Engine Control System Self-Diagnostics: Diagnosis Toyota Sequoia I

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 the tachometer 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 Violet/White wire and electrical connectors between MIL and Engine Control Module (ECM). See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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-133213-S42549162282002021900000).

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-133213-S06018343292002021900000) .
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-133213-S21645021812002021900000) .
4. Visual Inspection Inspect all electrical connectors and wiring for suspected circuit or component. Ensure all 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-133213-S06018343292002021900000) .
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-133213-S14575982052002021900000) table under DIAGNOSTIC TROUBLE CODE DEFINITIONS. If no DTCs are present and a no start condition exists, proceed to «BASIC DIAGNOSTIC PROCEDURES - V6 & V8»(ref-133197) article. If no DTCs are present and a driveability condition exists, proceed to «TROUBLE SHOOTING - NO CODES»(ref-133220) 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-133213-S21645021812002021900000) . 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 at driver's side of instrument panel. 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-133213-S05760061562002021900000) under SCAN TOOL PROBLEMS.
3. Record any DTCs and freeze frame data displayed for system diagnosis. If driveability problem exists and no DTCs are present, go to «TROUBLE SHOOTING - NO CODES»(ref-133220) article for diagnosis by symptom.
4. If any DTCs exist, perform appropriate DTC test under «DIAGNOSTIC TESTS»(ref-133213-S17518846152002021900000). For DTC descriptions, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-133213-S14575982052002021900000) table under DIAGNOSTIC TROUBLE CODE DEFINITIONS. For information on freeze frame data, see «FREEZE FRAME DATA»(ref-133213-S15903191492002021900000). For information on two-trip detection logic codes, see «TWO-TRIP DETECTION LOGIC»(ref-133213-S03515892222002021900000).
5. After repairs for DTC have been completed, DTC must be cleared from Engine Control Module (ECM). See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-133213-S21645021812002021900000). 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 Engine Control Module (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 transmission 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 at driver's side of instrument panel. 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 exists and no DTCs are present, go to «TROUBLE SHOOTING - NO CODES»(ref-133220) article for diagnosis by symptom.
4. If any DTCs exist, perform appropriate DTC test under «DIAGNOSTIC TESTS»(ref-133213-S17518846152002021900000). For DTC descriptions, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-133213-S14575982052002021900000) table under DIAGNOSTIC TROUBLE CODE DEFINITIONS. For information on freeze frame data, see «FREEZE FRAME DATA»(ref-133213-S15903191492002021900000). For information on two-trip detection logic DTCs, see «TWO-TRIP DETECTION LOGIC»(ref-133213-S03515892222002021900000).
5. After repairs for DTC have been completed, DTC must be cleared from Engine Control Module (ECM). See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-133213-S21645021812002021900000). 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 EFI No. 1 (20-amp) and ETCS (15-amp) fuses. EFI No. 1 and ETCS fuses are 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, test drive confirmation can be performed to verify repairs are made and that DTC does not reset. Test drive confirmation will duplicate conditions required to set specified DTCs.
2. Test drive confirmation lists the procedure to be performed to check that DTC does not reset. Test drive confirmation applies only to specific DTCs. Test drive confirmation 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 voltage and resistance between ground and specified terminal on DLC No. 3. See «DATA LINK CONNECTOR NO. 3 VOLTAGE & RESISTANCE SPECIFICATIONS»(ref-133213-S08644254032002021900000) table. (Scheme 46) If voltage or resistance are not within specification, check wiring circuit. See «WIRING DIAGRAMS»(ref-133228) article. For full wiring diagram of DLC No. 3, it may be necessary to see DATA LINK CONNECTORS article in WIRING DIAGRAMS.

DATA LINK CONNECTOR NO. 3 VOLTAGE & RESISTANCE SPECIFICATIONS

Scheme 46

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TESTS

Note. Before performing any diagnostic test, refer to 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 47)

Scheme 47

Diagnosis & Repair

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 top side of air intake hose, near upper cap on air cleaner assembly and contains a Black 5-pin electrical connector. See AIRFLOW METER under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3 at driver's side of instrument panel. 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 passenger's side of coolant pipe at front of engine, in front of intake manifold and contains Black 2-pin electrical connector with Green/White and Green/Yellow wires. ECM is located behind glove box and heater duct. see scheme 2
3. Turn ignition off. Disconnect electrical connector at ECT sensor. ECT sensor is located on passenger's side of coolant pipe at front of engine, in front of intake manifold and contains Black 2-pin electrical connector with Green/White and Green/Yellow wires. Connect jumper wire between both terminals on electrical connector for ECT sensor.
4. Turn ignition on. 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. See «ENGINE COOLANT TEMPERATURE SENSOR»(ref-133227-S21843869332002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
5. Turn ignition off. Remove jumper wire. Remove glove box and heater duct (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 terminals No. 14 (Green/Yellow wire) and No. 18 (Green/White wire) at ECM electrical connector E7 with all electrical connectors installed on ECM. (Scheme 47) This is the THW and E2 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 Green/Yellow wire or Green/White wire between ECT sensor and ECM. See «WIRING DIAGRAMS»(ref-133228) 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 passenger's side of coolant pipe at front of engine, in front of intake manifold and contains Black 2-pin electrical connector with Green/White and Green/Yellow wires.
9. Turn ignition on. 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. See «ENGINE COOLANT TEMPERATURE SENSOR»(ref-133227-S21843869332002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
10. Turn ignition off. Remove glove box and heater duct (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Disconnect ECM electrical connector E7. (Scheme 47) 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»(ref-133228) 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 on passenger's side front of engine where upper radiator hose is attached. If thermostat is defective, replace thermostat. If thermostat is okay, replace ECT sensor. ECT sensor is located on passenger's side of coolant pipe at front of engine, in front of intake manifold and contains Black 2-pin electrical connector with Green/White and Green/Yellow wires. See «ENGINE COOLANT TEMPERATURE SENSOR»(ref-133227-S21843869332002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

