Home ReviewsRefund
Home/Lexus/RX/Lexus RX I (1997-2003)/Repair manual/Testing & Diagnostics/Engine Controls - Self-Diagnostics: Diagnosis
Contents Wiring diagrams Section: Testing & Diagnostics All sections

Engine Controls - Self-Diagnostics: Diagnosis Lexus RX I

Testing & Diagnostics 13 illustrations ~12894 words

DIAGNOSTIC TESTS

Note. Before performing any diagnostic test, refer to SELF-DIAGNOSTICS - INTRODUCTION article for diagnostic system functions and system diagnostic procedures. For component locations (Scheme 31)

Diagnosis & Repair

  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Turn on scan tool. Start engine and allow it to idle. Monitor MAF rate. If scan tool reading is 0.0 gm/sec., go to next step. If reading is 271.0 gm/sec. or more once engine is at normal operating temperature, go to step 5.
  2. Disconnect MAF sensor connector. Turn ignition on. Using voltmeter, measure voltage between ground and terminal No. 1 (Black/Red wire) at MAF sensor wiring harness connector. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check for open in Black/Red wire between MAF sensor connector and EFI relay. EFI relay is located in junction block at left side of engine compartment. If circuit is okay, check EFI relay. See appropriate SYSTEM & COMPONENT TESTING article.
  3. Access ECM behind glove box. Start engine. Backprobing ECM connector, measure voltage between ground and terminal No. 10 (Yellow/Red wire) at ECM E6 connector. (Scheme 29) If voltage is 1.1-1.5 volts, replace ECM and retest system.
  4. If voltage is not 1.1-1.5 volts, locate and repair open or short circuit in Yellow/Red wire between MAF sensor and ECM E10 connector. If Yellow/Red wire is okay, replace MAF sensor and retest system.
  5. Access ECM behind glove box. Turn ignition off. Backprobing ECM E6 connector, check for continuity between ground and terminal No. 19 (Green/Black wire) at ECM E6 connector. (Scheme 29) If continuity does not exist, replace ECM and retest system. If continuity exists, go to next step.
  6. Check for an open in Green/Black wire between MAF sensor and ECM E6 connector. Repair as necessary. If circuit is okay, replace MAF sensor.

Scheme 28

Scheme 28
Scheme 28

Scheme 29

Scheme 29
Scheme 29

Circuit Description

MAF sensor uses a platinum hot wire maintained at a constant temperature. Airflow past sensor affects temperature and current flow through sensor. If DTC P0101 is set, ECM will operate in fail-safe mode, keeping ignition timing and injection volume constant. DTC P0101 is set when throttle valve is fully closed, MAF sensor output is more than 2.2 volts, and Engine Coolant Temperature (ECT) sensor indicates more than 158°F (70°C) for 10 seconds or more at engine speed of 900 RPM or less.

DTC P0101 will also set when Throttle Position (TP) sensor output is .63 volt or more, and MAF sensor output is less than 1.06 volts for 10 seconds or more at engine speed or 1500 or more. Possible cause is

  1. Faulty MAF sensor.

Diagnostic Aids

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

Retrieve trouble codes. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. If only DTC P0101 is displayed, replace MAF sensor and retest system. If other codes are displayed, diagnose and repair those codes first and retest system.

  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Turn scan tool on. Using scan tool, monitor IAT sensor temperature. If temperature displayed is same as actual intake air temperature, check IAT sensor and ECM connections. Problem is intermittent. If temperature displayed is 284°F (140°C) or more, go to step 4. If temperature displayed is -40°F (-40°C), go to next step.
  2. Turn ignition off. Disconnect MAF sensor connector. Connect a fused jumper wire between terminals No. 4 (Blue/Black wire) and No. 5 (Brown wire) at MAF sensor harness connector. Turn ignition on. Using scan tool, monitor IAT sensor temperature. If temperature displayed is 284°F (140°C) or more, ensure MAF connector is okay. If connector is okay, replace MAF sensor and retest system. If temperature displayed is less than 284°F (140°C), go to next step.
  3. Turn ignition off. Remove fused jumper wire. Access ECM behind glove box. Backprobing, connect a fused jumper wire between terminals No. 18 (Brown wire) and No. 22 (Blue/Black wire) at ECM E6 connector. (Scheme 29) If temperature displayed on scan tool is 284°F (140°C) or more, check and repair open in Blue/Black wire between MAF harness connector and ECM E6 connector. If temperature displayed on scan tool is not 284°F (140°C) or more, replace ECM and retest system.
  4. Turn ignition off. Disconnect MAF sensor connector. Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), replace MAF sensor and retest system. If temperature displayed is not -40°F (-40°C), turn ignition off and go to next step.
  5. Access ECM behind glove box. Disconnect ECM E6 connector. Turn ignition on. If temperature displayed is -40°F (-40°C), locate and repair short circuit in wiring harness between MAF sensor and ECM. (Scheme 29) If temperature displayed by scan tool is not -40°F (-40°C), replace ECM and retest system.
  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Turn scan tool on. Using scan tool, monitor ECT sensor temperature. If temperature displayed is same as actual coolant temperature, check component and ECM connections. Problem is intermittent If temperature displayed is 284°F (140°C), go to step 4. If temperature displayed is -40°F (-40°C), go to next step.
  2. Turn ignition off. Disconnect ECT sensor harness connector. Connect a fused jumper wire between terminals No. 2 (Green/White wire) and No. 1 (Brown wire) at ECT sensor harness connector. Turn ignition on. Using scan tool, monitor ECT sensor temperature. If temperature displayed is 284°F (140°C) or more, ensure ECT connector is okay. If connector is okay, replace ECT sensor and retest system. If temperature displayed is less than 284°F (140°C), go to next step.
  3. Turn ignition off. Remove fused jumper wire. Access ECM behind glove box. Backprobing, connect a fused jumper wire between terminals No. 14 (Green/White wire) and No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) If temperature displayed on scan tool is 284°F (140°C) or more, check and repair open in Green/White wire between ECT sensor harness connector and ECM E6 connector. If temperature displayed on scan tool is not 284°F (140°C) or more, replace ECM and retest system.
  4. Turn ignition off. Disconnect ECT sensor harness connector. Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), replace ECT sensor and retest system. If temperature displayed is not -40°F (-40°C), turn ignition off and go to next step.
  5. Access ECM behind glove box. Disconnect ECM E6 connector. Turn ignition on. If temperature displayed is -40°F (-40°C), locate and repair short circuit in wiring harness between ECT sensor and ECM E6 connector. (Scheme 29) If temperature displayed by scan tool is not -40°F (-40°C), replace ECM and retest system.

The ECT sensor is a thermistor that monitors coolant temperature. If DTC P0116 is set, ECM will operate in a fail-safe mode, in which engine coolant is assumed to be 176°F (80°C). DTC P0116 is set when after engine has been running for 20 minutes ECM detects a temperature of less than 19.4°F (-7°C) on THW circuit, and actual engine coolant temperature is 95°F (35°C). DTC P0116 is also set when after engine has been running for 5 minutes ECM detects a temperature of less than 50°F (10°C), or detects a temperature equal to or grater than 19.4°F (-7°C) on THW circuit, and actual engine coolant temperature is 95°F (35°C). DTC P0116 is set when after engine has been running for 2 minutes ECM detects a temperature of more than or equal to 50°F (10°C) on THW circuit, and actual engine coolant temperature is 95°F (35°C). Possible causes are

  1. Faulty ECT sensor.
  2. Faulty cooling system.

Note. If DTCs P0115 and P0116 are output together, diagnose DTC P0115 first. Inspect engine coolant temperature circuit for an open. Repair as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article.

After confirming DTC P0116, use scan tool to access CURRENT DATA to confirm engine coolant temperature. If temperature displayed on scan tool is -40°F (-40°C), ECT sensor circuit may be open. If temperature displayed on scan tool is 284°F (140°C) or more, ECT sensor circuit may be shorted. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

Retrieve trouble codes. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. If other codes are displayed, diagnose and repair those codes first and retest system. If only DTC P0116 is displayed, check cooling system thermostat. Replace thermostat as necessary and retest system. If thermostat is okay, replace ECT sensor and retest system.

