Engine Controls - Tests W/codes Toyota Land Cruiser 70

INTRODUCTION

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

Note. Diagnostic Trouble Codes (DTC) will be referred to as trouble codes in this article.

SYSTEM OVERVIEW

The ECM monitors engine and transmission operation and contains a self-diagnostic system which stores diagnostic trouble code(s). Models utilize On-Board Diagnostics Generation II (OBD-II) standards. Federal law mandates this type of diagnostic system for all vehicles by 1996.

The goal of OBD-II regulation is to provide the vehicle with an on-board diagnostic system which is capable of continuously monitoring the efficiency of emissions 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 Lamp (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 trips, the MIL goes off, but diagnostic trouble codes remain recorded in ECM memory. Trouble codes may only be retrieved using an appropriate scan tool or Toyota/Lexus scan tool connected to new standardized Data Link Connector (DLC). The scan tool also provides freeze-frame data and can be used to clear codes.

TWO-TRIP DETECTION LOGIC

When a malfunction initially occurs, trouble code 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 Two-Trip Detection Logic.

Note. When road testing vehicle in Check Mode, the Two Trip Detection Logic will not function. Also, MIL will illuminate the first time a malfunction is detected.

DATA LINK CONNECTOR

OBD-II regulations (SAE J-1850) standardizes DLC configurations. DLC3 connector is located in fuse box at lower left of instrument panel. The terminal arrangement of connector complies with SAE J-1962 regulations. (Scheme 39)

Scheme 39

FREEZE-FRAME DATA

The ECM records engine operating condition (fuel system, calculated load, coolant temperature, fuel trim (mixture), engine speed, vehicle speed, etc.) with 1st malfunction ONLY. The information is ONLY for the 1st recorded failure, no matter if more than one code has been recorded. The freeze-frame data is only updated when all codes have been cleared, or a misfire or fuel-trim malfunction has occurred.

MIL OPERATION

The MIL illuminates with the ignition switch in the ON position, engine off (KOEO). If MIL does not illuminate, see MALFUNCTION INDICATOR LIGHT (MIL) INSPECTION under SELF-DIAGNOSTIC SYSTEM.

MALFUNCTION INDICATOR LIGHT (MIL) INSPECTION

Note. The Malfunction Indicator Light (MIL) on the instrument panel may also be referred to as CHECK ENGINE light. Inspect MIL to ensure it is operational and will come on if a trouble code is stored.

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 panel and wiring circuit between MIL and ECM. (Scheme 41)for ECM location. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article.
2. Start engine and ensure MIL goes off. If MIL remains on with engine running, a malfunction is detected. Proceed to «RETRIEVING TROUBLE CODES»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__retrieving-trouble-codes) under TESTING & REPAIR PROCEDURE.

TESTING & REPAIR PROCEDURE

The following check list of procedures is suggested to be followed to ensure correct diagnosis and repair

1. Record Customer Complaint Ensure all customer complaints or observations are recorded. Test drive vehicle with customer when necessary for malfunction verification.
2. Retrieve Trouble Codes Connect appropriate OBD-II scan tool. Retrieve codes and record any freeze-frame data. See «RETRIEVING TROUBLE CODES»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__retrieving-trouble-codes) .
3. Clear Trouble Codes Clear codes using scan tool. See «CLEARING TROUBLE CODES»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__clearing-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. See «RETRIEVING TROUBLE CODES»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__retrieving-trouble-codes)
6. Diagnose & Repair Trouble Codes Perform diagnosis and repair procedures as needed. See applicable DIAGNOSTIC TESTING. If no codes are present, proceed to the «TESTS W/O CODES»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).
7. Confirmation Procedure After repairs have been completed, clear all trouble codes. See «CLEARING TROUBLE CODES»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__clearing-trouble-codes) . Perform road test. Confirm that no trouble codes are present and all symptoms and/or complaints have been repaired.

RETRIEVING TROUBLE CODES

Note. Trouble codes may be retrieved using Toyota scan tester or On-Board Diagnostic (OBD-II) scan tester that complies with SAE standard J-1978.

Normal mode is used to retrieve trouble codes from Engine Control Module (ECM). Check mode is used to check for trouble codes when operating vehicle to simulate conditions in which trouble code 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.

Normal Mode Code Retrieval

1. Connect scan tool to Data Link Connector No. 3 (DLC3). (Scheme 39) Turn ignition on. Turn on scan tool. Retrieve any trouble codes stored in memory following scan tool instructions. See the «TROUBLE CODE IDENTIFICATION»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes) table.
2. Codes recorded may not have illuminated MIL. When certain malfunctions or trouble codes initially occur, they will be temporarily stored in ECM memory, but MIL will not illuminate.
3. The second time malfunction or trouble code is detected, MIL will illuminate, provided ignition is turned off and then back on after malfunction or trouble code was first detected. This process is referred to as Two Trip Detection Logic and only applies to most trouble codes.
4. Also record freeze-frame data. If using Toyota scan tool, ensure tool is in normal mode. CHECK MODE will erase all codes.

Note. When scan tester is switched from normal mode to check mode, all trouble codes and freeze-frame data will be erased. DO NOT switch modes until all trouble codes and freeze-frame data are recorded.

