Engine Controls - Tests W/codes Toyota Land Cruiser 80 рестайлинг

INTRODUCTION

If no faults were found while performing BASIC TESTING , proceed with self-diagnostics. If no Diagnostic Trouble Codes (DTCs) are present after entering self-diagnostics, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).

SYSTEM OVERVIEW

The ECM monitors engine operation and contains a self-diagnostic system which stores Diagnostic Trouble Codes (DTCs) and complies to On-Board Diagnostics Generation II (OBD-II) standards.

Self-diagnostic system is used to provide vehicle with an on-board diagnostic system which is capable of continuously monitoring the efficiency of emission control system, and to improve diagnosis and repair when system failures occur.

The Federal Test Procedure (FTP) sets maximum allowable emission standards. A Malfunction Indicator Light (MIL) must illuminate if a system or component either fails or deteriorates to a point where the vehicle emissions could rise above 1 1/2 times FTP standards.

If malfunction does not reoccur in 3 ignition cycles, the MIL goes off, but DTCs remain recorded in ECM memory. DTCs may only be retrieved using an On-Board Diagnostic (OBD-II) scan tester that complies with SAE standard J-1978 or Toyota scan tester connected to new standardized Data Link Connector No. 3 (DLC3). The scan tester also provides freeze-frame data and can be used to clear codes.

TWO-TRIP DETECTION LOGIC

When a malfunction initially occurs, Diagnostic Trouble Code (DTC) will be temporarily stored in ECM memory, but MIL on instrument panel will not illuminate. The second time malfunction is detected, MIL on instrument panel will illuminate, provided ignition is turned off and then back on after first malfunction was detected. This is referred to as the 2-Trip Detection Logic and only applies to specific DTCs.

Note. When road testing vehicle in CHECK mode (Toyota scan tester only), the Two Trip Detection Logic will not function. Also, MIL will illuminate first time a malfunction is detected.

DATA LINK CONNECTOR

OBD-II regulations (SAE J-1850) standardizes Data Link Connector (DLC) configurations. See DATA LINK CONNECTOR NO . 3 (DLC3) LOCATION table.

DATA LINK CONNECTOR NO. 3 (DLC3) LOCATION

FREEZE-FRAME DATA

OBD-II or Toyota scan tester can by used to check freeze-frame data. The ECM records engine operating condition when a misfire, fuel trim (mixture) malfunction or other malfunction (fuel system, calculated load, coolant temperature, fuel trim (mixture), engine speed, vehicle speed, etc.) exists. If more than one fault is detected, only data from the first malfunction is recorded. Recorded data is useful for determining conditions in which the malfunction occurs.

MALFUNCTION INDICATOR LIGHT (MIL) INSPECTION

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

1. Turn ignition on with engine off. MIL should come on and remain on. If MIL does not come on, check bulb circuit on instrument cluster and wiring circuit between MIL and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. See «ECM LOCATION»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__ecm-location) .
2. Start engine and ensure MIL goes off. If MIL remains on with engine running, a malfunction is detected. Proceed to RETRIEVING DIAGNOSTIC TROUBLE CODES.

TESTING PROCEDURE

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

1. Record Customer Complaint: Ensure all customer complaints or observations are recorded. Test drive vehicle with customer when necessary for malfunction verification.
2. Retrieve Diagnostic Trouble Codes: Connect appropriate scan tool. Retrieve codes and record any freeze-frame data (if applicable). See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__retrieving-diagnostic-trouble-codes) .
3. Clear Trouble Codes: See «CLEARING DIAGNOSTIC TROUBLE CODES»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__clearing-diagnostic-trouble-codes) .
4. Visual Inspection: Inspect all connectors of suspect circuit or component. Ensure all connections are clean and tight.
5. Confirm Symptoms & Trouble Codes: Perform road test. Determine if original symptoms are still present. Retrieve codes.
6. Diagnose & Repair Diagnostic Trouble Codes: Perform diagnosis and repair procedures as necessary. See «TROUBLE CODE IDENTIFICATION»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If no codes are present, proceed to the TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).
7. Verification Procedure: After repairs have been completed, clear trouble codes. See «CLEARING DIAGNOSTIC TROUBLE CODES»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__clearing-diagnostic-trouble-codes) . Perform road test. Ensure no codes are present and all symptoms and/or complaints have been repaired.

RETRIEVING DIAGNOSTIC TROUBLE CODES

Note. Diagnostic Trouble Codes (DTCs) may be retrieved using Toyota scan tester or On-Board Diagnostic (OBD-II) scan tester that complies with SAE standard J-1978. Toyota scan tester or OBD-II scan tester may be operated in NORMAL mode when retrieving trouble codes. Only Toyota scan tester may be used in CHECK mode when retrieving DTCs.

NORMAL mode is used to retrieve DTCs from Engine Control Module (ECM). CHECK mode is used to check for DTCs when operating vehicle to simulate conditions in which DTC was set. CHECK mode contains a higher sensing ability to detect malfunctions. CHECK mode helps determine malfunctions caused by poor electrical connections, which are difficult to determine using NORMAL mode.

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

NORMAL Mode Code Retrieval

1. Connect scan tester to Data Link Connector No. 3 (DLC3). Turn ignition on with engine off. Turn scan tester on. Using scan tester manufacturer's instructions, check for DTCs and freeze-frame data.
2. If scan tester displays UNABLE TO CONNECT TO VEHICLE, DLC3 must be checked. See «DLC3 INSPECTION»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__dlc3-inspection) under SCAN TESTER PROBLEMS. If scan tester does not display UNABLE TO CONNECT TO VEHICLE, go to next step.
3. Record any DTCs and freeze-frame data displayed for system diagnosis. If driveability problem exists and no DTCs are present, go to TESTS W/O CODES article for diagnosis by symptom.
4. If any DTCs are present, perform appropriate circuit test. See «TROUBLE CODE IDENTIFICATION»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. For more information on freeze-frame data, see «FREEZE-FRAME DATA»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__freeze-frame-data) under INTRODUCTION. For information on 2-trip detection logic codes, see «TWO-TRIP DETECTION LOGIC»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__two-trip-detection-logic) under INTRODUCTION.
5. After repairs for DTC have been completed, DTCs must be cleared from ECM memory. See «CLEARING DIAGNOSTIC TROUBLE CODES»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__clearing-diagnostic-trouble-codes) .