  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Turn scan tool on. Using scan tool, monitor throttle valve opening percentage. Opening percentage should be approximately 10 percent with fully closed throttle. Depress accelerator pedal to floor (WOT). Opening percentage should be approximately 75 percent. If percentages are within specification, check all connections. Problem may be intermittent. If percentages are not within specification, go to next step.
  2. Disconnect TP sensor harness connector. Turn ignition on. Using voltmeter, measure voltage between ground and Yellow/Black wire at TP sensor 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 5.
  3. Turn ignition off. Using ohmmeter, measure resistance between terminals No. 1 (Yellow/Black wire) and No. 2 (Brown wire) at TP sensor component connector. Resistance should be 2500-5900 ohms. Measure resistance between terminals No. 2 (Brown wire) and No. 3 (Blue/White wire). Resistance should be 200-6300 ohms with throttle fully closed, and 2000-10,200 ohms with throttle fully open. If any readings are not within specification, replace TP sensor. If all readings are within specification, go to next step.
  4. Connect TP sensor harness connector. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 23 (Blue/White wire) and No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Voltage should be.3-1.0 volt with throttle fully closed, and 2.7-5.2 volts with throttle fully open (WOT). If voltages are as specified, replace ECM and retest system. If voltages are not as specified, locate and repair open or short in Blue wire between TP sensor and ECM E10 connector.
  5. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 2 (Yellow/Black wire) and No. 18 (Brown wire) at ECM E6 connector. If voltage is 4.5-5.5 volts, locate and repair open in Yellow/Black wire between TP sensor and ECM E6 connector. If voltage is not 4.5-5.5 volts, replace ECM and retest system.

The TP sensor is a variable resistor that monitors throttle opening. TP sensor is mounted in throttle body. The ECM determines vehicle driving condition and adjusts air/fuel mixture accordingly. DTC is set when after vehicle speed has exceeded 19 MPH and output value of TP sensor was out of range with vehicle speeds of 0-19 MPH. Possible cause is

  1. Faulty Throttle Position (TP) sensor.

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

Retrieve trouble codes. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. If only DTC P0121 is displayed, replace TP sensor and retest system. If other codes are displayed, diagnose and repair those codes first and retest system.

  1. If other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P0125 is displayed, go to next step.
  2. Check for open or short in wiring between ECM and suspect A/F sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  3. Disconnect suspect A/F sensor harness connector. One A/F sensor is located in each exhaust manifold. Measure resistance between terminal B+ (Black wire) and HT (Black/White wire on bank No. 1 or Black/Red wire on bank No. 2) at A/F sensor connector (component side). Measure resistance at both A/F sensors. Resistance should be .8-1.4 ohms at 68°F (20°C) or 1.8-3.2 ohms at 1472°F (800°C). If resistance is not as specified, replace appropriate A/F sensor. If resistance is as specified, go to next step.
  4. Connect scan tool to Data Link Connector (DLC) No. 3. Start engine and raise engine speed to 2500 RPM for approximately 90 seconds. Using scan tool, monitor each A/F sensor output voltage. See «AIR/FUEL RATIO SENSOR SPECIFICATIONS»(ref-2772-S16582213142000041300000) table. If voltage is as specified, go to next step. If voltage is not as specified, go to step 5 . AIR/FUEL RATIO SENSOR SPECIFICATIONS Application (1) Voltage Using OBD-II Scan Tool Engine Idling 0.66 Engine Racing 0.76 Or More Driving Vehicle (2) 0.56 Or Less Using Lexus Scan Tool Engine Idling 3.3 Engine Racing 3.8 Or More Driving Vehicle (2) 2.8 Or Less (1) Voltage should not remain at specification given. (2) Drive vehicle at 25 MPH or more with engine speed at 1500 RPM or more while opening and closing throttle valve.
  5. Perform test drive confirmation then go to next step. See «TEST DRIVE CONFIRMATION»(ref-2772-S23445173442000041300000) under DTC P1130 OR P1150: HEATED OXYGEN SENSOR FAULT.
  6. Clear and recheck for DTCs. If DTC P0125 is displayed again, replace ECM. If DTC P0125 is not displayed again, vehicle either ran out of fuel or problem is intermittent. Check component and ECM connections.
  1. Drain cooling system. Remove and test thermostat. Replace thermostat as necessary. If thermostat is okay, install thermostat and refill cooling system. Go to next step.
  2. If any other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P0128 is displayed, replace ECM and retest system.
  1. If any other DTCs are displayed, diagnose and repair those DTCs first. If only DTC P0136 is displayed, go to next step.
  2. Check for open or short in wiring between ECM and heated oxygen sensor No. 2. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  3. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Start and warm engine to normal operating temperature. Monitor heated oxygen sensor No. 2 output voltage. Snap accelerate engine to about 4000 RPM 3 times. Voltage should fluctuate from less than.4 volt to.6 volt or more. If voltage is as specified, problem is intermittent. Check component and ECM connections. If voltage is not as specified, replace heated oxygen sensor No. 2.
  1. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe between ground and terminal No. 9 (Black wire) at ECM harness connector E9. (Scheme 29) Voltage should be 9-14 volts. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
  2. Turn ignition off. Disconnect heated oxygen sensor No. 2 harness connector. Connector is located underneath driver's seat, near center console. It may be necessary to remove driver's seat to access connector. Measure resistance between terminals HT (Black wire) and B+ (Blue/White wire) at heated oxygen sensor No. 2 connector. Resistance should be 11-16 ohms at 68°F (20°C). If resistance is not as specified, replace heated oxygen sensor No. 2. If resistance is as specified, go to next step.
  3. Repair wiring between ECM and heated oxygen sensor No. 2 or between heated oxygen sensor No. 2 and EFI main relay. See appropriate wiring diagram in WIRING DIAGRAMS article.
  1. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, go to next step.
  2. Check fuel injectors. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  3. Check Mass Airflow (MAF) meter and Engine Coolant Temperature (ECT) sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace appropriate sensor(s). If problem does not exist, go to next step.
  4. Check spark and ignition system. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  5. Check fuel pressure. See FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
  6. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, go to next step.
  7. Connect scan tool to Data Link Connector (DLC) No. 3. Start engine and raise engine speed to 2500 RPM for approximately 90 seconds. Using scan tool, monitor each A/F sensor output voltage. See «AIR/FUEL RATIO SENSOR SPECIFICATIONS»(ref-2772-S28737923502000041300000) table. If voltage is not as specified, go to next step. If voltage is as specified, go to step 9 . AIR/FUEL RATIO SENSOR SPECIFICATIONS Application (1) Voltage Using OBD-II Scan Tool Engine Idling 0.66 Engine Racing 0.76 Or More Driving Vehicle (2) 0.56 Or Less Using Lexus Scan Tool Engine Idling 3.3 Engine Racing 3.8 Or More Driving Vehicle (2) 2.8 Or Less (1) Voltage should not remain at specification given. (2) Drive vehicle at 25 MPH or more with engine speed at 1500 RPM or more while opening and closing throttle valve.
  8. Check for open or short in wiring between ECM and A/F sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace A/F sensor.
  9. Perform test drive confirmation then go to next step. See «TEST DRIVE CONFIRMATION»(ref-2772-S23445173442000041300000) under DTC P1130 OR P1150: AIR/FUEL SENSOR CIRCUIT RANGE/PERFORMANCE FAULT.
  10. Clear and recheck for DTCs. If DTCs P0171 and/or P0172 are displayed again, replace ECM. If neither DTC P0171 and P0172 are displayed again, vehicle either ran out of fuel or problem is intermittent. Check component and ECM connections.

ECM uses signals provided by crankshaft and camshaft position sensors. If engine speed rate has changed enough to equal a preset number, a misfire is detected and MIL is illuminated. If misfire rate is high enough, and driving conditions will cause catalytic converter damage or overheating, 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. Faulty ignition system.
  2. Faulty fuel injector(s).
  3. Improper fuel pressure.
  4. Faulty engine compression.
  5. Improper valve clearance.
  6. Improper valve timing.
  7. Faulty Mass Airflow (MAF) meter.
  8. Faulty Engine Coolant Temperature (ECT) sensor.
  9. Open or short in wiring.
  10. Poor connector contact at ECM.
  11. Faulty ECM.

