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Engine Controls - Self-Diagnostics: Diagnosis Lexus IS I

Testing & Diagnostics 15 illustrations ~14275 words

MALFUNCTION INDICATOR LIGHT (MIL) INSPECTION

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

  1. Turn ignition on with engine off. MIL should come on and remain on. If MIL does not come on, check bulb circuit on instrument cluster and wiring circuit between MIL and ECM. See «WIRING DIAGRAMS»(ref-134952) article.
  2. Start engine and ensure MIL goes off. If MIL remains on with engine running, a malfunction is detected. Proceed to «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) .

TESTING PROCEDURE

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

  1. Record Customer Complaint Ensure all customer complaints or observations are recorded. Test drive vehicle with customer when necessary for malfunction verification.
  2. Retrieve Diagnostic Trouble Codes Connect appropriate OBD-II scan tool. Retrieve codes and record any freeze-frame data. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) .
  3. Clear Trouble Codes Clear DTCs using scan tool. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-134940-S42413103432002022100000) .
  4. Perform Visual Inspection Inspect all connectors of suspect circuit or component. Ensure all connections are clean and tight.
  5. Confirm Symptoms & Trouble Codes Perform road test. Determine if original symptoms are still present. Retrieve codes.
  6. Diagnose & Repair Diagnostic Trouble Codes Perform diagnosis and repair procedures as needed. See «DIAGNOSTIC TESTS»(ref-134940-S07245503672002022100000) . If no codes are present, proceed to «TROUBLE SHOOTING - NO CODES»(ref-134942) article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).
  7. Verification Procedure After repairs have been completed, clear all DTCs. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-134940-S42413103432002022100000) . Perform road test. Ensure no codes are present and all symptoms and/or complaints have been repaired.

RETRIEVING DIAGNOSTIC TROUBLE CODES

Diagnostic Trouble Codes (DTCs) may be retrieved using Lexus scan tool or On-Board Diagnostic (OBD-II) scan tool that complies with SAE standard J-1978. Lexus scan tool or OBD-II scan tool may be operated in NORMAL mode when retrieving trouble codes. If no codes are stored in NORMAL mode, Lexus scan tool may be used in CHECK mode to determine if any first trip DTCs are stored. OBD-II scan tools that comply with SAE standard J-1979 may be used in MODE 7 (CONTINUOUS TEST RESULTS function) to determine if any first trip DTCs are stored. NORMAL mode is used to retrieve DTCs from Engine Control Module (ECM). MODE 7 or CHECK mode is used to check for DTCs when operating vehicle to simulate conditions in which DTC was set. CHECK mode contains a higher sensing ability to detect malfunctions. CHECK mode helps determine malfunctions caused by poor electrical connections, which are difficult to determine using NORMAL mode.

Note. If using Lexus scan tool, when scan tool is switched from NORMAL mode to CHECK mode, all DTCs and freeze-frame data will be erased. DO NOT switch modes until all DTCs and freeze-frame data are recorded.

CHECK Mode Code Retrieval (Lexus Scan Tool Only)

  1. Ensure vehicle battery is fully charged (at least 11 volts). Shift transmission/transaxle into Neutral (M/T) or Park (A/T). Turn A/C and all accessories off. Ensure throttle is in idle position.
  2. Turn ignition off. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 DLC No. 3 connector is located under left side of instrument panel. Turn ignition on with engine off. Turn scan tool on.
  3. Switch scan tool from NORMAL mode to CHECK mode. CHECK mode is operational if MIL on instrument cluster flashes. Start engine. Ensure MIL goes off. Try to simulate conditions of driveability complaint described by customer. NOTE: If ignition is turned from ON to ACC or OFF position, all DTCs and freeze-frame data will be erased. DO NOT switch modes or turn ignition off until all DTCs and freeze-frame data are recorded.
  4. Record any DTCs and freeze-frame data displayed for system diagnosis. If driveability problem exists and no codes are present, go to «TROUBLE SHOOTING - NO CODES»(ref-134942) article for diagnosis by symptom.
  5. If any DTCs are present, perform appropriate circuit test. See «DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION»(ref-134940-S00748715062002022100000) table. For more information on freeze-frame data, see «FREEZE-FRAME DATA»(ref-134940-S30694302202002022100000) under INTRODUCTION. For information on 2-trip detection logic codes, see «TWO-TRIP DETECTION LOGIC»(ref-134940-S22234109652002022100000) under INTRODUCTION.
  6. After repairs for DTC have been completed, DTC must be cleared from ECM memory. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-134940-S42413103432002022100000).

CLEARING DIAGNOSTIC TROUBLE CODES

  1. After performing repairs, clear ECM memory of all stored Diagnostic Trouble Codes (DTCs) and freeze-frame data. DTCs and freeze-frame data may be cleared by using scan tool and scan tool manufacturer's instructions. NOTE: If using Lexus Scan Tool, DTCs and freeze-frame data may be cleared by switching from CHECK mode to NORMAL mode or from NORMAL mode to CHECK mode.
  2. DTCs and freeze-frame data may also be cleared by removing EFI fuse and ECTS fuses (if equipped with electronic throttle control system) from fuse/relay box located in engine compartment. DTCs and freeze-frame data may also be cleared by disconnecting negative battery cable. However, other memory functions (clock, radio, alarm, seats, etc.) will be cancelled and must be reset.

TROUBLE CODE TEST DRIVE CONFIRMATION

  1. On certain Diagnostic Trouble Codes (DTCs), once DTC has been cleared from ECM memory, a DTC test drive confirmation test can be performed to verify repairs made and that DTC does not reset. Test drive confirmation test will duplicate conditions required to set specified DTCs.
  2. Test drive confirmation test lists procedure to be performed to check that DTC does not reset. Test drive confirmation tests apply only to specific DTCs. Test drive confirmation test will be included with proper DTC diagnostic test in «DIAGNOSTIC TESTS»(ref-134940-S07245503672002022100000) .

DLC NO. 3 INSPECTION

  1. If scan tool displays UNABLE TO CONNECT TO VEHICLE when scan tool is connected, try scan tool on another vehicle. If scan tool operates on another vehicle, go to next step. If scan tool does not operate on another vehicle, problem is probably with scan tool.
  2. Check DLC No. 3 for loose or damaged terminals. Ensure DLC No. 3 terminals are in correct position in connector. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If connector and terminals are okay, go to next step.
  3. Check voltage and resistance between ground and specified terminal on DLC No. 3. See «DLC NO. 3 VOLTAGE & RESISTANCE SPECIFICATIONS»(ref-134940-S32514337962002022100000) table. (Scheme 22) If voltage and resistance readings are not as specified, check wiring circuit. See «WIRING DIAGRAMS»(ref-134952) article.
Terminal No. (Application)Specification
4 (Chassis Ground)One Ohm Or Less
5 (Signal)One Ohm Or Less
7 (BUS+ Line)(1)
16 (Battery Voltage)9-14 Volts
(1) Terminal No. 7 of DLC No. 3 provides a pulse generation during the information transmission from the Engine Control Module (ECM).
(1)Terminal No. 7 of DLC No. 3 provides a pulse generation during the information transmission from the Engine Control Module (ECM).

DLC NO. 3 VOLTAGE & RESISTANCE SPECIFICATIONS

Scheme 22

Scheme 22
Scheme 22

DIAGNOSTIC TESTS

CAUTIONPerform all resistance and voltage tests with a Digital Volt-ohmmeter (DVOM) with minimum 10-megohm impedance, unless stated otherwise in test procedures. Ensure ignition switch is in OFF position when performing resistance tests.

Note. For component locations, see appropriate illustration in THEORY & OPERATION article.

Note. For identification of circuits, terminals and wire colors referenced in following testing, see WIRING DIAGRAMS article.

