Engine Controls - Tests W/codes: Diagnosis Lexus LX J80

MALFUNCTION INDICATOR LIGHT (MIL) INSPECTION

Note. The CHECK engine light located on instrument cluster is known as Malfunction Indicator Light (MIL). Inspect MIL to ensure it is operational and will come on if a Diagnostic Trouble Code (DTC) is set.

1. Turn ignition on with engine off. MIL should come on and remain on. If MIL does not come on, check bulb circuit on instrument cluster and wiring circuit between MIL and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. See «ECM LOCATION»(ref-21947-S00760210922001010300000) .
2. Start engine and ensure MIL goes off. If MIL remains on with engine running, a malfunction is detected. Proceed to RETRIEVING DIAGNOSTIC TROUBLE CODES.

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: Connect appropriate scan tool. Retrieve codes and record any freeze-frame data (if applicable). See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-21947-S07359890972001010300000) .
3. Clear Trouble Codes: See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-21947-S42318431212001010300000) .
4. Visual Inspection: Inspect all connectors of suspect circuit or component. Ensure all connections are clean and tight.
5. Confirm Symptoms & Trouble Codes: Perform road test. Determine if original symptoms are still present. Retrieve codes.
6. Diagnose & Repair Diagnostic Trouble Codes: Perform diagnosis and repair procedures as necessary. See «TROUBLE CODE IDENTIFICATION»(ref-21947-S05787691322001010300000) table. If no codes are present, proceed to the TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).
7. Verification Procedure: After repairs have been completed, clear trouble codes. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-21947-S42318431212001010300000) . Perform road test. Ensure no codes are present and all symptoms and/or complaints have been repaired.

RETRIEVING DIAGNOSTIC TROUBLE CODES

Note. Diagnostic Trouble Codes (DTCs) may be retrieved using Toyota scan tester or On-Board Diagnostic (OBD-II) scan tester that complies with SAE standard J-1978. Toyota scan tester or OBD-II scan tester may be operated in NORMAL mode when retrieving trouble codes. Only Toyota scan 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 in which DTC was set. CHECK mode contains a higher sensing ability to detect malfunctions. CHECK mode helps determine malfunctions caused by poor electrical connections, which are difficult to determine using NORMAL mode.

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

CLEARING DIAGNOSTIC TROUBLE CODES

1. After performing repairs, clear ECM memory of all stored Diagnostic Trouble Codes (DTCs) and freeze-frame data. DTCs and freeze-frame data may be cleared by using scan tester and scan tester manufacturer's instructions. NOTE: If using Toyota scan tester, DTCs and freeze-frame data may be cleared by switching from CHECK mode to NORMAL mode or from NORMAL mode to CHECK mode.
2. DTCs and freeze-frame data may also be cleared by removing EFI fuse from fuse block, located in engine compartment. DTCs and freeze-frame data may also be cleared by disconnecting negative battery cable. However, other memory functions (clock, radio, alarm, seats, etc.) will be cancelled and must be reset.

Note. Not all codes listed in the following table are used on every vehicle.

TROUBLE CODE IDENTIFICATION

TROUBLE CODE TEST DRIVE CONFIRMATION

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

DLC3 INSPECTION

1. If scan tester displays UNABLE TO CONNECT TO VEHICLE when scan tester is connected, try scan tester on another vehicle. If scan tester operates on another vehicle, go to next step. If scan tester does not operate on another vehicle, problem is probably with scan tester.
2. Check DLC3 for loose or damaged terminals. Ensure DLC3 terminals are in correct position in connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If connector and terminals are okay, go to next step.
3. Check voltage and resistance between ground and specified terminal on DLC3. See «DLC3 VOLTAGE & RESISTANCE SPECIFICATIONS»(ref-21947-S12380273462001010300000) table. (Scheme 9) If voltage and resistance readings are not as specified, check wiring circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.

Note. Terminal No. 2 on DLC3 provides the pulse generation during the information transmission from the Engine Control Module (ECM).

DLC3 VOLTAGE & RESISTANCE SPECIFICATIONS

Scheme 9

Diagnosis & Repair Procedure

If only DTC P0101 is displayed, replace MAF sensor and retest. If other codes are displayed, diagnose and repair those codes first and retest.