1. If Toyota hand-held tester is available, 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 at driver's side of instrument panel. see scheme 1 Turn ignition on and then turn hand-held tester on.
3. Using hand-held tester, monitor throttle valve opening for VTA and VTA2 circuits with accelerator pedal released and with accelerator pedal depressed. VTA circuit is displayed as a percentage and VTA2 circuit is displayed as a voltage. With accelerator pedal released, VTA circuit should be 8-20 percent and VTA2 circuit should be 2.0-2.9 volts. With accelerator pedal depressed, VTA circuit should be 64-96 percent and VTA2 circuit should be 4.7-5.1 volts. If throttle valve opening readings are not within specification, go to next step. If throttle valve opening readings are within specification, replace ECM. ECM is located behind glove box and heater duct. see scheme 2
4. Remove glove box and heater duct (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2
5. Ensure ignition is on. Using voltmeter, check voltage between terminals No. 2 (Green/Black wire) and No. 18 (Green/White wire) at ECM electrical connector E7. (Scheme 47) This is the VC and E2 terminals on ECM. Voltage should be 4.5-5.5 volts. If voltage is specification, go to next step. If voltage is not within specification, replace ECM.
6. Ensure ignition is still on. Using voltmeter, check voltage between terminals No. 13 (Black/Yellow wire) and No. 18 (Green/White wire) at ECM electrical connector E7 with accelerator pedal released and with accelerator pedal depressed. (Scheme 47) This is the VTA and E2 terminals on ECM. Also, check voltage between terminals No. 18 (Green/White wire) and No. 20 (Pink/Blue wire) at ECM electrical connector E7 with accelerator pedal released and with accelerator pedal depressed. This is the E2 and VTA2 terminals on ECM. Ensure voltage is within specification. See «TP SENSOR VOLTAGE SPECIFICATIONS AT ECM»(ref-133213-S01619609112002021900000) table. If any voltage reading is not within specification, go to next step. If all voltage readings are within specification, replace ECM. TP SENSOR VOLTAGE SPECIFICATIONS AT ECM Accelerator Pedal Position & Terminals Volts Accelerator Pedal Released VTA & E2.4-1.0 VTA2 & E2 2.0-2.9 Accelerator Pedal Depressed VTA & E2 3.2-4.8 VTA2 & E2 4.7-5.1
7. Turn ignition off. Check TP sensor. See «THROTTLE BODY»(ref-133222-S04410230492002021900000) under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. If TP sensor is okay, go to next step. If TP sensor is defective, replace TP sensor. See «THROTTLE BODY»(ref-133227-S01273866582002021900000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
8. Check for open and short in wiring harness and electrical connectors between TP sensor and ECM. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness or electrical connector is defective, repair as necessary.

Circuit Description

Throttle Position (TP) sensor uses 2 sensors which detects throttle opening and a malfunction of the TP sensor. TP sensor is located on throttle body and provides an input voltage of 0-5 volts to VTA and VTA2 terminals at Engine Control Module (ECM) in proportion to throttle opening. ECM uses input signals and controls the throttle control motor to provide proper throttle valve opening in response to driving conditions. DTC is set when improper input signals from TP sensor are received at ECM. If DTC P0121 exists, ECM will turn off the power to throttle control motor and throttle valve is closed by the return spring. When this occurs, throttle valve is controlled by throttle cable connected to accelerator pedal. Possible cause is defective TP sensor.

Diagnostic Aids

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

TP sensor is defective. Replace TP sensor. See THROTTLE BODY under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. When performing test drive confirmation, procedures must be performed exactly as listed or the malfunction may not be detected. If Toyota hand-held tester is available, 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 at driver's side of instrument panel. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine and allow engine to idle for at least 100 seconds. Drive vehicle at 24 MPH or more for at least 20 seconds and then allow engine to idle for at least 30 seconds. 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.
4. Start engine and allow engine to idle for at least 100 seconds. Drive vehicle at 24 MPH or more for at least 20 seconds and then allow engine to idle for at least 30 seconds.
5. Turn ignition off. Repeat step 4 again 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 P0125 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
2. Check for any loose or defective PCV valve piping connections. PCV valve is located at front of driver's side valve cover, below oil fill cap. If PCV valve piping is okay, go to next step. If PCV valve piping is defective, repair or replace components as necessary.
3. With Toyota hand-held tester or scan tool still connected to DLC No. 3, start engine and warm engine to normal operating temperature. Allow engine to idle.
4. Using hand-held tester or scan tool, monitor output voltage for heated oxygen sensors on exhaust manifolds (bank No. 1 sensor No. 1 and bank No. 2 sensor No. 1) while quickly increasing engine speed to 4000 RPM 3 consecutive times. Output voltage should indicate a rich signal of.45 volt at least once. If output voltage is not within specification, go to next step. If output voltage is within specification, go to step 11.
5. Check for open and short in wiring harness and electrical connectors between appropriate heated oxygen sensor on each exhaust manifold (bank No. 1 sensor No. 1 and bank No. 2 sensor No. 1) and ECM. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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.
6. Using hand-held tester or scan tool, check if a misfire has occurred by monitoring DTCs and DATA LIST. If misfire has not occurred, go to next step. If a misfire has occurred, perform appropriate DTC test for misfire detected.
7. 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.
8. Check fuel pressure. See «FUEL PRESSURE»(ref-133197-S34294097522002021900000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Fuel pressure should be 38-44 psi (2.7-3.1 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.
9. Check operation of fuel injectors. See «FUEL CONTROL»(ref-133222-S30551786532002021900000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. Fuel injector volume should be 56-69 cc (.18-.23 oz.) within 15 seconds and difference in volume between each fuel injector should be less than 13 cc (.04 oz.). 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.
10. Check exhaust system for leaks. If no exhaust leak exists, replace appropriate heated oxygen sensor located on exhaust manifold. See «HEATED OXYGEN SENSOR»(ref-133227-S08172754992002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article. If exhaust leak exists, repair exhaust system as necessary.
11. 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-133213-S26225003642002021900000).
12. Recheck for DTCs. If DTC P0125 does not exist, go to next step. If DTC P0125 exists, replace ECM. ECM is located behind glove box and heater duct. see scheme 2
13. 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 glove box and heater duct. see scheme 2

1. Remove and inspect cooling system thermostat for damage and proper operation. Thermostat is located behind thermostat housing on passenger's side front of engine where upper radiator hose is attached. 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 glove box and heater duct. see scheme 2

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. When performing test drive confirmation, procedures must be performed exactly as listed or the malfunction may not be detected. If Toyota hand-held tester is available, 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 at driver's side of instrument panel. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine and allow engine to idle for at least 100 seconds. Drive vehicle at 24 MPH or more for at least 20 seconds and then allow engine to idle for at least 30 seconds. 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.
4. Start engine and allow engine to idle for at least 100 seconds. Drive vehicle at 24 MPH or more for at least 20 seconds and then allow engine to idle for at least 30 seconds.
5. Turn ignition off. Repeat step 4 again 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 P0130 and/or DTC P0150 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
2. With hand-held tester or scan tool still connected to DLC No. 3, start engine and increase engine speed to 2500 RPM for approximately 90 seconds and then allow engine to idle. Monitor output voltage for appropriate heated oxygen sensor on exhaust manifold with engine idling. Output voltage should fluctuate from less than.40 volt to more than.55 volt. If output voltage is not within specification, go to next step. If output voltage is within specification, go to step 7.
3. Check for open and short in wiring harness and electrical connectors between appropriate heated oxygen sensor on exhaust manifold and ECM. See «WIRING DIAGRAMS»(ref-133228) article. Heated oxygen sensor (bank No. 1 sensor No. 1) is located on driver's side exhaust manifold and heated oxygen sensor (bank No. 2 sensor No. 1) is located on passenger's side exhaust manifold. ECM is located behind glove box and heater duct. 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. Ensure engine oil dipstick, oil filler cap, Positive Crankcase Ventilation (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.
5. Check fuel pressure. See «FUEL PRESSURE»(ref-133197-S34294097522002021900000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Fuel pressure should be 38-44 psi (2.7-3.1 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 operation of fuel injectors. See «FUEL CONTROL»(ref-133222-S30551786532002021900000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. Fuel injector volume should be 56-69 cc (.18-.23 oz.) within 15 seconds and difference in volume between each fuel injector should be less than 13 cc (.04 oz.). Fuel injectors should not leak more than one drop every 12 minutes. If fuel injectors are okay, replace appropriate heated oxygen sensor located on exhaust manifold. See «HEATED OXYGEN SENSOR»(ref-133227-S08172754992002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article. If fuel injectors are defective, replace fuel injectors as necessary.
7. 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-133213-S15163442912002021900000).
8. Recheck for DTCs. If DTC P0130 and/or DTC P0150 exists, replace ECM. ECM is located behind glove box and heater duct. see scheme 2 If DTC P0130 or DTC P0150 does not exist, check for defective connections or intermittent problem in wiring between heated oxygen sensor on exhaust manifold and ECM. ECM is located behind glove box and heater duct. see scheme 2