When 2 or more codes for misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it indicates misfires were detected and recorded at different times. If misfire cannot be reproduced, reason may be because of driving with lack of fuel, improper fuel, fouled spark plug, etc. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

Test Drive Confirmation

  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Record any DTCs and freeze frame data. Switch scan tool to CHECK mode (Lexus scan tool only). 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 scan tool data list.
  2. Drive vehicle at specified engine speeds. See «DRIVING PATTERN»(ref-2772-S24263260182000041300000) table. Turn ignition off after symptom is simulated the first time, then repeat test drive again (OBD-II scan tool only). If a misfire is detected, a DTC will set and misfire will be indicated in freeze frame data. Turn ignition off and wait a minimum of 5 seconds. DRIVING PATTERN RPM (1) Minutes Idling 3 1/2 1000 3 2000 1 1/2 3000 1 (1) Minimum specification given.
  1. Check vacuum hoses for leaks, blockage and proper routing. Also, check wiring and connectors for damage or poor connections. If problem exists, repair as necessary and perform «TEST DRIVE CONFIRMATION»(ref-2772-S35400813562000041300000). If problem does not exist, go to next step.
  2. Check spark and ignition system. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  3. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM connector and measure voltage between ground and fuel injector terminals at specified ECM connector. See «IDENTIFYING FUEL INJECTOR TERMINALS»(ref-2772-S03555264352000041300000) table. (Scheme 29) If voltage is 9-14 volts at each terminal, go to step 5. If voltage is not 9-14 volts at each terminal, go to next step. IDENTIFYING FUEL INJECTOR TERMINALS Fuel Injector No. Terminal No. Wire Color 1 5 (1) White 2 6 (1) Yellow 3 1 (2) Black 4 2 (2) Blue 5 3 (2) Red 6 4 (2) Green (1) Terminal is located in ECM harness connector E6. (Scheme 29) (2) Terminal is located in ECM harness connector E7. (Scheme 29)
  4. Disconnect fuel injector harness connector at misfiring cylinder. Measure resistance between fuel injector terminals (component side). Resistance should be 13.4-14.2 ohms at 68°F (20°C). If resistance is as specified, repair open or short in power circuit to fuel injector or in wiring harness between ECM and fuel injector. See appropriate wiring diagram in WIRING DIAGRAMS article. If resistance is not as specified, replace fuel injector.
  5. Check fuel pressure. See FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
  6. Check fuel injectors. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  7. Check Mass Airflow (MAF) meter and Engine Coolant Temperature (ECT) sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace appropriate sensor(s). If problem does not exist, go to next step.
  8. Check engine compression. See BASIC DIAGNOSTIC PROCEDURES article. If engine compression is okay, check valve clearance. See ON-VEHICLE ADJUSTMENTS article. If valve clearance is okay, it may be necessary to check valve timing. See appropriate article in ENGINES.

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

  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 30) Disconnect EA1 connector. EA1 connector is a wire-to-wire connector located in engine compartment, near idle air control valve. Connector is a Dark Gray 4-pin connector.
  2. Connect a fused jumper wire between terminal No. 1 of male connector to terminal No. 2 of female connector. Connect another fused jumper wire between terminal No. 2 of male connector to terminal No. 1 of female connector. (Scheme 30) Turn ignition on. Turn scan tool on. Clear trouble codes. See CLEARING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. Start and warm engine to normal operating temperature.
  3. Snap accelerate engine 3 times to 4000 RPM. Retrieve trouble codes. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. If same code is repeated as before, go to next step. If code has changed, go to step 5.
  4. Check for open or short circuit(s) between EA1 connector and ECM harness connector. Repair as necessary. If circuits are okay, replace ECM and retest system.
  5. Check for open or short circuit(s) between EA1 connector and suspect knock sensor. If DTC P0325 has changed to DTC P0330, check knock sensor circuit on right bank. If DTC P0330 changed to DTC P0325, check knock sensor circuit on left bank. Repair as necessary. If harness is okay, replace knock sensor.

Scheme 30

Scheme 30
Scheme 30
  1. Disconnect CKP sensor harness connector. Using ohmmeter, measure resistance between sensor connector terminals. Resistance should be 1630-2740 ohms at 14-122°F (-10-50°C) or 2065-3225 ohms at 122-212°F (50-100°C). Replace sensor as necessary. If sensor is okay, go to next step.
  2. Check for open or short circuit in wiring harness between ECM and CKP sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring harness is okay, remove and inspect sensor. Also, inspect signal plate. Replace as necessary. If both components are okay, replace ECM and retest system.
  1. Disconnect VVT sensor harness connector. Using ohmmeter, measure resistance between sensor connector terminals. Resistance should be 835-1400 ohms at 14-122°F (-10-50°C) or 1060-1645 ohms at 122-212°F (50-100°C). Check resistance at each VVT sensor.
  2. Replace sensor(s) as necessary. If sensor(s) is okay, check for open or short circuit in wiring harness between ECM and VVT sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring harness is okay, remove and inspect sensor(s). Also, inspect signal plate. Replace as necessary. If both components are okay, replace ECM and retest system.
  1. If other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P0420 is displayed, go to next step.
  2. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, go to next step.
  3. Disconnect suspect A/F sensor harness connector. One A/F sensor is located in each exhaust manifold. Measure resistance between terminal B+ (Black/Red wire) and HT (Blue wire on bank No. 1 or Green wire on bank No. 2) at A/F sensor connector (component side). Measure resistance at both A/F sensors. Resistance should be .8-1.4 ohms at 68°F (20°C) or 1.8-3.2 ohms at 1472°F (800°C). If resistance is not as specified, replace appropriate A/F sensor. If resistance is as specified, go to next step.
  4. Check heated oxygen sensor No. 2 circuits. See «DTC P0136: HEATED OXYGEN SENSOR CIRCUIT»(ref-2772-S19297276692000041300000) . If problem exists, repair as necessary. If problem does not exist, replace catalytic converter.
  1. Check with vehicle driver if fuel tank cap was found loose at any time. If fuel tank cap was loose, it probably was cause of DTC P0440 to set. If fuel tank cap was not loose, check for cracks, deformations or loose connections in the following: Fuel tank. Charcoal canister. Fuel tank filler pipe. Hose and tubes around fuel tank and charcoal canister. Repair as necessary. If components are okay, go to next step.
  2. Check if fuel tank cap is an original manufacturer's cap. If fuel tank cap is an original manufacturer's cap, go to next step. If fuel tank cap is not an original manufacturer cap, replace cap with a manufacturer's cap.
  3. Check if fuel tank cap is installed properly. Reinstall fuel cap as necessary. If fuel cap is installed properly, go to next step.
  4. Check for damaged fuel tank cap and gasket. Replace fuel cap as necessary. If fuel tank cap and gasket are okay, go to next step.
  5. Remove fuel tank cap. Visually inspect fuel tank filler neck for damage. Replace filler neck as necessary. If filler neck is okay, go to next step.
  6. Check vacuum hoses between vapor pressure sensor and fuel tank, and between pressure switching valve VSV and charcoal canister. Check hoses for correct installation, looseness and damage. Repair as necessary. If vacuum hoses are okay, go to next step.
  7. Check hose and tube between fuel tank and charcoal canister for correct installation and damage. Repair as necessary. If hose and tube are okay, go to next step.
  8. Visually inspect charcoal canister for cracks or damage. Replace canister as necessary. If canister is okay, go to next step.
  9. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 2 (Yellow/Black wire) and No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM and retest system. NOTE: Vehicle may be equipped with one of 2 different types of vapor pressure sensor. Sensor is mounted on top of fuel tank and may either have 2 vacuum ports (old style) or no vacuum ports (new style).
  10. Locate vapor pressure sensor on top of fuel tank. (Scheme 31) Identify type of vapor pressure sensor used. If sensor does not have any vacuum ports, go to next step. If sensor has 2 vacuum ports, disconnect vacuum supply hose from vapor pressure sensor. (Scheme 32) Backprobing ECM harness connector, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E8 connector and terminal No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Connect a vacuum pump to sensor. Voltage should be 3.0-3.6 volts without vacuum applied, and 1.3-2.1 volts with.59 in. Hg (2.0 kPa) applied. If voltage is as specified, go to step 13. If voltage is not as specified, go to step 12.
  11. Backprobing ECM harness connector, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E8 connector and terminal No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Remove fuel tank cap and note voltmeter reading. If voltage is 3.0-3.6 volts, go to 13. If voltage is not 3.0-3.6 volts, go to next step.
  12. Check for an open or short in wiring harness between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor.
  13. Check fuel tank and fuel tank overfill check valves for cracks and damage. Overfill check valve is located on top of fuel tank. (Scheme 31) Replace fuel tank or overfill check valve as necessary. If fuel tank and overfill check valve are okay, probable cause of DTC P0440 to set was an incorrectly installed fuel tank cap. NOTE: Overfill check valve may also be referred to as fill check valve. Cut-off valve may also be referred to as fuel cut-off valve.