Diagnosis & Repair

  1. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on. Turn scan tool on. Start engine and allow it to idle. Using scan tool, monitor MAF rate. If scan tool reading is 0.0 grams/second, go to next step. If reading is 271.0 grams/second or more, go to step 5.
  2. Disconnect MAF sensor connector. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 1 (Black/Red wire) at MAF sensor harness connector. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, locate and repair open in Black/Red wire between MAF sensor connector and EFI main relay. EFI main relay is located in fuse/relay box No. 2 on passenger side, at rear of engine compartment.
  3. Access ECM under protective cover, behind left headlight in engine compartment. Start engine. Shift transmission into PARK or NEUTRAL and turn A/C off. Backprobing, measure voltage between ground and terminal No. 27 (Green/Black wire) at ECM E5 connector. (Scheme 23) If voltage is 1.1-1.5 volts, replace ECM and retest. If voltage is not 1.1-1.5 volts, go to next step.
  4. Check for an open or short in Green/Black wire between MAF sensor and ECM E5 connector. Repair wiring harness as necessary. If wiring is okay, replace MAF sensor and retest.
  5. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition off. Backprobing, check for continuity between ground and terminal No. 26 (Blue/White wire) at ECM E5 connector. If continuity does not exist, replace ECM and retest. If continuity exists, go to next step.
  6. Check for open in Blue/White wire between MAF sensor and ECM E5 connector. Repair as necessary. If wiring is okay, replace MAF sensor.

Scheme 23

Scheme 23
Scheme 23

Circuit Description

MAF sensor uses a platinum hot wire maintained at a constant temperature. Airflow past sensor affects temperature and current flow through sensor. ECM will operate in fail-safe mode if DTC P0101 is set. DTC P0101 is set when throttle valve is fully closed, MAF sensor output is more than 2.2 volts, and engine is at operating temperature for 10 seconds or more at engine speed of 1000 RPM or less.

DTC P0101 will also set when Throttle Position (TP) sensor output is .64 volt or more, and MAF sensor output is less than 1.0 volt for 6 seconds or more at engine speed of 2000 RPM or more. Possible cause is; 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. If only DTC P0101 is displayed, replace MAF sensor and retest. If other codes are displayed, diagnose and repair those codes first and retest.

  1. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 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. 1 (Blue/Black wire) and No. 2 (Brown wire) at ECM side of MAF sensor harness connector. Turn ignition on. Using scan tool, monitor IAT sensor temperature. If temperature displayed is 284°F (140°C) or more, check MAF sensor connector for corrosion, damage or loose terminals. If connector is okay, replace MAF sensor and retest. If temperature displayed is less than 284°F (140°C), go to next step.
  3. Turn ignition off. Remove fused jumper wire. Access ECM under protective cover, behind left headlight in engine compartment. Backprobing, connect fused jumper wire between terminals No. 32 (Blue/Black wire) at ECM E5 connector and No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) If temperature displayed on scan tool is 284°F (140°C) or more, check and repair wiring harness between MAF sensor harness connector and ECM E4 and E5 connectors. If temperature displayed on scan tool is not 284°F (140°C) or more, replace ECM and retest.
  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. If temperature displayed is not -40°F (-40°C), turn ignition off and go to next step.
  5. Access ECM under protective cover, behind left headlight in engine compartment. Disconnect ECM E4 and E5 connectors. Turn ignition on. If temperature displayed is -40°F (-40°C), locate and repair short in Black/Blue wire or Brown wire between MAF sensor and ECM E4 and E5 connectors. If temperature displayed by scan tool is not -40°F (-40°C), replace ECM and retest.
  1. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on. Turn scan tool on. Using scan tool, monitor ECT sensor temperature. If temperature displayed is same as actual coolant temperature, 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 connector. Connect a fused jumper wire between ECT sensor harness connector terminals. Turn ignition on. Using scan tool, monitor ECT sensor temperature. If temperature displayed is 284°F (140°C) or more, check ECT sensor connector for corrosion, damage or loose terminals. If sensor connector is okay, replace ECT sensor and retest. If temperature displayed is not 284°F (140°C) or more, go to next step.
  3. Turn ignition off. Remove fused jumper wire. Access ECM under protective cover, behind left headlight in engine compartment. Backprobing, connect fused jumper wire between terminals No. 24 (Red wire) at ECM E5 connector and No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) If temperature displayed on scan tool is 284°F (140°C) or more, check for an open in Red wire and Brown wire between ECT sensor harness connector and ECM E4 and E5 connectors. If temperature displayed on scan tool is not 284°F (140°C) or more, replace ECM and retest.
  4. Turn ignition off. Disconnect ECT sensor connector. Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), replace ECT sensor and retest. If temperature displayed is not -40°F (-40°C), turn ignition off and go to next step.
  5. Access ECM under protective cover, behind left headlight in engine compartment. Disconnect ECM connectors E4 and E5. Turn ignition on. If temperature displayed is -40°F (-40°C), check for short in Red wire or Brown wire between ECT sensor and ECM E4 and E5 connectors. If temperature displayed by scan tool is not -40°F (-40°C), replace ECM and retest.

ECT sensor is a thermistor that monitors coolant temperature. DTC P0116 is set when after engine has been running for a predetermined period, ECM checks coolant temperature value and determines coolant temperature is not within specified range. Possible causes are

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

Note. If DTCs P0115 and P0116 are output together, inspect ECT circuits for an open. Repair as necessary. See WIRING DIAGRAMS article. Repair DTC P0115 fist.

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

Diagnosis & Repair (Using Lexus Scan Tool)

  1. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on. Turn scan tool on. Using Lexus scan tool, monitor throttle valve opening percentage at VTA circuit and voltage at VTA2 circuit. Opening percentage should be 64-96 percent and voltage should be 4.6-5.1 volts with a fully closed throttle. Depress accelerator pedal to floor (WOT). Opening percentage should be 8-20 percent and voltage should be 2.0-2.9 volts with a fully open throttle. If readings are within specification, replace ECM and retest. If readings are not within specification, go to next step.
  2. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing, measure voltage between terminals No. 35 (Blue/Yellow wire) and No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) 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.
  3. Turn ignition on. Backprobing, measure voltage between terminals No. 34 (Brown wire) at ECM E4 connector and No. 25 (White/Red wire) at ECM E7 connector. Voltage should be.4-1.0 volt with throttle fully closed and 3.2-4.8 volts with throttle fully open. Backprobing, measure voltage between terminals No. 34 (Brown wire) and No. 24 (Green/Yellow wire) at ECM E4 connector. Voltage should be 2.0-2.9 volts with throttle fully closed and 4.6-5.1 volts with throttle fully open. If voltage is not as specified, go to next step. If voltage is as specified, replace ECM and retest.
  4. Check TP sensor operation. See «SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430»(ref-134943) article. Replace TP sensor as necessary. If TP sensor is okay, check for short or open circuit in wiring harness between ECM E4 and E7 connectors and TP sensor. Repair wiring as necessary.

Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing, measure voltage between terminals No. 35 (Blue/Yellow wire) and No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) 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.
  2. Turn ignition on. Backprobing, measure voltage between terminals No. 18 (Brown wire) and No. 23 (White/Red wire) at ECM E6 connector. Voltage should be.4-1.0 volt with throttle fully closed and 3.2-4.8 volts with throttle fully open. Backprobing, measure voltage between terminals No. 34 (Brown wire) at ECM E4 and No. 24 (Green/Yellow wire) at ECM E6 connector. Voltage should be 2.0-2.9 volts with throttle fully closed and 4.6-5.1 volts with throttle fully open. If voltage is not as specified, go to next step. If voltage is as specified, replace ECM and retest.
  3. Check TP sensor operation. See «SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430»(ref-134943) article. Replace TP sensor as necessary. If TP sensor is okay, check for short or open circuit in wiring harness between ECM E6 connector and TP sensor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary.