CHECK Mode Code Retrieval (Toyota Scan Tester Only)

1. Ensure vehicle battery is fully charged. Apply parking brake. 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 tester to Data Link Connector No. 3 (DLC3). See «DATA LINK CONNECTOR»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__data-link-connector) . Turn ignition on with engine off. Turn scan tester on.
3. Switch scan tester 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 switch is turned from ON to ACC or OFF position, all DTCs and freeze-frame data will be erased. DO NOT switch modes 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 TESTS W/O CODES article for diagnosis by symptom.
5. If any DTCs are present, perform appropriate circuit test. See «TROUBLE CODE IDENTIFICATION»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. For more information on freeze-frame data, see «FREEZE-FRAME DATA»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__freeze-frame-data) . For information on 2-trip detection logic codes, see «TWO-TRIP DETECTION LOGIC»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__two-trip-detection-logic) .
6. After repairs for DTC have been completed, DTC must be cleared from ECM memory. See «CLEARING DIAGNOSTIC TROUBLE CODES»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes__clearing-diagnostic-trouble-codes) .

CLEARING DIAGNOSTIC TROUBLE CODES

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

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

TROUBLE CODE IDENTIFICATION

TROUBLE CODE TEST DRIVE CONFIRMATION

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

ECM LOCATION

ECM LOCATION

DLC3 INSPECTION

1. If scan tester displays UNABLE TO CONNECT TO VEHICLE when scan tester is connected, try scan tester on another vehicle. If scan tester operates on another vehicle, go to next step. If scan tester does not operate on another vehicle, problem is probably with scan tester.
2. Check DLC3 for loose or damaged terminals. Ensure DLC3 terminals are in correct position in connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If connector and terminals are okay, go to next step.
3. Check voltage and resistance between ground and specified terminal on DLC3. See «DLC3 VOLTAGE & RESISTANCE SPECIFICATIONS»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. (Scheme 9) If voltage and resistance readings are not as specified, check wiring circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.

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

DLC3 VOLTAGE & RESISTANCE SPECIFICATIONS

Scheme 9

CIRCUIT TESTS

Note. For component location, see appropriate illustration in THEORY/OPERATION article.

DTC P0100 - MASS AIRFLOW (MAF) SENSOR CIRCUIT

Circuit Description

MAF sensor uses a platinum hot wire maintained at a constant temperature. Airflow past sensor affects temperature and current flow through sensor. DTC is set when ECM detects an open or short circuit with engine speed of 4000 RPM or less. ECM will operate in fail-safe mode if DTC P0100 is set. Possible causes are

1. MAF open or short circuit.
2. MAF sensor.
3. ECM.

Scheme 10

1. Connect scan tester to DLC3 connector. (Scheme 9) Start vehicle engine and allow to idle. Turn on scan tester. Monitor MAF flow rate. If scan tester reading is 0.0 gm/sec., go to next step. If reading is 439 gm/sec. or more once engine is at normal operating temperature, go to step 5).
2. Disconnect MAF sensor connector. Ensure ignition is on. Using DVOM, measure voltage between terminal No. 1 (Yellow/Red wire) and ground. (Scheme 11) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check for an open circuit in wiring harness between EFI main relay and MAF sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
3. Access ECM behind right instrument panel speaker. Start engine. Backprobing ECM connector, measure voltage between ground and terminal No. 2 (Green wire) at ECM E5 connector. (Scheme 12) If voltage is 1.1-1.5 volts, replace ECM and retest.
4. If voltage is not 1.1-1.5 volts, check for open or short circuit between MAF and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, replace MAF sensor and retest.
5. Access ECM behind right instrument panel speaker. Turn ignition off. Using ohmmeter, backprobe ECM connector. Check continuity between ground and terminal No. 16 (Brown wire) at ECM E5 connector. (Scheme 12) If continuity does not exist, replace ECM and retest. If continuity exists, check for open circuit between MAF sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, replace MAF sensor.

Scheme 11

Scheme 12

Condition

Following conditions continue with engine speed of 900 RPM or less

1. Closed throttle position switch in ON position.
2. MAF sensor output is 2.2 volts or less.

Diagnosis & Repair Procedure

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

DTC P0110 - INTAKE AIR TEMPERATURE (IAT) SENSOR CIRCUIT

The IAT sensor is a thermistor built into the MAF sensor and is used to monitor temperature of air flowing through MAF sensor. DTC is set when ECM detects an open or short circuit. ECM will operate in fail-safe mode if DTC P0110 is set. Possible causes are

1. IAT sensor open or short circuit.
2. IAT sensor.
3. ECM.

Note. If DTCs P0110, P0115 and P0120 are output together, inspect ECM terminal E2 (ground) circuit. Repair as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article.

Diagnosis & Repair

1. Connect scan tester to DLC3 connector. (Scheme 9) Turn ignition on. Turn on scan tester. Monitor IAT sensor temperature. If temperature displayed is same as outside temperature, inspect component and ECM connections. Problem is intermittent.
2. If temperature displayed is 284°F (140°C), go to step 5). If temperature displayed is -40°F (-40°C), turn ignition off. Disconnect MAF sensor connector. Using jumper wire, connect MAF wiring harness connector terminals No. 3 and 4. (Scheme 11) Turn ignition on. Monitor IAT sensor temperature on scan tester.
3. If temperature displayed is 284°F (140°C) or more, replace MAF sensor and retest. If temperature displayed is less than 284°F (140°C), turn ignition off. Remove jumper wire. Access ECM behind right instrument panel speaker. Connect jumper wire between terminals No. 3 (Blue/Yellow wire) and No. 9 (Brown/Black wire) at ECM E5 connector. (Scheme 12)
4. If temperature displayed on scan tester is 284°F (140°C) or more, inspect and repair circuits between MAF wiring harness connector and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed on scan tester is less than 284°F (140°C), replace ECM and retest.
5. Turn ignition off. Disconnect MAF sensor connector. Turn ignition on. If temperature displayed on scan tester is -40°F (-40°C), replace MAF sensor and retest. If temperature displayed is not -40°F (-40°C), turn ignition off.
6. Access ECM behind right instrument panel speaker. Disconnect ECM E5 connector. (Scheme 12) Turn ignition on. If temperature displayed is -40°F (-40°C), inspect and repair circuits between MAF sensor and ECM for short. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed by scan tester is not-40°F (-40°C), replace ECM and retest.