Diagnosis & Repair

1. Connect scan tester to DLC3 connector. (Scheme 9) Turn ignition on. Turn on scan tester. Monitor IAT sensor temperature. If temperature displayed is same as outside temperature, inspect component and ECM connections. Problem is intermittent.
2. If temperature displayed is 284°F (140°C), go to step 5). If temperature displayed is -40°F (-40°C), turn ignition off. Disconnect MAF sensor connector. Using jumper wire, connect MAF wiring harness connector terminals No. 3 and 4. see scheme 3 Turn ignition on. Monitor IAT sensor temperature on scan tester.
3. If temperature displayed is 284°F (140°C) or more, replace MAF sensor and retest. If temperature displayed is less than 284°F (140°C), turn ignition off. Remove jumper wire. Access ECM behind right instrument panel speaker. Connect jumper wire between terminals No. 3 (Blue/Yellow wire) and No. 9 (Brown/Black wire) at ECM E5 connector. see scheme 4
4. If temperature displayed on scan tester is 284°F (140°C) or more, inspect and repair circuits between MAF wiring harness connector and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed on scan tester is less than 284°F (140°C), replace ECM and retest.
5. Turn ignition off. Disconnect MAF sensor connector. Turn ignition on. If temperature displayed on scan tester is -40°F (-40°C), replace MAF sensor and retest. If temperature displayed is not -40°F (-40°C), turn ignition off.
6. Access ECM behind right instrument panel speaker. Disconnect ECM E5 connector. see scheme 4 Turn ignition on. If temperature displayed is -40°F (-40°C), inspect and repair circuits between MAF sensor and ECM for short. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed by scan tester is not-40°F (-40°C), replace ECM and retest.

1. Connect scan tester to DLC3 connector. (Scheme 9) Turn ignition on. Turn on scan tester. Monitor ECT sensor temperature. If temperature displayed is same as actual coolant temperature, inspect component and ECM connections. Problem is intermittent.
2. If temperature displayed is 284°F (140°C) or more, go to step 5). If temperature displayed is -40°F (-40°C), turn ignition off. Disconnect ECT sensor connector. Connect a jumper wire between ECT sensor wiring harness connector terminals. Turn ignition on. Using scan tester, monitor ECT sensor temperature.
3. If temperature displayed is 284°F (140°C) or more, replace ECT sensor and retest. If temperature displayed is less than 284°F (140°C), turn ignition off. Remove jumper wire. Access ECM behind right instrument panel speaker. Connect jumper wire between terminals No. 4 (Red/White wire) and No. 9 (Brown/Black wire) at ECM E5 connector. see scheme 4
4. If temperature displayed on scan tester is 284°F (140°C) or more, inspect and repair circuits for open between ECT sensor wiring harness connector and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed on scan tester is less than 284°F (140°C), replace ECM and retest.
5. Turn ignition off. Disconnect ECT sensor connector. Turn ignition on. If temperature displayed on scan tester is -40°F (-40°C), replace ECT sensor and retest. If temperature displayed is not -40°F (-40°C), turn ignition off.
6. Access ECM behind right instrument panel speaker. Disconnect ECM E5 connector. see scheme 4 Turn ignition on. If temperature displayed is -40°F (-40°C), inspect and repair circuits between ECT sensor and ECM for short. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed by scan tester is not-40°F (-40°C), replace ECM and retest.

If only DTC P0116 is displayed, replace ECT sensor and retest. If other codes are displayed, diagnose and repair those codes first and retest.

1. Connect scan tester to DLC3 connector. (Scheme 9) Turn ignition on. Turn on scan tester. Monitor throttle valve opening percentage. Opening percentage should be approximately 10 percent with fully closed throttle.
2. Depress accelerator pedal to floor (WOT). Opening percentage should be approximately 75 percent. If percentages are within specification, inspect all connections. Problem may be intermittent.
3. If percentages are not within specification, turn ignition off. Disconnect TP sensor connector. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 1 (Red/Green wire) at TP sensor wiring harness connector. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, go to step 7).
4. Check Throttle Position (TP) sensor. See ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS article. Replace sensor as necessary. If sensor is okay, go to next step.
5. Access ECM behind right instrument panel speaker. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 9 (Brown/Black wire) and No. 10 (Green/Black wire) at ECM E5 connector. see scheme 4 Voltage should be.3-.8 volt with throttle fully closed, and 3.2-4.9 volts with throttle fully open (WOT).
6. If voltage is as specified, replace ECM and retest. If voltage is not as specified, check for an open or short in Green/Black wire. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
7. Access ECM behind right instrument panel speaker. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 1 (Red/Green wire) and No. 9 (Brown/Black wire) at ECM E5 connector. see scheme 4 If voltage is 4.5-5.5 volts, check wiring harness for an open in Red/Green wire. If voltage is not 4.5-5.5 volts, replace ECM and retest.

