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Engine Controls - Self-Diagnostics: Diagnosis Lexus LX J100

Testing & Diagnostics 15 illustrations ~13364 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 location, see appropriate illustration in THEORY & OPERATION article. To identify circuits and wire colors referenced in testing, see appropriate wiring diagram in WIRING DIAGRAMS article.

Note. For information on engine immobilizer system, see COMPUTERIZED ENGINE CONTROLS in THEORY & OPERATION article.

CAUTIONIf ECM replacement is instructed in following testing, always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION.

Diagnosis & Repair

  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Start and warm engine to normal operating temperature. Using scan tool, monitor MAF flow rate. If scan tool reading is 0.0 gm/sec., go to next step. If scan tool reading is 271 gm/sec. or more, go to step 5.
  2. Turn ignition off. Disconnect MAF meter harness connector. Turn ignition on. Measure voltage between ground and terminal No. 3 (Black/Yellow wire) at MAF meter harness connector. (Scheme 29) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, repair open in Black/Yellow wire between EFI main relay and MAF meter. See appropriate wiring diagram in WIRING DIAGRAMS article.
  3. Turn ignition off. Connect MAF meter harness connector. Access ECM behind glove box. Ensure shift lever is in Neutral or Park. Ensure A/C switch is off. Start engine and let idle. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 10 (Blue/Yellow wire) at ECM harness connector E7. (Scheme 30) If voltage is not.5-3.0 volts, go to next step. If voltage is.5-3.0 volts, replace ECM.
  4. Check for open or short in Blue/Yellow wire between MAF meter and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace MAF meter.
  5. Turn ignition off. Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure resistance between ground and terminal No. 19 (Green/White wire) at ECM harness connector E7. (Scheme 30) If resistance is one ohm or less, go to next step. If resistance is greater than one ohm, replace ECM.
  6. Check for open in Green/White wire between MAF meter and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace MAF meter.

Scheme 28

Scheme 28
Scheme 28

Scheme 29

Scheme 29
Scheme 29

Scheme 30

Scheme 30
Scheme 30

Circuit Description

MAF meter uses a platinum hot wire maintained at a constant temperature. Airflow past sensor affects temperature and current flow through MAF meter. DTC is set when ECM detects either throttle valve is fully closed and MAF meter output is more than 2.2 volts for more than 10 seconds with engine speed of 900 RPM or less, or VTA circuit signal is .63 volt or more and MAF meter output is less than one volt for more than 10 seconds with engine speed of 1500 RPM or more. ECM will operate in fail-safe mode if DTC P0101 is set. Possible cause is

  1. Defective MAF meter.

Diagnostic Aids

After confirming DTC P0101, use scan tool to access CURRENT DATA to confirm mass airflow ratio. If ratio is 0.0 gm/sec., VG circuit may be open or shorted, or power source circuit may be open. If ratio is 271.0 gm/sec. or more, EVG circuit may be open. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

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

  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Using scan tool, monitor IAT sensor temperature. If temperature displayed on scan tool is same as outside temperature, problem is intermittent. Check component and ECM connections. If temperature displayed on scan tool is -40°F (-40°C), go to next step. If temperature displayed on scan tool is 284°F (140°C) or more, go to step 4.
  2. Turn ignition off. Disconnect MAF meter harness connector. Using a jumper wire, connect MAF meter harness connector terminals No. 1 (Brown/White wire) and No. 2 (Yellow/Black wire). (Scheme 29) Turn ignition on. Using scan tool, monitor IAT sensor temperature. If temperature displayed on scan tool is 284°F (140°C) or more, replace MAF meter. If temperature displayed on scan tool is less than 284°F (140°C), go to next step.
  3. Turn ignition off. Remove jumper wire. Access ECM behind glove box. Using a jumper wire, backprobe between terminals No. 18 (Brown/White wire) and No. 22 (Yellow/Black wire) at ECM harness connector E7. (Scheme 30) If temperature displayed on scan tool is 284°F (140°C) or more, repair open in Yellow/Black wire and/or Brown/White wire between MAF meter and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed on scan tool is less than 284°F (140°C), replace ECM.
  4. Turn ignition off. Disconnect MAF meter harness connector. Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), replace MAF meter. If temperature displayed on scan tool is not -40°F (-40°C), go to next step.
  5. Turn ignition off. Access ECM behind glove box. Disconnect ECM harness connector E7. (Scheme 30) Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), repair short in Yellow/Black wire between MAF meter and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed on scan tool is not -40°F (-40°C), replace ECM.
  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Using scan tool, monitor ECT sensor temperature. If temperature displayed on scan tool is same as actual coolant temperature, problem is intermittent. Check component and ECM connections. If temperature displayed on scan tool is -40°F (-40°C), go to next step. If temperature displayed on scan tool is 284°F (140°C) or more, go to step 4.
  2. Turn ignition off. Disconnect ECT sensor harness connector (2-pin harness connector with Green/Black wire and Brown/White wire). Using a jumper wire, connect ECT sensor harness connector terminals. Turn ignition on. Using scan tool, monitor ECT sensor temperature. If temperature displayed on scan tool is less than 284°F (140°C), go to next step. If temperature displayed on scan tool is 284°F (140°C) or more, replace ECT sensor.
  3. Turn ignition off. Remove jumper wire. Access ECM behind glove box. Using a jumper wire, backprobe between terminals No. 18 (Brown/White wire) and No. 14 (Green/Black wire) at ECM harness connector E7. (Scheme 30) If temperature displayed on scan tool is 284°F (140°C) or more, repair open in Green/Black wire and/or Brown/White wire between ECT sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed on scan tool is less than 284°F (140°C), replace ECM.
  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. If temperature displayed on scan tool is not -40°F (-40°C), go to next step.
  5. Turn ignition off. Access ECM behind glove box. Disconnect ECM harness connector E7. (Scheme 30) Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), repair short in Green/Black wire between ECT sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed on scan tool is not -40°F (-40°C), replace ECM.
  1. If any other DTCs are displayed, diagnose and repair those DTCs first and retest. If only DTC P0116 is displayed, go to next step.
  2. Remove and inspect cooling system thermostat. If problem exists, replace thermostat as necessary and retest. If problem does not exist, replace ECT sensor.