Scheme 31

Scheme 31
Scheme 31

Scheme 32

Scheme 32
Scheme 32

Diagnosis & Repair (Using Lexus Scan Tool)

  1. Check for cracks, deformations or loose connections in the following: Fuel tank. Charcoal canister. Fuel tank filler pipe. Hose and tubes around fuel tank and charcoal canister. Repair as necessary. If components are okay, go to next step.
  2. Check if fuel tank cap is an original manufacturer's cap. If fuel tank cap is an original manufacturer's cap, go to next step. If fuel tank cap is not an original manufacturer cap, replace cap with a manufacturer's cap.
  3. Check if fuel cap is installed properly. Reinstall cap as necessary. If fuel cap is installed properly, go to next step.
  4. Check for damaged fuel tank cap and gasket. Replace fuel tank cap as necessary. If fuel tank cap and gasket are okay, go to next step.
  5. Remove fuel tank cap. Visually inspect fuel tank filler neck for damage. Replace filler neck as necessary. If filler neck is okay, go to next step.
  6. Check vacuum hoses between vapor pressure sensor and fuel tank, and between pressure switching valve VSV and charcoal canister. Check hoses for correct installation, looseness and damage. Repair as necessary. If vacuum hoses are okay, go to next step.
  7. Check hose and tube between fuel tank and charcoal canister for correct installation and damage. Repair as necessary. If hose and tube are okay, go to next step.
  8. Check EVAP VSV, canister closed valve VSV, pressure switching valve VSV and vapor pressure sensor wiring harness connectors for damaged pins, corrosion and loose wires. Repair as necessary. If connectors are okay, go to next step. For component locations (Scheme 31)
  9. Check all EVAP related vacuum hoses between fuel tank and charcoal canister, and between fuel tank and fuel tank overfill check valve for damage, blockage, looseness and correct routing. Repair as necessary. If vacuum hoses are okay, go to next step. For proper vacuum hose routing (Scheme 31)
  10. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 2 (Yellow/Black wire) and No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM and retest system. NOTE: Vehicle may be equipped with one of 2 different types of vapor pressure sensor. Sensor is mounted on top of fuel tank and may either have 2 vacuum ports (old style) or no vacuum ports (new style).
  11. Locate vapor pressure sensor on top of fuel tank. (Scheme 31) Identify type of vapor pressure sensor used. If sensor does not have any vacuum ports, go to next step. If sensor has 2 vacuum ports, disconnect vacuum supply hose from vapor pressure sensor. (Scheme 32) Backprobing ECM harness connector, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E8 connector and terminal No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Connect a vacuum pump to sensor. Voltage should be 3.0-3.6 volts without vacuum applied, and 1.3-2.1 volts with.59 in. Hg (2.0 kPa) applied. If voltage is as specified, go to step 14. If voltage is not as specified, go to step 13.
  12. Backprobing ECM harness connector, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E8 connector and terminal No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Remove fuel tank cap and note voltmeter reading. If voltage is 3.0-3.6 volts, go to 14. If voltage is not 3.0-3.6 volts, go to next step.
  13. Check for an open or short in wiring harness between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor.
  14. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Using scan tool, select ACTIVE TEST mode. Disconnect vacuum hose from charcoal canister at EVAP VSV. (Scheme 31) Start engine. Connect a vacuum gauge to disconnected vacuum hose. Using scan tool, activate EVAP VSV. When EVAP VSV is activated, vacuum should be present. When EVAP VSV is not activated, no vacuum should be present. If vacuum is as specified, go to step 18. If vacuum is not as specified, go to next step.
  15. Check for correct routing, looseness, damage and blockage in vacuum hoses between intake manifold and EVAP VSV, and between EVAP VSV and charcoal canister. Repair as necessary. If hoses are okay, go to next step.
  16. Check EVAP VSV. See appropriate SYSTEM & COMPONENT TESTING article. If EVAP VSV is not okay, replace EVAP VSV and charcoal canister. Also clean vacuum hoses between throttle body and EVAP VSV, and EVAP VSV and charcoal canister. If EVAP VSV is okay, go to next step.
  17. Check for an open or short in wiring harness between EFI main relay, EVAP VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  18. Turn ignition off. Disconnect closed canister valve VSV vacuum hose. VSV is mounted on or near air filter housing. (Scheme 31) Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Select ACTIVE TEST mode on scan tool. Using scan tool, turn canister closed valve VSV on. Apply compressed air to port "A" of canister closed valve VSV. Air should not flow from port "B". (Scheme 33) Using scan tool, turn canister closed valve VSV off. Air should flow from port "B". If VSV operates correctly, go to step 21. If VSV does not operate correctly, go to next step.
  19. Check canister closed valve VSV. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If canister closed valve VSV is not okay, replace canister closed valve VSV and charcoal canister. Also clean vacuum hoses between charcoal canister and canister closed valve VSV. If canister closed valve VSV is okay, check vacuum hose between canister closed valve VSV and charcoal canister for looseness, damage and blockage. Replace vacuum hose as necessary. If vacuum hose is okay, go to next step.
  20. Check for an open or short in wiring harness between EFI main relay, pressure switching valve VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  21. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Ensure ignition is on. Select ACTIVE TEST mode on scan tool. Locate pressure switching valve VSV on charcoal canister. (Scheme 31) Disconnect vacuum hoses from pressure switching valve VSV. Using scan tool, activate pressure switching valve VSV. Apply compressed air to port "E" of pressure switching valve VSV. Air should flow from port "F". (Scheme 34) Using scan tool, turn pressure switching valve VSV off. Air should not flow from port "F". If VSV operates correctly, go to step 24. If VSV does not operate correctly, go to next step.
  22. Check pressure switching valve VSV. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If pressure switching valve VSV is not okay, replace pressure switching valve VSV and charcoal canister. Also clean vacuum hose between charcoal canister and pressure switching valve VSV, and between pressure switching valve VSV and fuel tank. If pressure switching valve VSV is okay, go to next step.
  23. Check for an open or short in wiring harness between EFI main relay, pressure switching valve VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  24. Access ECM behind glove box. Backprobing ECM harness connector, connect DVOM between terminal No. 17 (Blue/Orange wire) at ECM E8 connector and terminal No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Select ACTIVE TEST mode on scan tool. Start engine. EVAP VSV, canister closed valve VSV and pressure switching valve VSV should all be on. Observing DVOM, when voltage reaches 1.2 volts, switch EVAP VSV and pressure switching valve VSV off. (Scheme 35) Wait 30 seconds and note DVOM voltage reading. If voltage stays at 1.2 volts, fuel tank is okay. Go to next step. If voltage does not stay at 1.2 volts, replace fuel tank.
  25. Access ECM behind glove box. Backprobing ECM harness connector, connect DVOM between terminal No. 17 (Blue/Orange wire) at ECM E8 connector and terminal No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Select ACTIVE TEST mode on scan tool. Start engine. EVAP VSV, canister closed valve VSV and pressure switching valve VSV should all be on. Observing DVOM, when voltage reaches 1.2 volts, switch EVAP VSV off. (Scheme 36) Wait 30 seconds and note DVOM voltage reading. If voltage stays at 1.2 volts, go to next step. If voltage does not stay at 1.2 volts, replace charcoal canister.
  26. Charcoal canister or fuel tank overfill check valve maybe defective. Check fuel evaporation system. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. If no problem is indicated, replace ECM.