If only DTC P0121 is displayed, replace TP sensor and retest. If other codes are displayed, diagnose and repair those codes first and retest.

1. Connect scan tester to DLC3 connector. (Scheme 9) Start vehicle and warm engine to normal operating temperature. Turn on scan tester. Monitor sensor No. 1. Snap accelerate engine 3 times. Sensors should indicate a rich signal (.45 volt or more) at least once.
2. If a rich signal is indicated at least once, replace ECM and retest. If sensor does not display a rich signal at least once, check for an open or short circuit between ECM and sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuits are okay, replace oxygen sensor and retest.

Test Drive Confirmation

1. If using OBD-II scan tester, go to next step. If using Toyota scan tester, connect scan tester. (Scheme 9) Switch scan tester to CHECK mode. Start and warm engine to normal operating temperature. Drive vehicle at 31-40 MPH for 1-3 minutes. Stop vehicle and allow to idle for one minute. If malfunction exists, MIL will illuminate.
2. If using OBD-II scan tester, start and warm engine to normal operating temperature. Drive vehicle at 31-40 MPH for 1-3 minutes. Stop vehicle and allow to idle for one minute. Turn vehicle off. Repeat driving and idle part of test. If malfunction exists, MIL will illuminate.

1. Inspect circuits between ECM and oxygen sensor for opens or shorts. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If all circuits are okay, connect scan tester. (Scheme 9)
2. Start engine and warm to normal operating temperature. Monitor heated oxygen sensor output voltage and short-term fuel trim. If scan tester indicates a lean condition (.55 volt or less, +20 trim) or rich condition (.4 volt or more, -20 trim), see DTC P0171 - SYSTEM TOO LEAN (FUEL TRIM), DTC P0172 SYSTEM TOO RICH (FUEL TRIM) circuit test.
3. If scan tester indicates other than reading in step 2), operate engine at 2500 RPM for 90 seconds. Monitor oxygen sensor voltage. If voltage constantly fluctuates in wide range (.3-.9 volt), perform TEST DRIVE CONFIRMATION. If voltage does not fluctuate, or stays in narrow range, replace sensor and retest.

If only DTC P0133 is displayed, replace oxygen sensor and retest. If other codes are displayed, diagnose and repair those codes first and retest.

1. Access ECM behind right instrument panel speaker. Turn ignition on. Using DVOM, backprobe ECM connector. If DTC P0135 is set, measure voltage between ground and terminal No. 1 (Gray wire) at ECM E6 connector. If DTC P0141 is set, measure voltage between ground and terminal No. 25 (Orange wire) at ECM E6 connector. see scheme 4 Voltage for each circuit should be 9-14 volts.
2. If voltage is as specified, replace ECM and retest. If voltage is not as specified, turn ignition off. Disconnect appropriate oxygen sensor connector. Using ohmmeter, measure resistance between terminals No. 1 and 2 at oxygen sensor connector. See «IDENTIFYING OXYGEN SENSOR HEATER TERMINALS»(ref-21947-S11056187232001010300000) table. IDENTIFYING OXYGEN SENSOR HEATER TERMINALS Application Terminal No. 1 Terminal No. 2 Sensor No. 1 Gray Wire Yellow/Red Wire Sensor No. 2 Orange Wire Yellow/Red Wire
3. If resistance is 11-16 ohms at 68°F (20°C), inspect circuits between ECM and sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If resistance is not 11-16 ohms at 68°F (20°C), replace sensor and retest.

1. If any other codes are displayed other than DTC P0136, diagnose and repair those codes first. If only DTC P0136 is displayed, inspect circuits between ECM and sensor for opens or shorts. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
2. If all circuits are okay, connect scan tester. (Scheme 9) Start and warm engine to normal operating temperature. Monitor oxygen sensor output voltage. Snap accelerate engine 3 times. Voltage should fluctuate from.4-.5 volt or more.
3. If voltage responds correctly, inspect sensor wiring harness connector. Problem may be intermittent. If voltage does not respond correctly, replace sensor and retest.