Diagnosis & Repair (Using Lexus Scan Tool)

  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Using Lexus scan tool, monitor throttle valve opening percentage for VTA circuit and read voltage for VTA2 circuit. Throttle opening percentage for VTA circuit should be 8-20 percent with fully closed throttle and should be 64-96 percent with fully open throttle (WOT). Voltage reading for VTA2 circuit should be 2.0-2.9 volts with fully closed throttle and 4.7-5.1 volts with fully open throttle. If values are as specified, replace ECM. If values are not as specified, go to next step.
  2. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM.
  3. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown/White wire) and No. 13 (Red/Yellow wire) at ECM harness connector E7. With fully closed throttle, voltage should be.4-1.0 volt. With valve fully open throttle, voltage should be 3.2-4.8 volts. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown/White wire) and No. 20 (Yellow/Black wire) at ECM harness connector E7. With fully closed throttle, voltage should be 2.0-2.9 volts. With fully open throttle, voltage should be 4.7-5.1 volts. If voltage readings are as specified, replace ECM. If voltage readings are not as specified, go to next step.
  4. Check Throttle Position (TP) sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace TP sensor. If problem does not exist, check for an open or short in wiring between ECM and TP sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring harness as necessary.

Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM.
  2. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown/White wire) and No. 13 (Red/Yellow wire) at ECM harness connector E7. With fully closed throttle, voltage should be.4-1.0 volt. With fully open throttle, voltage should be 3.2-4.8 volts. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown/White wire) and No. 20 (Yellow/Black wire) at ECM harness connector E7. With fully closed throttle, voltage should be 2.0-2.9 volts. With fully open throttle, voltage should be 4.7-5.1 volts. If voltage readings are as specified, replace ECM. If voltage readings are not as specified, go to next step.
  3. Check Throttle Position (TP) sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace TP sensor. If problem does not exist, check for an open or short in wiring between ECM and TP sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring harness as necessary.

TP sensor is located on throttle body and has 2 variable resistors integral to TP sensor. TP sensor monitors throttle opening. ECM determines vehicle driving condition and adjusts air/fuel mixture accordingly. DTC is set when ECM detects TP sensor output voltage is out of range during vehicle operation. Possible cause is

  1. Defective Throttle Position (TP) sensor.

After confirming DTC P0120, use scan tool to access CURRENT DATA to confirm throttle valve opening percentage with throttle open and closed. If percentage displayed on scan tool is always zero percent, VC circuit may be open, or VTA circuit may be open or shorted. If percentage displayed on scan tool is always 8-20 percent, VTA2 circuit may be open or shorted. If percentage displayed on scan tool is always 100 percent, E2 circuit may be open. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

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

  1. If any other DTCs are displayed, diagnose and repair those DTCs first and retest. If only DTC P0125 is displayed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Start and warm engine to normal operating temperature. Using scan tool, monitor each heated oxygen sensor No. 1. Snap accelerate engine to about 4000 RPM 3 times. Both heated oxygen sensors No. 1 should indicate a rich signal (.45 volt or more) at least once. If a rich signal is indicated for both heated oxygen sensors No. 1 at least once, go to step 9. If either heated oxygen sensor No. 1 does not display a rich signal at least once, go to next step.
  3. Check for open or short in wiring between appropriate heated oxygen sensor(s) No. 1 and ECM. If problem does not exist, go to next step. If problem exists, repair wiring as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article.
  4. Using scan tool, check if a misfire has occurred by monitoring DTCs and DATA LIST. If a misfire has occurred, perform «DTC P0300: RANDOM MISFIRE DETECTED»(ref-2780-S39294412392000041300000). If misfire has not occurred, 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, go to next step.
  8. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, replace defective heated oxygen sensor(s) No. 1.
  9. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-2780-S35690942532000041300000) under DTC P0130 OR P0150: HEATED OXYGEN SENSOR NO. 1 CIRCUIT.
  10. Clear and recheck for DTCs. If DTC P0125 is displayed again, replace ECM. If DTC P0125 is not displayed again, go to next step.
  11. Vehicle either ran out of fuel or problem is intermittent. Check component and ECM connections.

Test Drive Confirmation

Note. If conditions in test drive confirmation procedure are not strictly followed, detection of malfunction will not be possible.

  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 31-40 MPH for 1-3 minutes. Stop vehicle and allow to idle for one minute. Repeat driving and idle part of test 3 times. If malfunction exists, MIL will illuminate.
  3. 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 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 P0130 and/or P0150 are displayed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Start engine and increase engine speed to 2500 RPM for approximately 90 seconds. Let engine idle. Using scan tool, monitor each heated oxygen sensor No. 1 output voltage. Voltage should alternate repeatedly between less than.4 volt and more than.55 volt. If voltage is as specified, go to step 7. If voltage is not as specified, go to next step.
  3. Check for open or short in wiring between ECM and heated oxygen sensors No. 1. 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. 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.
  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, replace appropriate heated oxygen sensor No. 1.
  7. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-2780-S35690942532000041300000).
  8. Clear and recheck for DTCs. If DTC P0130 and/or P0150 are displayed again, replace ECM. If neither DTC P0130 or P0150 are displayed again, problem is intermittent. Check component and ECM connections.
  1. If other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P0133 and/or P0153 are displayed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Start engine and increase engine speed to 2500 RPM for approximately 90 seconds. Let engine idle. Using scan tool, monitor each heated oxygen sensor No. 1 output voltage. Voltage should alternate repeatedly between less than.4 volt and more than.55 volt. If voltage is as specified, go to step 7. If voltage is not as specified, go to next step.
  3. Check for open or short in wiring between ECM and heated oxygen sensors No. 1. 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. 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.
  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, replace appropriate heated oxygen sensor No. 1.
  7. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-2780-S35690942532000041300000) under DTC P0130 OR P0150: HEATED OXYGEN SENSOR NO. 1 CIRCUIT.
  8. Clear and recheck for DTCs. If DTC P0133 and/or P0153 are displayed again, replace ECM. If neither DTC P0133 or P0153 are displayed again, problem is intermittent. Check component and ECM connections.
  1. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector. If DTC P0135 is set, measure voltage between ground and terminal No. 4 (Red wire) at ECM harness connector E7. If DTC P0155 is set, measure voltage between ground and terminal No. 3 (Yellow wire) at ECM harness connector E7. (Scheme 30) Voltage should be 9-14 volts at each terminal. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
  2. Disconnect suspect heated oxygen sensor No. 1 harness connector. Measure resistance between terminals B+ (Black/Yellow wire) and HT (Red wire on bank No. 1, or Yellow wire on bank No. 2) at heated oxygen sensor connector (component side). (Scheme 31) Resistance should be 11-16 ohms at 68°F (20°C). If resistance is not as specified, replace appropriate heated oxygen sensor No. 1. If resistance is as specified, go to next step.
  3. Repair wiring between ECM and appropriate heated oxygen sensor or between appropriate heated oxygen sensor and EFI main relay. See appropriate wiring diagram in WIRING DIAGRAMS article.