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. When performing test drive confirmation, procedures must be performed exactly as listed or the malfunction may not be detected. If Toyota hand-held tester is available, 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 at driver's side of instrument panel. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine and allow engine to idle for at least 100 seconds. Drive vehicle at 24 MPH or more for at least 20 seconds and then allow engine to idle for at least 30 seconds. 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.
4. Start engine and allow engine to idle for at least 100 seconds. Drive vehicle at 24 MPH or more for at least 20 seconds and then allow engine to idle for at least 30 seconds.
5. Turn ignition off. Repeat step 4 again 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 P0133 and/or DTC P0153 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
2. With hand-held tester or scan tool still connected to DLC No. 3, start engine and increase engine speed to 2500 RPM for approximately 90 seconds and then allow engine to idle. Monitor output voltage for appropriate heated oxygen sensor on exhaust manifold with engine idling. Output voltage should fluctuate from less than.40 volt to more than.55 volt. If output voltage is not within specification, go to next step. If output voltage is within specification, go to step 7.
3. Check for open and short in wiring harness and electrical connectors between appropriate heated oxygen sensor on exhaust manifold and ECM. See «WIRING DIAGRAMS»(ref-133228) article. Heated oxygen sensor (bank No. 1 sensor No. 1) is located on driver's side exhaust manifold and heated oxygen sensor (bank No. 2 sensor No. 1) is located on passenger's side exhaust manifold. ECM is located behind glove box and heater duct. 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. Ensure engine oil dipstick, oil filler cap, Positive Crankcase Ventilation (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.
5. Check fuel pressure. See «FUEL PRESSURE»(ref-133197-S34294097522002021900000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Fuel pressure should be 38-44 psi (2.7-3.1 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 operation of fuel injectors. See «FUEL CONTROL»(ref-133222-S30551786532002021900000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. Fuel injector volume should be 56-69 cc (.18-.23 oz.) within 15 seconds and difference in volume between each fuel injector should be less than 13 cc (.04 oz.). Fuel injectors should not leak more than one drop every 12 minutes. If fuel injectors are okay, replace appropriate heated oxygen sensor located on exhaust manifold. See «HEATED OXYGEN SENSOR»(ref-133227-S08172754992002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article. If fuel injectors are defective, replace fuel injectors as necessary.
7. 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-133213-S33510914402002021900000).
8. Recheck for DTCs. If DTC P0133 and/or DTC P0153 exists, replace ECM. ECM is located behind glove box and heater duct. see scheme 2 If DTC P0133 or DTC P0153 does not exist, check for defective connections or intermittent problem in wiring between heated oxygen sensor on exhaust manifold and ECM. ECM is located behind glove box and heater duct. see scheme 2

1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0136 and/or 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 appropriate heated oxygen sensor on exhaust pipe and ECM. See «WIRING DIAGRAMS»(ref-133228) article. Heated oxygen sensor (bank No. 1 sensor No. 2) is located on driver's side exhaust pipe behind catalytic converter and heated oxygen sensor (bank No. 2 sensor No. 2) is located on passenger's side exhaust pipe behind catalytic converter. ECM is located behind glove box and heater duct. 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. Increase engine speed to 2500 RPM for 3 minutes and then allow engine to idle. Monitor output voltage for appropriate heated oxygen sensor located on exhaust pipe behind catalytic converter while quickly accelerating engine to 4000 RPM 3 consecutive times. Output voltage should fluctuate from.40 volt or less to.50 volt or more. If output voltage is not within specification, replace appropriate heated oxygen sensor on exhaust pipe behind catalytic converter. See «HEATED OXYGEN SENSOR»(ref-133227-S08172754992002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article. If output voltage is within specification, problem is intermittent. Check for defective connections or intermittent problem in wiring between appropriate heated oxygen sensor on exhaust pipe behind catalytic converter and ECM.

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. When performing test drive confirmation, procedures must be performed exactly as listed or the malfunction may not be detected. If Toyota hand-held tester is available, 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 at driver's side of instrument panel. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine and allow engine to idle for at least 100 seconds. Drive vehicle at 24 MPH or more for at least 20 seconds and then allow engine to idle for at least 30 seconds. 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.
4. Start engine and allow engine to idle for at least 100 seconds. Drive vehicle at 24 MPH or more for at least 20 seconds and then allow engine to idle for at least 30 seconds.
5. Turn ignition off. Repeat step 4 again 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 for any loose or defective PCV valve piping connections. PCV valve is located at front of driver's side valve cover, below oil fill cap. If PCV valve piping is okay, go to next step. If PCV valve piping is defective, repair or replace components as necessary.
3. Check operation of fuel injectors. See «FUEL CONTROL»(ref-133222-S30551786532002021900000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. Fuel injector volume should be 56-69 cc (.18-.23 oz.) within 15 seconds and difference in volume between each fuel injector should be less than 13 cc (.04 oz.). 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.
4. Check Mass Airflow (MAF) meter and Engine Coolant Temperature (ECT) sensor. MAF meter may also be referred to as airflow meter. See «AIRFLOW METER»(ref-133222-S29311638152002021900000) and «ENGINE COOLANT TEMPERATURE SENSOR»(ref-133222-S34732452662002021900000) under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - V6 & V8 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. See «AIRFLOW METER»(ref-133227-S33806184422002021900000) or «ENGINE COOLANT TEMPERATURE SENSOR»(ref-133227-S21843869332002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
5. Check ignition system by performing spark test. See «SPARK TEST»(ref-133197-S27511875622002021900000) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. If ignition system operates properly and spark exists, go to next step. If ignition system does not operate properly and spark does not exist, repair ignition system as necessary.
6. Check fuel pressure. See «FUEL PRESSURE»(ref-133197-S34294097522002021900000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Fuel pressure should be 38-44 psi (2.7-3.1 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 exhaust system for leaks. If no exhaust leak exists, go to next step. If exhaust leak exists, repair exhaust system as necessary.
8. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3 at driver's side of instrument panel. see scheme 1 Start engine and maintain engine speed at 2500 RPM for about 90 seconds and then allow engine to idle. Monitor output voltage for heated oxygen sensor (bank No. 1 sensor No. 1) which is located on driver's side exhaust manifold with engine idling. Output voltage should fluctuate from less than.40 volt to more than.55 volt. If output voltage is not within specification, go to next step. If output voltage is within specification, go to step 10.
9. Check for open and short in wiring harness and electrical connectors between heated oxygen sensor (bank No. 1 sensor No. 1) and ECM. See «WIRING DIAGRAMS»(ref-133228) article. Heated oxygen sensor (bank No. 1 sensor No. 1) is located on driver's side exhaust manifold. ECM is located behind glove box and heater duct. see scheme 2 If wiring harness and electrical connectors are okay, replace heated oxygen sensor (bank No. 1 sensor No. 1). See «HEATED OXYGEN SENSOR»(ref-133227-S08172754992002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article. 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-133213-S13716590822002021900000).
11. Recheck for DTCs. If DTC P0171 or P0172 does not exist, go to next step. If DTC P0171 and/or P0172 exists, replace ECM. ECM is located behind glove box and heater duct. 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 glove box and heater duct. see scheme 2