1. Inspect all air induction components. Repair as necessary. If air induction components are okay, connect scan tool. (Scheme 9) Start engine and warm to normal operating temperature. Monitor heated oxygen sensor output voltage and short-term fuel trim.
2. If scan tester indicates a lean condition (.55 volt or less, +20 trim) or rich condition (.4 volt or more, -20 trim), go to next step. If results are other than shown, see DTC P0130 - HEATED OXYGEN SENSOR CIRCUIT (SENSOR NO. 1) circuit test.
3. Inspect fuel pressure. See «BASIC TESTING»(ref-21926) article. Repair as necessary. If fuel pressure is okay, inspect fuel injectors. See SYSTEM/COMPONENT TESTS article. Replace injectors as necessary.
4. If all injectors are okay, inspect Mass Airflow (MAF) sensor and Engine Coolant Temperature (ECT) sensor. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If both components are okay, inspect ignition system. See IGNITION CHECKS in «BASIC TESTING»(ref-21926) article. Repair as necessary. If ignition system is okay, replace ECM and retest.

Circuit Description

A misfire is determined by the ECM. The ECM uses signals provided by the crankshaft and camshaft position sensors. If the engine speed rate has changed enough to equal a preset number, a misfire is detected and the MIL is illuminated. If the misfire rate is high enough, and driving conditions will cause catalytic converter damage or overheating, the MIL blinks when a misfire is occurring.

DTC is set when misfiring of random cylinders is detected during any particular 200 or 1000 revolutions. Possible causes are

1. Ignition system.
2. Injector(s).
3. Fuel pressure.
4. EGR system.
5. Engine compression.
6. Valve clearance.
7. Valve timing.
8. Mass Airflow (MAF) sensor.
9. Engine Coolant Temperature (ECT) sensor.

1. Inspect spark plug and check for spark at misfiring cylinder. See «BASIC TESTING»(ref-21926) article. Repair as necessary. If spark plug is okay and spark is present, go to next step.
2. Access ECM behind right instrument panel speaker. Turn ignition on. Using DVOM, backprobe ECM connector. Measure voltage between ground and injector terminals at ECM E4 connector. See IDENTIFYING INJECTOR TERMINALS table. see scheme 4 If voltage is 9-14 volts for each circuit, go to step 4). If voltage is not 9-14 volts, go to next step. IDENTIFYING INJECTOR TERMINALS Injector No. (1) Terminal No. Wire Color 1 12 White/Blue 2 11 White/Red 3 25 White/Green 4 2 Yellow 5 1 Yellow/Red 6 15 Yellow/Blue (1) Terminals are located in ECM E4 connector.
3. Disconnect injector of misfiring cylinder. Using ohmmeter, measure resistance between injector terminals. If resistance is 13.4-14.2 ohms, inspect circuits between ECM and injector for open or short. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If resistance is not 13.4-14.2 ohms, replace injector.
4. Check fuel pressure. See «BASIC TESTING»(ref-21926) article. Repair as necessary. If fuel pressure is okay, inspect fuel injector performance. See SYSTEM/COMPONENT TESTS article. Replace as necessary.
5. If all injectors are okay, inspect EGR system. See SYSTEM/COMPONENT TESTS article. Repair as necessary. If EGR system is okay, inspect MAF sensor and ECT sensor. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If both components are okay, also inspect engine compression, valve clearance and valve timing. See «BASIC TESTING»(ref-21926) article.

See DTC P0300 - RANDOM MISFIRE DETECTED circuit test.

See DTC P0300 - RANDOM MISFIRE DETECTED circuit test.

1. Access ECM behind right instrument panel speaker. Disconnect ECM E5 connector. see scheme 4 Using ohmmeter, measure resistance between ground and terminals No. 6 (Black wire) and No. 14 (Blue/White wire) at ECM E5 connector. If resistance is infinite, go to step 3). If resistance is not infinite, go to next step.
2. Disconnect applicable knock sensor connector. (Scheme 10) Check continuity between sensor terminal and sensor housing. If continuity does not exist, go next step. If continuity exists, replace sensor.
3. Check for an open or short circuit between knock sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, substitute suspect knock sensor with known-good sensor. Clear codes. See SELF-DIAGNOSTIC SYSTEM. Start and warm engine to normal operating temperature. Retrieve codes. See «SELF-DIAGNOSTIC SYSTEM»(ref-21947-S28155237892001010300000). If code is still present, replace ECM. If code is no longer present, replace sensor.

Scheme 10

1. Disconnect distributor connector. Using ohmmeter, measure resistance between terminals No. 1 and 4 at distributor connector. (Scheme 11) Resistance should be 185-275 ohms (cold sensor) or 240-325 ohms (hot sensor).
2. If resistance is not as specified, replace distributor. If resistance is as specified, check for an open or short circuit between ECM and distributor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
3. If circuits are okay, check air gap between signal rotor and each pick-up coil. See IGNITION CHECKS in «BASIC TESTING»(ref-21926) article. If air gap is not to specification, replace distributor.