Scheme 33

Scheme 33
Scheme 33

Scheme 34

Scheme 34
Scheme 34

Scheme 35

Scheme 35
Scheme 35

Scheme 36

Scheme 36
Scheme 36

Scheme 37

Scheme 37: Diagnosis & Repair (Using OBD-II Scan Tool)
Scheme 37: Diagnosis & Repair (Using OBD-II Scan Tool)
  1. Check for cracks, deformations or loose connections in the following: Fuel tank. Charcoal canister. Fuel tank filler pipe. Hose and tubes around fuel tank and charcoal canister. Repair as necessary. If components are okay, go to next step.
  2. Check if fuel tank cap is an original manufacturer's cap. If fuel tank cap is an original manufacturer's cap, go to next step. If fuel tank cap is not an original manufacturer cap, replace cap with a manufacturer's cap.
  3. Check if fuel cap is installed properly. Reinstall cap as necessary. If fuel cap is installed properly, go to next step.
  4. Check for damaged fuel tank cap and gasket. Replace fuel tank cap as necessary. If fuel tank cap and gasket are okay, go to next step.
  5. Remove fuel tank cap. Visually inspect fuel tank filler neck for damage. Replace filler neck as necessary. If filler neck is okay, go to next step.
  6. Check vacuum hoses between vapor pressure sensor and fuel tank, and between pressure switching valve VSV and charcoal canister. Check hoses for correct installation, looseness and damage. Repair as necessary. If vacuum hoses are okay, go to next step.
  7. Check hose and tube between fuel tank and charcoal canister for correct installation and damage. Repair as necessary. If hose and tube are okay, go to next step.
  8. Check EVAP VSV, canister closed valve VSV, pressure switching valve VSV and vapor pressure sensor wiring harness connectors for damaged pins, corrosion and loose wires. Repair as necessary. If connectors are okay, go to next step. (Scheme 31)
  9. Check all EVAP related vacuum hoses between fuel tank and charcoal canister, and between fuel tank and fuel tank overfill check valve for damage, blockage, looseness and correct routing. (Scheme 31)
  10. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 2 (Yellow/Black wire) and No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM and retest system. NOTE: Vehicle may be equipped with one of 2 different types of vapor pressure sensor. Sensor is mounted on top of fuel tank and may either have 2 vacuum ports (old style) or no vacuum ports (new style).
  11. Locate vapor pressure sensor on top of fuel tank. (Scheme 31) Identify type of vapor pressure sensor used. If sensor does not have any vacuum ports, go to next step. If sensor has 2 vacuum ports, disconnect vacuum supply hose from vapor pressure sensor. (Scheme 32) Backprobing ECM harness connector, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E8 connector and terminal No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Connect a vacuum pump to sensor. Voltage should be 3.0-3.6 volts without vacuum applied, and 1.3-2.1 volts with.59 in. Hg (2.0 kPa) applied. If voltage is as specified, go to step 14. If voltage is not as specified, go to step 13.
  12. Backprobing ECM harness connector, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E8 connector and terminal No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Remove fuel tank cap and note voltmeter reading. If voltage is 3.0-3.6 volts, go to 14. If voltage is not 3.0-3.6 volts, go to next step.
  13. Check for an open or short in wiring harness between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor.
  14. Disconnect EVAP VSV vacuum hoses. (Scheme 31) Turn ignition on. Access ECM harness connectors behind glove box. Backprobing, connect a fused jumper wire between ground and terminal No. 7 (White/Blue wire) at ECM E6 connector. (Scheme 29)
  15. Apply compressed air to EVAP VSV port "E". (Scheme 37) Air should flow from port "F". Remove fused jumper wire. Air should not flow from port "F". If EVAP VSV functions as specified, go to step 18. If EVAP VSV does not function as specified, go to next step.
  16. Check EVAP VSV operation. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If VSV is okay, go to next step. If EVAP VSV is not okay, replace EVAP VSV. Also clean vacuum hose between throttle body and EVAP VSV, and EVAP VSV and charcoal canister, then check charcoal canister. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.
  17. Check for an open or short in wiring harness between EFI main relay, EVAP VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  18. Disconnect canister closed valve VSV vacuum hose. VSV is mounted on air filter housing. (Scheme 31) Access ECM harness connectors behind glove box. Turn ignition on. Backprobing, connect a fused jumper wire between ground and terminal No. 10 (Green wire) at ECM E8 connector. (Scheme 29) Apply compressed air to VSV port "A". (Scheme 33)
  19. Air should not flow from VSV port "B". Disconnect fused jumper wire. Air should flow from port "B". If VSV does not function as specified, go to next step. If VSV functions as specified, go to step 22.
  20. Check canister closed valve VSV. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If VSV is okay, go to next step. If VSV is not okay, replace canister closed valve VSV and charcoal canister. Also clean vacuum hose between charcoal canister and closed canister valve VSV.
  21. Check for an open or short in wiring harness between EFI main relay, closed canister valve VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  22. Turn ignition on. Access ECM harness connectors behind glove box. Backprobing, connect a fused jumper wire between ground and terminal No. 3 (Blue/Red wire) at ECM E9 connector. (Scheme 29) Disconnect pressure switching valve VSV vacuum hoses. VSV is located on charcoal canister. (Scheme 31) Apply compressed air to VSV port "E". (Scheme 34) Air should flow from port "F". Remove fused jumper wire. Air should not flow from port "F". If VSV functions as specified, go to step 25. If VSV does not function as specified, go to next step.
  23. Check pressure switching valve VSV. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If pressure switching valve VSV is not okay, replace pressure switching valve VSV and charcoal canister. Also clean vacuum hose between charcoal canister and pressure switching valve VSV, and between pressure switching valve VSV and fuel tank. If pressure switching valve VSV is okay, go to next step.
  24. Check for an open or short in wiring harness between EFI main relay, pressure switching valve VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  25. Charcoal canister or fuel tank overfill check valve maybe defective. Check fuel evaporation system. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. If no problem is indicated, replace ECM.
  1. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 2 (Yellow/Black wire) and No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM and retest system. NOTE: Vehicle may be equipped with one of 2 different types of vapor pressure sensor. Sensor is mounted on top of fuel tank and may either have 2 vacuum ports (old style) or no vacuum ports (new style).
  2. Locate vapor pressure sensor on top of fuel tank. (Scheme 31) Identify type of vapor pressure sensor used. If sensor does not have any vacuum ports, go to next step. If sensor has 2 vacuum ports, disconnect vacuum supply hose from vapor pressure sensor. (Scheme 32) Backprobing ECM harness connector, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E8 connector and terminal No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Connect a vacuum pump to sensor. Voltage should be 3.0-3.6 volts without vacuum applied, and 1.3-2.1 volts with.59 in. Hg (2.0 kPa) applied. If voltage is as specified, replace ECM and retest system. If voltage is not as specified, go to step 4.
  3. Backprobing ECM harness connector, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E8 connector and terminal No. 18 (Brown wire) at ECM E6 connector. (Scheme 29) Remove fuel tank cap and note voltmeter reading. If voltage is 3.0-3.6 volts, replace ECM and retest system. If voltage is not 3.0-3.6 volts, go to next step.
  4. Check for an open or short in wiring harness between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor. Retest system.
  1. Test drive vehicle and check operation of speedometer. If speedometer is not operating correctly, repair speedometer as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. If speedometer is operating correctly, go to next step.
  2. Access ECM behind glove box. Turn ignition off. Disconnect ECM E9 connector. (Scheme 29) Using voltmeter, check for continuity between ground and terminal No. 22 (Violet/White wire) at ECM E9 harness connector. If continuity does not exist, go to next step. If continuity exists, locate and repair short to ground in Violet/White wire between ECM E9 connector and instrument cluster.