DTC P0115 - ENGINE COOLANT TEMPERATURE (ECT) SENSOR CIRCUIT

The ECT sensor is a thermistor sensor that monitors water temperature. DTC is set when ECM detects an open or short circuit. Possible causes are

1. Open or short in ECT sensor circuit.
2. ECT sensor.
3. ECM.

Note. If DTCs P0110, P0115 and P0120 are output together, inspect ECM terminal E2 (ground) circuit. Repair as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article.

1. Connect scan tester to DLC3 connector. (Scheme 9) Turn ignition on. Turn on scan tester. Monitor ECT sensor temperature. If temperature displayed is same as actual coolant temperature, inspect component and ECM connections. Problem is intermittent.
2. If temperature displayed is 284°F (140°C) or more, go to step 5). If temperature displayed is -40°F (-40°C), turn ignition off. Disconnect ECT sensor connector. Connect a jumper wire between ECT sensor wiring harness connector terminals. Turn ignition on. Using scan tester, monitor ECT sensor temperature.
3. If temperature displayed is 284°F (140°C) or more, replace ECT sensor and retest. If temperature displayed is less than 284°F (140°C), turn ignition off. Remove jumper wire. Access ECM behind right instrument panel speaker. Connect jumper wire between terminals No. 4 (Red/White wire) and No. 9 (Brown/Black wire) at ECM E5 connector. (Scheme 12)
4. If temperature displayed on scan tester is 284°F (140°C) or more, inspect and repair circuits for open between ECT sensor wiring harness connector and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed on scan tester is less than 284°F (140°C), replace ECM and retest.
5. Turn ignition off. Disconnect ECT sensor connector. Turn ignition on. If temperature displayed on scan tester is -40°F (-40°C), replace ECT sensor and retest. If temperature displayed is not -40°F (-40°C), turn ignition off.
6. Access ECM behind right instrument panel speaker. Disconnect ECM E5 connector. (Scheme 12) Turn ignition on. If temperature displayed is -40°F (-40°C), inspect and repair circuits between ECT sensor and ECM for short. See appropriate wiring diagram in WIRING DIAGRAMS article. If temperature displayed by scan tester is not-40°F (-40°C), replace ECM and retest.

DTC is set when ECT sensor temperature is 86°F (30°C) or less for at least 20 minutes of engine operation. Possible causes are

1. Engine Coolant Temperature (ECT) sensor.
2. Cooling system.

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

DTC P0120 - THROTTLE POSITION (TP) SENSOR CIRCUIT MALFUNCTION

The TP sensor is a variable resistor that monitors throttle opening. The ECM determines vehicle driving condition and adjusts air/fuel mixture accordingly. DTC is set when ECM consistently detects less than .1 volt from VTA circuit and closed throttle position switch is off. DTC can also be set if ECM consistently detects 4.9 volts or more. DTC P0120 will not set if there is an open in IDL circuit. Possible causes are

1. Open or short in TP sensor circuit.
2. TP sensor.
3. ECM.

Note. If DTCs P0110, P0115 and P0120 are output together, inspect ECM terminal E2 (ground) circuit. Repair as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article.

1. Connect scan tester to DLC3 connector. (Scheme 9) Turn ignition on. Turn on scan tester. Monitor throttle valve opening percentage. Opening percentage should be approximately 10 percent with fully closed throttle.
2. Depress accelerator pedal to floor (WOT). Opening percentage should be approximately 75 percent. If percentages are within specification, inspect all connections. Problem may be intermittent.
3. If percentages are not within specification, turn ignition off. Disconnect TP sensor connector. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 1 (Red/Green wire) at TP sensor wiring harness connector. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, go to step 7).
4. Check Throttle Position (TP) sensor. See ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS article. Replace sensor as necessary. If sensor is okay, go to next step.
5. Access ECM behind right instrument panel speaker. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 9 (Brown/Black wire) and No. 10 (Green/Black wire) at ECM E5 connector. (Scheme 12) Voltage should be.3-.8 volt with throttle fully closed, and 3.2-4.9 volts with throttle fully open (WOT).
6. If voltage is as specified, replace ECM and retest. If voltage is not as specified, check for an open or short in Green/Black wire. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
7. Access ECM behind right instrument panel speaker. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 1 (Red/Green wire) and No. 9 (Brown/Black wire) at ECM E5 connector. (Scheme 12) If voltage is 4.5-5.5 volts, check wiring harness for an open in Red/Green wire. If voltage is not 4.5-5.5 volts, replace ECM and retest.

DTC is set when ECM consistently detects more than 2 volts from VTA circuit and closed throttle position switch is on. Possible cause is

1. Throttle Position (TP) sensor.

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

DTC P0125 - INSUFFICIENT COOLANT TEMPERATURE FOR CLOSED LOOP FUEL CONTROL

The oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. The ECM uses input signal to determine fuel injection system operation. Sensors include heater. DTC is set when sensor does not output a rich condition once engine is at normal operating temperature, engine speed of 1500 RPM or more, and vehicle speed is at least 25 MPH for at least 2 minutes. Possible causes are

1. Open or short in heated oxygen sensor circuit.
2. Heated oxygen sensor.

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

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

DTC P0130 - HEATED OXYGEN SENSOR CIRCUIT (SENSOR NO. 1)

DTC P0130 is set when sensor No. 1 voltage remains at .40-.55 volt during idle, once engine is at normal operating temperature. Possible causes are

1. Heated oxygen sensor.
2. Fuel trim.

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

Test Drive Confirmation

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

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

DTC is set when ECM detects a response time of one second or more from sensor to change from rich to lean, or lean to rich. Possible cause is

1. Heated oxygen sensor.

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

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

DTC P0135 - HEATED OXYGEN SENSOR CIRCUIT (SENSOR NO. 1), DTC P0141 - HEATED OXYGEN SENSOR CIRCUIT (SENSOR NO. 2)