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. Connect scan tester to Data Link Connector (DLC) No. 3. (Scheme 39) 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 panel flashes. Start engine. Ensure MIL goes off. Try to simulate conditions of driveability complaint described by customer. NOTE: DO NOT turn ignition off until trouble codes and freeze-frame data are recorded. If ignition is turned off, scan tester will switch from check mode to normal mode and all trouble codes and freeze-frame data will be erased.
4. Record any trouble codes and freeze-frame data displayed for system diagnosis. See «TROUBLE CODE IDENTIFICATION»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. Information may be useful for determining conditions in which the malfunction occurs.

CLEARING TROUBLE CODES

Once repairs have been performed, codes must be cleared from ECM memory. Codes may be cleared by following methods

1. Scan tool (follow manufacturer's instructions).
2. Remove EFI fuse (15-amp) from engine compartment fuse box, near the battery, for 10 seconds or more to clear memory in ECM.
3. Disconnecting negative battery cable (memory for electronic components will be also be canceled).

TROUBLE CODE IDENTIFICATION

DLC NO. 3 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, proceed to step 2). If scan tester does not operate on another vehicle, problem is probably with scan tester.
2. Note location of DLC No. 3 (Fig. (Scheme 39) ) and its terminals (Fig. (Scheme 40) ). Ensure voltage and resistance are correct at specified terminals when checking between terminal on DLC No. 3 and body ground. See «DLC NO»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes). 3 VOLTAGE & RESISTANCE SPECIFICATIONS table. If voltage and resistance are not as specified, check wiring circuit. See the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article.

Note. Terminal No. 2 on DLC No. 3 provides pulse generation during information transmission from Engine Control Module (ECM).

DLC NO. 3 VOLTAGE & RESISTANCE SPECIFICATIONS

Scheme 40

Scheme 41

ECM LOCATION

SUMMARY

If no hard trouble codes are present, driveability symptoms exist or intermittent trouble codes exist, see the TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent procedures.

DIAGNOSTIC TESTING

Note. For component location (Scheme 41)

CODE 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. Code 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 Code P0100 is set. Possible causes are

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

Diagnosis & Repair

1. Connect scan tester to DLC3 connector. (Scheme 39) 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 439.0 gm/sec. once engine is at normal operating temperature, go to step 5).
2. Disconnect MAF harness connector. Ensure ignition is on. Using DVOM, measure voltage between terminal No. 1 and ground. (Scheme 42) If 9-14 volts is present, go to next step. If 9-14 volts is NOT present, inspect circuit between MAF harness connector and ECM. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed.
3. Access ECM behind right instrument panel speaker. Start engine. Backprobing ECM connector, check voltage between terminal VG and ground. (Scheme 43) 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 wiring diagram in «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If circuit is okay, replace MAF sensor and retest.
5. Access ECM behind right instrument panel speaker. Turn ignition off. Using ohmmeter, backprobe ECM harness connector. Check continuity between terminal E21 and ground. (Scheme 43) If continuity does NOT exist, replace ECM and retest. If continuity does exist, check for open circuit between MAF sensor and ECM. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If circuit is okay, replace MAF sensor.

Scheme 42

Scheme 43

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.

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

CODE P0110 - INTAKE AIR TEMPERATURE (IAT) SENSOR CIRCUIT

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

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

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

1. Connect scan tester to DLC3 connector. (Scheme 39) 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 harness connector. Using jumper wire, connect MAF harness connector terminals No. 3 and 4. (Scheme 42) Turn ignition on. Monitor IAT sensor temperature on scan tester.
3. If temperature displayed is 284°F (140°C), replace MAF sensor and retest. If temperature displayed is NOT 284°F (140°C), turn ignition off. Remove jumper wire. Access ECM behind right instrument panel speaker. Connect jumper wire between ECM terminals E2 and THA. (Scheme 43)
4. If temperature displayed on scan tester is 284°F (140°C) or more, inspect and repair circuits between MAF harness connector and ECM. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. If temperature displayed on scan tester is NOT 284°F (140°C) or more, replace ECM and retest.
5. Turn ignition off. Disconnect MAF sensor harness 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 harness connector E5. (Scheme 43) Turn ignition on. If temperature displayed is -40°F (-40°C), inspect and repair circuits between MAF sensor and ECM for short. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. If temperature displayed by scan tester is NOT -40°F (-40°C), replace ECM and retest.

CODE P0115 - COOLANT TEMPERATURE SENSOR (CTS) CIRCUIT

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

1. CTS sensor open or short circuit.
2. CTS sensor malfunction.
3. ECM malfunction.

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

1. Connect scan tester to DLC3 connector. (Scheme 39) Turn ignition on. Turn on scan tester. Monitor CTS 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 CTS sensor harness connector. CTS is located in thermostat housing. Using jumper wire, connect CTS harness connector terminals. Turn ignition on. Monitor CTS sensor temperature on scan tester.
3. If temperature displayed is 284°F (140°C), replace CTS sensor and retest. If temperature displayed is NOT 284°F (140°C), turn ignition off. Remove jumper wire. Access ECM behind right instrument panel speaker. Connect jumper wire between ECM terminals E2 and THW. (Scheme 43)
4. If temperature displayed on scan tester is 284°F (140°C) or more, inspect and repair circuits for open between CTS harness connector and ECM. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. If temperature displayed on scan tester is NOT 284°F (140°C) or more, replace ECM and retest.
5. Turn ignition off. Disconnect CTS sensor harness connector. Turn ignition on. If temperature displayed on scan tester is -40°F (-40°C), replace CTS 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 harness connector E5. (Scheme 43) Turn ignition on. If temperature displayed is -40°F (-40°C), inspect and repair circuits between CTS sensor and ECM for short. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. If temperature displayed by scan tester is NOT -40°F (-40°C), replace ECM and retest.