TP sensor is a 2 variable resistor sensor that monitors throttle opening and TP sensor malfunction. Based on TP sensor signal, ECM determines vehicle driving condition and adjusts air/fuel mixture accordingly. DTC is set when TP sensor VTA and VTA2 circuit voltage is out of range for 2 seconds. Possible causes are

  1. Faulty TP sensor.
  2. Faulty ECM.

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

Replace TP sensor and retest.

  1. Retrieve trouble codes. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) under SELF-DIAGNOSTIC SYSTEM. If any other codes are displayed other than DTC P0125, diagnose and repair those codes first. If only DTC P0125 is displayed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Start engine and warm to normal operating temperature. Using scan tool, monitor bank No. 1, sensor No. 1 and bank No. 2, sensor No. 1. Snap accelerate engine 3 times to 4000 RPM. Sensors should indicate a rich signal (.45 volt or more) at least once. If a rich signal is indicated for both sensors, go to step 9. If either sensor does not display a rich signal, go to next step.
  3. Check for open or short circuit in wiring harness between ECM and suspect sensor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary. If wiring harness is okay, go to next step.
  4. Check for misfire. See «DTC P0300: RANDOM CYLINDER MISFIRE DETECTED»(ref-134940-S11809298652002022100000). Repair as necessary. If misfire is not detected, 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»(ref-134934-S01980397212002022100000) 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»(ref-134943-S07408494672002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 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.
  9. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-134940-S40634945052002022100000).
  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

Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 If using Lexus scan tool, switch to CHECK mode. On both scan tools, start and warm engine to normal operating temperature. Allow engine to idle for 100 seconds or more. Drive vehicle at 24 MPH or more for 20 seconds. Stop vehicle and allow to idle for 20 seconds. Repeat driving and idle part of test 2 more times. At last idle test, allow to idle for 30 seconds. If using OBD-II scan tool, turn engine off. Repeat this procedure. If using either scan tool, if malfunction exists, MIL will illuminate.

  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. Retrieve trouble codes. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) under SELF-DIAGNOSTIC SYSTEM. If any other codes are displayed other than DTC P0130 or DTC P0150, diagnose and repair those codes first. If only DTC P0130 or DTC P0150 is displayed, go to next step.
  2. Start engine and raise 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 circuit in wiring harness between ECM and suspect heated oxygen sensor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary. If wiring harness is okay, 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»(ref-134934-S01980397212002022100000) in BASIC DIAGNOSTIC PROCEDURES.
  6. Check fuel injectors. See «FUEL SYSTEM»(ref-134943-S07408494672002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 article. If problem exists, repair as necessary. If problem does not exist, replace suspect heated oxygen sensor.
  7. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-134940-S14892140212002022100000) .
  8. Clear and recheck for DTCs. If DTC P0130 or DTC P0150 is displayed again, replace ECM. If DTC P0130 or DTC P0150 is not displayed again, problem is intermittent. Check component and ECM connections.

Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 If using Lexus scan tool, switch to CHECK mode. On both scan tools, start and warm engine to normal operating temperature. Allow engine to idle for 100 seconds or more. Drive vehicle at 24 MPH or more for 20 seconds. Stop vehicle and allow to idle for 20 seconds. Repeat driving and idle part of test 2 more times. At last idle test, allow to idle for 30 seconds. If using OBD-II scan tool, turn engine off. Repeat this procedure. If using either scan tool, if malfunction exists, MIL will illuminate.

  1. Retrieve trouble codes. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) under SELF-DIAGNOSTIC SYSTEM. If any other codes are displayed other than DTC P0133 or DTC P0153, diagnose and repair those codes first. If only DTC P0133 or DTC P0153 is displayed, go to next step.
  2. Start engine and raise 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 circuit in wiring harness between ECM and suspect heated oxygen sensor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary. If wiring harness is okay, 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»(ref-134934-S01980397212002022100000) 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»(ref-134943-S07408494672002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 article. If problem exists, repair as necessary. If problem does not exist, replace suspect heated oxygen sensor.
  7. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-134940-S15705898592002022100000) .
  8. Clear and recheck for DTCs. If DTC P0133 or DTC P0153 is displayed again, replace ECM. If DTC P0133 or DTC P0153 is not displayed again, problem is intermittent. Check component and ECM connections.

Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 If using Lexus scan tool, switch to CHECK mode. On both scan tools, start and warm engine to normal operating temperature. Allow engine to idle for 100 seconds or more. Drive vehicle at 24 MPH or more for 20 seconds. Stop vehicle and allow to idle for 20 seconds. Repeat driving and idle part of test 2 more times. At last idle test, allow to idle for 30 seconds. If using OBD-II scan tool, turn engine off. Repeat this procedure. If using either scan tool, if malfunction exists, MIL will illuminate.

  1. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition on. Using DVOM, backprobe at following ECM harness connector: If DTC P0135 is set, measure voltage between ground and terminal No. 9 (Light Green wire) at ECM harness connector E6. If DTC P0141 is set, measure voltage between ground and terminal No. 7 (Green/Black wire) at ECM harness connector E4. If DTC P0155 is set, measure voltage between ground and terminal No. 30 (Pink wire) at ECM harness connector E5. If DTC P0161 is set, measure voltage between ground and terminal No. 8 (Red/White wire) at ECM harness connector E4. For ECM connector and terminal locations (Scheme 23) 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 harness connector. Measure resistance between terminals B+ (Black/Red wire) and HT (Light Green wire on bank No. 1 sensor No. 1, Red/White wire on bank No. 2 sensor No. 2, Green/Black wire on bank No. 1 sensor No. 2 or Red/White wire on bank No. 2 sensor No. 2) at heated oxygen sensor connector (component side). Resistance should be 11-16 ohms at 68°F (20°C). If resistance is not as specified, replace appropriate heated oxygen sensor. 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 «WIRING DIAGRAMS»(ref-134952) article.
  1. Retrieve trouble codes. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) under SELF-DIAGNOSTIC SYSTEM. If any other codes are displayed other than DTC P0136 or DTC P0156, diagnose and repair those codes first. If only DTC P0136 and P0156 are displayed, go to next step.
  2. Check for open or short circuit in wiring harness between ECM and suspect oxygen sensor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary. If wiring harness is okay, go to next step.
  3. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Start and warm engine to normal operating temperature. Monitor bank No. 1 and No. 2, sensor No. 2. Raise engine speed to 2500 RPM for 3 minutes. Return engine to idle. Snap accelerate engine 3 times to 4000 RPM. Voltage should fluctuate from.4 volt or less to.55 volt or more. If voltage responds correctly, check wiring harness connections. Problem may be intermittent. If voltage does not respond correctly, replace appropriate oxygen sensor and retest.
  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»(ref-134943-S07408494672002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 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»(ref-134943-S25250629962002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 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»(ref-134934-S31811742762002022100000) 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»(ref-134934-S01980397212002022100000) 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. Let engine idle. Using scan tool, monitor each No. 1 heated oxygen sensor's 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 sensor No. 1. See «WIRING DIAGRAMS»(ref-134952) article. If problem exists, repair wiring as necessary. If problem does not exist, replace appropriate No. 1 heated oxygen sensor(s).
  9. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-134940-S19255123662002022100000) .
  10. Clear and recheck for DTCs. If DTCs P0171, P0172, P0174 or P0175 are displayed again, replace ECM. If DTCs P0171, P0172, P0174 or P0175 are not displayed again, go to next step.
  11. Vehicle either ran out of fuel or problem is intermittent. Check component and ECM connections.

Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 If using Lexus scan tool, switch to CHECK mode. On both scan tools, start and warm engine to normal operating temperature. Allow engine to idle for 100 seconds or more. Drive vehicle at 24 MPH or more for 20 seconds. Stop vehicle and allow to idle for 20 seconds. Repeat driving and idle part of test 2 more times. At last idle test, allow to idle for 30 seconds. If using OBD-II scan tool, turn engine off. Repeat this procedure. If using either scan tool, if malfunction exists, MIL will illuminate.

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. Open or short in wiring.
  2. Poor connector contact at ECM.
  3. Vacuum hose leaks.
  4. Faulty ignition system.
  5. Faulty fuel injector(s).
  6. Improper fuel pressure.
  7. Faulty Mass Airflow (MAF) meter.
  8. Faulty Engine Coolant Temperature (ECT) sensor.
  9. Faulty engine compression.
  10. Improper valve clearance.
  11. Improper valve timing.
  12. 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.

  1. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 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-134940-S24503861212002022100000) table. Turn ignition off after symptom is simulated 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.

Note. If any DTCs other than P0300-P0306 are stored, perform appropriate repair procedure on that DTC first.

  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-134940-S35160376392002022100000). If problem does not exist, go to next step.
  2. Check spark and ignition system. See «IGNITION CHECKS»(ref-134934-S31811742762002022100000) in BASIC DIAGNOSTIC PROCEDURES article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  3. Access ECM under protective cover, behind left headlight in engine compartment. 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-134940-S08190037012002022100000) table. (Scheme 23) 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 15 (1) Red 2 17 (2) Blue 3 14 (1) Green 4 16 (2) Red/White 5 13 (1) Blue/Red 6 15 (2) Black/White (1) Terminal is located in ECM harness connector E7. (Scheme 23) (2) Terminal is located in ECM harness connector E5. (Scheme 23)
  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 «WIRING DIAGRAMS»(ref-134952) article. If resistance is not as specified, replace fuel injector.
  5. Check fuel pressure. See «FUEL SYSTEM»(ref-134934-S01980397212002022100000) 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»(ref-134943-S07408494672002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 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»(ref-134943-S25250629962002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 article. If problem exists, replace appropriate sensor(s). If problem does not exist, go to next step.
  8. Check engine compression. See «MECHANICAL INSPECTION»(ref-134934-S08938672832002022100000) in 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 MISFIRE DETECTED .

  1. Access ECM under protective cover, behind left headlight in engine compartment. Disconnect ECM E6 connector. Measure resistance between ground and terminals No. 1 (Black wire) and No. 2 (White wire) at ECM E6 harness connector. (Scheme 23) If both readings are infinite, go to step 3. If any reading is not infinite, go to next step.
  2. Disconnect suspect knock sensor connector. Using an ohmmeter, check for continuity between suspect knock sensor terminal and knock sensor body. If continuity exists, replace sensor. If continuity does not exist, go to next step.
  3. Check for an open or short in Black or White wires between knock sensors and ECM E6 connector. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring is okay, go to next step.
  4. Substitute knock sensor with a known-good sensor and retest. If malfunction is corrected, replace knock sensor. If malfunction is still present, replace ECM and retest.
  1. Disconnect CKP sensor connector. Using ohmmeter, measure resistance between CKP sensor terminals. Resistance should be 1630-2740 ohms with engine temperature at 14-122°F (-10-50°C) or 2065-3225 ohms with engine temperature at 122-212°F (50-100°C). If resistance is as specified, go to next step. If resistance is not as specified, replace CKP sensor.
  2. Check for short or open circuits in wire harness between ECM E7 connector and CKP sensor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary. If wiring is okay, go to next step.
  3. Check CKP sensor and signal plate for proper installation. Ensure CKP sensor and signal plate are not loose. Replace as necessary. If CKP sensor and signal plate are okay, replace ECM and retest.
  1. Disconnect CMP sensor connector. Using ohmmeter, measure resistance between CMP sensor terminals. Resistance should be 835-1400 ohms with engine temperature at 14-122°F (-10-50°C) or 1060-1645 ohms with engine temperature at 122-212°F (50-100°C). If resistance is as specified, go to next step. If resistance is not as specified, replace CMP sensor.
  2. Check for open or short circuits in wire harness between ECM E7 connector and CMP sensor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary. If wiring harness is okay, go to next step.
  3. Check CMP sensor for proper installation. Tighten CMP sensor as necessary. If CMP sensor is okay, replace ECM and retest.

Confirmation Test

Connect Lexus scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Ensure all accessories are turned off. Start and warm engine to normal operating temperature. Increase engine speed to 2500-3000 RPM for 3 minutes. Using Lexus scan tool, ensure heated oxygen sensors (bank No. 1 and 2, sensor No. 1 and 2) feedback to ECM fluctuates around.5 volt.

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

  1. Retrieve trouble codes. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) under SELF-DIAGNOSTIC SYSTEM. If only DTC P0420 or DTC P0430 is displayed, go to next step. If other codes are displayed, diagnose and repair those codes first and retest.
  2. Check for exhaust leaks. Repair as necessary. If exhaust system is okay, check heated oxygen sensor circuits (bank No. 1, sensor No. 1 and bank No. 2, sensor No. 1). See «DTC P0130 OR DTC P0150: HEATED OXYGEN SENSOR CIRCUIT MALFUNCTION»(ref-134940-S20285365632002022100000) test. Repair as necessary. If no problems are indicated, go to next step.
  3. Check heated oxygen sensor circuits (bank No. 1, sensor No. 2 and bank No. 2, sensor No. 2). See «DTC P0136 OR DTC P0156: HEATED OXYGEN SENSOR CIRCUIT MALFUNCTION»(ref-134940-S36867615622002022100000) test. Repair as necessary. If oxygen sensor circuits are okay, replace catalytic converter and retest.
  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 following: Fuel tank. Faulty 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 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, charcoal canister and pressure switching valve VSV, and between vapor pressure sensor 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 under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing, measure voltage between terminals No. 35 (Blue/Yellow wire) and No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) 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: DO NOT apply more than 19.7 in. Hg of vacuum to vapor pressure sensor.
  10. Locate vapor pressure sensor mounted on vapor canister. (Scheme 24) Sensor has a Black 3-pin connector with Brown, Blue/Yellow and Blue/White wires. Disconnect vacuum supply hose (hose closest to electrical connector) from vapor pressure sensor. Backprobing ECM harness connector, connect voltmeter between terminals No. 25 (Blue/White wire) and No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) Connect a vacuum pump to sensor. Voltage should be 2.9-3.7 volts without vacuum applied, and.5 volt or less with 1.18 in. Hg (4.0 kPa) 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 harness between vapor pressure sensor and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring is okay, replace vapor pressure sensor.
  12. Check fuel tank and fuel tank overfill check valve for cracks and damage. Overfill check valve is located on top of fuel tank. 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.

