24 MPH or more for at least 40 seconds and then allow engine to idle for at least 10 seconds. Repeat this procedure 9 times and then check operation of Malfunction Indicator Light (MIL). If MIL illuminates, malfunction exists and DTC is set. If MIL does not illuminate, malfunction does not exist.

1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P1133 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
2. With Toyota hand-held tester or scan tool still connected to DLC No. 3, start engine and maintain engine speed at 2500 RPM for about 90 seconds to fully warm the A/F sensors. Allow engine to idle.
3. Using hand-held tester or scan tool, monitor A/F sensor (bank No. 1, sensor No. 1) output voltage with engine idling, engine racing and while driving vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. Ensure A/F sensor output voltage is as specified. See «AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS»(ref-91210-S18467966652001051100000) table. If A/F sensor output voltage is not within specification, go to next step. If A/F sensor output voltage is within specification, go to step 9. NOTE: If A/F sensor output voltage remains 3.30 volts (Toyota hand-held tester) or.66 volt (OBD-II scan tool) during all conditions, A/F sensor circuit may be open. If A/F sensor output voltage remains 3.80 volts or more (Toyota hand-held tester) or.76 volt or more (OBD-II scan tool) during all conditions, A/F sensor circuit may be shorted. If A/F sensor output voltage remains 2.80 volts or less (Toyota hand-held tester) or.56 volt or less (OBD-II scan tool) during all conditions, A/F sensor circuit may be shorted. During fuel enrichment, A/F sensor output voltage may be less than 2.8 volts (Toyota hand-held tester) or.56 volt (OBD-II scan tool) which is normal. During fuel cut, A/F sensor output voltage may be more than 3.8 volts (Toyota hand-held tester) or.76 volt (OBD-II scan tool) which is normal. AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS Application & Operating Condition Specification Using OBD-II Scan Tool Engine Idling, Engine Racing & Driving Vehicle (1) (2) Using Toyota Hand-Held Tester Engine Idling, Engine Racing & Driving Vehicle (1) (3) (1) Drive vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. (2) Voltage should not remain at.56 volt or less,.66 volt, or.76 volt or more. (3) Voltage should not remain at 2.80 volts or less, 3.30 volts, or 3.80 volts or more.
4. Check for open and short in wiring harness and electrical connectors between A/F sensor (bank No. 1, sensor No. 1) and ECM. See WIRING DIAGRAMS article. A/F sensor (bank No. 1, sensor No. 1) is located on exhaust manifold above catalytic converters. see scheme 20 ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
5. Disconnect electrical connector for A/F sensor (bank No. 1, sensor No. 1). Using ohmmeter, check resistance for heater on A/F sensor between +B and HT terminals on electrical connector for A/F sensor. see scheme 21 Resistance should be.8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistance is within specification, go to next step. If resistance is not within specification, replace A/F sensor (bank No. 1, sensor No. 1).
6. Ensure engine oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem does not exist, go to next step. If problem exists, repair as necessary.
7. Check fuel pressure. See FUEL PRESSURE under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ) with engine idling and should remain at least 21 psi (1.5 kg/cm 2 ) for a minimum of 5 minutes after engine is shut off. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, repair fuel system as necessary.
8. Check operation of fuel injectors. See FUEL CONTROL under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Fuel injector volume should be 53-65 cc (3.2-3.9 cu. in.) within 15 seconds and difference in volume between each fuel injector should be less than 6 cc (.4 cu. in.). Fuel injectors should not leak more than one drop every 12 minutes. If fuel injectors are okay, replace A/F sensor (bank No. 1, sensor No. 1). If fuel injectors are defective, replace fuel injectors as necessary.
9. Using Toyota hand-held tester or scan tool, clear DTCs from ECM. Perform test drive confirmation and then go to next step. See «TEST DRIVE CONFIRMATION»(ref-91210-S37935410852001051100000).
10. Recheck for DTCs. If DTC P1133 does not exist, go to next step. If DTC P1133 exists, replace ECM. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2
11. Verify if vehicle ran out of fuel. If vehicle ran out of fuel, DTC P1133 was caused by the vehicle running out of fuel. If vehicle did not run out of fuel, problem is intermittent. Check for defective connections or intermittent problem in wiring. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2

1. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 5 (White/Blue wire) at ECM electrical connector E5. (Scheme 298) This is the HAF1A terminal on ECM. Voltage should be 9-14 volts. If voltage is not within specification, go to next step. If voltage is within specification, replace ECM.
2. Disconnect electrical connector for A/F sensor (bank No. 1, sensor No. 1). see scheme 20 Using ohmmeter, check resistance for heater on A/F sensor between +B and HT terminals on electrical connector for A/F sensor. see scheme 21 Resistance should be.8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistance is within specification, go to next step. If resistance is not within specification, replace A/F sensor (bank No. 1, sensor No. 1).
3. Check A/F heater relay. A/F heater relay may also be referred to as A/F HTR relay, A/F sensor relay or A/F relay. See A/F HEATER RELAY under MODULES, MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If A/F heater relay is okay, go to next step. If A/F heater relay is defective, replace A/F heater relay.
4. Check wiring harness and electrical connectors between A/F heater relay and A/F sensor (bank No. 1, sensor No. 1), and between A/F sensor (bank No. 1, sensor No. 1) and ECM. See WIRING DIAGRAMS article. It may be necessary to check A/F fuse (20-amp) which is located in fuse/relay box at driver's side front corner of engine compartment.

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. If using Toyota hand-held tester, go to next step. If Toyota hand-held tester is not available, go to step 3.
2. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine. Allow engine to idle for at least 60 seconds.
4. Drive vehicle at 24 MPH or more for at least 40 seconds and then allow engine to idle for at least 10 seconds. Repeat this procedure 9 times and then check operation of Malfunction Indicator Light (MIL). If MIL illuminates, malfunction exists and DTC is set. If MIL does not illuminate, malfunction does not exist.

1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P1153 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
2. With Toyota hand-held tester or scan tool still connected to DLC No. 3, start engine and maintain engine speed at 2500 RPM for about 90 seconds to fully warm the A/F sensors. Allow engine to idle.
3. Using hand-held tester or scan tool, monitor A/F sensor (bank No. 2, sensor No. 1) output voltage with engine idling, engine racing and while driving vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. Ensure A/F sensor output voltage is as specified. See «AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS»(ref-91210-S13037470952001051100000) table. If A/F sensor output voltage is not within specification, go to next step. If A/F sensor output voltage is within specification, go to step 9. NOTE: If A/F sensor output voltage remains 3.30 volts (Toyota hand-held tester) or.66 volt (OBD-II scan tool) during all conditions, A/F sensor circuit may be open. If A/F sensor output voltage remains 3.80 volts or more (Toyota hand-held tester) or.76 volt or more (OBD-II scan tool) during all conditions, A/F sensor circuit may be shorted. If A/F sensor output voltage remains 2.80 volts or less (Toyota hand-held tester) or.56 volt or less (OBD-II scan tool) during all conditions, A/F sensor circuit may be shorted. During fuel enrichment, A/F sensor output voltage may be less than 2.8 volts (Toyota hand-held tester) or.56 volt (OBD-II scan tool) which is normal. During fuel cut, A/F sensor output voltage may be more than 3.8 volts (Toyota hand-held tester) or.76 volt (OBD-II scan tool) which is normal. AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS Application & Operating Condition Specification Using OBD-II Scan Tool Engine Idling, Engine Racing & Driving Vehicle (1) (2) Using Toyota Hand-Held Tester Engine Idling, Engine Racing & Driving Vehicle (1) (3) (1) Drive vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. (2) Voltage should not remain at.56 volt or less,.66 volt, or.76 volt or more. (3) Voltage should not remain at 2.80 volts or less, 3.30 volts, or 3.80 volts or more.
4. Check for open and short in wiring harness and electrical connectors between A/F sensor (bank No. 2, sensor No. 1) and ECM. See WIRING DIAGRAMS article. A/F sensor (bank No. 2, sensor No. 1) is located on exhaust manifold above catalytic converters. see scheme 20 ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
5. Disconnect electrical connector for A/F sensor (bank No. 2, sensor No. 1). Using ohmmeter, check resistance for heater on A/F sensor between +B and HT terminals on electrical connector for A/F sensor. see scheme 21 Resistance should be.8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistance is within specification, go to next step. If resistance is not within specification, replace A/F sensor (bank No. 2, sensor No. 1).
6. Ensure engine oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem does not exist, go to next step. If problem exists, repair as necessary.
7. Check fuel pressure. See FUEL PRESSURE under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ) with engine idling and should remain at least 21 psi (1.5 kg/cm 2 ) for a minimum of 5 minutes after engine is shut off. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, repair fuel system as necessary.
8. Check operation of fuel injectors. See FUEL CONTROL under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Fuel injector volume should be 53-65 cc (3.2-3.9 cu. in.) within 15 seconds and difference in volume between each fuel injector should be less than 6 cc (.4 cu. in.). Fuel injectors should not leak more than one drop every 12 minutes. If fuel injectors are okay, replace A/F sensor (bank No. 2, sensor No. 1). If fuel injectors are defective, replace fuel injectors as necessary.
9. Using Toyota hand-held tester or scan tool, clear DTCs from ECM. Perform test drive confirmation and then go to next step. See «TEST DRIVE CONFIRMATION»(ref-91210-S26682195612001051100000).
10. Recheck for DTCs. If DTC P1153 does not exist, go to next step. If DTC P1153 exists, replace ECM. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2
11. Verify if vehicle ran out of fuel. If vehicle ran out of fuel, DTC P1153 was caused by the vehicle running out of fuel. If vehicle did not run out of fuel, problem is intermittent. Check for defective connections or intermittent problem in wiring. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2

1. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 4 (White/Red wire) at ECM electrical connector E5. (Scheme 298) This is the HAF2A terminal on ECM. Voltage should be 9-14 volts. If voltage is not within specification, go to next step. If voltage is within specification, replace ECM.
2. Disconnect electrical connector for A/F sensor (bank No. 2, sensor No. 1). see scheme 20 Using ohmmeter, check resistance for heater on A/F sensor between +B and HT terminals on electrical connector for A/F sensor. see scheme 21 Resistance should be.8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistance is within specification, go to next step. If resistance is not within specification, replace A/F sensor (bank No. 2, sensor No. 1).
3. Check A/F heater relay. A/F heater relay may also be referred to as A/F HTR relay, A/F sensor relay or A/F relay. See A/F HEATER RELAY under MODULES, MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If A/F heater relay is okay, go to next step. If A/F heater relay is defective, replace A/F heater relay.
4. Check wiring harness and electrical connectors between A/F heater relay and A/F sensor (bank No. 2, sensor No. 1), and between A/F sensor (bank No. 2, sensor No. 1) and ECM. See WIRING DIAGRAMS article. It may be necessary to check A/F fuse (20-amp) which is located in fuse/relay box at driver's side front corner of engine compartment.

1. Check for spark at cylinder No. 1 by performing spark test. See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Cylinder No. 1 is the front cylinder at timing chain end of engine and uses the ignition coil No. 1. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open and short in Green/Black and Red wires and electrical connectors between ECM and ignition coil No. 1. See WIRING DIAGRAMS article. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
3. Disconnect electrical connector at ignition coil No. 1. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 25 (Red wire) at ECM electrical connector E4. (Scheme 298) This is the IGF terminal on ECM. Voltage should 4.5-5.5 volts. If voltage is within specification, replace ignition coil No. 1. If voltage is not within specification, replace ECM.
4. Check for open and short in Green/Black wire and electrical connectors between ECM and ignition coil No. 1. See WIRING DIAGRAMS article. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
5. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Using voltmeter, check voltage between body ground and terminal No. 10 (Green/Black wire) at ECM electrical connector E4 while cranking engine. (Scheme 298) This is the IGT1 terminal on ECM. Voltage should be more than.1 volt and less than 4.5 volts. If voltage is not within specification, go to next step. If voltage is within specification, go to step 7.
6. Disconnect electrical connector at ignition coil No. 1. Using voltmeter, check voltage between body ground and terminal No. 10 (Green/Black wire) at ECM electrical connector E4 while cranking engine. (Scheme 298) Voltage should be more than.1 volt and less than 4.5 volts. If voltage is within specification, replace ignition coil No. 1. If voltage is not within specification, replace ECM.
7. Using voltmeter, check voltage between body ground and terminal No. 1 (Black/White wire) at electrical connector for ignition coil No. 1 with ignition switch in ON and START positions. (Scheme 303) Voltage should be 9-14 volts. If voltage is within specification, go to next step. If voltage is not within specification, check power supply circuit between ignition switch, IG2 relay and ignition coil No. 1. See WIRING DIAGRAMS article. IG2 relay provides voltage for power supply circuit to ignition coil No. 1. IG2 relay is located in fuse/relay box at driver's side front corner of engine compartment.
8. Check for open in White/Black wire and electrical connectors between ground and ignition coil No. 1. See WIRING DIAGRAMS article. If wiring harness and electrical connectors are okay, replace ignition coil No. 1. If wiring harness or electrical connector is defective, repair as necessary.