DTC is set when either of the following conditions is present

1. Sensor heater current draw exceeds 2 amps.
2. Sensor heater current draw is .25 amp or less.

Possible causes are

1. Heated oxygen sensor open or short circuit.
2. Heated oxygen sensor heater.
3. ECM.

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

1. Access ECM behind right instrument panel speaker. Turn ignition on. Using DVOM, backprobe ECM connector. If DTC P0135 is set, measure voltage between ground and terminal No. 1 (Gray wire) at ECM E6 connector. If DTC P0141 is set, measure voltage between ground and terminal No. 25 (Orange wire) at ECM E6 connector. (Scheme 12) Voltage for each circuit should be 9-14 volts.
2. If voltage is as specified, replace ECM and retest. If voltage is not as specified, turn ignition off. Disconnect appropriate oxygen sensor connector. Using ohmmeter, measure resistance between terminals No. 1 and 2 at oxygen sensor connector. See «IDENTIFYING OXYGEN SENSOR HEATER TERMINALS»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. IDENTIFYING OXYGEN SENSOR HEATER TERMINALS Application Terminal No. 1 Terminal No. 2 Sensor No. 1 Gray Wire Yellow/Red Wire Sensor No. 2 Orange Wire Yellow/Red Wire
3. If resistance is 11-16 ohms at 68°F (20°C), inspect circuits between ECM and sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If resistance is not 11-16 ohms at 68°F (20°C), replace sensor and retest.

DTC is set when sensor No. 2 voltage remains at .40-.55 volt during vehicle operation (25 MPH or more), once engine is at normal operating temperature. Possible cause is

1. Heated oxygen sensor.

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

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

DTC P0171 - SYSTEM TOO LEAN (FUEL TRIM), DTC P0172 - SYSTEM TOO RICH (FUEL TRIM)

Fuel trim refers to feedback compensation value compared against basic injection time. Fuel trim includes short-term and long-term fuel trim.

DTC P0171 is set when fuel trim is rich beyond a certain value. Possible causes are

1. Air intake hose loose.
2. Fuel line pressure.
3. Injector blockage.
4. Heated oxygen sensor.
5. Mass Airflow (MAF) sensor.
6. Engine Coolant Temperature (ECT) sensor.

DTC P0172 is set when fuel trim is lean beyond a certain value. Possible causes are

1. Fuel line pressure.
2. Injector blockage or leak.
3. Heated oxygen sensor.
4. Mass Airflow (MAF) sensor.
5. Engine Coolant Temperature (ECT) sensor.

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

1. Inspect all air induction components. Repair as necessary. If air induction components are okay, connect scan tool. (Scheme 9) Start engine and warm to normal operating temperature. Monitor heated oxygen sensor output voltage and short-term fuel trim.
2. If scan tester indicates a lean condition (.55 volt or less, +20 trim) or rich condition (.4 volt or more, -20 trim), go to next step. If results are other than shown, see DTC P0130 - HEATED OXYGEN SENSOR CIRCUIT (SENSOR NO. 1) circuit test.
3. Inspect fuel pressure. See «BASIC TESTING»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-basic-testing) article. Repair as necessary. If fuel pressure is okay, inspect fuel injectors. See SYSTEM/COMPONENT TESTS article. Replace injectors as necessary.
4. If all injectors are okay, inspect Mass Airflow (MAF) sensor and Engine Coolant Temperature (ECT) sensor. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If both components are okay, inspect ignition system. See IGNITION CHECKS in «BASIC TESTING»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-basic-testing) article. Repair as necessary. If ignition system is okay, replace ECM and retest.

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

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

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

1. Inspect spark plug and check for spark at misfiring cylinder. See «BASIC TESTING»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-basic-testing) article. Repair as necessary. If spark plug is okay and spark is present, go to next step.
2. Access ECM behind right instrument panel speaker. Turn ignition on. Using DVOM, backprobe ECM connector. Measure voltage between ground and injector terminals at ECM E4 connector. See IDENTIFYING INJECTOR TERMINALS table. (Scheme 12) If voltage is 9-14 volts for each circuit, go to step 4). If voltage is not 9-14 volts, go to next step. IDENTIFYING INJECTOR TERMINALS Injector No. (1) Terminal No. Wire Color 1 12 White/Blue 2 11 White/Red 3 25 White/Green 4 2 Yellow 5 1 Yellow/Red 6 15 Yellow/Blue (1) Terminals are located in ECM E4 connector.
3. Disconnect injector of misfiring cylinder. Using ohmmeter, measure resistance between injector terminals. If resistance is 13.4-14.2 ohms, inspect circuits between ECM and injector for open or short. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If resistance is not 13.4-14.2 ohms, replace injector.
4. Check fuel pressure. See «BASIC TESTING»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-basic-testing) article. Repair as necessary. If fuel pressure is okay, inspect fuel injector performance. See SYSTEM/COMPONENT TESTS article. Replace as necessary.
5. If all injectors are okay, inspect EGR system. See SYSTEM/COMPONENT TESTS article. Repair as necessary. If EGR system is okay, inspect MAF sensor and ECT sensor. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If both components are okay, also inspect engine compression, valve clearance and valve timing. See «BASIC TESTING»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-basic-testing) article.

DTCS P0301-P0306 - CYLINDERS NO. 1-6 MISFIRE DETECTED

Note. When 2 or more codes for a misfiring cylinder are recorded repeatedly, but DTC P0300 is not recorded, it indicates that misfires were detected and stored into ECM memory at different times.

See DTC P0300 - RANDOM MISFIRE DETECTED circuit test.

Two conditions can cause code to set. These are

1. During any particular 200 revolutions of engine, misfiring is detected which can cause catalytic converter overheating and/or damage.
2. During any particular 1000 revolutions of engine, misfiring is detected which can cause a deterioration in emission levels.

For possible causes, see DTC P0300 - RANDOM MISFIRE DETECTED circuit test.

See DTC P0300 - RANDOM MISFIRE DETECTED circuit test.