Scheme 24

Scheme 24
Scheme 24
  1. Check for cracks, deformations or loose connections in 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's 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, see appropriate illustration in «THEORY & OPERATION»(ref-134932) article.
  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, see appropriate illustration in «VACUUM DIAGRAMS»(ref-134950) article.
  10. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing, measure voltage between terminals No. 34 (Brown wire) and No. 35 (Blue/Yellow wire) at ECM E4 connector. (Scheme 23) 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.
  11. Locate vapor pressure sensor mounted on vapor canister. (Scheme 24) Sensor has a Black 3-pin connector with Brown, Blue/Yellow and Blue/White wires. Disconnect vacuum supply hose (hose closest to electrical connector) from vapor pressure sensor. Backprobing ECM harness connector, connect voltmeter between terminal No. 25 (Blue/White wire) and terminal No. 35 (Blue/Yellow wire) at ECM E4 connector. (Scheme 23) Connect a vacuum pump to sensor. Voltage should be 2.9-3.7 volts without vacuum applied, and.5 volt or less with 1.18 in. Hg (4.0 kPa) applied. If voltage is as specified, go to step 13. If voltage is not as specified, go to next step.
  12. Check for an open or short circuit in wiring harness and connector between vapor pressure sensor and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring harness and connector are okay, replace vapor pressure sensor and retest.
  13. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Using scan tool, select ACTIVE TEST mode. Disconnect vacuum hose from charcoal canister at EVAP VSV. (Scheme 25) Start engine. 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 17. If vacuum is not as specified, go to next step.
  14. Turn ignition off. Check for correct routing, damage, looseness and blockage in vacuum hoses between throttle body and EVAP VSV, and between EVAP VSV and charcoal canister. Repair as necessary. If vacuum hoses are okay, go to next step.
  15. Check EVAP VSV. See «FUEL EVAPORATION SYSTEM»(ref-134943-S22369286222002022100000) under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 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.
  16. Check for open or short circuit in wiring harness and connector between EFI main relay, EVAP VSV and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring harness and connector are okay, replace ECM and retest.
  17. Turn ignition off. Disconnect canister closed valve VSV vacuum hose. VSV is mounted on or near air filter housing and has a 2-pin connector with Black/Red and Yellow/Red wires. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on. Select ACTIVE TEST mode on scan tool. Using scan tool, turn canister closed valve VSV on. Apply compressed air to port "B" of canister closed valve VSV. Air should not flow from port "A". (Scheme 26) Using scan tool, turn canister closed valve VSV off. Air should flow from port "A". If VSV operates correctly, go to step 20. If VSV does not operate correctly, go to next step.
  18. Check canister closed valve VSV. See «FUEL EVAPORATION SYSTEM»(ref-134943-S22369286222002022100000) under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 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.
  19. Check for an open or short in wiring harness between EFI main relay, canister closed valve VSV and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  20. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Ensure ignition is on. Select ACTIVE TEST mode on scan tool. Locate pressure switching valve VSV on charcoal canister. (Scheme 24) Pressure switching valve VSV has 2 vacuum ports and a 2-pin connector with Pink and Black/Red wires. 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 27) Using scan tool, turn pressure switching valve VSV off. Air should not flow from port "F". If VSV operates correctly, go to step 23. If VSV does not operate correctly, go to next step.
  21. Check pressure switching valve VSV. See «FUEL EVAPORATION SYSTEM»(ref-134943-S22369286222002022100000) under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 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.
  22. Check for an open or short in wiring harness between EFI main relay, pressure switching valve VSV and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  23. Access ECM under protective cover, behind left headlight in engine compartment. Backprobing ECM harness connector, connect DVOM between terminals No. 25 (Blue/White wire) and terminal No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) 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 28) 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.
  24. Access ECM under protective cover, behind left headlight in engine compartment. Backprobing ECM harness connector, connect DVOM between terminals No. 25 (Blue/White wire) and terminal No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) 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 29) 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.
  25. Charcoal canister or fuel tank overfill check valve maybe defective. Check fuel evaporation system. See «FUEL EVAPORATION SYSTEM»(ref-134943-S22369286222002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 article. Repair as necessary. If no problem is indicated, replace ECM.

Scheme 25

Scheme 25
Scheme 25

Scheme 26

Scheme 26
Scheme 26

Scheme 27

Scheme 27
Scheme 27

Scheme 28

Scheme 28
Scheme 28

Scheme 29

Scheme 29
Scheme 29

Scheme 30

Scheme 30: Diagnosis & Repair (Using OBD-II Scan Tool)
Scheme 30: Diagnosis & Repair (Using OBD-II Scan Tool)
  1. Check for cracks, deformations or loose connections in 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, see appropriate illustration in «THEORY & OPERATION»(ref-134932) article.
  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, see appropriate illustration in «VACUUM DIAGRAMS»(ref-134950) article.
  10. Turn ignition on. Backprobing, measure voltage between terminals No. 34 (Brown wire) and No. 35 (Blue/Yellow wire) at ECM E4 connector. (Scheme 23) 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.
  11. Locate vapor pressure sensor mounted on vapor canister. (Scheme 24) Sensor has a 3-pin connector with Brown, Blue/Yellow and Blue/White wires. Disconnect vacuum supply hose (hose closest to electrical connector) from vapor pressure sensor. Backprobing ECM harness connector, connect voltmeter between terminal No. 25 (Blue/White wire) and terminal No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) Connect a vacuum pump to sensor. Voltage should be 2.9-3.7 volts without vacuum applied, and.5 volt or less with 1.18 in. Hg (4.0 kPa) applied. If voltage is as specified, go to step 13. If voltage is not as specified, go to next step.
  12. Check for an open or short circuit in wiring harness and connector between vapor pressure sensor and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring harness and connector are okay, replace vapor pressure sensor and retest.
  13. Turn ignition on. Disconnect EVAP VSV vacuum hoses. VSV is located on top of air intake chamber, near PCV valve. Backprobing, connect fused jumper wire between ground and terminal No. 11 (White/Green wire) at ECM E7 connector. Apply compressed air to EVAP VSV port "E". (Scheme 30) Air should flow from port "F". Disconnect fused jumper wire. Air should not flow from port "F". If EVAP VSV does not function as specified, go to next step. If EVAP VSV functions as specified, go to step 16.
  14. Remove EVAP VSV. Using ohmmeter, measure resistance between VSV terminals. With VSV temperature at 68°F (20°C), resistance should be 27-33 ohms. Measure resistance between each terminal and body of valve. Resistance should be infinite. If resistance is as specified, using fused jumper wires, apply battery voltage and ground to EVAP VSV terminals. Apply compressed air to EVAP VSV port "E". Air should flow from port "F". (Scheme 30) Disconnect fused jumper wires. Air should not flow from port "F". If EVAP VSV does not operate as specified, or if resistance was not as specified, replace EVAP VSV and charcoal canister. After replacing components, clean vacuum hoses between EVAP VSV and throttle body, and between EVAP VSV and charcoal canister. If EVAP VSV operates as specified, go to next step.
  15. Check for open or short circuit in wiring harness and connector between EFI main relay, EVAP VSV and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring harness is okay, replace ECM and retest.
  16. Turn ignition off. Disconnect canister closed valve VSV vacuum hose. VSV is mounted on or near air filter housing and has a 2-pin connector with Black/Red and Yellow/Red wires. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing, connect a fused jumper wire between ground and terminal No. 22 (Yellow/Red wire) at ECM E5 connector. (Scheme 23) Apply compressed air to port "A" of canister closed valve VSV. (Scheme 26) 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 19.
  17. Check canister closed valve VSV. See «FUEL EVAPORATION SYSTEM»(ref-134943-S22369286222002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 article. If VSV is okay, go to next step. If VSV is not okay, replace canister closed VSV and charcoal canister. Also clean vacuum hose between charcoal canister and canister closed valve VSV.
  18. Check for an open or short in wiring harness between EFI main relay, canister closed valve VSV and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  19. Turn ignition on. Access ECM under protective cover, behind left headlight in engine compartment. Backprobing, connect a fused jumper wire between ground and terminal No. 10 (Pink wire) at ECM E4 connector. (Scheme 23) Locate pressure switching valve VSV on charcoal canister. (Scheme 24) Apply compressed air to VSV port "E". (Scheme 27) 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 22. If VSV does not function as specified, go to next step.
  20. Check pressure switching valve VSV. See «FUEL EVAPORATION SYSTEM»(ref-134943-S22369286222002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 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.
  21. Check for an open or short in wiring harness between EFI main relay, pressure switching valve VSV and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  22. Charcoal canister or fuel tank overfill check valve may be defective. Check fuel evaporation system. See «FUEL EVAPORATION SYSTEM»(ref-134943-S22369286222002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 article. Repair as necessary.
  1. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 34 (Brown wire) and No. 35 (Blue/Yellow wire) at ECM E4 connector. (Scheme 23) 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: DO NOT apply more than 19.7 in. Hg of vacuum to vapor pressure sensor.
  2. Locate vapor pressure sensor mounted on vapor canister. (Scheme 24) Sensor has a 3-pin connector with Brown, Blue/Yellow and Blue/White wires. Disconnect vacuum supply hose (hose closest to electrical connector) from vapor pressure sensor. Backprobing ECM harness connector, connect voltmeter between terminal No. 25 (Blue/White wire) and No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) Connect a vacuum pump to sensor. Voltage should be 2.9-3.7 volts without vacuum applied, and.5 volt or less with 1.18 in. Hg (4.0 kPa) applied. If voltage is as specified, replace ECM and retest system. If voltage is not as specified, go to next step.
  3. Check for an open or short in wiring harness between vapor pressure sensor and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring is okay, replace vapor pressure sensor. Retest system.
  1. Connect scan tool to Data Link Connector (DLC) No. 3. Test drive vehicle and compare actual vehicle speed to speed indicated by scan tool. If actual vehicle speed and indicated scan tool speed match, replace ECM and retest system. If actual vehicle speed and indicated scan tool speed do not match, go to next step.
  2. Check speedometer operation. If speedometer is operating properly, go to next step. If speedometer is not operating properly, repair speedometer as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
  3. Access ECM under protective cover, behind left headlight in engine compartment. Disconnect ECM E6 connector. Using an ohmmeter, measure resistance between terminals No. 22 (Red/Blue wire) and No. 23 (Blue/Yellow wire) at ECM E6 connector. (Scheme 23) If resistance is 560-680 ohms, replace ECM and retest system. If resistance is not 560-680 ohms, go to next step.
  4. Remove VSS from rear of transmission. Using an ohmmeter, measure resistance between VSS connector terminals. Resistance should be 560-680 ohms. Using a voltmeter set to AC voltage, measure voltage between VSS connector terminals. Place a magnet close to front of VSS and quickly remove (to generate a voltage pulse). If voltage pulse is not generated or resistance is not as specified, replace VSS and retest. If voltage pulse is generated, check wiring harness between VSS and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary.