  3. Turn ignition on. Measure voltage between ground and terminal No. 22 (Violet/White wire) at ECM E9 harness connector. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, locate and repair open in Violet/White wire between junction connector IJ1 and ECM. Connector IJ1 is a 16-pin connector located behind glove box.
  4. Check for open in Violet/White wire between junction block IJ1 and instrument cluster. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary and retest system. If wiring is okay, replace ECM and retest system.
  1. If using Lexus scan tool, go to next step. If using OBD-II scan tool, go to step 3.
  2. Warm engine to operating temperature. Turn accessories and A/C off. Place transmission in Neutral. Connect Lexus scan tool to DLC No. 3 and select ACTIVE TEST MODE. (Scheme 28) Using Lexus scan tool, turn TE1 on and off. Record engine speed 5 seconds before and after TE1 is turned on and off. If engine speed changes more than 100 RPM, go to step 10. If engine speed does not change more than 100 RPM, go to step 4.
  3. Warm engine to operating temperature. Turn accessories and A/C off. Place transmission in Neutral. Connect OBD-II scan tool to DLC No. 3. Connect Jumper Wire (09843-18020) between DLC No. 1 connector terminals No. 8 (Pink/Black wire) and No. 3 (Brown/White wire). DLC No. 1 is located on left side of engine compartment, behind fuse box. Connect and disconnect Jumper Wire (09843-18020) several times. Record engine speed 5 seconds before and after Jumper Wire (09843-18020) is connected and disconnected. If engine speed changes more than 100 RPM, go to step 10. If engine speed does not change more than 100 RPM, go to next step.
  4. Access ECM behind glove box. Turn ignition off. Disconnect ECM E7 connector. (Scheme 29) Turn ignition on. Using voltmeter, measure voltage between ground and terminal No. 26 (Yellow/Red wire) at ECM E7 connector. If voltage is 9-14 volts, go to step 7. If voltage is not 9-14 volts, go to next step.
  5. Turn ignition off. Disconnect IAC valve harness connector. Measure voltage between ground and terminal No. 2 (Black/Red wire) at IAC valve harness connector. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, repair IAC valve power distribution circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  6. Check for open or short in Yellow/Red wire between terminal No. 1 at IAC valve harness connector and terminal No. 26 at ECM harness connector E7. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace IAC valve.
  7. Check IAC system operation. See IDLE CONTROL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, go to next step. If problem does not exist, go to step 9
  8. Check for open in White/Black wire between ground and terminal No. 3 at IAC valve harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace IAC valve.
  9. Check IAC valve and passages for carbon build-up and blockage. Repair as necessary. If no build-up or blockage exists, replace ECM.
  10. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, an open or short in A/C switch signal circuit may exist. Check A/C amplifier. See appropriate article in AIR CONDITIONING & HEATING. Repair as necessary.
  1. If using OBD-II scan tool, go to step 3. If using Lexus scan tool, connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Switch scan tool to CHECK mode and go to next step.
  2. Start and warm engine to normal operating temperature with all accessories off. Drive vehicle at 38-75 MPH and engine speed at 1600-3200 RPM for 3-5 minutes. Stop vehicle and allow to idle for one minute. If malfunction exists, MIL will illuminate.
  3. Start and warm engine to normal operating temperature. Drive vehicle at 38-75 MPH and engine speed at 1600-3200 RPM for 3-5 minutes. Stop vehicle and allow to idle for one minute. Turn ignition off. Repeat driving and idle part of test. If malfunction exists, MIL will illuminate.
  1. If other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P1130 and/or P1150 is displayed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC) No. 3. Start engine and raise engine speed to 2500 RPM for approximately 90 seconds. Using scan tool, monitor each A/F sensor output voltage. See «AIR/FUEL RATIO SENSOR SPECIFICATIONS»(ref-2772-S25460284882000041300000) table. If voltage is as specified, go to next step. If voltage is not as specified, go to step 8 . AIR/FUEL RATIO SENSOR SPECIFICATIONS Application (1) Voltage Using OBD-II Scan Tool Engine Idling 0.66 Engine Racing 0.76 Or More Driving Vehicle (2) 0.56 Or Less Using Lexus Scan Tool Engine Idling 3.3 Engine Racing 3.8 Or More Driving Vehicle (2) 2.8 Or Less (1) Voltage should not remain at specification given. (2) Drive vehicle at 25 MPH or more with engine speed at 1500 RPM or more while opening and closing throttle valve.
  3. Check for open or short in wiring between ECM and suspect A/F sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  4. Disconnect suspect A/F sensor harness connector. One A/F sensor is located in each exhaust manifold. Measure resistance between terminal B+ (Black/Red wire) and HT (Blue wire on bank No. 1 or Green wire on bank No. 2) at A/F sensor connector (component side). Resistance should be .8-1.4 ohms at 68°F (20°C) or 1.8-3.2 ohms at 1472°F (800°C). If resistance is not as specified, replace appropriate A/F sensor. If resistance is as specified, go to next step.
  5. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, go to next step.
  6. Check fuel pressure. See FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
  7. Check fuel injectors. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, repair as necessary. If problem does not exist, replace defective A/F sensor.
  8. Perform test drive confirmation then go to next step. See «TEST DRIVE CONFIRMATION»(ref-2772-S23445173442000041300000) .
  9. Clear and recheck for DTCs. If DTC P1130 and/or P1150 is displayed again, replace ECM. If DTC P1130 and P1150 are not displayed again, vehicle either ran out of fuel or problem is intermittent. Check component and ECM connections.
  1. If using OBD-II scan tool, go to step 3. If using Lexus scan tool, connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Switch scan tool to CHECK mode and go to next step.
  2. Start and warm engine to normal operating temperature with all accessories off. Drive vehicle at 38-75 MPH and engine speed at 1600-3200 RPM for 3-5 minutes. Stop vehicle and allow to idle for one minute. If malfunction exists, MIL will illuminate.
  3. Start and warm engine to normal operating temperature. Drive vehicle at 38-75 MPH and engine speed at 1600-3200 RPM for 3-5 minutes. Stop vehicle and allow to idle for one minute. Turn ignition off. Repeat driving and idle part of test. If malfunction exists, MIL will illuminate.
  1. If other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P1133 and/or P1153 is displayed, go to next step.
  2. Disconnect suspect A/F sensor harness connector. One A/F sensor is located in each exhaust manifold. Measure resistance between terminal B+ (Black/Red wire) and HT (Blue wire on bank No. 1 or Green wire on bank No. 2) at A/F sensor connector (component side). Resistance should be .8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistances are not as specified, replace appropriate A/F sensor. If resistances are as specified, go to next step.
  3. Perform test drive confirmation then go to next step. See «TEST DRIVE CONFIRMATION»(ref-2772-S40256249662000041300000) .
  4. Clear and recheck for DTCs. If DTC P1133 and/or P1153 is displayed again, replace ECM. If DTC neither P1133 and P1153 are displayed again, go to next step.
  5. Vehicle either ran out of fuel or problem is intermittent. Check component and ECM connections.
  1. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and terminals No. 3 (Blue wire) and No. 4 (Green wire) at ECM harness connector E8. (Scheme 29) If both voltages are 9-14 volts, replace ECM. If either voltage is not 9-14 volts, go to next step.
  2. Disconnect suspect A/F sensor harness connector. One A/F sensor is located in each exhaust manifold. Measure resistance between terminal B+ (Black/Red wire) and HT (Blue wire on bank No. 1 or Green wire on bank No. 2) at A/F sensor connector (component side). Resistance should be.8-1.4 ohms at 68°F (20°C) or 1.8-3.2 ohms at 1472°F (800°C). If resistance is not as specified, replace appropriate A/F sensor. If resistance is as specified, go to next step.
  3. Check for faulty A/F sensor heater relay located in relay box next to battery. See RELAYS & SOLENOIDS in appropriate SYSTEM & COMPONENT TESTING article. If A/F sensor heater relay is defective, replace as necessary and retest system. If A/F sensor heater relay is okay, go to next step.
  4. Check for open or short in wiring between A/F sensor heater relay, A/F sensor and ECM. See WIRING DIAGRAMS article. Repair as necessary.