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

1. Coolant temperature sensor.
2. Cooling system.

If only Code P0116 is displayed, replace CTS and retest. If other codes are displayed, diagnose and repair those codes first and retest.

CODE P0120 - THROTTLE POSITION SENSOR (TPS) CIRCUIT MALFUNCTION

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

1. TPS sensor open or short circuit.
2. TPS sensor malfunction.
3. ECM malfunction.

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

1. Connect scan tester to DLC3 connector. (Scheme 39) 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 TPS harness connector. Turn ignition on. Using DVOM, measure voltage between harness connector terminal No. 1 and ground. (Scheme 44) If voltage measured is 4.5-5.5 volts, go to next step. If voltage is NOT 4.5-5.5 volts, go to step 8).
4. Turn ignition off. Using ohmmeter, measure resistance between TPS component connector terminals No. 1 and 4. Resistance should be 4.25-5.90 k/ohms. Measure resistance between terminals No. 2 and 4. Resistance should be.2-5.7 k/ohms with throttle fully closed and 2.0-10.2 k/ohms with throttle fully open.
5. If any resistances measured are NOT within specification, replace TPS. See the REMOVE/INSTALL/OVERHAUL article. If all resistances measured are within specification, connect TPS harness connector.
6. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals VTA and E2. (Scheme 43) Voltage should be.3-.8 volt with throttle fully closed and 3.2-4.9 volts with throttle fully open (WOT).
7. If voltages measured are within specification, replace ECM and retest. If voltages are NOT within specification, inspect VTA circuit for open or short. See the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed.
8. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals VCC and E2. (Scheme 43) Voltage should be 4.5-5.5 volts.
9. If voltage is within specification, inspect VCC circuit for open. If voltage is NOT within specification, replace ECM and retest.

Scheme 44

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

1. Throttle Position Sensor (TPS).

If only Code P0121 is displayed, replace TPS and retest. If other codes are displayed, diagnose and repair those codes first and retest.

CODE 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. Code 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. Oxygen sensor open or short circuit.
2. Heated oxygen sensor malfunction.

1. Connect scan tester to DLC3 connector. (Scheme 39) Start vehicle and warm engine to normal operating temperature. Turn on scan tester. Monitor each oxygen sensor. Snap accelerate engine 3 times. Sensors should indicate a rich signal (.45 volt or more).
2. If a rich signal is indicated for both sensors, replace ECM and retest. If either sensor does NOT display a rich signal, inspect circuits between ECM and suspect sensor for open or short circuits. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If circuits are okay, replace oxygen sensor and retest.

CODE P0130 - HEATED OXYGEN SENSOR (FRONT SENSOR) CIRCUIT

Code is set when front oxygen sensor 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 malfunction.

Test Drive Confirmation

1. Connect scan tester. (Scheme 39) If using Toyota scan tester, switch 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 wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If all circuits are okay, connect scan tester. (Scheme 39)
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 «CODE P0170»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__code-p0170-fuel-trim-malfunction) - FUEL TRIM MALFUNCTION.
3. If scan tester indicates other than in step 2), operate engine at 2500 RPM for 90 seconds. Monitor oxygen sensor voltage. If voltage constantly fluctuates in wide range (.3-.9 volts), repeat Test Drive Confirmation. If voltage does NOT fluctuate, or stays in narrow range, replace sensor and retest.

Code 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 heated oxygen sensor.

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

CODE P0135 - HEATED OXYGEN SENSOR (RIGHT SIDE, NO. 1) CIRCUIT

Code is set when either of the following conditions is present

1. Sensor heater current draw exceeds 2 amps, or voltage drop of circuit exceeds 5 volts.
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.

1. Access ECM harness connectors behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector. Measure voltage between terminals HT1, HT2, and ground. (Scheme 43) Voltage for each circuit should be 9-14 volts.
2. If voltage is within specification, replace ECM and retest. If voltage is NOT within specification, turn ignition off. Disconnect oxygen sensor harness connector. Using ohmmeter, measure resistance between sensor connector terminals No. 1 and 2. (Scheme 45)
3. If resistance is 11-16 ohms at 68°F (20°C), inspect circuits between ECM and sensor. See the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If resistance is NOT 11-16 ohms at 68°F (20°C), replace sensor and retest.

Scheme 45

Code is set when right side oxygen sensor voltage remains at .4-.5 volt during vehicle operation (25 MPH or more), once engine is at normal operating temperature. Possible cause is

1. Heated oxygen sensor.

1. If any other codes are displayed other than Code P0136, diagnose and repair those codes first. If only Code P0136 is displayed, inspect circuits between ECM and sensor for opens or shorts. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed.
2. If all circuits are okay, connect scan tester. (Scheme 39) 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 harness connection. Problem may be intermittent. If voltage does NOT respond correctly, replace sensor and retest.