Idle speed is controlled by Electronic Throttle Control System (ETCS). ETCS is composed of throttle motor, magnetic clutch, TP sensor, accelerator pedal position sensor, ECM and throttle body. ECM controls throttle motor to adjust throttle valve opening angle. DTC P0505 is set if idle speed continues to vary greatly from target speed. Possible causes are

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

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

  1. Retrieve trouble codes. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) under SELF-DIAGNOSTIC SYSTEM. If only DTC P0505 is displayed, go to next step. If other codes are displayed, diagnose and repair those codes first and retest.
  2. Check for loose, damaged or cracked air intake hose between throttle body and air cleaner. Check for loose or damaged dipstick, oil fill cap or PCV hose. Repair as necessary. If all components are okay, check throttle system control. See «THROTTLE CONTROLS»(ref-134943-S42466754522002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 article. Repair as necessary.

ECM controls idle speed based in part on input signal received from power steering pressure sensor. DTC P0550 sets if power steering pressure sensor signal is less than .28 volt or more than 4.9 volts for .5 second or more. Possible causes are

  1. Open in power steering pressure sensor circuit.
  2. Faulty power steering pressure sensor.
  3. Faulty ECM.

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

  1. Connect 3 1.5 volt batteries in series. Disconnect power steering pressure sensor electrical connector. Connect batteries, voltmeter and test harness as shown. (Scheme 31) Connect power steering pressure tester SST (09023-12700) to power steering pump. (Scheme 32) Measure sensor voltage at different power steering pressures. See «POWER STEERING PRESSURE/SENSOR VOLTAGE SPECIFICATIONS»(ref-134940-S16591753122002022100000) table. If voltage is not as specified, replace power steering pressure sensor. If voltage reading is as specified, go to next step. POWER STEERING PRESSURE/SENSOR VOLTAGE SPECIFICATIONS Pressure PSI (kPa) Volts 0 (0) 0.45 512 (3500) (1) 2.25 1010 (7000) (1) 4.05 (1) Start engine, turn steering wheel and increase RPM as necessary to obtain required pressure readings.
  2. Check for opens in following circuits: In Blue/Yellow wire between power steering pressure sensor connector and terminal No. 35 of ECM connector E4. In Purple wire between power steering pressure sensor connector and terminal No. 23 of ECM connector E5. In Brown wire between power steering pressure sensor connector and terminal No. 34 of ECM connector E4. For ECM terminal identification (Scheme 23) Repair any problems as necessary. If no problem was found, replace ECM and retest system.

Scheme 31

Scheme 31
Scheme 31

Scheme 32

Scheme 32
Scheme 32
  1. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on. Turn scan tool on. Using Lexus scan tool, monitor accelerator pedal position sensor voltage at VPA and VPA2 circuits. With throttle fully closed, accelerator pedal position sensor voltage should be.3-.9 volt at VPA circuit and 1.8-2.7 volts at VPA2 circuit. Depress accelerator pedal to floor (WOT). With throttle fully open, accelerator pedal position sensor voltage should be 3.2-4.8 volts at VPA circuit and 4.7-5.1 volts at VPA2 circuit. If voltages are as specified, replace ECM and retest. If voltages are not as specified, go to next step.
  2. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing, measure voltage between terminals No. 35 (Blue/Yellow wire) and No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) 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.
  3. Turn ignition on. Backprobing, measure voltage between terminals No. 34 (Brown wire) and No. 33 (Pink/Blue wire) at ECM E4 connector. With fully closed throttle, voltage should be.3-.9 volt. With Wide Open Throttle (WOT), voltage should be 3.2-4.8 volts. Measure voltage between terminals No. 34 (Brown wire) and No. 32 (Blue/White wire) at ECM E4 connector. With fully closed throttle, voltage should be 1.8-2.7 volts. With WOT, voltage should be 4.7-5.1 volts. If voltage is not as specified, go to next step. If voltage is as specified, replace ECM and retest.
  4. Check accelerator pedal position sensor operation. See «ENGINE SENSORS & SWITCHES»(ref-134943-S25250629962002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 article. Replace accelerator pedal position sensor as necessary. If accelerator pedal position sensor is okay, check for short or open circuit in wiring harness and sensor connector between ECM E6 connector and accelerator pedal position sensor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary.
  1. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing, measure voltage between terminals No. 35 (Blue/Yellow wire) and No. 34 (Brown wire) at ECM E4 connector. (Scheme 23) 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.
  2. Turn ignition on. Backprobing, measure voltage between terminals No. 34 (Brown wire) and No. 33 (Pink/Blue wire) at ECM E4 connector. With fully closed throttle, voltage should be.3-.9 volt. With Wide Open Throttle (WOT), voltage should be 3.2-4.8 volts. Measure voltage between terminals No. 34 (Brown wire) and No. 32 (Blue/White wire) at ECM E4 connector. With fully closed throttle, voltage should be 1.8-2.7 volts. With WOT, voltage should be 4.7-5.1 volts. If voltage is not as specified, go to next step. If voltage is as specified, replace ECM and retest.
  3. Check accelerator pedal position sensor operation. See «ENGINE SENSORS & SWITCHES»(ref-134943-S25250629962002022100000) in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 article. Replace accelerator pedal position sensor as necessary. If accelerator pedal position sensor is okay, check for short or open circuit in wiring harness and sensor connector between ECM E4 connector and accelerator pedal position sensor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary.

Accelerator pedal position sensor is a 2 variable resistor sensor that monitors throttle opening and accelerator pedal position sensor malfunction. Accelerator pedal position sensor determines vehicle accelerator pedal position. ECM controls throttle motor and electromagnetic clutch based on signal from accelerator pedal position sensor. If DTC P1121 is set, ECM shuts down power to throttle control motor and electromagnetic clutch.