DTC P0325 - KNOCK SENSOR NO. 1 CIRCUIT, DTC P0330 - KNOCK SENSOR NO. 2 CIRCUIT

Knock sensors are located under intake manifold. Sensor generates voltage when engine block vibrates due to knocking. DTC P0325 is for front knock sensor. DTC P0330 is for rear knock sensor. DTC is set when there is no knock sensor signal to ECM with engine speed of 550 RPM or more. Possible causes are

1. Open or short in knock sensor circuit.
2. Knock sensor (loose).
3. ECM.

1. Access ECM behind right instrument panel speaker. Disconnect ECM E5 connector. (Scheme 12) Using ohmmeter, measure resistance between ground and terminals No. 6 (Black wire) and No. 14 (Blue/White wire) at ECM E5 connector. If resistance is infinite, go to step 3). If resistance is not infinite, go to next step.
2. Disconnect applicable knock sensor connector. (Scheme 13) Check continuity between sensor terminal and sensor housing. If continuity does not exist, go next step. If continuity exists, replace sensor.
3. Check for an open or short circuit between knock sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, substitute suspect knock sensor with known-good sensor. Clear codes. See SELF-DIAGNOSTIC SYSTEM. Start and warm engine to normal operating temperature. Retrieve codes. See «SELF-DIAGNOSTIC SYSTEM»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes). If code is still present, replace ECM. If code is no longer present, replace sensor.

Scheme 13

DTC P0335 OR P1335 - CRANKSHAFT POSITION (CKP) SENSOR "A" CIRCUIT

The CKP sensor (NE signal) is a pick-up coil mounted next to a 24-tooth signal plate in distributor. Code is set when either no cranking or engine running signal is received by ECM from sensor. Possible causes are

1. CKP sensor open or short circuit.
2. CKP sensor.
3. Starter.
4. ECM.

1. Disconnect distributor connector. Using ohmmeter, measure resistance between terminals No. 1 and 4 at distributor connector. (Scheme 14) Resistance should be 185-275 ohms (cold sensor) or 240-325 ohms (hot sensor).
2. If resistance is not as specified, replace distributor. If resistance is as specified, check for an open or short circuit between ECM and distributor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
3. If circuits are okay, check air gap between signal rotor and each pick-up coil. See IGNITION CHECKS in «BASIC TESTING»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-basic-testing) article. If air gap is not to specification, replace distributor.

Scheme 14

DTC P0340 - CAMSHAFT POSITION (CMP) SENSOR CIRCUIT

The CMP sensors (2) are pick-up coils (G1 and G2 signals) mounted next to 1-tooth signal plates in distributor. DTC is set when no CMP sensor signal is received by ECM with engine speed at 550 RPM or more sensor. Possible causes are

1. CMP sensor open or short circuit.
2. CMP sensor.
3. ECM.

1. Disconnect distributor connector. Check resistance of pick-up coils. See IGNITION CHECKS in «BASIC TESTING»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-basic-testing) article. If resistance is not as specified, replace distributor. If resistance is as specified, go to next step.
2. Check for an open or short in G1, G2 and G- circuits between ECM and distributor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
3. If circuits are okay, check air gap between signal rotor and each pick-up coil. See IGNITION CHECKS in «BASIC TESTING»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-basic-testing) article. If air gap is not to specification, replace distributor. If air gap is to specification, replace ECM and retest.

DTC P0385 - CRANKSHAFT POSITION (CKP) SENSOR "B" CIRCUIT

The CKP sensor (NE2 signal) is a pick-up coil mounted next to a 34-tooth signal plate mounted on crankshaft. DTC is set when no engine running signal is received by ECM from sensor. Possible causes are

1. CKP sensor open or short circuit.
2. CKP sensor.
3. ECM.

1. Disconnect CKP (NE2 signal) sensor connector. (Scheme 15) Using ohmmeter, measure resistance between terminals No. 1 and 2 at CKP sensor terminals. Resistance should be 1630-2740 ohms (cold sensor) or 2065-3225 ohms (hot sensor).
2. If resistance is not as specified, replace sensor. If resistance is as specified, inspect NE2 circuit between CKP sensor and ECM for open or short. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
3. If circuit is okay, inspect sensor installation and teeth of signal plate. Repair or replace as necessary. If both sensor and signal plate are okay, replace ECM and retest.

Scheme 15

DTC P0401 - INSUFFICIENT EXHAUST GAS RECIRCULATION (EGR) FLOW DETECTED

The EGR system recirculates exhaust gas through intake system to reduce combustion temperature and NOx emissions. The amount of EGR valve opening is regulated by the EGR vacuum modulator according to engine load. Vacuum source to valve is controlled by the Vacuum Switching Valve (VSV), which is controlled by ECM.

The EGR valve is closed (VSV on) under the following conditions

1. Engine is not warmed up.
2. Vehicle under deceleration.
3. Light engine load.
4. Engine racing.

DTC is set when EGR temperature sensor value does not exceed ambient air temperature by more than 104°F (40°C) after vehicle is operated for 3 to 5 minutes (50 MPH or more). Possible causes are

1. EGR valve stuck closed.
2. VSV short circuit.
3. EGR temperature sensor open circuit.
4. EGR vacuum hose disconnected.
5. ECM.

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

Diagnosis & Repair (Using Toyota Scan Tester)