CODE P0141 - HEATED OXYGEN SENSOR (REAR SENSOR) CIRCUIT

See CODE P0135 - HEATED OXYGEN SENSOR (FRONT SENSOR) CIRCUIT.

CODE P0170 - FUEL TRIM MALFUNCTION

Fuel trim refers to feedback compensation value compared against basic injection time. Fuel trim includes short-term and long-term fuel trim. Code is set when both short-term and long-term fuel trim are lean or rich beyond a certain value. Possible causes are

1. Air intake.
2. Fuel line pressure.
3. Injector blockage or leak.
4. Heated oxygen sensor malfunction.
5. Mass airflow sensor.
6. Coolant temperature sensor.

1. Inspect all air induction components. Repair as needed. Connect scan tester. (Scheme 39) 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 «CODE P0130»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__code-p0130-heated-oxygen-sensor) - HEATED OXYGEN SENSOR (FRONT SENSOR) CIRCUIT.
3. Inspect fuel pressure. See the «BASIC TESTING»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-basic-testing) article. Repair as needed. If fuel pressure is okay, inspect fuel injector performance. See the «SYSTEM/COMPONENT TESTS»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article. Replace as needed.
4. If all injectors are okay, inspect Mass Airflow (MAF) sensor and Coolant Temperature Sensor (CTS). See procedures in the «SYSTEM/COMPONENT TESTS»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article. Replace as needed. If both components are okay, inspect ignition system. See procedures in the «BASIC TESTING»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-basic-testing) article. Repair as needed. 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.

Code 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. Coolant Temperature Sensor (CTS).

1. Inspect spark plugs and ignition system. See procedures in the «BASIC TESTING»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-basic-testing) article. Repair as needed. If ignition system is okay, ensure ignition is off.
2. Access ECM harness connectors behind glove box. Turn ignition on. Using DVOM, backprobe ECM connector. Measure voltage between individual terminals No. #10, #20, #30, #40, #50, #60, and ground. (Scheme 43) If voltage is 9-14 volts for each circuit, go to step 4). If voltage is NOT 9-14 volts, go to next step.
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 wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If resistance is NOT 13.4-14.2 ohms, replace injector.
4. Inspect fuel pressure. See the «BASIC TESTING»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-basic-testing) article. Repair as needed. If fuel pressure is okay, inspect fuel injector performance. See the «SYSTEM/COMPONENT TESTS»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article. Replace as needed.
5. If all injectors are okay, inspect EGR system. See the «SYSTEM/COMPONENT TESTS»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article. Repair as needed. If EGR system is okay, inspect MAF sensor and CTS. See the SYSTEM/COMPONENT TESTS article. Replace as needed. If both components are okay, also inspect engine compression, valve clearance and valve timing. See the «BASIC TESTING»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-basic-testing) article.

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

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

See CODE P0300 - RANDOM MISFIRE DETECTED.

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.

See CODE P0300 - RANDOM/MULTIPLE MISFIRE DETECTED.

CODES P0325 & P0330 - KNOCK SENSOR NO. 1 (FRONT) & NO. 2 (REAR) CIRCUIT

Knock sensors are located on either side of cylinder block under intake manifold. Sensor generates voltage when engine block vibrates due to knocking. Code is set when there is no knock sensor signal to ECM with engine speed of 2000 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 E5 harness connector. (Scheme 43) Using ohmmeter, measure resistance between harness connector individual terminals KNK1, KNK2, and ground.
2. If infinite resistance is present, go to step 3). If infinite resistance is NOT present, disconnect applicable knock sensor harness connector. (Scheme 46) Measure resistance between sensor terminal and sensor housing. If infinite resistance exists, go to next step. If infinite does NOT exist, replace sensor.
3. Inspect circuit between sensor and ECM for open or short. Repair as needed. If circuit is okay, substitute suspect knock sensor with known good sensor. Clear codes. See «CLEARING TROUBLE CODES»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__clearing-trouble-codes). Retrieve codes. See «RETRIEVING TROUBLE CODES»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__retrieving-trouble-codes). If code is still present, replace ECM. If code is no longer present, replace sensor.

Scheme 46

CODE P0335 - 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 harness connector. Using ohmmeter, measure resistance between distributor connector terminals No. 1 and 4. (Scheme 47) Resistance should be 185-275 ohms (cold sensor), 240-32 5 ohms (hot sensor).
2. Replace distributor as needed. See procedures in the REMOVE/INSTALL/OVERHAUL article. If sensor is okay, inspect NE circuit between ECM and distributor for open or short. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed.
3. If circuit is okay, check sensor-to-signal plate air gap. See the REMOVE/INSTALL/OVERHAUL article. If air gap is okay, replace ECM and retest. If air gap is not within specification, replace distributor.

Scheme 47

CODE P0340 - CAMSHAFT POSITION (CMP) SENSOR CIRCUIT

The CMP sensors (2) are pick-up coils (G1 and G2 signals) mounted next to one tooth signal plates in distributor. Code is set when no engine running signal is received by ECM from sensor. Possible causes are

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

1. Disconnect distributor harness connector. Using ohmmeter, measure resistance between distributor connector terminals No. 2, 3 and 4. (Scheme 47) Resistance should be 185-275 ohms (cold sensor) or 240-325 ohms (hot sensor).
2. Replace distributor as needed. See procedures in the REMOVE/INSTALL/OVERHAUL article. If sensor is okay, inspect G1, G2 and G- circuits between ECM and distributor for open or short. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed.
3. If circuit is okay, check sensor-to-signal plate air gap. See the REMOVE/INSTALL/OVERHAUL article. If air gap is okay, replace ECM and retest. If air gap is not within specification, replace distributor.