Scheme 31

Scheme 31
Scheme 31
  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 appropriate 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 appropriate 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.5 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 ECM harness connector. If DTC P0141 is set, measure voltage between ground and terminal No. 8 (Blue wire) at ECM harness connector E9. If DTC P0161 is set, measure voltage between ground and terminal No. 7 (Red/Black wire) at ECM harness connector E9. (Scheme 30) Voltage should be 9-14 volts at each terminal. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
  2. Disconnect suspect heated oxygen sensor No. 2 harness connector. Measure resistance between terminals B+ (Black/Yellow wire) and HT (Blue wire on bank No. 1; Red/Black wire on bank No. 2) at heated oxygen sensor connector (component side). (Scheme 31) Resistance should be 11-16 ohms at 68°F (20°C). If resistance is not as specified, replace appropriate heated oxygen sensor No. 1. If resistance is as specified, go to next step.
  3. Repair wiring between ECM and appropriate heated oxygen sensor or between appropriate heated oxygen sensor 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. (Scheme 28) Start engine and increase engine speed to 2500 RPM for approximately 90 seconds. Let engine idle. Using scan tool, monitor each heated oxygen sensors No. 1 output voltage. Voltage should alternate repeatedly between less than.4 volt to more than.55 volt. If voltage is as specified, go to step 9. If voltage is not as specified, go to next step.
  8. Check for open or short in wiring between ECM and heated oxygen sensors No. 1. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace appropriate heated oxygen sensor(s) No. 1.
  9. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-2780-S35690942532000041300000) under DTC P0130 OR P0150: HEATED OXYGEN SENSOR NO. 1 CIRCUIT.
  10. Clear and recheck for DTCs. If DTCs P0171 and/or P0172 are displayed again, replace ECM. If neither DTC P0171 or P0172 are displayed again, go to next step.
  11. 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. Ignition system malfunction.
  2. Defective fuel injector(s).
  3. Improper fuel pressure.
  4. Defective engine compression.
  5. Improper valve clearance.
  6. Improper valve timing.
  7. Defective Mass Airflow (MAF) meter.
  8. Defective Engine Coolant Temperature (ECT) sensor.
  9. Open or short in wiring.
  10. Poor contact at ECM or component.
  11. Defective 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.

  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-2780-S40465493502000041300000) 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 is 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-2780-S34852036762000041300000). 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-2780-S21012336022000041300000) table. (Scheme 30) If voltage is 9-14 volts at each terminal, go to step 6. 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) Yellow 2 6 (1) Black 3 1 (2) Blue 4 2 (2) Red 5 3 (2) Green 6 4 (2) Red/Blue 7 5 (2) White 8 6 (2) Black/White (1) Terminal is located in ECM harness connector E7. (Scheme 30) (2) Terminal is located in ECM harness connector E6. (Scheme 30)
  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, go to next step. If resistance is not as specified, replace fuel injector.
  5. Check for open or short in wiring between ECM and fuel injector. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair as necessary. If problem does not exist, repair open or short in injector power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  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, go to next step.
  8. Check Mass Airflow (MAF) sensor 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.
  9. 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.

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 during any particular 200 revolutions of engine, misfiring is detected which can cause catalytic converter overheating and/or damage or during any particular 1000 revolutions of engine, misfiring is detected which can cause a deterioration in emission levels. Possible causes are

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

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

  1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Disconnect EC1 harness connector. EC1 harness connector is a in-line harness connector located at rear of intake manifold. EC1 harness connector is a 3-pin Black connector. Remove, switch and install terminals No. 1 and 2 from male harness connector. (Scheme 32) Connect EC1 harness connector. Turn ignition on. Clear DTCs. Start and warm engine to normal operating temperature. Snap accelerate engine to about 4000 RPM 3 times. Retrieve DTCs. If same DTC is repeated, go to next step. If DTC changed, go to step 3.
  2. Check for open or short in wiring between EC1 connector and ECM. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM. Ensure EC1 male connector terminals are returned to their original position. NOTE: If DTC P0325 changed to P0330, check knock sensor circuit on right bank. If DTC P0330 changed to P0325, check knock sensor circuit on left bank.
  3. Check for open or short in wiring between EC1 connector and knock sensor(s). To access harness, it may be necessary to remove intake manifold. See REMOVAL, OVERHAUL & INSTALLATION article. If problem exists, repair wiring as necessary. If problem does not exist, replace knock sensor. Ensure EC1 male connector terminals are returned to their original position.

Scheme 32

Scheme 32
Scheme 32
  1. Disconnect CKP sensor harness connector. Measure resistance between CKP sensor terminals (component side). Resistance should be 1630-2740 ohms (cold sensor) or 2065-3225 ohms (hot sensor). If resistance is not as specified, replace CKP sensor. If resistance is as specified, go to next step.
  2. Check for open or short in wiring between ECM and CKP sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, remove and inspect CKP sensor. Also inspect signal plate. Replace CKP sensor and/or signal plate as necessary. If both components are okay, replace ECM.
  1. Disconnect CMP sensor harness connector. Measure resistance between CMP sensor terminals (component side). Resistance should be 835-1400 ohms (cold sensor) or 1060-1645 ohms (hot sensor). If resistance is as specified, go to next step. If resistance is not as specified, replace CMP sensor.
  2. Check for open or short in wiring between ECM and CMP 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. Remove and inspect CMP sensor. Also inspect signal plate. If problem exists, replace CMP sensor and/or signal plate as necessary. If problem does not exist, replace ECM.
  1. If other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P0420 and/or P0430 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. Check heated oxygen sensors No. 1 circuits. See «DTC P0130 OR P0150: HEATED OXYGEN SENSOR NO. 1 CIRCUIT»(ref-2780-S42261376962000041300000) . If problem exists, repair as necessary. If problem does not exist, go to next step.
  4. Check heated oxygen sensor No. 2 circuits. See «DTC P0136 OR P0156: HEATED OXYGEN SENSOR NO. 2 CIRCUIT»(ref-2780-S17489004552000041300000) . If problem exists, repair as necessary. If problem does not exist, replace catalytic converter.