1. Test drive confirmation may be performed to operate vehicle under conditions which may cause DTC to be set. When performing test drive confirmation, procedures must be performed exactly as listed or the malfunction may not be detected. If Toyota hand-held tester is available, 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 at driver's side of instrument panel. see scheme 1 Switch hand-held tester from NORMAL mode to CHECK mode.
3. Start engine and allow engine to idle for at least 100 seconds. Drive vehicle at 24 MPH or more for at least 20 seconds and then allow engine to idle for at least 30 seconds. 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.
4. Start engine and allow engine to idle for at least 100 seconds. Drive vehicle at 24 MPH or more for at least 20 seconds and then allow engine to idle for at least 30 seconds.
5. Turn ignition off. Repeat step 4 again 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 for any loose or defective PCV valve piping connections. PCV valve is located at front of driver's side valve cover, below oil fill cap. If PCV valve piping is okay, go to next step. If PCV valve piping is defective, repair or replace components as necessary.
3. Check operation of fuel injectors. See «FUEL CONTROL»(ref-133222-S30551786532002021900000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. Fuel injector volume should be 56-69 cc (.18-.23 oz.) within 15 seconds and difference in volume between each fuel injector should be less than 13 cc (.04 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.
4. Check Mass Airflow (MAF) meter and Engine Coolant Temperature (ECT) sensor. MAF meter may also be referred to as airflow meter. See «AIRFLOW METER»(ref-133222-S29311638152002021900000) and «ENGINE COOLANT TEMPERATURE SENSOR»(ref-133222-S34732452662002021900000) under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - V6 & V8 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. See «AIRFLOW METER»(ref-133227-S33806184422002021900000) or «ENGINE COOLANT TEMPERATURE SENSOR»(ref-133227-S21843869332002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
5. Check ignition system by performing spark test. See «SPARK TEST»(ref-133197-S27511875622002021900000) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. If ignition system operates properly and spark exists, go to next step. If ignition system does not operate properly and spark does not exist, repair ignition system as necessary.
6. Check fuel pressure. See «FUEL PRESSURE»(ref-133197-S34294097522002021900000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Fuel pressure should be 38-44 psi (2.7-3.1 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 exhaust system for leaks. If no exhaust leak exists, go to next step. If exhaust leak exists, repair exhaust system as necessary.
8. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3 at driver's side of instrument panel. see scheme 1 Start engine and maintain engine speed at 2500 RPM for about 90 seconds and then allow engine to idle. Monitor output voltage for heated oxygen sensor (bank No. 2 sensor No. 1) which is located on passenger's side exhaust manifold with engine idling. Output voltage should fluctuate from less than.40 volt to more than.55 volt. If output voltage is not within specification, go to next step. If output voltage is within specification, go to step 10.
9. Check for open and short in wiring harness and electrical connectors between heated oxygen sensor (bank No. 2 sensor No. 1) and ECM. See «WIRING DIAGRAMS»(ref-133228) article. Heated oxygen sensor (bank No. 2 sensor No. 1) is located on passenger's side exhaust manifold. ECM is located behind glove box and heater duct. see scheme 2 If wiring harness and electrical connectors are okay, replace heated oxygen sensor (bank No. 2 sensor No. 1). See «HEATED OXYGEN SENSOR»(ref-133227-S08172754992002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article. 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-133213-S05139023112002021900000).
11. Recheck for DTCs. If DTC P0174 or P0175 does not exist, go to next step. If DTC P0174 and/or P0175 exists, replace ECM. ECM is located behind glove box and heater duct. 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 glove box and heater duct. 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.
12. Defective Positive Crankcase Ventilation (PCV) valve piping.

This DTC uses two-trip detection logic. 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 the fuel injector signal waveform pattern and fuel injector duration signal waveform pattern which may be checked by connecting oscilloscope between terminal No. 21 (White/Black wire) at ECM electrical connector E8 and fuel injector driver terminal at ECM with engine idling. Terminal No. 21 is the E01 terminal on ECM. For ECM electrical connector terminal identification (Scheme 47) For fuel injector driver identification, see IDENTIFYING ECM FUEL INJECTOR DRIVER TERMINALS table. ECM is located behind glove box and heater duct. see scheme 2 Fuel injector signal waveform pattern and fuel injector duration signal waveform pattern should be properly displayed within proper intervals. (Scheme 48)

1. When performing test drive confirmation, procedures must be performed exactly as listed or the malfunction may not be detected. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3 at driver's side of instrument panel. 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 3 1/2 minutes and then drive vehicle at specified engine speeds for specified amount of time. See «DRIVING PATTERN»(ref-133213-S28880563132002021900000) 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 Engine RPM Specified Time 1000 3 Minutes Or More 2000 1 1/2 Minutes Or More 3000 1 Minute Or More