Scheme 11

1. Disconnect distributor connector. Check resistance of pick-up coils. See IGNITION CHECKS in «BASIC TESTING»(ref-21926) article. If resistance is not as specified, replace distributor. If resistance is as specified, go to next step.
2. Check for an open or short in G1, G2 and G- circuits between ECM and distributor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
3. If circuits are okay, check air gap between signal rotor and each pick-up coil. See IGNITION CHECKS in «BASIC TESTING»(ref-21926) article. If air gap is not to specification, replace distributor. If air gap is to specification, replace ECM and retest.

1. Disconnect CKP (NE2 signal) sensor connector. (Scheme 12) Using ohmmeter, measure resistance between terminals No. 1 and 2 at CKP sensor terminals. Resistance should be 1630-2740 ohms (cold sensor) or 2065-3225 ohms (hot sensor).
2. If resistance is not as specified, replace sensor. If resistance is as specified, inspect NE2 circuit between CKP sensor and ECM for open or short. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
3. If circuit is okay, inspect sensor installation and teeth of signal plate. Repair or replace as necessary. If both sensor and signal plate are okay, replace ECM and retest.

Scheme 12

1. Connect scan tester. (Scheme 9) Start and warm engine to normal operating temperature. Operate vehicle at 43-56 MPH for 3 minutes or more. Stop vehicle and allow to idle for about 2 minutes. Turn ignition off.
2. Start engine and allow to idle. Operate vehicle at 43-56 MPH for 3 minutes or more. Stop vehicle and allow to idle for about 2 minutes.
3. Using scan tester, check READINESS TESTS. If COMPL is displayed on scan tester and MIL is not illuminated, system is normal. If INCMPL is displayed and MIL is not illuminated, repeat test drive procedure.

Diagnosis & Repair (Using Toyota Scan Tester)

1. Connect scan tester. (Scheme 9) Turn ignition on. Read EGR gas temperature. If temperature is 50°F (10°C), go to step 5). If temperature is 37.6°F (3.1°C), there is an open EGR temperature sensor circuit. If temperature is not 50°F (10°C), go to next step.
2. Disconnect EGR temperature sensor connector. Connect jumper wire between wiring harness connector terminals. If EGR temperature displayed is not about 316°F (158°C), go to next step. If temperature displayed is about 316°F (158°C), inspect sensor connectors and terminals. Repair as necessary. If connectors are okay, replace sensor and retest.
3. Remove jumper wire. Turn ignition off. Access ECM behind right instrument panel speaker. Connect jumper wire between terminal No. 19 (Green/Yellow wire) at ECM E4 connector and terminal No. 9 (Brown/Black wire) at ECM E5 connector. see scheme 4 Turn ignition on.
4. If EGR temperature displayed is about 316°F (158°C), inspect and repair open in circuits between ECM and EGR temperature sensor. If temperature displayed is not about 316°F (158°C), replace ECM and retest.
5. Inspect vacuum hoses. See appropriate illustration in VACUUM DIAGRAMS article. Repair as necessary. If all hoses are okay, inspect VSV. Using scan tester, select ACTIVE TEST mode. Check operation of VSV when activated by scan tester. VSV is located under intake plenum cover.
6. Start and run engine. With EGR system off, air from port "G" should exhaust from port "E". (Scheme 13) With EGR system on, air from port "G" should not exhaust from port "E". If VSV operates correctly, go to step 9). If VSV does not operate correctly, go to next step.
7. Remove EGR VSV. Air intake chamber may have to be removed to access VSV. Using ohmmeter, measure resistance between VSV terminals. Resistance should be 30-34 ohms at 68°F (20°C). Check for continuity between each VSV terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.
8. Check VSV operation. Apply battery voltage to VSV terminals. Air from port "G" should not exhaust from port "E". (Scheme 13) Remove battery voltage from valve terminals. Air from port "G" should exhaust from port "E". Replace VSV as necessary. If VSV operates as specified, check for an open in wiring harness between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
9. Inspect EGR vacuum modulator. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If modulator is okay, inspect EGR valve. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If components are okay, go to next step.
10. Ensure all components are connected. Start and run engine. Using scan tester, select ACTIVE TEST mode (EGR system ON). Run engine at 4000 RPM for 3 minutes. Monitor EGR gas temperature. If temperature is 284°F (140°C) or more, replace ECM and retest. If temperature is less than 284°F (140°C), replace sensor.