Scheme 303

1. Check for spark at cylinder No. 2 by performing spark test. See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Cylinder No. 2 is second cylinder from timing chain end of engine and uses the ignition coil No. 2. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open and short in Blue/Black and Red wires and electrical connectors between ECM and ignition coil No. 2. See WIRING DIAGRAMS article. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
3. Disconnect electrical connector at ignition coil No. 2. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 25 (Red wire) at ECM electrical connector E4. (Scheme 298) This is the IGF terminal on ECM. Voltage should 4.5-5.5 volts. If voltage is within specification, replace ignition coil No. 2. If voltage is not within specification, replace ECM.
4. Check for open and short in Blue/Black wire and electrical connectors between ECM and ignition coil No. 2. See WIRING DIAGRAMS article. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
5. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Using voltmeter, check voltage between body ground and terminal No. 11 (Blue/Black wire) at ECM electrical connector E4 while cranking engine. (Scheme 298) This is the IGT2 terminal on ECM. Voltage should be more than.1 volt and less than 4.5 volts. If voltage is not within specification, go to next step. If voltage is within specification, go to step 7.
6. Disconnect electrical connector at ignition coil No. 2. Using voltmeter, check voltage between body ground and terminal No. 11 (Blue/Black wire) at ECM electrical connector E4 while cranking engine. (Scheme 298) Voltage should be more than.1 volt and less than 4.5 volts. If voltage is within specification, replace ignition coil No. 2. If voltage is not within specification, replace ECM.
7. Using voltmeter, check voltage between body ground and terminal No. 1 (Black/White wire) at electrical connector for ignition coil No. 2 with ignition switch in ON and START positions. (Scheme 303) Voltage should be 9-14 volts. If voltage is within specification, go to next step. If voltage is not within specification, check power supply circuit between ignition switch, IG2 relay and ignition coil No. 2. See WIRING DIAGRAMS article. IG2 relay provides voltage for power supply circuit to ignition coil No. 2. IG2 relay is located in fuse/relay box at driver's side front corner of engine compartment.
8. Check for open in White/Black wire and electrical connectors between ground and ignition coil No. 2. See WIRING DIAGRAMS article. If wiring harness and electrical connectors are okay, replace ignition coil No. 2. If wiring harness or electrical connector is defective, repair as necessary.

1. Check for spark at cylinder No. 3 by performing spark test. See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Cylinder No. 3 is third cylinder from timing chain end of engine and uses the ignition coil No. 3. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open and short in Green and Red wires and electrical connectors between ECM and ignition coil No. 3. See WIRING DIAGRAMS article. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
3. Disconnect electrical connector at ignition coil No. 3. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 25 (Red wire) at ECM electrical connector E4. (Scheme 298) This is the IGF terminal on ECM. Voltage should 4.5-5.5 volts. If voltage is within specification, replace ignition coil No. 3. If voltage is not within specification, replace ECM.
4. Check for open and short in Green wire and electrical connectors between ECM and ignition coil No. 3. See WIRING DIAGRAMS article. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
5. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Using voltmeter, check voltage between body ground and terminal No. 12 (Green wire) at ECM electrical connector E4 while cranking engine. (Scheme 298) This is the IGT3 terminal on ECM. Voltage should be more than.1 volt and less than 4.5 volts. If voltage is not within specification, go to next step. If voltage is within specification, go to step 7.
6. Disconnect electrical connector at ignition coil No. 3. Using voltmeter, check voltage between body ground and terminal No. 12 (Green wire) at ECM electrical connector E4 while cranking engine. (Scheme 298) Voltage should be more than.1 volt and less than 4.5 volts. If voltage is within specification, replace ignition coil No. 3. If voltage is not within specification, replace ECM.
7. Using voltmeter, check voltage between body ground and terminal No. 1 (Black/White wire) at electrical connector for ignition coil No. 3 with ignition switch in ON and START positions. (Scheme 303) Voltage should be 9-14 volts. If voltage is within specification, go to next step. If voltage is not within specification, check power supply circuit between ignition switch, IG2 relay and ignition coil No. 3. See WIRING DIAGRAMS article. IG2 relay provides voltage for power supply circuit to ignition coil No. 3. IG2 relay is located in fuse/relay box at driver's side front corner of engine compartment.
8. Check for open in White/Black wire and electrical connectors between ground and ignition coil No. 3. See WIRING DIAGRAMS article. If wiring harness and electrical connectors are okay, replace ignition coil No. 3. If wiring harness or electrical connector is defective, repair as necessary.