Scheme 48

1. Check vacuum hoses for leaks, restrictions and proper routing. See «VACUUM DIAGRAMS»(ref-133225) 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-133213-S38605103862002021900000).
2. Check for any loose or defective PCV valve piping connections. PCV valve is located at front of driver's side valve cover, below oil fill cap. If PCV valve piping is okay, go to next step. If PCV valve piping is defective, repair or replace components as necessary.
3. Remove spark plug for misfiring cylinder. Ensure no carbon deposits exist, spark plug is not fouled and spark plug gap is.031" (.80 mm). Check ignition system by performing spark test. See «SPARK TEST»(ref-133197-S27511875622002021900000) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 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.
4. Remove glove box and heater duct (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-133213-S24609219232002021900000) table. For ECM electrical connector terminal identification (Scheme 47) 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 7. IDENTIFYING ECM FUEL INJECTOR DRIVER TERMINALS Fuel Injector No. (1) ECM Electrical Connector & Terminal (2) Wire Color 1 E7 Terminal No. 5 Red 2 E7 Terminal No. 6 White 3 E8 Terminal No. 1 Green 4 E8 Terminal No. 2 Red/Black 5 E8 Terminal No. 3 Blue 6 E8 Terminal No. 4 Yellow 7 E8 Terminal No. 5 Blue/Red 8 E8 Terminal No. 6 Red/White (1) Fuel injectors No. 1, 3, 5 and 7 are on driver's side of engine with No. 1 at timing belt end of engine and No. 7 at flywheel end of engine. Fuel injectors No. 2, 4, 6 and 8 are on passenger's side of engine with No. 2 at timing belt end of engine and No. 8 at flywheel end of engine. (2) For ECM electrical connector terminal identification (Scheme 47)
5. 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. See «FUEL RAILS & FUEL INJECTORS»(ref-133227-S30147931282002021900000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
6. Check for open and short in wiring harness and electrical connectors between fuel injector on misfiring cylinder and ECM. See «WIRING DIAGRAMS»(ref-133228) 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»(ref-133228) article.
7. Check fuel pressure. See «FUEL PRESSURE»(ref-133197-S34294097522002021900000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Fuel pressure should be 38-44 psi (2.7-3.1 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 injector on misfiring cylinder. See «FUEL CONTROL»(ref-133222-S30551786532002021900000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. Fuel injector volume should be 56-69 cc (.18-.23 oz.) within 15 seconds and difference in volume between each fuel injector should be less than 13 cc (..02 oz.). 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 Mass Airflow (MAF) meter and Engine Coolant Temperature (ECT) sensor. MAF meter may also be referred to as airflow meter. See «AIRFLOW METER»(ref-133222-S29311638152002021900000) and «ENGINE COOLANT TEMPERATURE SENSOR»(ref-133222-S34732452662002021900000) under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - V6 & V8 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. See «AIRFLOW METER»(ref-133227-S33806184422002021900000) or «ENGINE COOLANT TEMPERATURE SENSOR»(ref-133227-S21843869332002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
10. Check engine compression on misfiring cylinder. See «MECHANICAL INSPECTION»(ref-133197-S33183330212002021900000) under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Check valve clearance on misfiring cylinder. See «V8 VALVE CLEARANCE»(ref-133194-S02362508332002021900000) under ENGINE MECHANICAL in ON-VEHICLE ADJUSTMENTS - V6 & V8 article. Check valve timing. See appropriate article in ENGINES. Repair engine as necessary.

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

1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3 at driver's side of instrument panel. see scheme 1 Disconnect EB2 electrical connector on 4WD models or EB3 electrical connector on 2WD models. see scheme 11 EB2 or EB3 electrical connector is an in-line Gray 3-pin electrical connector located near the starter.
2. Note wire terminal identification in male side of EB2 or EB3 electrical connector. see scheme 12 On 2WD models, remove wires from terminals No. 2 and 3 in male side of EB3 electrical connector. Reverse wire location for terminals No. 2 and 3 and reinstall wires in male side of EB3 electrical connector. Reconnect EB3 electrical connector. On 4WD models, remove wires from terminals No. 1 and 2 in male side of EB2 electrical connector. Reverse wire location for terminals No. 1 and 2 and reinstall wires in male side of EB2 electrical connector. Reconnect EB2 electrical connector.
3. On all models, turn ignition on and then turn hand-held tester or scan tool on. Using Toyota hand-held tester or scan tool, clear DTCs from ECM. Start engine and warm engine to normal operating temperature. Suddenly accelerate engine to 4000 RPM for 3 consecutive times. Recheck for DTCs. If DTC P0330 still exists and DTC did not change from original DTC of P0330, go to next step. If DTC changes from original DTC of P0330 to P0325, go to step 5.
4. Check for open and short in wiring harness and electrical connectors between EB2 or EB3 electrical connector and ECM for knock sensor No. 2. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness or electrical connector is defective, repair as necessary. If wiring harness and electrical connectors are okay, replace ECM. ECM is located behind glove box and heater duct. see scheme 2
5. Check for open and short in wiring harness and electrical connectors between EB2 or EB3 electrical connector and knock sensor No. 2. See «WIRING DIAGRAMS»(ref-133228) article. Knock sensor No. 2 is located below intake manifold on cylinder block. see scheme 13 If wiring harness or electrical connector is defective, repair as necessary. If wiring harness and electrical connectors are okay, replace knock sensor No. 2. See «KNOCK SENSOR»(ref-133227-S37923688532002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

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. Check heated oxygen sensor (bank No. 1 sensor No. 1). See «DTC P0130: HEATED OXYGEN SENSOR CIRCUIT (BANK NO. 1 SENSOR NO. 1), OR DTC P0150: HEATED OXYGEN SENSOR CIRCUIT (BANK NO. 2 SENSOR NO. 1)»(ref-133213-S20907877862002021900000) . If heated oxygen sensor (bank No. 1 sensor No. 1) is okay, go to next step. If heated oxygen sensor (bank No. 1 sensor No. 1) does not operate as specified, repair or replace components as necessary.
4. Check heated oxygen sensor (bank No. 1 sensor No. 2). See «DTC P0136: HEATED OXYGEN SENSOR CIRCUIT (BANK NO. 1 SENSOR NO. 2), OR DTC P0156: HEATED OXYGEN SENSOR CIRCUIT (BANK NO. 2 SENSOR NO. 2)»(ref-133213-S33508734252002021900000) . If heated oxygen sensor (bank No. 1 sensor No. 2) is okay, replace catalytic converter on driver's side exhaust pipe. If heated oxygen sensor (bank No. 1 sensor No. 2) does not operate as specified, repair or replace components as necessary.

Engine Control Module (ECM) compares waveform pattern of heated oxygen sensor (bank No. 2 sensor No. 1) located on passenger's side exhaust manifold with waveform pattern of heated oxygen sensor (bank No. 2 sensor No. 2) located on passenger's side exhaust pipe behind catalytic converter to determine if catalytic converter performance has deteriorated. If catalytic converter is functioning properly, waveform pattern for heated oxygen sensor (bank No. 2 sensor No. 2) should switch back and forth from rich to lean more slowly than heated oxygen 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 heated oxygen 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 heated oxygen sensor.
3. Defective catalytic converter.

This DTC uses two-trip detection logic. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

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. Check heated oxygen sensor (bank No. 2 sensor No. 1). See «DTC P0130: HEATED OXYGEN SENSOR CIRCUIT (BANK NO. 1 SENSOR NO. 1), OR DTC P0150: HEATED OXYGEN SENSOR CIRCUIT (BANK NO. 2 SENSOR NO. 1)»(ref-133213-S20907877862002021900000) . If heated oxygen sensor (bank No. 2 sensor No. 1) is okay, go to next step. If heated oxygen sensor (bank No. 2 sensor No. 1) does not operate as specified, repair or replace components as necessary.
4. Check heated oxygen sensor (bank No. 2 sensor No. 2). See «DTC P0136: HEATED OXYGEN SENSOR CIRCUIT (BANK NO. 1 SENSOR NO. 2), OR DTC P0156: HEATED OXYGEN SENSOR CIRCUIT (BANK NO. 2 SENSOR NO. 2)»(ref-133213-S33508734252002021900000) . If heated oxygen sensor (bank No. 2 sensor No. 2) is okay, replace catalytic converter on passenger's side exhaust pipe. If heated oxygen sensor (bank No. 2 sensor No. 2) does not operate as specified, repair or replace components as necessary.