Note. If DTC P0441, P0446, P0450 or P0451 is output after DTC P0440, perform appropriate test first before performing DTC P0440 test.

  1. Check for cracks, deformations in fuel tank, charcoal canister and fuel tank filler pipe. Check for disconnect hose and tubes around fuel tank and charcoal canister. If problem exists, repair as necessary. If problem does not exist, go to next step.
  2. Check fuel cap. If fuel cap is not an OEM cap, replace cap with an OEM cap. If fuel cap is an OEM cap, go to next step.
  3. Check if fuel cap is properly installed. If problem exists, install fuel cap properly. If fuel cap is properly installed, go to next step.
  4. Check for damaged fuel cap and gasket. If problem exists, replace fuel cap with OEM cap. If problem does not exist, go to next step.
  5. Remove fuel cap. Visually inspect fuel tank filler neck for damage. If problem exists, replace fuel tank filler neck as necessary. If problem does not exist, go to next step.
  6. Check vacuum hoses between vapor pressure sensor and vapor pressure sensor VSV, and between vapor pressure sensor and charcoal canister. Check hoses for correct installation, looseness and damage. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
  7. Check hose and tube between fuel tank and charcoal canister for correct installation and damage. If problem exists, repair as necessary. If problem does not exist, go to next step.
  8. Visually inspect charcoal canister for cracks, holes and damage. If problem exists, replace charcoal canister. If problem does not exist, go to next step.
  9. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) If voltage is not 4.5-5.5 volts, replace ECM. If voltage is 4.5-5.5 volts, go to next step.
  10. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 22 (Blue/Black wire) at ECM harness connector E8 and terminal No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) Disconnect vacuum hose from vapor pressure sensor. Connect a vacuum pump to vapor pressure sensor. Voltage should be 2.9-3.7 volts without vacuum applied and.5 volt or less with 1.18 in. Hg applied. If voltage is as specified, go to step 12. If voltage is not as specified, go to next step.
  11. Check for an open or short in wiring between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.
  12. Connect all previously disconnected components and hoses. Disconnect vacuum hose from charcoal canister (vacuum hose from fuel tank-to-charcoal canister). Ensure fuel cap is installed properly. Using apply.71 psi (.05 kg/cm 2 ) pressure to disconnected vacuum hose. If fuel tank does not hold pressure for a minimum of one minute, replace fuel tank or fuel tank overfill valve as necessary. If fuel tank holds pressure, no fault is indicated at this time. Probable cause of DTC to set was an incorrectly installed fuel cap.
  1. Check EVAP VSV, vapor pressure sensor VSV and vapor pressure sensor harness connectors for damaged pins, corrosion and loose wires. If problem exists, repair connectors as necessary. If problem does not exist, go to next step.
  2. Check all EVAP related vacuum hoses for cracks, looseness and correct routing. For proper vacuum hose routing, see appropriate illustration in VACUUM DIAGRAMS article. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
  3. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) If voltage is not 4.5-5.5 volts, replace ECM. If voltage is 4.5-5.5 volts, go to next step.
  4. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 22 (Blue/Black wire) at ECM harness connector E8 and terminal No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) Disconnect vacuum hose from vapor pressure sensor. Connect a vacuum pump to vapor pressure sensor. Voltage should be 2.9-3.7 volts without vacuum applied and.5 volt or less with 1.18 in. Hg applied. If voltage is as specified, go to step 6. If voltage is not as specified, go to next step.
  5. Check for an open or short in wiring between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.
  6. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Using scan tool, select ACTIVE TEST mode. Disconnect vacuum hose from port "B" (purge port) at charcoal canister. (Scheme 33) Start engine. Connect a vacuum gauge to disconnected vacuum hose. When EVAP VSV is activated by scan tool, vacuum should exist. When EVAP VSV is not activated, vacuum should not exist. If vacuum is as specified, go to step 10. If vacuum is not as specified, go to next step.
  7. Check vacuum hose between intake manifold and EVAP VSV, and vacuum hose between EVAP VSV and charcoal canister. If problem exists, replace vacuum hoses as necessary. If problem does not exist, go to next step.
  8. Check EVAP VSV operation. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EVAP VSV. If problem does not exist, go to next step.
  9. Check for an open or short in wiring between EFI main relay, EVAP VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
  10. Turn ignition on. Using scan tool, select ACTIVE TEST mode. Disconnect vacuum hoses from vapor pressure sensor VSV. Apply air pressure to vapor pressure sensor VSV port "E". (Scheme 34) When vapor pressure sensor VSV is activated by scan tool, air should flow from port "F". When vapor pressure sensor VSV is not activated, air should flow from port "G". If vapor pressure sensor VSV operates as specified, go to step 13. If vapor pressure sensor VSV does not operate as specified, go to next step.
  11. Check vapor pressure sensor VSV. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace vapor pressure sensor VSV. If problem does not exist, go to next step.
  12. Check for open or short in wiring between EFI main relay, vapor pressure sensor VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
  13. Disconnect vapor pressure sensor VSV harness connector. Start engine. Using scan tool, select ACTIVE TEST mode. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 22 (Blue/Black wire) at ECM harness connector E9 and terminal No. 18 (Brown/White wire) at ECM harness connector E8. (Scheme 30) With EVAP VSV activated by scan tool, voltage should be 2 volts or less. If voltage is as specified, go to step 15. If voltage is not as specified, go to next step.
  14. Check vacuum hose between charcoal canister and vapor pressure sensor VSV, and vacuum hose between vapor pressure sensor and vapor pressure sensor VSV. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
  15. Remove fuel cap. Disconnect vapor pressure sensor VSV harness connector. Using scan tool, select ACTIVE TEST mode. Start engine. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 22 (Blue/Black wire) at ECM harness connector E9 and terminal No. 18 (Brown/White wire) at ECM harness connector E7 5 seconds after switching EVAP VSV from on to off. If voltage is 2.5 volts or less, replace charcoal canister. If voltage is more than 2.5 volts, go to next step.
  16. Perform appropriate fuel EVAP system test. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, repair as necessary. If problem does not exist, replace ECM.