CODE 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. Code 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 48) Using ohmmeter, measure resistance between component terminals No. 1 and 2. Resistance should be 1630-2740 ohms (cold sensor) or 2065-3225 ohms (hot sensor).
2. If resistance measured is NOT within specification, replace sensor. If resistance measured is within specification, inspect NE2 circuit between CKP sensor and ECM for open or short. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed.
3. If circuit is okay, inspect sensor installation and teeth of signal plate. Repair or replace as needed. If both sensor and signal plate are okay, replace ECM and retest.

Scheme 48

CODE 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 operated by ECM.

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

1. Coolant temperature below 140°F (60°C).
2. Vehicle under deceleration.
3. Light engine load.
4. Engine racing.

Code is set when EGR gas temperature sensor value does not exceed 72°F (40°C) above ambient air temperature 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 gas temperature sensor open circuit.
4. EGR vacuum hose disconnected.
5. ECM.

1. Connect scan tester. (Scheme 39) 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". May also be known as I/M flag. If COMPL is displayed on scan tester and MIL is not illuminated, system is normal. If INCPL is displayed and MIL is not illuminated, repeat test drive procedure.

Diagnosis & Repair (Toyota Scan Tester ONLY)

1. Connect scan tester. (Scheme 39) Turn ignition on. Read EGR gas temperature. Temperature should be 50°F (10°C). If temperature is within specification, go to step 6). If temperature is NOT within specification, go to next step. If temperature displayed is 37.6°F (3.1°C), there is an open EGR gas temperature sensor circuit.
2. Disconnect EGR gas temperature sensor harness connector. Sensor is mounted in manifold running from EGR valve to intake plenum. Connect jumper wire between harness connector terminals.
3. EGR gas temperature displayed should be 315.5°F (157.5°C). If temperature displayed is NOT within specification, go to next step. If temperature displayed is within specification, inspect sensor connectors and terminals. Repair as needed. If connectors are okay, replace sensor and retest.
4. Remove jumper wire. Turn ignition off. Access ECM behind right instrument panel speaker. Connect jumper wire between ECM harness connector terminals THG and E2. (Scheme 43) Turn ignition on. EGR gas temperature displayed should be 315.5°F (157.7°C).
5. If temperature displayed is within specification, inspect and repair open in circuits between ECM and EGR gas temperature sensor. If temperature displayed is NOT within specification, replace ECM and retest.
6. Inspect vacuum hoses. Repair as needed. If all hoses are okay, inspect VSV. On scan tester, select active test mode. Check operation of VSV when activated by scan tester. VSV is located on intake plenum.
7. Start and run engine. With system in OFF mode, air should flow from tube "E". (Scheme 49) With system in ON mode, air should NOT pass through valve. If valve operates correctly, go to step 11). If valve does NOT operate correctly, go to next step.
8. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 30-34 ohms at 68°F (20°C). Measure resistance between each terminal and body of valve. Resistance should be infinite. Replace VSV as needed.
9. Check VSV operation. Apply battery voltage to valve terminals. Air should NOT pass through valve. Remove battery voltage from valve terminals. Air should pass through valve. Replace as needed.
10. If valve meets all specifications in steps 8) and 9), inspect circuits between EGR VSV and ECM. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed.
11. Inspect EGR vacuum modulator. See procedures in the «SYSTEM/COMPONENT TESTS»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article. Replace as needed. Inspect EGR valve. See the SYSTEM/COMPONENT TESTS article. Replace as needed.
12. Ensure all components are connected. Inspect EGR gas temperature sensor. Start and run engine. Select active test mode on scan tester (EGR system ON). Run engine at 4000 RPM for 3 minutes. Monitor EGR gas temperature. Temperature should be 284°F (140°C) or more.
13. If temperature is NOT within specification, replace sensor. If temperature is within specification, replace ECM and retest.

Scheme 49

Diagnosis & Repair (OBD-II Scan Tester ONLY)