1. Remove glove box and heater duct (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 (Green/Black wire) and No. 18 (Green/White wire) at ECM electrical connector E7 with all electrical connectors installed on ECM. (Scheme 47) 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. 22 (Red/Green wire) at ECM electrical connector E5 and No. 18 (Green/White wire) at ECM electrical connector E7 with all electrical connectors installed on ECM. (Scheme 47) This is the PTNK and E2 terminals on ECM. 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»(ref-133228) article. Vapor pressure sensor is located on top of fuel pump assembly on top of fuel tank and contains a Black 3-pin electrical connector with Red/Green, Green/Black and Green/White wires. see scheme 17 If wiring harness and electrical connectors are okay, replace vapor pressure sensor. See «VAPOR PRESSURE SENSOR»(ref-133227-S36014885312002021900000) under EMISSION SYSTEMS & SUB-SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 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. Vehicle speed sensor is located near rear of transmission or transfer case and contains a Black 3-pin electrical connector with Yellow, Yellow/Red and Red/Blue wires. For testing of vehicle speed sensor, see «VEHICLE SPEED SENSOR»(ref-133222-S16555450122002021900000) under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - V6 & V8 article.
2. Remove glove box and heater duct (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Raise and support vehicle with one rear wheel off the ground. Turn ignition on. Place transmission in Neutral. Using voltmeter, check voltage between body ground and terminal No. 5 (Green/Orange wire) at ECM electrical connector E5 while rotating rear wheel. (Scheme 47) This is the SPD terminal on ECM. Voltage should pulse between zero volts and 4-6 volts. If voltage is within specification, replace ECM. If voltage is not within specification, repair open or short in Green/Orange wire and electrical connectors between ECM and instrument cluster. See «WIRING DIAGRAMS»(ref-133228) article.

Idle speed is controlled by Electronic Throttle Control System (ETCS). ETCS uses throttle control motor to operate throttle valve opening angle to obtain target idle speed. DTC is set when idle speed continues to vary greatly from target speed. Possible causes are

1. Defective ETCS.
2. Air induction system malfunction.
3. Defective Positive Crankcase Ventilation (PCV) valve piping.

This DTC uses two-trip detection logic. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0505 exists, go to next step. If other DTCs exists, diagnose and repair those DTCs first and then retest.
2. Check for any loose or defective PCV valve piping connections. PCV valve is located at front of driver's side valve cover, below oil fill cap. If PCV valve piping is okay, go to next step. If PCV valve piping is defective, repair or replace components as necessary.
3. 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.
4. Check throttle body and components for ETCS. See «THROTTLE BODY»(ref-133222-S04410230492002021900000) under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article.

1. If Toyota hand-held tester is available, go to next step. If Toyota hand-held tester is not available, go to step 3.
2. Connect Toyota hand-held tester to Data Link Connector (DLC) No. 3 at driver's side of instrument panel. see scheme 1 Turn ignition on and then turn hand-held tester on. Using hand-held tester, monitor accelerator pedal position sensor voltages for VPA and VPA2 circuits with accelerator pedal depressed and released. See «ACCELERATOR PEDAL POSITION SENSOR VOLTAGE»(ref-133213-S08502296592002021900000) table. If voltages are not within specification, go to next step. If voltages are within specification, replace ECM. ECM is located behind glove box and heater duct. see scheme 2 ACCELERATOR PEDAL POSITION SENSOR VOLTAGE Accelerator Pedal Position & Circuit Identification Volts Accelerator Pedal Depressed VPA Circuit 3.2-4.8 VPA2 Circuit 4.7-5.1 Accelerator Pedal Released VPA Circuit.3-.9 VPA2 Circuit 1.8-2.7
3. Remove glove box and heater duct (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 (Green/Black wire) and No. 18 (Green/White wire) at ECM electrical connector E7 with all electrical connectors installed on ECM. (Scheme 47) 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.
4. Ensure ignition is still on. Using voltmeter, check voltage between terminals No. 18 (Green/White wire) and No. 21 (Green/Red wire) at ECM electrical connector E7 with accelerator pedal released and with accelerator pedal depressed. (Scheme 47) This is the E2 and VPA terminals on ECM. Also, check voltage between terminals No. 9 (Blue/Yellow wire) and No. 18 (Green/White wire) and at ECM electrical connector E7 with accelerator pedal released and with accelerator pedal depressed. This is the VPA2 and E2 terminals on ECM. Ensure voltage is within specification. See «ACCELERATOR PEDAL POSITION SENSOR VOLTAGE»(ref-133213-S08502296592002021900000) table. If any voltage reading is not within specification, go to next step. If all voltage readings are within specification, replace ECM.
5. Turn ignition off. Check accelerator pedal position sensor. See «THROTTLE BODY»(ref-133222-S04410230492002021900000) under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. If accelerator pedal position sensor is okay, go to next step. If accelerator pedal position sensor is defective, replace accelerator pedal position sensor. See «THROTTLE BODY»(ref-133227-S01273866582002021900000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
6. Check for open and short in wiring harness and electrical connectors between accelerator pedal position sensor and ECM. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness or electrical connector is defective, repair as necessary.

Accelerator pedal position sensor is located on throttle body and uses 2 sensors which monitor accelerator position. Accelerator pedal position sensor delivers input signals to VPA and VPA2 terminals at Engine Control Module (ECM) in proportion to throttle opening. ECM uses input signals for controlling the throttle control motor. DTC is set when ECM determines voltage is out of range on VPA or VPA2 circuits between accelerator pedal position sensor and ECM. If DTC P1121 exists, ECM will turn off the power to throttle control motor and throttle valve is closed by the return spring. When this occurs, throttle valve is controlled by throttle cable connected to accelerator pedal. Possible cause is defective accelerator pedal position sensor.

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

If DTC P1121 exists, replace accelerator pedal position sensor. See THROTTLE BODY under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

1. Remove and inspect ETCS fuse (15-amp). ETCS fuse is located in fuse/relay box at driver's side front corner of engine compartment. If ETCS fuse is okay, reinstall fuse and go to next step. If ETCS fuse is defective, replace fuse and check for short in White/Green wire between ETCS fuse and ECM. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. see scheme 2 Repair wiring as necessary.
2. Remove glove box and heater duct (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. 7 (White/Green wire) at ECM electrical connector E4. (Scheme 47) This is the +BM terminal on ECM. If voltage is 9-14 volts, replace ECM. If voltage is not 9-14 volts, repair open between battery, ETCS fuse and White/Green wire and electrical connectors between ETCS fuse and ECM. See «WIRING DIAGRAMS»(ref-133228) article.