Scheme 33

Scheme 33
Scheme 33

Scheme 34

Scheme 34
Scheme 34
  1. Check EVAP VSV, vapor pressure sensor VSV and vapor pressure sensor connectors for damaged pins, corrosion and loose wires. If problem exists, repair connectors as necessary. If problem does not exist, go to next step.
  2. Check all EVAP related vacuum hoses for cracks, looseness and correct routing. For proper vacuum hose routing, see appropriate illustration in VACUUM DIAGRAMS article. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
  3. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) If voltage is not 4.5-5.5 volts, replace ECM. If voltage is 4.5-5.5 volts, go to next step.
  4. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 22 (Blue/Black wire) at ECM harness connector E9 and terminal No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) Disconnect vacuum hose from vapor pressure sensor. Connect a vacuum pump to vapor pressure sensor. Voltage should be 2.9-3.7 volts without vacuum applied and.5 volt or less with 1.18 in. Hg applied. If voltage is as specified, go to step 6. If voltage is not as specified, go to next step.
  5. Check for open or short in wiring between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.
  6. Disconnect EVAP VSV vacuum hoses. Apply air pressure to EVAP VSV port "E". (Scheme 35) Air should not flow from port "F". Access ECM behind glove box. Turn ignition on. Using a jumper wire, backprobe between ground and terminal No. 7 (Blue/Black wire) at ECM harness connector E7. (Scheme 30) Air should flow from port "F". If EVAP VSV operates as specified, go to step 10. If EVAP VSV does not operate as specified, go to next step.
  7. Check vacuum hose between intake manifold and EVAP VSV, and vacuum hose between EVAP VSV and charcoal canister. If problem exists, replace vacuum hoses as necessary. If problem does not exist, go to next step.
  8. Check EVAP VSV. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EVAP VSV. If problem does not exist, go to next step.
  9. Check for open or short in wiring between EFI main relay, EVAP VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
  10. Disconnect vapor pressure sensor VSV vacuum hoses. Apply air pressure to vapor pressure sensor VSV port "E". (Scheme 34) Air should flow from port "G". Access ECM behind glove box. Turn ignition on. Using a jumper wire, backprobe between ground and terminal No. 10 (Blue wire) at ECM harness connector E9. (Scheme 30) Air should flow from port "F". If vapor pressure sensor VSV does not operate as specified, go to next step. If vapor pressure sensor VSV operates as specified, check charcoal canister. Perform fuel EVAP system test. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
  11. Check vapor pressure sensor VSV. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace vapor pressure sensor VSV. If problem does not exist, go to next step.
  12. Check for open or short in wiring between EFI main relay, vapor pressure sensor VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring harness as necessary. If problem does not exist, replace ECM.

Scheme 35

Scheme 35
Scheme 35
  1. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) If voltage is not 4.5-5.5 volts, replace ECM. If voltage is 4.5-5.5 volts, go to next step.
  2. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 22 (Blue/Black wire) at ECM harness connector E9 and terminal No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) Disconnect vacuum hose from vapor pressure sensor. Connect a vacuum pump to vapor pressure sensor. Voltage should be 2.9-3.7 volts without vacuum applied and.5 volt or less with 1.18 in. Hg applied. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
  3. Check for open or short in wiring between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.
  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. Raise and support one rear wheel. Turn ignition on. Shift transmission lever into Neutral. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 15 (Violet wire) at ECM harness connector E9. (Scheme 30) Observe voltage reading while rotating rear wheel. Voltage should pulse between zero volts and 4.5-5.5 volts. If voltage is as specified, replace ECM. If voltage is not as specified, repair open or short in wiring between instrument cluster and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article.

Idle speed is controlled by Electronic Throttle Control System (ETCS). Description of ECTS components are as follows

  1. Throttle motor is used to operate throttle valve.
  2. Magnetic clutch is used to connect throttle motor with the throttle valve.
  3. Throttle position sensor is used to detect opening angle of throttle valve.
  4. Accelerator pedal position sensor is used to detect accelerator pedal position.
  5. Engine Control Module (ECM) controls the ETCS.

DTC is set when idle speed continues to vary greatly from target speed. Possible causes are

  1. Defective ETCS.
  2. Leaking air induction system.

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

  1. If any other DTCs are displayed, diagnose and repair those DTCs first and retest. If only DTC P0505 is displayed, go to next step.
  2. 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.
  3. Check Electronic Throttle Control System (ETCS). See THROTTLE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article. Replace components as necessary.
  1. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Using scan tool, monitor APP sensor voltage for VPA and VPA2 circuits. See «ACCELERATOR PEDAL POSITION SENSOR VOLTAGE»(ref-2780-S24671734512000041300000) table. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step. ACCELERATOR PEDAL POSITION SENSOR VOLTAGE Accelerator Pedal Volts Depressed VPA Circuit 3.2-4.8 VPA2 Circuit 4.7-5.1 Released VPA Circuit 0.3-0.9 VPA2 Circuit 1.8-2.7
  2. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM.
  3. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown/White wire) and No. 21 (Red wire) at ECM harness connector E7. With fully closed throttle, voltage should be.3-.9 volt. With fully open throttle, voltage should be 3.2-4.8 volts. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown/White wire) and No. 9 (Red/Black wire) at ECM harness connector E7. With fully closed throttle, voltage should be 1.8-2.7 volts. With fully open throttle, voltage should be 4.7-5.1 volts. If voltage readings are as specified, replace ECM. If voltage readings are not as specified, go to next step.
  4. Check APP sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace APP sensor. If problem does not exist, repair open or short in wiring between ECM and APP sensor. See appropriate wiring diagram in WIRING DIAGRAMS article.
  1. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (Brown/White wire) at ECM harness connector E7. (Scheme 30) If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM.
  2. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown/White wire) and No. 21 (Red wire) at ECM harness connector E7. With fully closed throttle, voltage should be.3-.9 volt. With fully open throttle, voltage should be 3.2-4.8 volts. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown/White wire) and No. 9 (Red/Black wire) at ECM harness connector E7. With fully closed throttle, voltage should be 1.8-2.7 volts. With fully open throttle, voltage should be 4.7-5.1 volts. If voltage readings are as specified, replace ECM. If voltage readings are not as specified, go to next step.
  3. Check APP sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace APP sensor. If problem does not exist, repair open or short in wiring between ECM and APP sensor. See appropriate wiring diagram in WIRING DIAGRAMS article.