1. Connect scan tester. (Scheme 9) Turn ignition on. Read EGR gas temperature. If temperature is 50°F (10°C), go to step 5). If temperature is 37.6°F (3.1°C), there is an open EGR temperature sensor circuit. If temperature is not 50°F (10°C), go to next step.
2. Disconnect EGR temperature sensor connector. Connect jumper wire between wiring harness connector terminals. If EGR temperature displayed is not about 316°F (158°C), go to next step. If temperature displayed is about 316°F (158°C), inspect sensor connectors and terminals. Repair as necessary. If connectors are okay, replace sensor and retest.
3. Remove jumper wire. Turn ignition off. Access ECM behind right instrument panel speaker. Connect jumper wire between terminal No. 19 (Green/Yellow wire) at ECM E4 connector and terminal No. 9 (Brown/Black wire) at ECM E5 connector. (Scheme 12) Turn ignition on.
4. If EGR temperature displayed is about 316°F (158°C), inspect and repair open in circuits between ECM and EGR temperature sensor. If temperature displayed is not about 316°F (158°C), replace ECM and retest.
5. Inspect vacuum hoses. See appropriate illustration in VACUUM DIAGRAMS article. Repair as necessary. If all hoses are okay, inspect VSV. Using scan tester, select ACTIVE TEST mode. Check operation of VSV when activated by scan tester. VSV is located under intake plenum cover.
6. Start and run engine. With EGR system off, air from port "G" should exhaust from port "E". (Scheme 16) With EGR system on, air from port "G" should not exhaust from port "E". If VSV operates correctly, go to step 9). If VSV does not operate correctly, go to next step.
7. Remove EGR VSV. Air intake chamber may have to be removed to access VSV. Using ohmmeter, measure resistance between VSV terminals. Resistance should be 30-34 ohms at 68°F (20°C). Check for continuity between each VSV terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.
8. Check VSV operation. Apply battery voltage to VSV terminals. Air from port "G" should not exhaust from port "E". (Scheme 16) Remove battery voltage from valve terminals. Air from port "G" should exhaust from port "E". Replace VSV as necessary. If VSV operates as specified, check for an open in wiring harness between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
9. Inspect EGR vacuum modulator. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If modulator is okay, inspect EGR valve. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If components are okay, go to next step.
10. Ensure all components are connected. Start and run engine. Using scan tester, select ACTIVE TEST mode (EGR system ON). Run engine at 4000 RPM for 3 minutes. Monitor EGR gas temperature. If temperature is 284°F (140°C) or more, replace ECM and retest. If temperature is less than 284°F (140°C), replace sensor.

Scheme 16

Diagnosis & Repair (Using OBD-II Scan Tester)

1. Disconnect EGR temperature sensor. Using ohmmeter, measure resistance between sensor terminals. If resistance is 600 k/ohms or less, go to next step. If resistance is more than 600 k/ohms, inspect sensor. See SYSTEM/COMPONENT TESTS. Replace as necessary.
2. Turn ignition on. Using DVOM, measure voltage between sensor wiring harness connector terminals. If voltage is 4.5-5.5 volts, go to step 4). If voltage is not 4.4-5.5 volts, go to next step.
3. Access ECM behind right instrument panel speaker. Using DVOM, backprobe connector. Measure voltage between terminal No. 19 (Green/Yellow wire) at ECM E4 connector and No. 9 (Brown/Black wire) at ECM E5 connector. (Scheme 12) If voltage is 4.5-5.5 volts, inspect circuits between EGR temperature sensor and ECM for open. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If voltage is not 4.4-5.5 volts, replace ECM and retest.
4. Inspect all EGR system vacuum hoses. Replace as necessary. Access ECM behind right instrument panel speaker. Ensure ignition is off. Disconnect ECM E4 connector. Turn ignition on. Connect a jumper wire between ground and terminal No. 22 (Blue/White wire) at ECM E4 connector.
5. With jumper wire connected, Vacuum Switching Valve (VSV) is on. Air from port "G" should not exhaust from port "E". (Scheme 16) Disconnect jumper wire. Air from port "G" should exhaust from port "E". If valve operates correctly, go to step 8). If valve does not operate correctly, go to next step.
6. Turn ignition off. Remove EGR VSV. It may be necessary to remove air intake chamber to access VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 30-34 ohms at 68°F (20°C). Check continuity between each VSV terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.
7. Check VSV operation. Apply battery voltage to VSV terminals. Air from port "G" should not exhaust from port "G". (Scheme 16) Remove battery voltage from valve terminals. Air from port "G" should exhaust from port "G". Replace VSV as necessary. If VSV operates as specified, check for an open in wiring harness between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
8. Inspect EGR vacuum modulator. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If modulator is okay, inspect EGR valve. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If EGR valve is okay, go to next step.
9. Disconnect EGR temperature sensor connector. Start engine. Ensure engine is at normal operating temperature. Run engine at 4000 RPM for 3 minutes and measure resistance between EGR temperature sensor terminals. If resistance is 4300 ohms or less, replace ECM and retest. If resistance is more than 4300 ohms, replace sensor.

DTC P0402 - EXCESSIVE EXHAUST GAS RECIRCULATION (EGR) FLOW DETECTED

The EGR system recirculates exhaust gas through intake system to reduce combustion temperature and NOx emissions. The amount of EGR valve opening is regulated by the EGR vacuum modulator according to engine load. Vacuum source to valve is controlled by the Vacuum Switching Valve (VSV), which is controlled by ECM.

The EGR valve is closed (VSV on) under the following conditions

1. Engine is not warmed up.
2. Vehicle under deceleration.
3. Light engine load.
4. Engine racing.

DTC is set when EGR temperature sensor value is high. Engine not yet at normal operating temperature. Possible causes are

1. EGR valve stuck open.
2. EGR Vacuum Switching Valve (VSV).
3. EGR VSV open circuit.
4. EGR temperature sensor short circuit.
5. ECM.

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

1. Connect scan tester. (Scheme 9) Turn ignition on. Read EGR gas temperature. If temperature is 302°F (150°C), go to step 4). If temperature is not 302°F (150°C), go to next step. If temperature displayed is 318.7°F (159.3°C), there is a short in EGR temperature sensor circuit.
2. Disconnect EGR temperature sensor connector. Using scan tester, read EGR gas temperature. If EGR gas temperature is not 37.6°F (3.1°C), go to next step. If temperature is 37.6°F (3.1°C), replace sensor and retest.
3. Turn ignition off. Access ECM behind right instrument panel speaker. Disconnect ECM E4 connector. (Scheme 12) Turn ignition on. Using scan tester, read EGR gas temperature. If EGR gas temperature is 37.6°F (3.1°C), inspect and repair open in circuits between ECM and EGR temperature sensor. If temperature is not 37.6°F (3.1°C), replace ECM and retest.
4. Using scan tester, select ACTIVE TEST mode. Check operation of VSV when activated by scan tester. VSV is located under intake plenum cover. Start and run engine. With EGR system off, air from port "G" should exhaust from port "E". (Scheme 16) With EGR system on, air from port "G" should not exhaust from port "E". If VSV operates correctly, check EGR valve. See SYSTEM/COMPONENT TESTS article. If VSV does not operate correctly, go to next step.
5. Remove EGR VSV. Air intake chamber may have to be removed to access VSV. Using ohmmeter, measure resistance between VSV terminals. Resistance should be 30-34 ohms at 68°F (20°C). Check for continuity between each VSV terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.
6. Check for an open circuit in wiring harness between VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.