This system is equipped with a Direct Ignition System (DIS), with a coil/ignitor devoted to each cylinder. Primary circuit is turned off when ECM delivers a signal to ignitor on the IGT wire, causing ignition coil to fire spark plug. After delivering a command to turn off primary circuit on IGT wire, the ECM monitors ignition confirmation signal on the IGF circuit to ensure primary switching has occurred. If IGF signal is not input to ECM, the ECM will stop fuel injection as a fail-safe function. DTC will set if there is no IGF signal to ECM with engine running. DTC 1300 is for cylinder No. 1. DTC 1305 is for cylinder No. 2. DTC 1310 is for cylinder No. 3. DTC 1315 is for cylinder No. 4. DTC 1320 is for cylinder No. 5. DTC 1325 is for cylinder No. 6. Possible causes are

  1. Open or short in IGF or IGT circuit.
  2. Faulty ignition coil/ignitor.
  3. Faulty ECM.

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

  1. Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES 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 and IGT circuits between ECM E7 connector and suspect ignition coil/ignitor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuits are okay, go to next step.
  3. Disconnect Black 4-pin connector at suspect ignition coil/ignitor. Turn ignition on. Backprobing, measure voltage between ground and terminal No. 25 (Black wire) at ECM E7 connector. (Scheme 29) If voltage is 4.5-5.5 volts, replace suspect ignition coil/ignitor. If voltage is not 4.5-5.5 volts, replace ECM and retest.
  4. Check for open or short in suspect IGT circuit between ECM E7 connector and suspect ignition coil/ignitor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, go to next step.
  5. Backprobing, measure voltage between ground and suspect IGT circuit terminal at ECM E7 connector while cranking engine. See «IDENTIFYING IGT CIRCUIT ECM E7 CONNECTOR TERMINALS»(ref-2772-S29662247442000041300000) table. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM and retest. IDENTIFYING IGT CIRCUIT ECM E7 CONNECTOR TERMINALS Ignition Coil/Ignitor No. Circuit (Terminal No.) Wire Color 1 IGT1 (11) Black/Yellow 2 IGT2 (12) Blue/Red 3 IGT3 (13) Yellow/Green 4 IGT4 (14) Blue/Yellow 5 IGT5 (15) Yellow 6 IGT6 (16) Green/Black
  6. Disconnect all ignition coil/ignitor connectors. Backprobing, measure voltage between ground and each IGT circuit terminal of ECM E7 connector while cranking engine. See «IDENTIFYING IGT CIRCUIT ECM E7 CONNECTOR TERMINALS»(ref-2772-S29662247442000041300000) table. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM and retest.
  7. Ensure suspect ignition coil/ignitor connector is disconnected. Measure voltage between ground and suspect coil/ignitor harness connector terminal No. 1 (White/Red wire). Turn ignition switch to ON, then to START position. If voltage is not 9-14 volts, go to next step. If voltage is 9-14 volts, check open in White/Black wire between suspect ignition coil/ignitor connector terminal No. 4 and ground. Repair as necessary.
  8. Check for open or short in wire harness and connector between ignition switch and suspect ignition coil/ignitor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, go to next step.
  9. Check EFI main relay. See appropriate SYSTEM & COMPONENT TESTING article. EFI main relay is located in underhood engine compartment at left side of engine. Replace as necessary. If EFI main relay is okay, replace suspect ignition coil/ignitor.

Note. Variable Valve Timing (VVT) sensor is also known as camshaft position sensor.

The Variable Valve Timing (VVT) sensor consists of a signal plate and pick-up coil. The signal plate has one tooth and is mounted on each intake camshaft. The VVT sensor provides feedback to ECM in order to control intake valve timing. DTC P1345 or P1350 is set when ECM does not sense VVT sensor signal during cranking for 4 or more seconds. DTC P1345 or P1350 is also set if ECM does not sense VVT sensor signal with engine speed at 600 RPM or more for 5 or more seconds. DTC P1345 or P1350 is also set if ECM senses VVT sensor signal 5 times while crankshaft rotates 2 times. DTC P1345 is for bank No. 1 (right cylinder head). DTC P1350 is for bank No. 2 (leftt cylinder head). Possible causes are

  1. Open or short in VVT sensor circuit.
  2. Faulty VVT sensor.
  3. ECM.

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

  1. Disconnect suspect VVT sensor connector. Measure resistance between VVT sensor harness connector terminals. Resistance should be 835-1400 ohms at 14-122°F (-10-50°C), or 1060-1645 ohms at 122-212°F (50-100°C). Replace VVT sensor as necessary. If resistance is as specified, go to next step.
  2. Check for open or short circuit in wiring harness between ECM connector and appropriate VVT sensor. Repair as necessary. If wiring harness is okay, inspect VVT sensor installation. Tighten sensor as necessary. If VVT sensor is installed properly, replace ECM and retest.

Note. Variable Valve Timing (VVT) sensor is also known as camshaft position sensor.

The Variable Valve Timing (VVT) sensor consists of a signal plate and pick-up coil. The signal plate has one tooth and is mounted on each intake camshaft. The VVT sensor provides feedback to ECM in order to control intake valve timing. DTC P1346 is set when ECM detects a deviation in crankshaft position sensor and VVT sensor for bank No. 1 (right cylinder head). DTC P1351 is set when ECM detects a deviation in crankshaft position sensor and VVT sensor for bank No. 2 (left cylinder head). Possible causes are

  1. Mechanical system malfunction (timing belt stretched or timing belt teeth jumped).
  2. Faulty ECM.

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

Check valve timing. Check for loose, stretched or jumped teeth of timing belt. See appropriate article in ENGINES. Repair as necessary. If valve timing and timing belt are okay, replace ECM.

Note. Variable Valve Timing (VVT) sensor is also known as camshaft position sensor.

The Variable Valve Timing (VVT) system controls intake valve timing in response to driving conditions. Electronic Control Module (ECM) controls Oil Control Valve (OCV) to ensure correct valve timing. A OCV is located in each cylinder head at flywheel end of engine. Oil pressure controlled by the OCV is supplied to the VVT controller. VVT controller then changes relative position between camshaft and crankshaft. VVT controller is located on the front of each intake camshaft. DTC P1349 is set if ECM detects valve timing does not change (fixed timing) for bank No. 1 (right cylinder head). DTC P1354 is set if ECM detects valve timing does not change for bank No. 2 (leftt cylinder head). Possible causes are

  1. Incorrect valve timing.
  2. Faulty oil control valve.
  3. Faulty VVT controller assembly.
  4. Faulty ECM.

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

  1. Check valve timing. See appropriate article in ENGINES. Repair as necessary. If valve timing is okay, go to next step.
  2. Using scan tool, select ACTIVE TEST mode. Select VVT. Note idle speed when OCV is activated by scan tool. If idle speed is normal with OCV off and engine idles rough or stalls when OCV is on, VVT is functioning properly at this time. DTC may have been set because of a foreign object that was temporarily caught in the engine oil system but after a short time system returned to normal. If idle speed does not function as specified, go to next step.
  3. With engine idling, check voltage to OCV. If checking OCV for bank No. 1 (right cylinder head), backprobing, connect oscilloscope between ECM E7 connector terminals No. 29 (Green/Red wire) and No. 18 (Green/Yellow wire). If checking OCV for bank No. 2 (leftt cylinder head), backprobing, connect oscilloscope between ECM E7 connector terminals No. 5 (Green/White wire) and No. 6 (Yellow/Black wire). On all applications, ensure oscilloscope pattern is as shown. (Scheme 38) As engine speed is increased, waveform frequency ("A") should lengthen. If waveform pattern is as shown, go to next step. If waveform pattern is not as shown, replace ECM.
  4. Remove timing belt cover and timing belt. See appropriate article in ENGINES. Remove OCV. Place a shop towel under OCV cylinder head opening. Rotate VVT pulley from left to right about 30 degrees 2-3 times. Oil should drain from OCV cylinder head opening. If oil does not drain from opening, replace VVT pulley/gear assembly and go to next step. If oil drains from opening, go to next step.
  5. With OCV removed, connect a jumper wire between positive battery terminal and terminal No. 1 at OCV. (Scheme 39) Connect another jumper wire between negative battery terminal and terminal No. 2 at OCV and note OCV plunger operation. With battery voltage applied, plunger on end of OCV should extend. Disconnect a jumper wire. Without battery voltage applied, plunger should retract. If OCV operates as specified, go to next step. If OCV does not operate as specified, replace OCV and go to next step.
  6. Check for blockage in OCV. Check oil check valve and oil pipe located under OCV. Repair as necessary and retest. If components are okay, go to next step.
  7. Clear DTCs. Start engine and allow it to idle. Turn ignition off. Turn ignition on and check for DTCs. If DTC P1349 or P1354 is not present, no problem is indicated at this time. DTC may have been set because of a foreign object that was temporarily caught in the engine oil system but after a short time system returned to normal. If DTC P1349 or P1354 is present, replace ECM and retest.