APP sensor is located on throttle body and has 2 variable resistors integral to APP sensor. APP sensor monitors accelerator position and is connected with the accelerator pedal by the accelerator wire. APP sensor signal voltage (0-5 volts) to ECM changes in proportion to accelerator pedal opening angle. ECM turns off power to throttle motor based on APP sensor voltage signals. DTC is set when ECM detects voltage is out of range on VPA circuit or VPA2 circuit. Possible cause is

  1. Defective APP sensor.

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

If DTC P1121 is present, replace APP sensor.

  1. Turn ignition off. Access ECM behind glove box. Connect an oscilloscope by backprobing between terminal No. 17 (Brown wire) at ECM harness connector E7 and terminal No. 8 (Red wire; circuit M+) or No. 7 (White wire; circuit M-) at ECM harness connector E6. Start engine and allow to idle. Observe waveform. (Scheme 36)and (Scheme 37). If waveform is okay, replace ECM. If waveform is not okay, go to next step.
  2. Disconnect throttle control motor Gray, 4-pin harness connector. Measure resistance between terminals No. 1 (White wire terminal) and No. 2 (Red wire terminal) at throttle control motor (component side). Resistance should be.3-100.0 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace throttle control motor.
  3. Check for open or short in wiring between throttle control motor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.

Scheme 36

Scheme 36
Scheme 36

Scheme 37

Scheme 37
Scheme 37
  1. If not using Lexus scan tool, go to step 3. If using Lexus scan tool, go to next step.
  2. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 28) Turn ignition on. Using scan tool, read magnetic clutch current value. If reading is.8-1.0 amp, go to step 4. If reading is not.8-1.0 amp, go to step 6.
  3. Turn ignition off. Access ECM behind glove box. Connect an oscilloscope by backprobing between terminals No. 24 (Blue wire) and No. 29 (Green wire) at ECM harness connector E6. (Scheme 30) Start engine and allow it to idle. Observe waveform. (Scheme 38) If waveform is not okay, go to next step. If waveform is okay, go to step 6.
  4. Disconnect throttle control motor Gray 4-pin harness connector. Measure resistance between terminals No. 3 (Green wire terminal) and No. 4 (Blue wire terminal) at throttle control motor (component side). Resistance should be 4.2-5.2 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace throttle control motor.
  5. Check for open or short in wiring between throttle control motor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  6. Clear DTC. Start engine. Turn ignition off and wait 3 seconds. Turn ignition on and check for DTCs. If DTC P1126 is not present, replace ECM. If DTC P1126 is present, replace throttle control motor.

Scheme 38

Scheme 38
Scheme 38
  1. Remove and inspect THROTTLE fuse (15-amp) from left side engine compartment fuse block. If fuse is okay, go to next step. If fuse is blown, check for cause of fuse to blow. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary and retest.
  2. Access ECM behind glove box. Using DVOM, backprobe and measure voltage between ground and terminal No. 7 (Yellow/Black wire) at ECM harness connector E10. (Scheme 30) If voltage is 9-14 volts, replace ECM. If voltage is not 9-14 volts, repair open in power source circuit.

Throttle valve opening angle is detected by Throttle Position (TP) sensor and sends a signal to the ECM. ECM then uses this signal to control throttle control motor which opens and closes throttle valve in response to driving conditions. If DTC P1128 is present, ECM turns off power to throttle motor and magnetic clutch and throttle valve is fully closed by return spring. When this occurs, opening angle of throttle valve is controlled by accelerator pedal by means of a throttle cable. DTC is set when ECM detects a locked throttle control motor. Possible causes are

  1. Defective throttle body assembly.
  2. Defective throttle control motor.
  3. Defective ECM.

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

  1. Turn ignition off. Disconnect throttle control motor Gray 4-pin harness connector. Measure resistance between terminals No. 1 (White wire terminal) and No. 2 (Red wire terminal) at throttle control motor (component side). Resistance should be .3-100.0 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace throttle control motor.
  2. Remove air inlet hose from throttle body. Visually inspect throttle body for carbon build-up or foreign material holding throttle valve open. If problem exists, repair as necessary. If problem does not exist, replace throttle body.

Replace ECM. Clear DTCs and retest. Retrieve DTCs. If DTC P1129 is present, replace throttle body and retest.

  1. Check fuel pump operation. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, go to next step. If problem does not exist, go to step 7.
  2. Disconnect fuel pump ECU 10-pin harness connector. ECU is located behind trim left panel at left rear quarter trim panel. (Scheme 39) Turn ignition on. Measure voltage between ground and terminal No. 10 (Black/Yellow wire) at fuel pump ECU harness connector. (Scheme 40) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check for open or short in Black/Yellow wire between EFI main relay and fuel pump ECU. See appropriate wiring diagram in WIRING DIAGRAMS article.
  3. With ignition switch in START position, measure voltage between terminals No. 5 (White/Black wire) and No. 8 (Green/White wire) at fuel pump ECU harness connector. If voltage is 3.3-4.3 volts, go to step 5. If voltage is not 3.3-4.3 volts, go to next step.
  4. Check for open or short in Green/White wire (FPC circuit) between ECM and fuel pump ECU. Also check fuel pump ECU ground circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
  5. Check fuel pump resistance. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If resistance is not as specified, replace fuel pump. If resistance is as specified, go to next step.
  6. Check for open or short in wiring between fuel pump and fuel pump ECU. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace fuel pump.
  7. Check for open or short in Green/Red wire between terminal No. 4 at ECM harness connector E10 and terminal No. 9 at fuel pump ECU harness connector. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.

Scheme 39

Scheme 39
Scheme 39

Scheme 40

Scheme 40
Scheme 40
  1. Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If spark exists, go to next step. If spark does not exist, go to step 4.
  2. Check for open or short in Black wire between terminal No. 11 at ECM harness connector E6 and ignition coil/ignitor No. 1. Also, check for open or short in Black/White wire between terminal No. 27 at ECM harness connector E6 and ignition coil/ignitor No. 1. 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 ignition coil/ignitor No. 1 harness connector. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and terminal No. 27 (Black/White wire) at ECM harness connector E6. (Scheme 30) If voltage is 4.5-5.5 volts, replace ignition coil/ignitor No. 1. If voltage is not 4.5-5.5 volts, replace ECM.
  4. Check for open or short in Black wire between terminal No. 11 at ECM harness connector E6 and ignition coil/ignitor No. 1. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  5. Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 11 (Black wire) at ECM harness connector E6 while cranking engine. (Scheme 30) If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  6. Disconnect ignition coil/ignitor No. 1 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 11 (Black wire) at ECM harness connector E6 while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black/Red wire) at ignition coil/ignitor No. 1 harness connector. (Scheme 41) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 1 power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  8. Check for open or short in wiring between ground and ignition coil/ignitor No. 1. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  9. Check EFI main relay. See MOTORS & RELAYS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EFI main relay. If problem does not exist, replace ignition coil/ignitor No. 1.