Scheme 13

Diagnosis & Repair (Using OBD-II Scan Tester)

1. Disconnect EGR temperature sensor. Using ohmmeter, measure resistance between sensor terminals. If resistance is 600 k/ohms or less, go to next step. If resistance is more than 600 k/ohms, inspect sensor. See SYSTEM/COMPONENT TESTS. Replace as necessary.
2. Turn ignition on. Using DVOM, measure voltage between sensor wiring harness connector terminals. If voltage is 4.5-5.5 volts, go to step 4). If voltage is not 4.4-5.5 volts, go to next step.
3. Access ECM behind right instrument panel speaker. Using DVOM, backprobe connector. Measure voltage between terminal No. 19 (Green/Yellow wire) at ECM E4 connector and No. 9 (Brown/Black wire) at ECM E5 connector. see scheme 4 If voltage is 4.5-5.5 volts, inspect circuits between EGR temperature sensor and ECM for open. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If voltage is not 4.4-5.5 volts, replace ECM and retest.
4. Inspect all EGR system vacuum hoses. Replace as necessary. Access ECM behind right instrument panel speaker. Ensure ignition is off. Disconnect ECM E4 connector. Turn ignition on. Connect a jumper wire between ground and terminal No. 22 (Blue/White wire) at ECM E4 connector.
5. With jumper wire connected, Vacuum Switching Valve (VSV) is on. Air from port "G" should not exhaust from port "E". (Scheme 13) Disconnect jumper wire. Air from port "G" should exhaust from port "E". If valve operates correctly, go to step 8). If valve does not operate correctly, go to next step.
6. Turn ignition off. Remove EGR VSV. It may be necessary to remove air intake chamber to access VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 30-34 ohms at 68°F (20°C). Check continuity between each VSV terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.
7. Check VSV operation. Apply battery voltage to VSV terminals. Air from port "G" should not exhaust from port "G". (Scheme 13) Remove battery voltage from valve terminals. Air from port "G" should exhaust from port "G". Replace VSV as necessary. If VSV operates as specified, check for an open in wiring harness between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
8. Inspect EGR vacuum modulator. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If modulator is okay, inspect EGR valve. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If EGR valve is okay, go to next step.
9. Disconnect EGR temperature sensor connector. Start engine. Ensure engine is at normal operating temperature. Run engine at 4000 RPM for 3 minutes and measure resistance between EGR temperature sensor terminals. If resistance is 4300 ohms or less, replace ECM and retest. If resistance is more than 4300 ohms, replace sensor.

1. Connect scan tester. (Scheme 9) Start and warm engine to normal operating temperature. Operate vehicle at 43-56 MPH for 3 minutes or more. Stop vehicle and allow to idle for about 2 minutes. Turn ignition off.
2. Start engine and allow to idle. Operate vehicle at 43-56 MPH for 3 minutes or more. Stop vehicle and allow to idle for about 2 minutes.
3. Check READINESS TESTS. If COMPL is displayed on scan tester and MIL is not illuminated, system is normal. If INCMPL is displayed and MIL is not illuminated, repeat test drive procedure.

1. Connect scan tester. (Scheme 9) Turn ignition on. Read EGR gas temperature. If temperature is 302°F (150°C), go to step 4). If temperature is not 302°F (150°C), go to next step. If temperature displayed is 318.7°F (159.3°C), there is a short in EGR temperature sensor circuit.
2. Disconnect EGR temperature sensor connector. Using scan tester, read EGR gas temperature. If EGR gas temperature is not 37.6°F (3.1°C), go to next step. If temperature is 37.6°F (3.1°C), replace sensor and retest.
3. Turn ignition off. Access ECM behind right instrument panel speaker. Disconnect ECM E4 connector. see scheme 4 Turn ignition on. Using scan tester, read EGR gas temperature. If EGR gas temperature is 37.6°F (3.1°C), inspect and repair open in circuits between ECM and EGR temperature sensor. If temperature is not 37.6°F (3.1°C), replace ECM and retest.
4. Using scan tester, select ACTIVE TEST mode. Check operation of VSV when activated by scan tester. VSV is located under intake plenum cover. Start and run engine. With EGR system off, air from port "G" should exhaust from port "E". (Scheme 13) With EGR system on, air from port "G" should not exhaust from port "E". If VSV operates correctly, check EGR valve. See SYSTEM/COMPONENT TESTS article. If VSV does not operate correctly, go to next step.
5. Remove EGR VSV. Air intake chamber may have to be removed to access VSV. Using ohmmeter, measure resistance between VSV terminals. Resistance should be 30-34 ohms at 68°F (20°C). Check for continuity between each VSV terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.
6. Check for an open circuit in wiring harness between VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.