Throttle Position (TP) sensor is located on throttle body and delivers input signals to Engine Control Module (ECM) in proportion to throttle opening. ECM uses input signal and controls the throttle control motor to provide proper throttle valve opening in response to driving conditions. DTC is set when ECM detects throttle control motor becomes locked. If DTC P1128 exists, ECM will turn off the power to throttle control motor and throttle valve is closed by the return spring. When this occurs, throttle valve is controlled by throttle cable connected to accelerator pedal. Possible causes are defective throttle control motor or throttle body.

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

1. Disconnect electrical connector at throttle control motor located on side of throttle body. see scheme 22 Using ohmmeter, check resistance between terminals No. 1 and 2 on electrical connector on throttle control motor. see scheme 22 Resistance should be.3-100.0 ohms at 68°F (20°C). If resistance is within specification, go to next step. If resistance is not within specification, replace throttle control motor. See «THROTTLE BODY»(ref-133227-S01273866582002021900000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
2. Remove air inlet hose from throttle body. Visually inspect throttle body for foreign material which may be caught between throttle valve and throttle body. If foreign material exists, remove foreign material and clean throttle body as necessary. If foreign material does not exist, replace throttle body. See «THROTTLE BODY»(ref-133227-S01273866582002021900000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

Replace ECM. ECM is located behind glove box and heater duct. see scheme 2 Using Toyota hand-held tester or scan tool, ensure DTCs are cleared from ECM. Turn ignition on and then use Toyota hand-held tester or scan tool to check for DTCs. If DTC P1129 exists, replace throttle body. See THROTTLE BODY under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

1. Remove glove box and heater duct (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. 4 (Violet wire) at ECM electrical connector E4 with ignition switch in ON and START positions. (Scheme 47) This is the FPR terminal on ECM. Voltage should be 0-3 volts with ignition switch in ON position and 9-14 volts with ignition switch in START position. If voltage is not within specification, go to next step. If voltage is within specification, replace ECM.
2. Check operation of fuel pump relay. See «FUEL PUMP RELAY»(ref-133222-S06445025452002021900000) under MODULES, MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING - V6 & V8 article. If fuel pump relay does not operate properly, replace fuel pump relay and retest. If fuel pump relay operates properly, repair wiring harness and electrical connectors between fuel pump relay and ECM. See «WIRING DIAGRAMS»(ref-133228) article.

1. Check for spark at cylinder No. 2 by performing spark test. See «SPARK TEST»(ref-133197-S27511875622002021900000) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Cylinder No. 2 is first cylinder back from timing belt end of engine at passenger's side 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 Light Green/Black and Black/White wires and electrical connectors between ECM and ignition coil No. 2. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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 heater duct (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. 28 (Black/White wire) at ECM electrical connector E8. (Scheme 47) This is the IGF2 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 Light Green/Black wire and electrical connectors between ECM and ignition coil No. 2. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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 heater duct (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 (Light Green/Black wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) 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. 12 (Light Green/Black wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) 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/Red wire) at electrical connector for ignition coil No. 2 with ignition switch in ON and START positions. see scheme 24 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 and ignition coil No. 2. See «WIRING DIAGRAMS»(ref-133228) article. If necessary to check IGN2 fuse (20-amp), IGN2 fuse is located in fuse box located behind driver's side of instrument panel.
8. Check for open in Brown wire and electrical connectors between ground and ignition coil No. 2. See «WIRING DIAGRAMS»(ref-133228) 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»(ref-133197-S27511875622002021900000) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Cylinder No. 3 is the second cylinder back from timing belt end of engine at driver's side 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/Black and Black/White wires and electrical connectors between ECM and ignition coil No. 3. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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 heater duct (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. 28 (Black/White wire) at ECM electrical connector E8. (Scheme 47) This is the IGF2 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/Black wire and electrical connectors between ECM and ignition coil No. 3. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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 heater duct (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 (Green/Black wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) 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. 13 (Green/Black wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) 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/Red wire) at electrical connector for ignition coil No. 3 with ignition switch in ON and START positions. see scheme 24 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 and ignition coil No. 3. See «WIRING DIAGRAMS»(ref-133228) article. If necessary to check IGN2 fuse (20-amp), IGN2 fuse is located in fuse box located behind driver's side of instrument panel.
8. Check for open in Brown wire and electrical connectors between ground and ignition coil No. 3. See «WIRING DIAGRAMS»(ref-133228) 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»(ref-133197-S27511875622002021900000) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Cylinder No. 4 is the second cylinder back from timing belt end of engine at passenger's side 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/Red and Red/White wires and electrical connectors between ECM and ignition coil No. 4. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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 heater duct (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. 27 (Black/Red wire) at ECM electrical connector E8. (Scheme 47) This is the IGF1 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 Red/White wire and electrical connectors between ECM and ignition coil No. 4. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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 heater duct (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. 14 (Red/White wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) 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. 14 (Red/White wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) 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/Red wire) at electrical connector for ignition coil No. 4 with ignition switch in ON and START positions. see scheme 24 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 and ignition coil No. 4. See «WIRING DIAGRAMS»(ref-133228) article. If necessary to check IGN2 fuse (20-amp), IGN2 fuse is located in fuse box located behind driver's side of instrument panel.
8. Check for open in Brown wire and electrical connectors between ground and ignition coil No. 4. See «WIRING DIAGRAMS»(ref-133228) 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.

1. Check for spark at cylinder No. 5 by performing spark test. See «SPARK TEST»(ref-133197-S27511875622002021900000) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Cylinder No. 5 is the third cylinder back from timing belt end of engine at driver's side of engine and uses the ignition coil No. 5. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open and short in Green/White and Black/White wires and electrical connectors between ECM and ignition coil No. 5. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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. 5. Remove glove box and heater duct (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. 28 (Black/White wire) at ECM electrical connector E8. (Scheme 47) This is the IGF2 terminal on ECM. Voltage should 4.5-5.5 volts. If voltage is within specification, replace ignition coil No. 5. If voltage is not within specification, replace ECM.
4. Check for open and short in Green/White wire and electrical connectors between ECM and ignition coil No. 5. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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 heater duct (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. 15 (Green/White wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) This is the IGT5 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. 5. Using voltmeter, check voltage between body ground and terminal No. 15 (Green/White wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) Voltage should be more than.1 volt and less than 4.5 volts. If voltage is within specification, replace ignition coil No. 5. If voltage is not within specification, replace ECM.
7. Using voltmeter, check voltage between body ground and terminal No. 1 (Black/Red wire) at electrical connector for ignition coil No. 5 with ignition switch in ON and START positions. see scheme 24 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 and ignition coil No. 5. See «WIRING DIAGRAMS»(ref-133228) article. If necessary to check IGN2 fuse (20-amp), IGN2 fuse is located in fuse box located behind driver's side of instrument panel.
8. Check for open in Brown wire and electrical connectors between ground and ignition coil No. 5. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness and electrical connectors are okay, replace ignition coil No. 5. If wiring harness or electrical connector is defective, repair as necessary.