Scheme 41

Scheme 41
Scheme 41
  1. Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If spark exists, go to next step. If spark does not exist, go to step 4.
  2. Check for open or short in Red wire between terminal No. 12 at ECM harness connector E6 and ignition coil/ignitor No. 2. Also, check for open or short in Black/Red wire between terminal No. 28 at ECM harness connector E6 and ignition coil/ignitor 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. Disconnect ignition coil/ignitor No. 2 harness connector. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and terminal No. 28 (Black/Red wire) at ECM harness connector E6. (Scheme 30) If voltage is 4.5-5.5 volts, replace ignition coil/ignitor No. 2. If voltage is not 4.5-5.5 volts, replace ECM.
  4. Check for open or short in Red wire between terminal No. 12 at ECM harness connector E6 and ignition coil/ignitor 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.
  5. Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 12 (Red wire) at ECM harness connector E6 while cranking engine. (Scheme 30) If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  6. Disconnect ignition coil/ignitor No. 2 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 12 (Red wire) at ECM harness connector E6 while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black/Red wire) at ignition coil/ignitor No. 2 harness connector. (Scheme 41) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 2 power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  8. Check for open or short in wiring between ground and ignition coil/ignitor 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.
  9. Check EFI main relay. See MOTORS & RELAYS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EFI main relay. If problem does not exist, replace ignition coil/ignitor No. 2.
  1. Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If spark exists, go to next step. If spark does not exist, go to step 4.
  2. Check for open or short in Blue wire between terminal No. 13 at ECM harness connector E6 and ignition coil/ignitor No. 3. Also, check for open or short in Black/Red wire between terminal No. 28 at ECM harness connector E6 and ignition coil/ignitor No. 3. 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 ignition coil/ignitor No. 3 harness connector. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and terminal No. 28 (Black/Red wire) at ECM harness connector E6. (Scheme 30) If voltage is 4.5-5.5 volts, replace ignition coil/ignitor No. 3. If voltage is not 4.5-5.5 volts, replace ECM.
  4. Check for open or short in Blue wire between terminal No. 13 at ECM harness connector E6 and ignition coil/ignitor No. 3. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  5. Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 13 (Blue wire) at ECM harness connector E6 while cranking engine. (Scheme 30) If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  6. Disconnect ignition coil/ignitor No. 3 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 13 (Blue wire) at ECM harness connector E6 while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black/Red wire) at ignition coil/ignitor No. 3 harness connector. (Scheme 41) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 3 power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  8. Check for open or short in wiring between ground and ignition coil/ignitor No. 3. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  9. Check EFI main relay. See MOTORS & RELAYS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EFI main relay. If problem does not exist, replace ignition coil/ignitor No. 3.
  1. Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If spark exists, go to next step. If spark does not exist, go to step 4.
  2. Check for open or short in Green wire between terminal No. 14 at ECM harness connector E6 and ignition coil/ignitor No. 4. Also, check for open or short in Black/White wire between terminal No. 27 at ECM harness connector E6 and ignition coil/ignitor No. 4. 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 ignition coil/ignitor No. 4 harness connector. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and terminal No. 27 (Black/White wire) at ECM harness connector E6. (Scheme 30) If voltage is 4.5-5.5 volts, replace ignition coil/ignitor No. 4. If voltage is not 4.5-5.5 volts, replace ECM.
  4. Check for open or short in Green wire between terminal No. 14 at ECM harness connector E6 and ignition coil/ignitor No. 4. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  5. Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 14 (Green wire) at ECM harness connector E6 while cranking engine. (Scheme 30) If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  6. Disconnect ignition coil/ignitor No. 4 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 14 (Green wire) at ECM harness connector E6 while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black/Red wire) at ignition coil/ignitor No. 4 harness connector. (Scheme 41) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 4 power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  8. Check for open or short in wiring between ground and ignition coil/ignitor No. 4. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  9. Check EFI main relay. See MOTORS & RELAYS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EFI main relay. If problem does not exist, replace ignition coil/ignitor No. 4.
  1. Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If spark exists, go to next step. If spark does not exist, go to step 4.
  2. Check for open or short in Yellow wire between terminal No. 15 at ECM harness connector E6 and ignition coil/ignitor No. 5. Also, check for open or short in Black/Red wire between terminal No. 28 at ECM harness connector E6 and ignition coil/ignitor No. 5. 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 ignition coil/ignitor No. 5 harness connector. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and terminal No. 28 (Black/Red wire) at ECM harness connector E6. (Scheme 30) If voltage is 4.5-5.5 volts, replace ignition coil/ignitor No. 5. If voltage is not 4.5-5.5 volts, replace ECM.
  4. Check for open or short in Yellow wire between terminal No. 15 at ECM harness connector E6 and ignition coil/ignitor No. 5. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  5. Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 15 (Yellow wire) at ECM harness connector E6 while cranking engine. (Scheme 30) If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  6. Disconnect ignition coil/ignitor No. 5 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 15 (Yellow wire) at ECM harness connector E6 while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black/Red wire) at ignition coil/ignitor No. 5 harness connector. (Scheme 41) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 5 power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  8. Check for open or short in wiring between ground and ignition coil/ignitor No. 5. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  9. Check EFI main relay. See MOTORS & RELAYS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EFI main relay. If problem does not exist, replace ignition coil/ignitor No. 5.
  1. Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If spark exists, go to next step. If spark does not exist, go to step 4.
  2. Check for open or short in Black/Yellow wire between terminal No. 16 at ECM harness connector E6 and ignition coil/ignitor No. 6. Also, check for open or short in Black/White wire between terminal No. 27 at ECM harness connector E6 and ignition coil/ignitor No. 6. 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 ignition coil/ignitor No. 6 harness connector. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and terminal No. 27 (Black/White wire) at ECM harness connector E6. (Scheme 30) If voltage is 4.5-5.5 volts, replace ignition coil/ignitor No. 6. If voltage is not 4.5-5.5 volts, replace ECM.
  4. Check for open or short in Black/Yellow wire between terminal No. 16 at ECM harness connector E6 and ignition coil/ignitor No. 6. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  5. Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 16 (Black/Yellow wire) at ECM harness connector E6 while cranking engine. (Scheme 30) If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  6. Disconnect ignition coil/ignitor No. 6 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 16 (Black/Yellow wire) at ECM harness connector E6 while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black/Red wire) at ignition coil/ignitor No. 6 harness connector. (Scheme 41) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 6 power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  8. Check for open or short in wiring between ground and ignition coil/ignitor No. 6. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  9. Check EFI main relay. See MOTORS & RELAYS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EFI main relay. If problem does not exist, replace ignition coil/ignitor No. 6.
  1. Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If spark exists, go to next step. If spark does not exist, go to step 4.
  2. Check for open or short in Black/Blue wire between terminal No. 25 at ECM harness connector E6 and ignition coil/ignitor No. 7. Also, check for open or short in Black/White wire between terminal No. 27 at ECM harness connector E6 and ignition coil/ignitor No. 7. 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 ignition coil/ignitor No. 7 harness connector. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and terminal No. 27 (Black/White wire) at ECM harness connector E6. (Scheme 30) If voltage is 4.5-5.5 volts, replace ignition coil/ignitor No. 7. If voltage is not 4.5-5.5 volts, replace ECM.
  4. Check for open or short in Black/Blue wire between terminal No. 25 at ECM harness connector E6 and ignition coil/ignitor No. 7. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  5. Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 25 (Black/Blue wire) at ECM harness connector E6 while cranking engine. (Scheme 30) If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  6. Disconnect ignition coil/ignitor No. 7 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 25 (Black/Blue wire) at ECM harness connector E6 while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black/Red wire) at ignition coil/ignitor No. 7 harness connector. (Scheme 41) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 7 power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  8. Check for open or short in wiring between ground and ignition coil/ignitor No. 7. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  9. Check EFI main relay. See MOTORS & RELAYS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EFI main relay. If problem does not exist, replace ignition coil/ignitor No. 7.
  1. Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If spark exists, go to next step. If spark does not exist, go to step 4.
  2. Check for open or short in Blue/Black wire between terminal No. 26 at ECM harness connector E6 and ignition coil/ignitor No. 8. Also, check for open or short in Black/Red wire between terminal No. 28 at ECM harness connector E6 and ignition coil/ignitor No. 8. 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 ignition coil/ignitor No. 8 harness connector. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and terminal No. 28 (Black/Red wire) at ECM harness connector E6. (Scheme 30) If voltage is 4.5-5.5 volts, replace ignition coil/ignitor No. 8. If voltage is not 4.5-5.5 volts, replace ECM.
  4. Check for open or short in Blue/Black wire between terminal No. 26 at ECM harness connector E6 and ignition coil/ignitor No. 8. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  5. Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 26 (Blue/Black wire) at ECM harness connector E6 while cranking engine. (Scheme 30) If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  6. Disconnect ignition coil/ignitor No. 8 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 26 (Blue/Black wire) at ECM harness connector E6 while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM.
  7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black/Red wire) at ignition coil/ignitor No. 8 harness connector. (Scheme 41) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 8 power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  8. Check for open or short in wiring between ground and ignition coil/ignitor No. 8. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  9. Check EFI main relay. See MOTORS & RELAYS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EFI main relay. If problem does not exist, replace ignition coil/ignitor No. 8.
  1. Check stoplight operation. If stoplights do not operate properly, repair as necessary and retest system. See appropriate wiring diagram in EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT. If stoplights operate properly, go to next step.
  2. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 6 (Green/White wire) at ECM harness connector E9. (Scheme 30) Voltage should be 7.5-14.0 volts with brake pedal depressed and less than 1.5 volts with brake pedal released. If voltage is not as specified, go to next step. If voltage is as specified, problem is intermittent. Check component and ECM connections.
  3. Check for short in wiring between ECM and stoplight switch. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
  1. Turn ignition off. Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 1 (Black/Red wire) at ECM harness connector E10. (Scheme 30) If voltage is 9-14 volts, replace ECM. If voltage is not 9-14 volts, go to next step. NOTE: EFI fuse may also be referred to as ECD fuse.
  2. Remove and inspect EFI fuse. EFI fuse is located in engine compartment fuse box. If fuse is blown, check for short to ground in wiring between EFI fuse and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary and replace fuse. If fuse is okay, check for open in wiring between EFI fuse and ECM. Repair as necessary.