Scheme 38

Scheme 38
Scheme 38

Scheme 39

Scheme 39
Scheme 39

Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Check valve timing. See appropriate article in ENGINES. Repair as necessary. If valve timing is okay, go to next step.
  2. Start engine and allow it to idle. Disconnect suspect Oil Control Valve (OCV) and note idle speed. OCV is located in each cylinder head at flywheel end of engine. Engine idle speed should not change. Using jumper wires, apply battery voltage to OCV. Engine should idle rough or stall. If OCV operates as specified, go to next step. If OCV does no operate as specified, go to step 4.
  3. With engine idling, check voltage to OCV. If checking OCV for bank No. 1 (right cylinder head), backprobing, connect oscilloscope between ECM E7 connector terminals No. 29 (Green/Red wire) and No. 18 (Green/Yellow wire). If checking OCV for bank No. 2 (leftt cylinder head), backprobing, connect oscilloscope between ECM E7 connector terminals No. 5 (Green/White wire) and No. 6 (Yellow/Black wire). On all applications, ensure oscilloscope waveform pattern is as shown. (Scheme 38) As engine speed is increased, waveform frequency ("A") should lengthen. If waveform pattern is not as shown, replace ECM. If waveform pattern is as shown, no problem is indicated at this time. DTC may have been set because of a foreign object that was temporarily caught in the engine oil system but after a short time system returned to normal.
  4. Remove timing belt cover and timing belt. See appropriate article in ENGINES. Remove OCV. Place a shop towel under OCV cylinder head opening. Rotate VVT pulley from left to right about 30 degrees 2-3 times. Oil should drain from OCV cylinder head opening. If oil does not drain from opening, replace VVT pulley/gear assembly and go to next step. If oil drains from head opening, go to next step.
  5. With OCV removed, connect a jumper wire between positive battery terminal and terminal No. 1 at OCV. (Scheme 39) Connect another jumper wire between negative battery terminal and terminal No. 2 at OCV. With battery voltage applied, plunger on end of OCV should extend. Disconnect jumper wires. Without battery voltage applied, plunger should retract. If OCV operates as specified, go to next step. If OCV does not operate as specified, replace OCV and go to next step.
  6. Check for blockage in OCV. Check oil check valve and oil pipe located under OCV. Repair as necessary and retest. If components are okay, go to next step.
  7. Clear DTCs. Start engine and allow it to idle. Turn ignition off. Turn ignition on and check for DTCs. If DTC P1349 or P1354 is not present, no problem is indicated at this time. DTC may have been set because of a foreign object that was temporarily caught in the engine oil system but after a short time system returned to normal. If DTC P1349 or P1354 is present, replace ECM and retest.
  1. Check stoplights. If stoplights do not function properly, repair as necessary and retest system. See appropriate wiring diagram in EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT. If stoplights function properly, go to next step.
  2. Access ECM behind glove box. Turn ignition on. Backprobing ECM E8 connector, measure voltage between ground and terminal No. 15 (Green/Orange wire) at ECM E8 connector. (Scheme 29) 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 as specified, go to next step. If voltage is as specified, problem is intermittent.
  3. Check wiring harness between ECM E8 connector and stoplight switch. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary and retest system. If wiring harness is okay, replace ECM. Retest system.
  1. Access ECM behind glove box. Locate ECM E8 connector. (Scheme 29) Backprobing ECM connector, measure voltage between ground and terminal No. 1 (Black/Yellow wire) at ECM E8 connector. If voltage is not 9-14 volts, go to next step. If voltage is 9-14 volts, replace ECM and retest system.
  2. Remove and inspect EFI fuse (20-amp) from junction block, located in left side of engine compartment. If fuse is blown, check cause of blown fuse and repair as necessary. If fuse is okay, check and repair wiring harness or connector between battery, EFI fuse and ECM.

If DTC P1645 is set, diagnose multiplex communication system. See appropriate MULTIPLEX CONTROL SYSTEMS article in ACCESSORIES & EQUIPMENT. Repair as necessary.

Note. Variable Valve Timing (VVT) sensor is also known as camshaft position sensor.

The Variable Valve Timing (VVT) system controls intake valve timing in response to driving conditions. Electronic Control Module (ECM) controls Oil Control Valve (OCV) to ensure correct valve timing. An OCV is located in each cylinder head at flywheel end of engine. Oil pressure controlled by the OCV is supplied to the VVT controller. VVT controller then changes relative position between camshaft and crankshaft. VVT controller is located on the front of each intake camshaft. DTC P1656 or P1663 is set if ECM detects an open or short in OCV circuit. DTC P1656 is for bank No. 1 (right cylinder head) OCV circuit. DTC P1663 is for bank No. 2 (leftt cylinder head) OCV circuit. Possible causes are

  1. Open or short in OCV circuit.
  2. Faulty OCV.
  3. Faulty ECM.

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

  1. Using scan tool, select ACTIVE TEST mode. Select VVT. Note idle speed when OCV is activated by scan tool. If idle speed is normal with OCV off and engine idles rough or stalls when OCV is on, VVT is functioning properly at this time. Fault is intermittent. DTC may have been set because of a foreign object that was temporarily caught in the engine oil system but after a short time system returned to normal. If idle speed does not function as specified, go to next step.
  2. Start engine and allow it to idle. Disconnect suspect Oil Control Valve (OCV) and note idle speed. OCV is located in each cylinder head at flywheel end of engine. Engine idle speed should not change. Using jumper wires, apply battery voltage to OCV. Engine should idle rough or stall. If OCV operates as specified, go to next step. If OCV does not operate as specified, replace OCV.
  3. With engine idling, check voltage to OCV. If checking OCV for bank No. 1 (right cylinder head), backprobing, connect oscilloscope between ECM E7 connector terminals No. 29 (Green/Red wire) and No. 18 (Green/Yellow wire). If checking OCV for bank No. 2 (leftt cylinder head), backprobing, connect oscilloscope between ECM E7 connector terminals No. 5 (Green/White wire) and No. 6 (Yellow/Black wire). On all applications, ensure oscilloscope pattern is as shown. (Scheme 38) As engine speed is increased, waveform frequency ("A") should lengthen. If waveform pattern is as shown, go to next step. If waveform pattern is not as shown, replace ECM.
  4. Check for an open or short circuit in wiring harness between suspect OCV and ECM. Repair wiring harness as necessary. If wiring harness is okay, fault is intermittent.
  1. Start engine and allow it to idle. Disconnect suspect Oil Control Valve (OCV) and note idle speed. OCV is located in each cylinder head at flywheel end of engine. Engine idle speed should not change. Using jumper wires, apply battery voltage to OCV. Engine should idle rough or stall. If OCV operates as specified, go to next step. If OCV does not operate as specified, replace OCV.
  2. With engine idling, check voltage to OCV. If checking OCV for bank No. 1 (right cylinder head), backprobing, connect oscilloscope between ECM E7 connector terminals No. 29 (Green/Red wire) and No. 18 (Green/Yellow wire). If checking OCV for bank No. 2 (leftt cylinder head), backprobing, connect oscilloscope between ECM E11 connector terminals No. 5 (Green/White wire) and No. 6 (Yellow/Black wire). On all applications, ensure oscilloscope pattern is as shown. (Scheme 38) As engine speed is increased, waveform frequency ("A") should lengthen. If waveform pattern is as shown, go to next step. If waveform pattern is not as shown, replace ECM.
  3. Check for an open or short circuit in wiring harness between suspect OCV and ECM. Repair wiring harness as necessary. If wiring harness is okay, fault is intermittent.
  1. If using Lexus scan tool, go to next step. If not using Lexus scan tool, go to step 3.
  2. Connect Lexus scan tool to DLC No. 3. (Scheme 28) Turn ignition on. Turn scan tool on. Using scan tool, read transaxle shift positions while shifting transaxle shift lever through all gear positions. If scan tool display does not indicate correct shifter positions, go to next step. If scan tool display indicates correct shifter positions, Park/Neutral Position (PNP) switch is functioning properly. Problem is internal transaxle. Identify symptom and repair as necessary. See appropriate article in AUTOMATIC TRANSMISSIONS.
  3. Access ECM behind glove box. Turn ignition on. Backprobing, measure voltage between ground and ECM E9 connector NSW circuit terminal No. 20 (Black/White wire). Also measure voltage between ground and ECM E5 connector "R" circuit terminal No. 8 (Red/Black wire), "2" circuit terminal No. 14 (Green/Yellow wire) and "L" circuit terminal No. 13 (Green/Orange wire). (Scheme 29) Shift lever through all gear positions. (Scheme 40) If voltage is not as specified, go to next step. If voltage is as specified, PNP switch is functioning properly. Problem is internal transaxle. Identify symptom and repair as necessary. See appropriate article in AUTOMATIC TRANSMISSIONS.
  4. Check PNP switch. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article. Replace PNP switch as necessary. If PNP switch is okay, check short circuit in wiring harness between battery and PNP switch. Also check wiring harness between ECM and PNP switch. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary and retest system. If wiring harness is okay, replace ECM and retest system.

Scheme 40

Scheme 40
Scheme 40

More articles — Engine Controls - Self-Diagnostics