DTC P1121 is set when ECM consistently detects difference between VPA and VPA2 circuits out of tolerance. Possible cause is; faulty accelerator pedal position sensor.

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

Replace accelerator pedal position sensor and retest.

  1. Access ECM at left front of engine compartment. Start engine. Using oscilloscope, check signal circuits of M+ and M- circuits between ECM and throttle control motor. Backprobe ECM at following terminals: For M+ Circuit Connect oscilloscope between terminal No. 3 of ECM connector E7 (White wire) and terminal No. 7 of ECM connector E6 (Brown wire). For M- Circuit Connect oscilloscope between terminal No. 2 of ECM connector E7 (Red wire) and terminal No. 7 of ECM connector E6 (Brown wire). NOTE: For ECM terminal identification (Scheme 23) Compare to specified oscilloscope patterns. (Scheme 33) Waveform frequency should vary with engine speed. If either circuit does not display specified waveform, go to next step. If both circuits display specified waveform, replace ECM and retest system.
  2. Disconnect throttle control motor connector. Using an ohmmeter, measure resistance between throttle control motor connector White wire and Red wire. Resistance should be.3-100.0 ohms at 68°F (20°C). If resistance is not as specified, replace throttle control motor. If resistance is as specified, go to next step.
  3. Check for open or short circuit in wiring harness or connector between throttle control motor and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary. If wiring and connectors are okay, replace ECM and retest.

Scheme 33

Scheme 33
Scheme 33
  1. If using an oscilloscope, go to next step. If using Lexus scan tool, connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on. Using scan tool, monitor magnetic clutch current value. If magnetic clutch current is.8-1.0 amp, go to step 3. If magnetic clutch current is not.8-1.0 amp, go to step 5.
  2. Backprobing, connect oscilloscope between terminals No. 9 (Yellow wire) and No. 10 (Red/White wire) at ECM E7 connector. Start engine and allow it to idle. Waveform should be as illustrated. (Scheme 34) If waveform is as illustrated, go to next step. If waveform is not as illustrated, go to step 5.
  3. Disconnect throttle control motor and magnetic clutch connector. Using an ohmmeter, measure resistance between throttle control motor connector Red/White wire and Yellow wire. Resistance should be 4.2-5.2 ohms at 68°F (20°C). If resistance is at specified, go to next step. If resistance is not as specified, replace throttle control motor/clutch assembly.
  4. Check for open or short circuit in wiring harness and connector between magnetic clutch and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary. If wiring is okay, go to next step.
  5. Clear DTCs. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-134940-S42413103432002022100000) under SELF-DIAGNOSTIC SYSTEM. Turn ignition on. Start engine. Turn ignition off for 3 seconds. Turn ignition on. Retrieve trouble codes. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) under SELF-DIAGNOSTIC SYSTEM. If DTC P1126 is not displayed, replace ECM and retest. If DTC P1126 is displayed, replace throttle control motor and retest.

Scheme 34

Scheme 34
Scheme 34
  1. Check ETCS fuse (15-amp) from fuse/relay box located at passenger side of firewall in engine compartment. If ETCS fuse is okay, go to next step. If ETCS fuse is blown, check for short circuit in wiring harness between ETCS fuse and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary.
  2. Access ECM under protective cover, behind left headlight in engine compartment. Backprobing, measure voltage between ground and terminal No. 7 (Blue/White wire) at ECM E3 connector. (Scheme 23) If voltage is 9-14 volts, replace ECM and retest. If voltage is not 9-14 volts, check circuits in wiring harness between battery voltage, ETCS fuse and ECM. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary.

Throttle control motor opens and closes throttle valve as commanded by ECM. ECM determines throttle valve position using throttle position sensor. If DTC P1128 is set, ECM shuts down power to throttle control motor and electromagnetic clutch.

DTC P1128 is set when throttle control motor locks. Possible causes are

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

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

Check throttle control motor. See DTC P1125: THROTTLE CONTROL MOTOR CIRCUIT MALFUNCTION . Replace throttle control motor as necessary. If throttle control motor is okay, remove intake air duct. Visually inspect throttle valve for foreign material. If throttle valve is clean, replace throttle body.

Retrieve DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. If any DTCs other than P1129 are stored, perform appropriate repair procedure on that DTC first. If only DTC P1129 is displayed, replace ECM and clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. Recheck for DTCs. If DTC P1129 resets, replace throttle body and retest.

Fuel pump speed is controlled in 2 stages (high and low speeds) based on engine conditions. During engine starting or under heavy load conditions, ECM turns fuel pump relay off to operate fuel pump at high speed. During idling or under light load, ECM turns fuel pump relay on to operate fuel pump at low speed. DTC will set if open or short is detected in fuel pump relay circuit for .5 seconds or more while engine is cranking. Possible causes are

  1. Open or short circuit in fuel pump relay circuit.
  2. Faulty fuel pump relay.
  3. Faulty ECM.

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

Note. This diagnostic testing procedure is based on the assumption that engine starts. If engine does not start, see SYMPTOMS in TROUBLE SHOOTING - NO CODES article.

  1. Check fuel pump relay operation. See «RELAYS»(ref-134943-S02255558432002022100000) under MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430 & LS430 article. Replace fuel pump relay as necessary. If fuel pump relay is okay, go to next step.
  2. Locate fuel pump resistor mounted under protective cover on driver's side inner fender well. Disconnect fuel pump resistor electrical connector. Using DVOM, measure resistance between fuel pump resistor terminals. If resistance is .30-.35 ohm, go to next step. If resistance is not .30-.35 ohm, replace fuel pump resistor and retest system.
  3. Check for open or short circuit in Green/Red wire between terminal No. 4 of ECM E3 connector and fuel pump relay. Repair as necessary and retest system. If no problem was found, replace ECM and retest system.
  1. Check for spark at misfiring cylinder. See «IGNITION CHECKS»(ref-134934-S31811742762002022100000) 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 circuit (Black/Blue wire) between terminal No. 7 at ECM E5 connector and ignitor. Ignitor is located on driver's side of engine compartment, on shock tower. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If circuit is okay, go to next step.
  3. Disconnect ignitor Black 10-pin connector. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing, measure voltage between ground and terminal No. 7 (Black/Blue wire) at ECM E5 connector. (Scheme 23) If voltage is 4.5-5.5 volts, replace ignitor. If voltage is not 4.5-5.5 volts, replace ECM and retest.
  4. Check for open or short in IGT circuits (Gray/Black, Black/Red and Black/Yellow wires) between ECM E5 and E7 connectors and ignitor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary. If circuits are okay, go to next step.
  5. Access ECM under protective cover, behind left headlight in engine compartment. Backprobing, measure voltage between ground and terminal No. 13 (Gray/Black wire), No. 27 (Black/Red wire) and No. 26 (Black/Yellow wire) at ECM E5 and E7 connectors while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM and retest.
  6. Disconnect ignitor Black 10-pin connector. Backprobing, measure voltage between ground and terminal No. 13 (Gray/Black wire), No. 27 (Black/Red wire) and No. 26 (Black/Yellow wire) at ECM E5 and E7 connectors while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM and retest.
  7. Turn ignition switch to ON position and then to START position. Measure voltage between ground and terminal No. 9 (Black/White wire) at ignitor wiring harness connector. If voltage is not 9-14 volts, repair ignitor power source circuit. If voltage is 9-14 volts, go to next step.
  8. Check for open or short in wiring harness between ignition switch and ignition coil, and between ignition coil and ignitor. See «WIRING DIAGRAMS»(ref-134952) article. Repair wiring as necessary. If wiring is okay, go to next step.
  9. Check ignition coils. See «IGNITION CHECKS»(ref-134934-S31811742762002022100000) in BASIC DIAGNOSTIC PROCEDURES article. Replace ignition coils as necessary. If ignition coils are okay, check ignitor ground circuit (Brown wire). Repair wiring as necessary. If ground circuit is okay, replace ignitor.