1. Check for spark at cylinder No. 4 by performing spark test. See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Cylinder No. 4 is fourth cylinder from timing chain end of engine and uses the ignition coil No. 4. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open and short in Black and Red wires and electrical connectors between ECM and ignition coil No. 4. See WIRING DIAGRAMS article. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
3. Disconnect electrical connector at ignition coil No. 4. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 25 (Red wire) at ECM electrical connector E4. (Scheme 298) This is the IGF terminal on ECM. Voltage should 4.5-5.5 volts. If voltage is within specification, replace ignition coil No. 4. If voltage is not within specification, replace ECM.
4. Check for open and short in Black wire and electrical connectors between ECM and ignition coil No. 4. See WIRING DIAGRAMS article. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
5. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Using voltmeter, check voltage between body ground and terminal No. 13 (Black wire) at ECM electrical connector E4 while cranking engine. (Scheme 298) This is the IGT4 terminal on ECM. Voltage should be more than.1 volt and less than 4.5 volts. If voltage is not within specification, go to next step. If voltage is within specification, go to step 7.
6. Disconnect electrical connector at ignition coil No. 4. Using voltmeter, check voltage between body ground and terminal No. 13 (Black wire) at ECM electrical connector E4 while cranking engine. (Scheme 298) Voltage should be more than.1 volt and less than 4.5 volts. If voltage is within specification, replace ignition coil No. 4. If voltage is not within specification, replace ECM.
7. Using voltmeter, check voltage between body ground and terminal No. 1 (Black/White wire) at electrical connector for ignition coil No. 4 with ignition switch in ON and START positions. (Scheme 303) Voltage should be 9-14 volts. If voltage is within specification, go to next step. If voltage is not within specification, check power supply circuit between ignition switch, IG2 relay and ignition coil No. 4. See WIRING DIAGRAMS article. IG2 relay provides voltage for power supply circuit to ignition coil No. 4. IG2 relay is located in fuse/relay box at driver's side front corner of engine compartment.
8. Check for open in White/Black wire and electrical connectors between ground and ignition coil No. 4. See WIRING DIAGRAMS article. If wiring harness and electrical connectors are okay, replace ignition coil No. 4. If wiring harness or electrical connector is defective, repair as necessary.

Check valve timing while checking for loose, stretched or jumped teeth on timing chain. See appropriate article in ENGINES. If no problem exist, replace ECM. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If problem exists, repair or replace components as necessary.