1. Disconnect EGR temperature sensor. Using ohmmeter, measure resistance between sensor terminals. If resistance is 2500 ohms or more, go to next step. If resistance is less than 2500 ohms, replace sensor.
2. Inspect circuits between EGR temperature sensor and ECM for short. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuits are okay, go to next step.
3. Access ECM behind right instrument panel speaker. Ensure ignition is off. Disconnect ECM E4 connector. Turn ignition on. Connect a jumper wire between ground and terminal No. 22 (Blue/White wire) at ECM E4 connector.
4. With jumper wire connected, Vacuum Switching Valve (VSV) is on. Air from port "G" should not exhaust from port "E". (Scheme 13) Disconnect jumper wire. Air from port "G" should exhaust from port "E". If valve operates correctly, check EGR valve. See SYSTEM/COMPONENT TESTS article. If VSV does not operate correctly, go to next step.
5. Remove EGR VSV. Air intake chamber may have to be removed to access VSV. Using ohmmeter, measure resistance between VSV terminals. Resistance should be 30-34 ohms at 68°F (20°C). Check for continuity between each VSV terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.
6. Check for an open circuit in wiring harness between VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.

The ECM compares waveform of oxygen sensor located before catalytic converter with waveform of oxygen sensor located after converter to determine if converter performance has deteriorated. If both waveforms change at similar rate, catalyst performance has deteriorated. DTC is set when both oxygen sensors have same amplitude after vehicle is driven for 6 minutes at 20-50 MPH. Possible causes are

1. Catalytic converter.
2. Oxygen sensor open or short circuit.
3. Oxygen sensor.

Note. Oxygen sensor located in front of catalytic converter is referred to as sensor No. 1. Oxygen sensor located behind catalytic converter is referred to as sensor No. 2.

1. Connect scan tester. (Scheme 9) Start and warm engine to normal operating temperature. Drive vehicle at 31-40 MPH for 5-10 minutes. Stop vehicle. Retrieve codes. See «SELF-DIAGNOSTIC SYSTEM»(ref-21947-S28155237892001010300000).
2. If codes other than P0420 are present, diagnose and repair those codes first. If DTC P0420 is only displayed, check oxygen sensor. See SYSTEM/COMPONENT TESTS article. Repair as necessary. If oxygen sensors are okay, replace catalytic converter and retest.

1. Test drive vehicle and check operation of speedometer. If speedometer is not functioning correctly, see INSTRUMENT PANELS article. If speedometer is functioning correctly, go to next step.
2. Access ECM behind right instrument panel speaker. Ensure ignition is off. Disconnect cruise control ECU. Cruise control ECU is located on left side of steering column, behind instrument panel. Connector is a Gray 26-pin connector.
3. Shift gear selector to Neutral. Lift and support rear of vehicle. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 8 (Blue/White wire) at ECM E7 connector, while rotating rear wheels. see scheme 4
4. As rear wheels are rotated, voltage should pulse between zero and 9-14 volts. If voltage is as specified, replace ECM and retest. If voltage is not as specified, inspect Blue/White wire between instrument cluster and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.

Repair & Diagnosis

1. Inspect air induction system for leaks. Repair as necessary. If air induction system is okay, go to next step.
2. Ensure ignition is off. Access ECM behind right instrument panel speaker. Disconnect ECM E4 connector. Turn ignition on. Using DVOM, measure voltage between ground and IAC circuit terminals at ECM E4 connector. See IDENTIFYING IAC VALVE TERMINALS table. see scheme 4 If all readings are 9-14 volts, go to step 4). If any reading is not 9-14 volts, go to next step. IDENTIFYING IAC VALVE TERMINALS Terminal No. (1) Wire Color 4 Yellow/Blue 5 Green/Yellow 6 Red/Black 7 Red/Green (1) Terminals are located in ECM E4 connector.
3. Check IAC valve. See SYSTEM/COMPONENT TESTS article. Replace IAC valve as necessary. If IAC valve is okay, check for an open or short in wiring harness between EFI main relay and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
4. Inspect IAC valve operation. See SYSTEM/COMPONENT TESTS article. Replace IAC valve as necessary. If valve is okay, replace ECM and retest.