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.

  1. Check valve timing. See appropriate article in ENGINES. Repair as necessary. If valve timing is okay, go to next step.
  2. Start and run engine. Allow engine to reach normal operating temperature. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Select VVT from scan tool ACTIVE TEST menu. Using scan tool, turn OCV on and off. 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 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. Access ECM under protective cover, behind left headlight in engine compartment. Backprobe ECM E7 connector. Start engine. Using oscilloscope, check waveform pattern between terminals No. 5 (Yellow/Black wire) and No. 6 (Red/Yellow wire) at ECM E7 connector. (Scheme 23) Slowly increase engine speed. Waveform frequency "A" should lengthen as engine speed increases. (Scheme 35) If readings are not as specified, replace ECM and retest. If readings are as specified, go to next step.
  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 fused jumper wires between positive battery terminal and OCV connector terminal No. 1, and negative battery terminal and OCV connector terminal No. 2. (Scheme 36) OCV plunger should move away from connector. Remove fused jumper wires. OCV plunger should move back in direction of connector. If OCV plunger does not move as specified, replace OCV and go to next step. If OCV plunger moves as specified, go to next step.
  6. Check for blockage in OCV. Check oil check valve and oil pipe located under OCV. Repair as necessary. If components are okay, go to next step.
  7. Clear DTCs. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-134940-S42413103432002022100000) under SELF-DIAGNOSTIC SYSTEM. Duplicate driving conditions under which DTC P1349 was set. Retrieve DTCs. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) under SELF-DIAGNOSTIC SYSTEM. If DTC P1349 is displayed, replace ECM and retest. If DTC P1349 is not displayed, VVT system is functioning properly at this time. DTC may have been set because of a foreign object that was temporarily caught in engine oil system but after a short time system returned to normal.

Scheme 35

Scheme 35
Scheme 35

Scheme 36

Scheme 36
Scheme 36
  1. Check valve timing. See appropriate article in ENGINES. Repair as necessary. If valve timing is okay, go to next step.
  2. Start and run engine. Allow engine to reach normal operating temperature. Disconnect OCV connector. Connect fused jumper wires between positive battery terminal and OCV connector terminal No. 1, and negative battery terminal and OCV connector terminal No. 2. (Scheme 36) If engine speed does not change with OCV disconnected and changes (rough idle or stalls) with fused jumper wires connected, go to next step. If results are not as specified, go to step 4.
  3. Access ECM under protective cover, behind left headlight in engine compartment. Backprobe ECM E7 connector. Start engine. Using oscilloscope, check waveform pattern between ECM E7 connector terminals No. 5 (Yellow/Black wire) and No. 6 (Red/Yellow wire). (Scheme 23) Slowly increase engine speed. Waveform frequency "A" should lengthen as engine speed increases. (Scheme 35) If readings are not as specified, replace ECM and retest. If readings are as specified, VVT system is functioning properly at this time. DTC may have been set because of a foreign object that was temporarily caught in engine oil system but after a short time system returned to normal. If readings are not as specified, replace ECM and retest.
  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 fused jumper wires between positive battery terminal and OCV connector terminal No. 1, and negative battery terminal and OCV connector terminal No. 2. (Scheme 36) OCV plunger should move away from connector. Remove fused jumper wires. OCV plunger should move back in direction of connector. If OCV plunger does not move as specified, replace OCV and go to next step. If OCV plunger moves as specified, go to next step.
  6. Check for blockage in OCV. Check oil check valve and oil pipe located under OCV. Repair as necessary. If components are okay, go to next step.
  7. Clear DTCs. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-134940-S42413103432002022100000) under SELF-DIAGNOSTIC SYSTEM. Duplicate driving conditions under which DTC P1349 was set. Retrieve DTCs. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-134940-S22896487582002022100000) under SELF-DIAGNOSTIC SYSTEM. If DTC P1349 is displayed, replace ECM and retest. If DTC P1349 is not displayed, VVT system is functioning properly at this time. DTC may have been set because of a foreign object that was temporarily caught in engine oil system, but after a short time system returned to normal.
  1. Check stoplights. If stoplights do not function properly, repair as necessary and retest system. See EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT. If stoplights function properly, go to next step.
  2. If using Lexus scan tool, go to next step. If not using Lexus scan tool, go to step 4.
  3. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on. Using scan tool, read STP signal while depressing and releasing brake pedal. STP signal should be on when brake pedal is depressed. STP signal should be off when brake pedal is released. If STP signal does not operate as specified, go to step 5. If STP signal operates as specified, check wire harness and connectors. Problem is intermittent.
  4. Access ECM under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing, measure voltage between ground and terminal No. 4 (Green/White wire) at ECM E4 connector. (Scheme 23) 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, check wire harness and connectors. Problem is intermittent.
  5. Check for short circuit in wiring harness between ECM and stoplight switch. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary and retest system. If wiring harness is okay, replace ECM. Retest system.
  1. Access ECM under protective cover, behind left headlight in engine compartment. Backprobing, measure voltage between ground and terminal No. 4 (Black/Yellow wire) at ECM E4 connector. (Scheme 23) If voltage is not 9-14 volts, go to next step. If voltage is 9-14 volts, replace ECM and retest.
  2. Remove and inspect EFI fuse (15-amp) from fuse/relay box located on passenger's side firewall. 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. See «WIRING DIAGRAMS»(ref-134952) article.

Replace ECM and retest.

If DTC P1645 is set, malfunction exists in data communication lines between EMC Body ECU and A/C ECU. Diagnose multiplex communication system. See appropriate MULTIPLEX CONTROL SYSTEMS article in ACCESSORIES & EQUIPMENT. Repair as necessary.

  1. Start and run engine. Allow engine to reach normal operating temperature. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Select VVT from scan tool ACTIVE TEST menu. Using scan tool, turn OCV on and off. 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 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. With engine running. Disconnect OCV connector and note idle speed. Engine idle speed should not change. Connect fused jumper wires between positive battery terminal and OCV connector terminal No. 1, and negative battery terminal and OCV connector terminal No. 2. (Scheme 36) 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. Access ECM under protective cover, behind left headlight in engine compartment. Backprobe ECM E7 connector. Start engine. Backprobing, connect oscilloscope between ECM E7 connector terminals No. 5 (Yellow/Black wire) and No. 6 (Red/Yellow wire). (Scheme 23) Ensure waveform pattern is as illustrated. (Scheme 35) Slowly increase engine speed. Waveform frequency "A" should lengthen as engine speed increases. 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 and connector in wire harness between OCV and ECM E7 connector. Repair as necessary. If circuit and connector are okay, problem is intermittent.
  1. Start and run engine. Allow engine to reach normal operating temperature. Disconnect OCV connector and note idle speed. Engine idle speed should not change. Connect fused jumper wires between positive battery terminal and OCV connector terminal No. 1, and negative battery terminal and OCV connector terminal No. 2. (Scheme 36) If engine speed does not change with OCV disconnected and changes (rough idle or stalls) with fused jumper wires connected, go to next step. If results are not as specified, replace OCV and retest.
  2. Access ECM under protective cover, behind left headlight in engine compartment. Backprobe ECM E7 connector. Start engine. Using oscilloscope, check waveform pattern between ECM E7 connector terminals No. 5 (Yellow/Black wire) and No. 6 (Red/Yellow wire). (Scheme 23) Slowly increase engine speed. Waveform frequency "A" should lengthen as engine speed increases. (Scheme 35) 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 and connector in wire harness between OCV and ECM E7 connector. Repair as necessary. If circuit and connector are okay, problem is intermittent.

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