1. Check valve timing. See appropriate article in ENGINES. If no problem exist, go to next step. If problem exists, repair or replace components as necessary.
2. If using Toyota hand-held tester, go to next step. If Toyota hand-held tester is not available, go to step 11.
3. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Start engine and warm engine to normal operating temperature. Allow engine to idle.
4. Select ACTIVE TEST mode and then VVT on hand-held tester to operate the VVT OCV. Note engine idle when VVT OCV is operated by hand-held tester. Engine idle should be normal with VVT OCV off and should become rough or engine may stall when VVT OCV is on. If engine idle does not function as specified, shut engine off. Go to next step. If engine idle is as specified, VVT OCV is functioning properly at this time. DTC may have been set because of a foreign object that was temporarily caught in engine oil system but after a short time system returned to normal.
5. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Connect oscilloscope between terminals No. 19 (White/Red wire) and No. 29 (White wire) at ECM electrical connector E4. (Scheme 298) This is the OCV+ and OCV- terminals on ECM.
6. Start engine and allow engine to idle. Ensure VVT OCV signal waveform pattern is as shown in illustration. (Scheme 304) As engine speed is increased, waveform frequency "A" should lengthen. If signal waveform pattern is as shown, shut engine off. Go to next step. If signal waveform pattern is not as shown, shut engine off. Replace ECM.
7. Check VVT controller assembly for proper operation. See appropriate article in ENGINES. If VVT controller assembly operates properly, go to next step. If VVT controller assembly does not operate properly, replace VVT controller assembly and go to next step.
8. Check VVT OCV resistance and operation. See VARIABLE VALVE TIMING CAMSHAFT TIMING OIL CONTROL VALVE under VARIABLE VALVE TIMING SYSTEM in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If VVT OCV is okay, go to next step. If VVT OCV is defective, replace VVT OCV and go to next step.
9. Check for restrictions in VVT OCV and oil passage. If no problem exist, go to next step. If problem exists, repair or replace components as necessary.
10. Using hand-held tester, clear DTCs from ECM. Start engine and allow engine to idle. Shut engine off. Turn ignition on. Using hand-held tester, check for DTCs. If DTC P1349 exists, replace ECM. If DTC P1349 does not exist, no problem is indicated at this time. DTC may have been set because of a foreign object that was temporarily caught in engine oil system but after a short time system returned to normal.
11. Start engine and warm engine to normal operating temperature. Allow engine to idle. Note engine idle while disconnecting electrical connector at VVT OCV. VVT OCV is located at intake manifold side of cylinder head, near timing chain end of engine. (Scheme 305) Engine idle should not change. Using jumper wires, apply battery voltage and ground to electrical terminals on VVT OCV. Engine should idle rough or stall. If VVT OCV operates as specified, shut engine off. Go to next step. If VVT OCV does not operate as specified, shut engine off. Go to step 14.
12. Reinstall electrical connector on VVT OCV. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Connect oscilloscope between terminals No. 19 (White/Red wire) and No. 29 (White wire) at ECM electrical connector E4. (Scheme 298) This is the OCV+ and OCV- terminals on ECM.
13. Start engine and allow engine to idle. Ensure VVT OCV signal waveform pattern is as shown in illustration. (Scheme 304) As engine speed is increased, waveform frequency "A" should lengthen. If signal waveform pattern is not as shown, shut engine off. Replace ECM. If signal waveform pattern is as shown, shut engine off. VVT OCV is functioning properly at this time. DTC may have been set because of a foreign object that was temporarily caught in engine oil system but after a short time system returned to normal.
14. Check VVT controller assembly for proper operation. See appropriate article in ENGINES. If VVT controller assembly operates properly, go to next step. If VVT controller assembly does not operate properly, replace VVT controller assembly and go to next step.
15. Check VVT OCV resistance and operation. See VARIABLE VALVE TIMING CAMSHAFT TIMING OIL CONTROL VALVE under VARIABLE VALVE TIMING SYSTEM in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If VVT OCV is okay, go to next step. If VVT OCV is defective, replace VVT OCV. and go to next step.
16. Check for blockage in VVT OCV and oil passage. If no problem exist, go to next step. If problem exists, repair or replace components as necessary.
17. Using scan tool, clear DTCs from ECM. Start engine and allow engine to idle. Shut engine off. Turn ignition on. Using scan tool, check for DTCs. If DTC P1349 exists, replace ECM. If DTC P1349 does not exist, no problem is indicated at this time. DTC may have been set because of a foreign object that was temporarily caught in engine oil system but after a short time system returned to normal.

Scheme 304

Scheme 305

1. If using Toyota hand-held tester, go to next step. If Toyota hand-held tester is not available, go to step 6.
2. Check stoplight operation. If stoplights operate properly, go to next step. If stoplights do not operate properly, repair as necessary and retest system. See EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT.
3. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on and then turn hand-held tester on.
4. Monitor STP signal on hand-held tester while depressing and releasing brake pedal. STP signal should indicate ON with brake pedal depressed and OFF with brake pedal released. If STP signal is not as specified, go to next step. If STP signal is as specified, problem is intermittent. Check for defective connections or intermittent problem in wiring between stoplight switch and ECM. See WIRING DIAGRAMS article. Stoplight switch is located near top of brake pedal. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2
5. Check wiring harness and electrical connectors between stoplight switch and ECM. See WIRING DIAGRAMS article. Stoplight switch is located near top of brake pedal. ECM is located behind passenger's side kick panel, just below instrument panel. see scheme 2 If wiring harness and electrical connectors are okay, replace ECM. If wiring harness or electrical connectors are defective, repair as necessary.
6. Check stoplight operation. If stoplights operate properly, go to next step. If stoplights do not operate properly, repair as necessary and retest system. See EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT.
7. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on.
8. Using voltmeter, check voltage between body ground and terminal No. 15 (Green/White or White wire) at ECM electrical connector E8 while depressing and releasing brake pedal. (Scheme 298) This is the STP terminal on ECM. There are 2 different wiring harnesses used and wire color varies according to wiring harness used.
9. With brake pedal depressed, voltage should be 7.5-14.0 volts. With brake pedal released, voltage should be less than 1.5 volts. If voltage is not within specification, go to next step. If voltage is within specification, problem is intermittent. Check for defective connections or intermittent problem in wiring harness and electrical connectors between stoplight switch and ECM and for intermittent problem with stoplight switch. See WIRING DIAGRAMS article. Stoplight switch is located near top of brake pedal.
10. Check wiring harness and electrical connectors between stoplight switch and ECM. See WIRING DIAGRAMS article. Stoplight switch is located near top of brake pedal. If wiring harness and electrical connectors are okay, replace ECM. If wiring harness or electrical connectors are defective, repair as necessary.

1. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2
2. Using voltmeter, check voltage between body ground and terminal No. 1 (Red/White or Sky Blue wire) at ECM electrical connector E8. (Scheme 298) This is the BATT terminal on ECM. There are 2 different wiring harnesses used and wire color varies according to wiring harness used. Voltage should be 9-14 volts. If voltage is not within specification, go to next step. If voltage is within specification, replace ECM.
3. Remove EFI1 fuse (20-amp) and EFI2 fuse (5-amp) from fuse/relay box at driver's side front corner of engine compartment. Check both fuses. If fuses are okay, reinstall fuses. Check wiring harness and electrical connectors between EFI2 fuse and ECM. See WIRING DIAGRAMS article. It may be necessary to check wiring between battery and EFI1 fuse. For additional wiring for EFI1 fuse to the battery, see POWER DISTRIBUTION article in WIRING DIAGRAMS. If fuses are defective, replace fuse and check for short in wiring harness and components connected to EFI1 and EFI2 fuses. See WIRING DIAGRAMS article. Repair wiring as necessary.

1. If using Toyota hand-held tester, go to next step. If Toyota hand-held tester is not available, go to step 4.
2. Connect hand-held tester to Data Link Connector (DLC) No. 3. see scheme 1 Start engine and warm engine to normal operating temperature. Allow engine to idle.
3. Select ACTIVE TEST mode and then VVT on hand-held tester to operate the VVT OCV. Note engine idle when VVT OCV is operated by hand-held tester. Engine idle should be normal with VVT OCV off and should become rough or engine may stall when VVT OCV is on. If engine idle does not function as specified, shut engine off. Go to next step. If engine idle is as specified, VVT OCV is functioning properly at this time. DTC may have been set due to intermittent problem in wiring harness or electrical connectors between ECM and VVT OCV.
4. Disconnect electrical connector at VVT OCV. VVT OCV is located at intake manifold side of cylinder head, near timing chain end of engine. (Scheme 305) Start engine and allow engine to idle. With engine idling, using jumper wires, apply battery voltage and ground to electrical terminals on VVT OCV. Engine should idle rough or stall. If VVT OCV operates as specified, shut engine off. Go to next step. If VVT OCV does not operate as specified, shut engine off. Replace VVT OCV. See VARIABLE VALVE TIMING CAMSHAFT TIMING OIL CONTROL VALVE under VARIABLE VALVE TIMING SYSTEM in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
5. Reinstall electrical connector on VVT OCV. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Connect oscilloscope between terminals No. 19 (White/Red wire) and No. 29 (White wire) at ECM electrical connector E4. (Scheme 298) This is the OCV+ and OCV- terminals on ECM.
6. Start engine and allow engine to idle. Ensure VVT OCV signal waveform pattern is as shown in illustration. (Scheme 304) As engine speed is increased, waveform frequency "A" should lengthen. If signal waveform pattern is as shown, shut engine off. Go to next step. If signal waveform pattern is not as shown, shut engine off. Replace ECM.
7. Check for open and short in wiring harness and electrical connectors between VVT OCV and ECM. See WIRING DIAGRAMS article. If wiring harness and electrical connectors are okay, problem is intermittent. Check for defective connections or intermittent problem in wiring between VVT OCV and ECM. If wiring harness or electrical connector is defective, repair as necessary.