1. Disconnect EGR temperature sensor. Using ohmmeter, measure resistance between sensor terminals. If resistance is 2500 ohms or more, go to next step. If resistance is less than 2500 ohms, replace sensor.
2. Inspect circuits between EGR temperature sensor and ECM for short. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuits are okay, go to next step.
3. Access ECM behind right instrument panel speaker. Ensure ignition is off. Disconnect ECM E4 connector. Turn ignition on. Connect a jumper wire between ground and terminal No. 22 (Blue/White wire) at ECM E4 connector.
4. With jumper wire connected, Vacuum Switching Valve (VSV) is on. Air from port "G" should not exhaust from port "E". (Scheme 16) Disconnect jumper wire. Air from port "G" should exhaust from port "E". If valve operates correctly, check EGR valve. See SYSTEM/COMPONENT TESTS article. If VSV does not operate correctly, go to next step.
5. Remove EGR VSV. Air intake chamber may have to be removed to access VSV. Using ohmmeter, measure resistance between VSV terminals. Resistance should be 30-34 ohms at 68°F (20°C). Check for continuity between each VSV terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.
6. Check for an open circuit in wiring harness between VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.

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

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

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

1. Connect scan tester. (Scheme 9) Start and warm engine to normal operating temperature. Drive vehicle at 31-40 MPH for 5-10 minutes. Stop vehicle. Retrieve codes. See «SELF-DIAGNOSTIC SYSTEM»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-tests-wcodes).
2. If codes other than P0420 are present, diagnose and repair those codes first. If DTC P0420 is only displayed, check oxygen sensor. See SYSTEM/COMPONENT TESTS article. Repair as necessary. If oxygen sensors are okay, replace catalytic converter and retest.

DTC P0500 - VEHICLE SPEED SENSOR MALFUNCTION

VSS outputs a 4-pulse signal for every revolution of the rotor shaft, which is driven by transaxle output shaft. Signal is used by ECM to determine vehicle speed. DTC is set if there is no VSS signal to ECM while vehicle is being driven or if park/neutral switch is off. Possible causes are

1. Vehicle speed sensor.
2. Open or short circuit in VSS circuit.
3. Instrument cluster.
4. ECM.

1. Test drive vehicle and check operation of speedometer. If speedometer is not functioning correctly, see INSTRUMENT PANELS article. If speedometer is functioning correctly, go to next step.
2. Access ECM behind right instrument panel speaker. Ensure ignition is off. Disconnect cruise control ECU. Cruise control ECU is located on left side of steering column, behind instrument panel. Connector is a Gray 26-pin connector.
3. Shift gear selector to Neutral. Lift and support rear of vehicle. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 8 (Blue/White wire) at ECM E7 connector, while rotating rear wheels. (Scheme 12)
4. As rear wheels are rotated, voltage should pulse between zero and 9-14 volts. If voltage is as specified, replace ECM and retest. If voltage is not as specified, inspect Blue/White wire between instrument cluster and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.

DTC P0505 - IDLE AIR CONTROL (IAC) SYSTEM MALFUNCTION

The ECM operates IAC valve to perform idle-up and provide feedback for target idling speed. DTC is set when idle speed continues to vary greatly from target speed. Possible causes are

1. Idle Air Control (IAC) valve stuck or closed.
2. IAC valve circuit open or short.
3. Air intake leak.

Repair & Diagnosis

1. Inspect air induction system for leaks. Repair as necessary. If air induction system is okay, go to next step.
2. Ensure ignition is off. Access ECM behind right instrument panel speaker. Disconnect ECM E4 connector. Turn ignition on. Using DVOM, measure voltage between ground and IAC circuit terminals at ECM E4 connector. See IDENTIFYING IAC VALVE TERMINALS table. (Scheme 12) If all readings are 9-14 volts, go to step 4). If any reading is not 9-14 volts, go to next step. IDENTIFYING IAC VALVE TERMINALS Terminal No. (1) Wire Color 4 Yellow/Blue 5 Green/Yellow 6 Red/Black 7 Red/Green (1) Terminals are located in ECM E4 connector.
3. Check IAC valve. See SYSTEM/COMPONENT TESTS article. Replace IAC valve as necessary. If IAC valve is okay, check for an open or short in wiring harness between EFI main relay and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
4. Inspect IAC valve operation. See SYSTEM/COMPONENT TESTS article. Replace IAC valve as necessary. If valve is okay, replace ECM and retest.

DTC P0510 - CLOSED THROTTLE POSITION (CTP) SWITCH MALFUNCTION

The TP sensor is a variable resistor that monitors throttle opening. The ECM determines vehicle driving condition and adjusts air/fuel mixture accordingly. The CTP switch is located inside of TP sensor. If CTP switch is defective, TP sensor must be replaced. DTC is set if CTP switch does not turn on when vehicle is driven. Possible causes are

1. Open in CTP switch circuit.
2. CTP switch.
3. ECM.

Note. If DTC P0110, P0115 and P0120 are output simultaneously, ground (E2) circuit may be open.

1. Connect scan tester. (Scheme 9) Disconnect TP sensor connector. Connect a jumper wire between terminals No. 1 (Brown/Black wire) and No. 2 (Green/White wire) at TP sensor wiring harness connector. Turn ignition on. Using scan tester, read CTP switch signal. If CTP switch signal is on, replace TP sensor and retest. If CTP switch signal is off, go to next step.
2. Turn ignition off. Remove jumper wire. Access ECM behind right instrument panel speaker. Connect jumper wire between terminals No. 11 (Green/White wire) and No. 9 (Brown/Black wire) at ECM E5 connector. (Scheme 12) Turn ignition on. Using scan tester, read CTP switch signal. If CTP switch signal is on, check for an open in wiring harness between TP sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If CTP switch signal is off, replace ECM and retest.