1. Disconnect EGR gas temperature sensor. Sensor is located on manifold between EGR valve and intake plenum. Using ohmmeter, measure resistance between sensor terminals. If resistance is 600 k/ohms or less, go to next step. If resistance is NOT 600 k/ohms or less, inspect sensor. See the «SYSTEM/COMPONENT TESTS»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article. Replace as needed.
2. Turn ignition on. Using DVOM, measure voltage between sensor 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 harness connector. Measure voltage between ECM terminals THG and E2. (Scheme 43) If voltage is 4.5-5.5 volts, inspect circuits between EGR gas temperature sensor and ECM for open. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If voltage is NOT 4.4-5.5 volts, replace ECM and retest.
4. Inspect all EGR system vacuum hoses. Replace as needed. Check operation of EGR Vacuum Switching Valve (VSV). Access ECM behind right instrument panel speaker. Ensure ignition is off. Disconnect E6 harness connector. Turn ignition on. Using jumper wire, connect ECM terminal EGR to ground.
5. VSV is located on intake plenum. With jumper wire connected, VSV is on. Air should NOT pass through valve. (Scheme 49) Disconnect jumper wire. Air should pass through valve. If valve operates correctly, go to step 9).
6. If valve does operate correctly, turn ignition off. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 30-34 ohms at 68°F (20°C). Measure resistance between each terminal and body of valve. Resistance should be infinite. Replace VSV as needed.
7. Check VSV operation. Apply battery voltage to valve terminals. Air should NOT pass through valve. Remove battery voltage from valve terminals. Air should pass through valve. Replace as needed.
8. If valve meets all specifications in steps 6) and 7), inspect circuits between EGR VSV and ECM. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed.
9. Inspect EGR vacuum modulator. See procedures in the «SYSTEM/COMPONENT TESTS»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article. Replace as needed. Inspect EGR valve. See the SYSTEM/COMPONENT TESTS article. Replace as needed.
10. Inspect EGR gas temperature sensor. Disconnect EGR gas temperature sensor harness connector. Start and run engine. Disconnect VSV connector for EGR. Run engine at 4000 RPM for 3 minutes. Measure resistance between sensor terminals after 3 minutes. Resistance should be 4.3 k/ohms or less.
11. If resistance is NOT within specification, replace sensor. If resistance is within specification, replace ECM and retest.

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

See CODE P0401 - INSUFFICIENT EXHAUST GAS RECIRCULATION (EGR) FLOW DETECTED. Code is set when EGR gas 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 gas temperature sensor short circuit.
5. ECM.

1. Connect scan tester. (Scheme 39) 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". May also be known as I/M flag. If COMPL is displayed on scan tester and MIL is not illuminated, system is normal. If INCPL is displayed and MIL is not illuminated, repeat test drive procedure.

1. Connect scan tester. (Scheme 39) Turn ignition on. Read EGR gas temperature. Temperature should be 302°F (150°C). If temperature is within specification, go to step 6). If temperature is NOT within specification, go to next step. If temperature displayed is 315.5°F (157.5°C), there is a short in EGR gas temperature sensor circuit.
2. Disconnect EGR gas temperature sensor harness connector. Sensor is mounted in manifold running from EGR valve to intake plenum.
3. EGR gas temperature displayed should be 37.6°F (3.1°C). If temperature displayed is NOT within specification, go to next step. If temperature displayed is within specification, replace sensor and retest.
4. Turn ignition off. Access ECM behind right instrument panel speaker. Disconnect ECM harness connector E4. (Scheme 43) Turn ignition on. EGR gas temperature displayed should be 37.6°F (3.1°C).
5. If temperature displayed is within specification, inspect and repair open in circuits between ECM and EGR gas temperature sensor. If temperature displayed is NOT within specification, replace ECM and retest.
6. Inspect VSV. On scan tester, select active test mode. Check operation of VSV when activated by scan tester. VSV is located on back of intake plenum.
7. Start and run engine. With system in OFF mode, air should NOT pass through valve. (Scheme 49) With system in ON mode, air should pass through valve. If valve operates correctly, go to step 11). If valve does NOT operate correctly, go to next step.
8. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 30-34 ohms at 68°F (20°C). Measure resistance between each terminal and body of valve. Resistance should be infinite. Replace VSV as needed.
9. Check VSV operation. Apply battery voltage to valve terminals. Air should NOT pass through valve. (Scheme 49) Remove battery voltage from valve terminals. Air should pass through valve. Replace as needed.
10. If valve meets all specifications in steps 8) and 9), inspect circuits for short between EGR VSV and ECM. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed.

1. Disconnect EGR gas temperature sensor. Sensor is located on manifold between EGR valve and throttle body. Using ohmmeter, measure resistance between sensor terminals. If resistance is approximately 2.5 k/ohms or less, go to next step. If resistance is NOT approximately 2.5 k/ohms or less, replace sensor.
2. Inspect circuits between EGR gas temperature sensor and ECM for short. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If circuits are okay, go to next step.
3. Check operation of EGR Vacuum Switching Valve (VSV). VSV located on back of intake plenum. See the «SYSTEM/COMPONENT TESTS»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article. Replace valve as needed. If valve is okay, inspect EGR valve. Replace as needed.
4. Inspect circuits for short between EGR VSV and ECM. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If circuits are 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. Code is set when all oxygen sensors have same amplitude after vehicle is driven for 5 minutes at 20-50 MPH. Possible causes are

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

1. Connect scan tester. (Scheme 39) Start and warm engine to normal operating temperature. Drive vehicle at 31-40 MPH for 5-10 minutes. Stop vehicle. Retrieve codes. See «RETRIEVING TROUBLE CODES»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__retrieving-trouble-codes).
2. If codes other than P0420 are present, diagnose and repair those codes first. If Code P0420 is only displayed, inspect oxygen sensor circuits. See «CODE P0130»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes__code-p0130-heated-oxygen-sensor) - HEATED OXYGEN SENSOR (RIGHT SIDE, NO. 1) CIRCUIT. Repair systems as needed. If oxygen sensor circuits and sensors are okay, replace catalytic converter and retest.