1. Connect scan tester. (Scheme 9) Disconnect TP sensor connector. Connect a jumper wire between terminals No. 1 (Brown/Black wire) and No. 2 (Green/White wire) at TP sensor wiring harness connector. Turn ignition on. Using scan tester, read CTP switch signal. If CTP switch signal is on, replace TP sensor and retest. If CTP switch signal is off, go to next step.
2. Turn ignition off. Remove jumper wire. Access ECM behind right instrument panel speaker. Connect jumper wire between terminals No. 11 (Green/White wire) and No. 9 (Brown/Black wire) at ECM E5 connector. see scheme 4 Turn ignition on. Using scan tester, read CTP switch signal. If CTP switch signal is on, check for an open in wiring harness between TP sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If CTP switch signal is off, replace ECM and retest.

1. Ensure ignition is off. Disconnect TP sensor connector. Turn ignition on. Using DVOM, measure voltage between terminals No. 1 (Brown/Black wire) and No. 2 (Green/White wire) at TP sensor wiring harness connector. If voltage is 9-14 volts, replace TP sensor and retest. If voltage is not 9-14 volts, go to next step.
2. Turn ignition off. Check for an open in wiring harness between TP sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.

1. Check for spark at misfiring cylinder. See IGNITION CHECKS in «BASIC TESTING»(ref-21926) article. If spark is present, go to next step. If spark is not present, go to step 4).
2. Check for open or short in IGF circuit between ECM and igniter. Igniter is located near left shock tower. See appropriate wiring diagram in WIRING DIAGRAMS. Repair as necessary. If circuit is okay, go to next step.
3. Disconnect igniter 5-pin Gray connector. Access ECM behind right instrument panel speaker. Turn ignition on. Measure voltage between ground and terminal No. 17 (Black/Yellow wire) at ECM E4 connector. see scheme 4 If voltage is 4.5-5.5 volts, replace igniter. If voltage is not 4.5-5.5 volts, replace ECM and retest.
4. Check for an open or short in IGT circuit between ECM and igniter. See appropriate wiring diagram in WIRING DIAGRAMS. Repair as necessary. If circuit is okay, go to next step.
5. Access ECM behind right instrument panel speaker. Locate ECM E4 connector. see scheme 4 Backprobing ECM connector, measure voltage between ground and terminal No. 23 (Black/Green wire) at ECM E4 connector while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM and retest.
6. Disconnect igniter 5-pin Gray connector. Backprobing ECM connector, measure voltage between ground and terminal No. 23 (Black/Green wire) at ECM E4 connector while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM and retest.
7. Turn ignition on. Measure voltage between ground and terminal No. 3 (Black/Red wire) at igniter wiring harness connector. see scheme 9 If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair igniter power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
8. Check for an open or short in wiring harness between ignition switch and ignition coil, and between ignition coil and igniter. Repair as necessary. If wiring is okay, go to next step.
9. Check ignition coil. See IGNITION CHECKS described in «BASIC TESTING»(ref-21926) article. Replace coil as necessary. If coil is okay, replace igniter.

1. Connect Toyota scan tester. (Scheme 9) Turn ignition and scan tester on. Using scan tester, read STA signal. Turn ignition switch to START position and release.
2. STA signal should be OFF with ignition switch in ON position. STA signal should be ON with ignition switch in START position. If STA signal is not as specified, go to next step. If STA signal is as specified, inspect all applicable connectors. See appropriate wiring diagram in WIRING DIAGRAMS article. Malfunction may be intermittent.
3. Check for an open in wiring harness between starter relay and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, replace ECM and retest.

1. Turn ignition off. Access ECM behind right instrument panel speaker. Using DVOM, measure voltage between ground and terminal No. 2 (Red/Yellow wire) at ECM E7 connector. see scheme 4 If voltage is 9-14 volts, replace ECM and retest. If voltage is not 9-14 volts, go to next step.
2. Remove and inspect EFI fuse. EFI fuse is located in engine compartment fuse box. Replace as necessary. If fuse is okay, inspect circuit between EFI fuse and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.

If any codes other than DTC P1605 are displayed, diagnose and repair those codes first. If only DTC P1605 is displayed, replace ECM and retest.

1. Disconnect PNP switch connector. PNP switch is located at transmission where shifter select cable is mounted. Using ohmmeter, check continuity of switch terminals in specified positions. (Scheme 14)and (Scheme 15). Replace switch as necessary.
2. If switch is okay, access ECM behind glove box. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 22 (Black/White wire) at ECM E7 connector. see scheme 4
3. Voltage should be zero volts in "P" or "N" position. Voltage should be 9-14 volts in any other shift selector position. If all voltages measured are as specified, replace ECM and retest.
4. If any voltage is not as specified, check for an open or short in wiring harness between PNP switch and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.

Scheme 14

Scheme 15