If DTC P1633 is present, replace ECM and retest.

Note. Lexus scan tool can be used to confirm PNP switch signal from CURRENT DATA.

  1. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and specified terminal at ECM harness connector E9 with shift lever in appropriate position. See «PARK/NEUTRAL POSITION SWITCH VOLTAGE»(ref-2780-S30252019532000041300000) table. (Scheme 30) If voltage is as specified, no problem is indicated at this time. If voltage is not as specified, go to next step. PARK/NEUTRAL POSITION SWITCH VOLTAGE Shift Lever Position Terminal No. Volts Park & Neutral 2 Zero 3 Zero 4 Zero 19 Zero 20 Zero Reverse 2 (1) 7.5-14.0 3 Zero 4 Zero 19 Zero 20 (1) 9-14 Drive 2 Zero 3 Zero 4 Zero 19 7.5-14.0 20 9-14 2 2 Zero 3 7.5-14.0 4 Zero 19 Zero 20 9-14 Low 2 Zero 3 Zero 4 7.5-14.0 19 Zero 20 9-14 (1) Voltage may be slightly less due to lighting of reverse lights.
  2. Disconnect PNP switch Gray 9-pin harness connector. Check continuity between appropriate PNP switch terminals (component side) with shift lever in appropriate position. See «PARK/NEUTRAL POSITION SWITCH CONTINUITY»(ref-2780-S13720078402000041300000) table. (Scheme 42) If problem exists, replace PNP switch. If problem does not exist, go to next step. IDENTIFYING PARK/NEUTRAL SWITCH CONTINUITY Gear Position Terminals No. Park 1-3 & 6-9 Reverse 2-3 Neutral 3-5 & 6-9 Drive 3-7 2 3-4 Low 3-8
  3. Check wiring between battery and PNP switch and between PNP switch and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.

Scheme 42

Scheme 42
Scheme 42

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