CODE P0500 - VEHICLE SPEED SENSOR MALFUNCTION

No. 1 Vehicle Speed Senor (VSS), driven by transfer case, outputs a signal to combination meter. Combination meter converts signal to a more precise waveform for ECM. Code is set when ECM does not detect any signal while vehicle is in motion. Possible causes are

1. No. 1 VSS open or short circuit.
2. No. 1 VSS failure.
3. Combination meter.
4. ECM.

1. Test drive vehicle and check operation of speedometer. If speedometer is not functioning correctly, see the INSTRUMENT PANEL article in the ACCESSORIES/SAFETY EQUIPMENT section. 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 color is Gray (26-pin).
3. Shift gear selector to Neutral. Lift and support rear of vehicle. Turn ignition on. Using DVOM, measure voltage between terminal SPD and ground, while rotating rear wheels. (Scheme 43)
4. As rear wheels are rotated, voltage should pulse between zero and 9-14 volts. If voltage is within specification, replace ECM and retest. If voltage is NOT within specification, inspect SPD circuit between combination meter and ECM. Repair as needed.

CODE P0505 - IDLE AIR CONTROL (IAC) SYSTEM MALFUNCTION

The ECM operates the IAC valve (stepper motor) to control idle speed by regulating air by-passing the throttle valve. Code 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. A/C signal open or short circuit.
4. Air intake leak.

Repair & Diagnosis

1. Inspect air induction system for leaks. Repair as needed. If air induction system is okay, access ECM behind instrument panel right speaker. Ensure ignition is off. Disconnect E4 harness connector. (Scheme 43)
2. Turn ignition on. Using DVOM, measure voltage between individual terminals ISC1, ISC2, ISC3, ISC4, and ground. Voltage for each circuit should be 9-14 volts. If voltage for all circuits are within specification, go to step 5). If voltage for any circuit is NOT within specification, go to next step.
3. Disconnect IAC valve harness connector. IAC valve is next to TPS on throttle body. Using ohmmeter, check resistances between specified IAC valve terminals. (Scheme 50) See «IAC RESISTANCE»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. IAC RESISTANCE Terminal No. Ohms 1 & 2 10-30 2 & 3 10-30 4 & 5 10-30 5 & 6 10-30
4. If all circuit resistances measured are within specification, inspect circuits between EFI main relay and IAC valve, and IAC valve and ECM for opens or shorts. Repair as needed. If any resistance measured is not within specification, replace IAC valve. NOTE: If using Toyota scan tester, operate IAC valve in active test mode to check valve operation.
5. Check IAC valve operation. Remove IAC valve. Using vehicle battery and 6 jumper wires, connect 2 positive leads to valve terminals No. 2 and 5. (Scheme 50) In the following order, connect negative leads to terminals No. 4, 1, 6, and then 3. Valve plunger should move in outward direction.
6. Disconnect all leads from valve connector. Connect 2 positive leads to valve terminals No. 2 and 5. (Scheme 50) In the following order, connect negative leads to terminals No. 3, 6, 1, and then 4. Valve plunger should move in inward direction.
7. If valve operates as specified in previous steps 5) and 6), replace ECM and retest. If valve does NOT operate correctly, replace IAC valve.

Scheme 50

CODE P0510 - CLOSED THROTTLE POSITION SWITCH MALFUNCTION

Built into Throttle Position Sensor (TPS), the closed throttle position switch turns off whenever the throttle position is NOT fully closed. Code is set when ECM never receives a ON signal from switch. Possible causes are

1. Closed throttle position switch open circuit.
2. Closed throttle position switch.
3. ECM.

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

1. Connect scan tester. (Scheme 39) Disconnect TPS harness connector. Using jumper wire, connect wire to TPS harness connector terminals No. 1 and 2. (Scheme 44)
2. Turn ignition on. Read CTP switch signal on scan tester. If CTP switch signal displayed is ON, replace TPS and retest. If signal displayed is OFF, go to next step.
3. Turn ignition off. Remove jumper wire. Access ECM behind right instrument panel speaker. Connect jumper wire between ECM connector terminals IDL and E2. (Scheme 43) Turn ignition on. Read CTP switch signal on scan tester. If CTP switch signal displayed is ON, inspect circuits between TPS and ECM. Repair as needed. If signal displayed is OFF, replace ECM and retest.

1. Ensure ignition is off. Disconnect TPS harness connector. Turn ignition on. Using DVOM, measure voltage between terminals No. 1 and 2. (Scheme 44) If voltage is 9-14 volts, replace TPS and retest. If voltage is NOT 9-14 volts, go to next step.
2. Turn ignition off. Inspect circuits between TPS and ECM for open. Repair as needed. If circuits are okay, replace ECM and retest.

CODE P1300 - IGNITOR 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 ignitor on the IGT wire, causing ignition coil to fire spark plug. After delivering a command to turn off primary circuit on IGT wire, the ECM monitors IGF circuit to ensure primary switching occurred. Code is set when 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 ignitor to ECM.
2. Ignitor.
3. ECM.