1. Check for spark at cylinder No. 6 by performing spark test. See «SPARK TEST»(ref-133197-S27511875622002021900000) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Cylinder No. 6 is the third cylinder back from timing belt end of engine at passenger's side of engine and uses the ignition coil No. 6. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open and short in Black/Red and Pink/Blue wires and electrical connectors between ECM and ignition coil No. 6. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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. 6. Remove glove box and heater duct (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. 27 (Black/Red wire) at ECM electrical connector E8. (Scheme 47) This is the IGF1 terminal on ECM. Voltage should 4.5-5.5 volts. If voltage is within specification, replace ignition coil No. 6. If voltage is not within specification, replace ECM.
4. Check for open and short in Pink/Blue wire and electrical connectors between ECM and ignition coil No. 6. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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 heater duct (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. 16 (Pink/Blue wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) This is the IGT6 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. 6. Using voltmeter, check voltage between body ground and terminal No. 16 (Pink/Blue wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) Voltage should be more than.1 volt and less than 4.5 volts. If voltage is within specification, replace ignition coil No. 6. If voltage is not within specification, replace ECM.
7. Using voltmeter, check voltage between body ground and terminal No. 1 (Black/Red wire) at electrical connector for ignition coil No. 6 with ignition switch in ON and START positions. see scheme 24 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 and ignition coil No. 6. See «WIRING DIAGRAMS»(ref-133228) article. If necessary to check IGN2 fuse (20-amp), IGN2 fuse is located in fuse box located behind driver's side of instrument panel.
8. Check for open in Brown wire and electrical connectors between ground and ignition coil No. 6. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness and electrical connectors are okay, replace ignition coil No. 6. If wiring harness or electrical connector is defective, repair as necessary.

1. Check for spark at cylinder No. 7 by performing spark test. See «SPARK TEST»(ref-133197-S27511875622002021900000) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Cylinder No. 7 is the fourth cylinder back from timing belt end of engine at driver's side of engine and uses the ignition coil No. 7. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open and short in Black/Red and Green/Red wires and electrical connectors between ECM and ignition coil No. 7. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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. 7. Remove glove box and heater duct (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. 27 (Black/Red wire) at ECM electrical connector E8. (Scheme 47) This is the IGF1 terminal on ECM. Voltage should 4.5-5.5 volts. If voltage is within specification, replace ignition coil No. 7. If voltage is not within specification, replace ECM.
4. Check for open and short in Green/Red wire and electrical connectors between ECM and ignition coil No. 7. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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 heater duct (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. 25 (Green/Red wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) This is the IGT7 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. 7. Using voltmeter, check voltage between body ground and terminal No. 25 (Green/Red wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) Voltage should be more than.1 volt and less than 4.5 volts. If voltage is within specification, replace ignition coil No. 7. If voltage is not within specification, replace ECM.
7. Using voltmeter, check voltage between body ground and terminal No. 1 (Black/Red wire) at electrical connector for ignition coil No. 7 with ignition switch in ON and START positions. see scheme 24 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 and ignition coil No. 7. See «WIRING DIAGRAMS»(ref-133228) article. If necessary to check IGN2 fuse, IGN2 fuse is located in fuse box located behind driver's side of instrument panel.
8. Check for open in Brown wire and electrical connectors between ground and ignition coil No. 7. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness and electrical connectors are okay, replace ignition coil No. 7. If wiring harness or electrical connector is defective, repair as necessary.

1. Check for spark at cylinder No. 8 by performing spark test. See «SPARK TEST»(ref-133197-S27511875622002021900000) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Cylinder No. 8 is the fourth cylinder back from timing belt end of engine at passenger's side of engine and uses the ignition coil No. 8. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open and short in Light Green and Black/White wires and electrical connectors between ECM and ignition coil No. 8. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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. 8. Remove glove box and heater duct (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. 28 (Black/White wire) at ECM electrical connector E8. (Scheme 47) This is the IGF2 terminal on ECM. Voltage should 4.5-5.5 volts. If voltage is within specification, replace ignition coil No. 8. If voltage is not within specification, replace ECM.
4. Check for open and short in Light Green wire and electrical connectors between ECM and ignition coil No. 8. See «WIRING DIAGRAMS»(ref-133228) article. ECM is located behind glove box and heater duct. 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 heater duct (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. 26 (Light Green wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) This is the IGT8 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. 8. Using voltmeter, check voltage between body ground and terminal No. 26 (Light Green wire) at ECM electrical connector E8 while cranking engine. (Scheme 47) Voltage should be more than.1 volt and less than 4.5 volts. If voltage is within specification, replace ignition coil No. 8. If voltage is not within specification, replace ECM.
7. Using voltmeter, check voltage between body ground and terminal No. 1 (Black/Red wire) at electrical connector for ignition coil No. 8 with ignition switch in ON and START positions. see scheme 24 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 and ignition coil No. 8. See «WIRING DIAGRAMS»(ref-133228) article. If necessary to check IGN2 fuse (20-amp), IGN2 fuse is located in fuse box located behind driver's side of instrument panel.
8. Check for open in Brown wire and electrical connectors between ground and ignition coil No. 8. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness and electrical connectors are okay, replace ignition coil No. 8. If wiring harness or electrical connector is defective, repair as necessary.

1. If Toyota hand-held tester is available, 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 Toyota hand-held tester to Data Link Connector (DLC) No. 3 at driver's side of instrument panel. 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 harness between stoplight switch and ECM, and for intermittent problem with stoplight switch. ECM is located behind glove box and heater duct. see scheme 2 See «WIRING DIAGRAMS»(ref-133228) article. Stoplight switch is located near top of brake pedal.
5. Check wiring harness and electrical connectors between stoplight switch and ECM. See «WIRING DIAGRAMS»(ref-133228) article. Stoplight switch is located near top of brake pedal. ECM is located behind glove box and heater duct. 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 heater duct (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2
8. Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 15 (Green/Yellow wire) at ECM electrical connector E4 while depressing and releasing brake pedal. (Scheme 47) This is the STP terminal on ECM.
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»(ref-133228) 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»(ref-133228) 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 heater duct (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. 1 (Black/Yellow wire) at ECM electrical connector E4. (Scheme 47) This is the BATT 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. Remove EFI No. 1 fuse (20-amp) from fuse/relay box at driver's side front corner of engine compartment. Inspect EFI No. 1 fuse. If EFI No. 1 fuse is okay, reinstall fuse. Check wiring harness and electrical connectors between EFI No. 1 fuse and ECM. See «WIRING DIAGRAMS»(ref-133228) article. It may be necessary to check wiring between battery and EFI No. 1 fuse. For additional wiring for EFI No. 1 fuse to the battery, see POWER DISTRIBUTION article in WIRING DIAGRAMS. If EFI No. 1 fuse is defective, replace fuse and check for short in wiring harness and components connected to EFI No. 1 fuse. See «WIRING DIAGRAMS»(ref-133228) article. Repair wiring harness or electrical connectors as necessary.

If DTC P1633 exists, replace ECM. ECM is located behind glove box and heater duct. see scheme 2