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

DTC P1300 - IGNITER CIRCUIT MALFUNCTION

The ECM uses pick-up coil input signals to switch primary ignition circuit on and off. Primary circuit is turned off when ECM delivers a signal to igniter on the IGT wire, causing ignition coil to fire spark plug. After delivering a command to turn off primary circuit on IGT wire, the ECM monitors IGF circuit to ensure primary switching occurred. DTC is set when there is no IGF signal to ECM for 6 consecutive IGT signals during engine operation. Possible causes are

1. IGF or IGT open or short circuit from igniter to ECM.
2. Igniter.
3. ECM.

1. Check for spark at misfiring cylinder. See IGNITION CHECKS in «BASIC TESTING»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-basic-testing) article. If spark is present, go to next step. If spark is not present, go to step 4).
2. Check for open or short in IGF circuit between ECM and igniter. Igniter is located near left shock tower. See appropriate wiring diagram in WIRING DIAGRAMS. Repair as necessary. If circuit is okay, go to next step.
3. Disconnect igniter 5-pin Gray connector. Access ECM behind right instrument panel speaker. Turn ignition on. Measure voltage between ground and terminal No. 17 (Black/Yellow wire) at ECM E4 connector. (Scheme 12) If voltage is 4.5-5.5 volts, replace igniter. If voltage is not 4.5-5.5 volts, replace ECM and retest.
4. Check for an open or short in IGT circuit between ECM and igniter. See appropriate wiring diagram in WIRING DIAGRAMS. Repair as necessary. If circuit is okay, go to next step.
5. Access ECM behind right instrument panel speaker. Locate ECM E4 connector. (Scheme 12) Backprobing ECM connector, measure voltage between ground and terminal No. 23 (Black/Green wire) at ECM E4 connector while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM and retest.
6. Disconnect igniter 5-pin Gray connector. Backprobing ECM connector, measure voltage between ground and terminal No. 23 (Black/Green wire) at ECM E4 connector while cranking engine. If voltage is.1-4.5 volts, go to next step. If voltage is not.1-4.5 volts, replace ECM and retest.
7. Turn ignition on. Measure voltage between ground and terminal No. 3 (Black/Red wire) at igniter wiring harness connector. see scheme 9 If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair igniter power source circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
8. Check for an open or short in wiring harness between ignition switch and ignition coil, and between ignition coil and igniter. Repair as necessary. If wiring is okay, go to next step.
9. Check ignition coil. See IGNITION CHECKS described in «BASIC TESTING»(/toyota/land-cruiser/80-1995-1997/remont/testing-diagnostics/#engine-controls-basic-testing) article. Replace coil as necessary. If coil is okay, replace igniter.

DTC P1335 - CRANKSHAFT POSITION (CKP) SENSOR CIRCUIT

See DTC P0335 OR P1335 - CRANKSHAFT POSITION (CKP) SENSOR CIRCUIT test.

DTC P1500 - STARTER SIGNAL CIRCUIT MALFUNCTION

While engine is being cranked, battery voltage is applied to ECM terminal STA. Signal is mainly used to increase fuel injection volume for starting injection control and after-start injection control. DTC is set when ECM does not receive starter signal. Possible causes are

1. Starter signal open or short circuit.
2. Ignition switch or starter relay open or short circuit.
3. ECM.

Note. Scan tester diagnosis can only be attempted with Toyota scan tester operated in CHECK mode.

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

DTC P1600 - ECM BATT MALFUNCTION

Battery voltage is supplied to ECM BATT terminal (constant). DTC is set when open in back-up power source is detected. Possible causes are

1. Back-up power source open circuit.
2. ECM.

1. Turn ignition off. Access ECM behind right instrument panel speaker. Using DVOM, measure voltage between ground and terminal No. 2 (Red/Yellow wire) at ECM E7 connector. (Scheme 12) If voltage is 9-14 volts, replace ECM and retest. If voltage is not 9-14 volts, go to next step.
2. Remove and inspect EFI fuse. EFI fuse is located in engine compartment fuse box. Replace as necessary. If fuse is okay, inspect circuit between EFI fuse and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.

DTC P1605 - KNOCK CONTROL CPU MALFUNCTION

Knock sensors are located under intake manifold. Sensor generates voltage when engine block vibrates due to knocking. Possible cause is

1. ECM.

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

DTC P1780 - PARK/NEUTRAL POSITION (PNP) SWITCH

The PNP switch sends a signal to ECM when transmission is in Neutral or Park. This signal is used for air/fuel correction and for idle speed control. DTC is set under 2 conditions

1. When 2 or more switches are on simultaneously for "N", "2" and "L" position.
2. ECM is receiving an ON signal from PNP switch when vehicle is being operated for more than 30 seconds at 44 MPH or more (1500-2500 RPM).

1. PNP switch short circuit.
2. PNP switch.
3. ECM.

Note. Toyota scan tester can be used to confirm PNP switch.

1. Disconnect PNP switch connector. PNP switch is located at transmission where shifter select cable is mounted. Using ohmmeter, check continuity of switch terminals in specified positions. (Scheme 17)and (Scheme 18). Replace switch as necessary.
2. If switch is okay, access ECM behind glove box. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 22 (Black/White wire) at ECM E7 connector. (Scheme 12)
3. Voltage should be zero volts in "P" or "N" position. Voltage should be 9-14 volts in any other shift selector position. If all voltages measured are as specified, replace ECM and retest.
4. If any voltage is not as specified, check for an open or short in wiring harness between PNP switch and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.

Scheme 17

Scheme 18

See also:
• BASIC TESTING
• THEORY/OPERATION
• DATA LINK CONNECTOR NO
• ECM LOCATION
• RETRIEVING DIAGNOSTIC TROUBLE CODES
• CLEARING DIAGNOSTIC TROUBLE CODES
• DLC3 INSPECTION
• FREEZE-FRAME DATA
• TWO-TRIP DETECTION LOGIC
• DATA LINK CONNECTOR
• P0100
• P0110
• P0115
• P0120
• P0125
• P0130
• P0135
• P0171
• P0301
• P0325
• P0335
• P0340
• P0385
• P0401
• P0402
• P0500
• P0505
• P0510
• P1300
• P1335
• P1500
• P1600
• P1605
• P1780