1. Inspect for spark at plugs. Remove plug wire from individual spark plug. Remove spark plug and insert into wire. Disconnect appropriate injector harness connector. Ground spark plug and crank engine. Ensure spark is present.
2. If spark does not exist, go to step 5). If spark does exist, inspect IGF circuit between ignitor and ECM for short or open. (Scheme 43)and (Scheme 51). See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article.
3. Repair as needed. If circuit is okay, disconnect ignitor connector. Ignitor is mounted to left inner fender, on left side of brake master cylinder. Access ECM behind instrument panel right speaker. Turn ignition on. Using DVOM, backprobe ECM connector.
4. Measure voltage between terminal IGF and ground. (Scheme 43) If voltage is 4.5-5.5 volts, replace ignitor and retest. If voltage is not 4.5-5.5 volts, replace ECM and retest.
5. Access ECM behind instrument panel right speaker. Turn ignition on. Using DVOM, backprobe ECM connector. Measure voltage between terminal IGT of ECM connector and ground, while cranking engine. Voltage should be.5-1.0 volt.
6. If voltage is within specification, go to next step. If voltage for any circuit is NOT within specification, go to step 10).
7. Disconnect ignitor connector. Ignitor is mounted to left inner fender, on left side of brake master cylinder. Measure voltage between ignitor harness connector terminal No. 3 and ground. (Scheme 51) Turn ignition switch to ON position. Voltage should be 9-14 volts. Turn ignition switch to START position. Voltage should be 9-14 volts.
8. If voltage is NOT within specification, inspect ignitor power supply circuit. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If voltage is within specification, inspect circuit between ignition switch and coil, and coil and ignitor for open or short. Repair as needed.
9. If circuits are okay, inspect ignition coil. See the «BASIC TESTING»(/toyota/land-cruiser/70-1984-2007/remont/testing-diagnostics/#engine-controls-basic-testing) article. Replace as needed. If coil is okay, replace ignitor and retest.
10. Access ECM behind instrument panel right speaker. Turn ignition on. Using DVOM, backprobe ECM connector. Ensure ignitor connector is disconnected. Measure voltage between terminal IGT of ECM connector and ground, while cranking engine. (Scheme 43) Voltage should be.5-1.0 volt for each circuit.
11. If voltage is within specification, replace ignitor and retest. If voltage is NOT within specification, inspect IGT circuit between ignitor and ECM for open or short. Repair as needed. If circuit is okay, replace ECM and retest.

Scheme 51

See CODE P0335 - CRANKSHAFT POSITION (CKP) SENSOR "A" CIRCUIT. Code is set when ECM receives no CKP sensor signal with engine speed of 1000 RPM or more. Possible causes are

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

See CODE P0335 - CRANKSHAFT POSITION (CKP) SENSOR "A" CIRCUIT.

CODE 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. Code is set when ECM does not receive starter signal. Possible causes are

1. Starter signal open or short circuit.
2. ECM.

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

1. Connect Toyota scan tester. (Scheme 39) Turn ignition and scan tester on. Read STA signal on scan tester. 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 correct as shown, inspect all applicable connectors. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Malfunction may be intermittent.
3. If STA signal is NOT as specified in step 2), inspect circuit between starter relay and ECM for open. See wiring diagram in the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed. If circuit is okay, replace ECM and retest.

CODE P1600 - ECM BATT MALFUNCTION

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

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

1. Ensure ignition is off (LOCK position). Access ECM behind right instrument panel speaker. Using DVOM, measure voltage between BATT terminal of ECM connector and ground. (Scheme 43) If voltage is 9 -14 volts, replace ECM and retest. If voltage is NOT 9-14 volts, go to next test.
2. Remove and inspect EFI fuse. EFI fuse is located in engine compartment fuse box. Replace as needed. If fuse is okay, inspect circuit between EFI fuse and ECM. See the «WIRING DIAGRAMS»(/toyota/land-cruiser/70-1984-2007/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. Repair as needed.

CODE P1605 - KNOCK CONTROL CPU MALFUNCTION

See CODES P0325 & P0330 - KNOCK SENSOR NO. 1 (FRONT) & NO. 2 (REAR) CIRCUIT. Code is set when ECM is detected to be faulty in regard to knock control. ECM is the only possible cause.

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

CODE P1780 - PARK/NEUTRAL POSITION (PNP) SWITCH

The PNP switch sends a signal to ECM when transmission is in Neutral or Park position. This signal is used for air/fuel correction and for idle speed control. Code 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 harness connector. PNP switch is located at transmission where shifter select cable is mounted. Using ohmmeter, check continuity of switch terminals in specified positions. (Scheme 52)and (Scheme 53). Replace as needed.
2. If switch is okay, access ECM behind right instrument panel speaker. Turn ignition on. Using DVOM, measure voltage between terminal NSW and ground. (Scheme 43)
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 within specification, replace ECM and retest.
4. If any voltages measured are NOT within specification, inspect circuit between PNP switch and ECM for open or short. Repair as needed.

Scheme 52

Scheme 53

See also:
• TESTS W/O CODES
• WIRING DIAGRAMS
• BASIC TESTING
• SYSTEM/COMPONENT TESTS
• MALFUNCTION INDICATOR LIGHT (MIL) INSPECTION
• RETRIEVING TROUBLE CODES
• CLEARING TROUBLE CODES
• TROUBLE CODE IDENTIFICATION
• P0100
• P0110
• P0115
• P0120
• P0125
• P0130
• P0135
• P0141
• P0170
• P0301
• P0325
• P0335
• P0340
• P0401
• P0402
• P0500
• P0505
• P0510
• P1300
• P1500
• P1600
• P1605
• P1780