Engine Controls - System/component Tests - 2.4L: Other Toyota Tacoma I

Power & Ground Circuits

For testing of Engine Control Module (ECM) power and ground circuits, see PIN VOLTAGE CHARTS - 2.4L article. See ECM LOCATION table for identifying ECM mounting locations.

ECM LOCATION

AIRFLOW METER

Note. Airflow meter may be referred to as Mass Airflow (MAF) meter.

1. Airflow meter resistance specification is not available from manufacturer at time of publication. Airflow meter is located between air intake hose and the upper cap on air cleaner assembly.
2. To check airflow meter operation, ensure electrical connector is installed on airflow meter. Connect voltmeter leads to proper terminals on airflow meter with electrical connector installed. (Scheme 13) Turn ignition on.
3. Apply air into hole on rear of airflow meter and note voltage reading. (Scheme 13) While air is being applied, voltage reading should fluctuate. Replace airflow meter if voltage reading does not fluctuate. Remove voltmeter.

Scheme 13

CAMSHAFT POSITION SENSOR

Camshaft position sensor is a pick-up coil located in the distributor. For checking of pick-up coil, see PICK-UP COIL RESISTANCE and PICK-UP COIL AIR GAP under IGNITION CHECKS (DISTRIBUTOR TYPE IGNITION SYSTEM) in BASIC TESTING - 2.4L article.

CRANKSHAFT POSITION SENSOR

For testing crankshaft position sensor, see CRANKSHAFT POSITION SENSOR under IGNITION CHECKS (DISTRIBUTOR TYPE IGNITION SYSTEM) in BASIC TESTING - 2.4L article.

EGR GAS TEMPERATURE SENSOR

1. Remove EGR gas temperature sensor. EGR gas temperature sensor is located near EGR valve. Place threaded end of EGR gas temperature sensor and thermometer in container of oil.
2. Attach ohmmeter between electrical terminals on EGR gas temperature sensor. Heat oil and note resistance at specified temperature. See «EGR GAS TEMPERATURE SENSOR RESISTANCE»(ref-22458-S30739532112001010300000) table. Replace EGR gas temperature sensor if resistance is not within specification. Reinstall EGR gas temperature sensor.

EGR GAS TEMPERATURE SENSOR RESISTANCE

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

1. Ensure ignition is off. Disconnect electrical connector from ECT sensor. See «ENGINE COOLANT TEMPERATURE (ECT) SENSOR LOCATION»(ref-22458-S02367974522001010300000) table. To verify wire colors for proper sensor identification, see appropriate wiring diagram in «WIRING DIAGRAMS - 2.4L»(ref-22460) article. NOTE: The ECT sensor may be also identified using appropriate illustration in «THEORY/OPERATION - 2.4L»(ref-22459) article.
2. Drain cooling system and remove ECT sensor. Place probe end of ECT sensor and thermometer in container of water. Attach ohmmeter between electrical terminals on ECT sensor. Heat water and note that resistance is within specification in relation to temperature. (Scheme 14) Replace ECT sensor if resistance is not within specification.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR LOCATION

Scheme 14

HEATED OXYGEN SENSOR

See OXYGEN SENSOR under ENGINE SENSORS & SWITCHES.

INTAKE AIR TEMPERATURE SENSOR

1. Ensure ignition is off. Disconnect electrical connector from intake air temperature sensor. Intake air temperature sensor is located on top cover of air filter housing. NOTE: Intake air temperature sensor may be also identified using appropriate illustration in «THEORY/OPERATION - 2.4L»(ref-22459) article.
2. Remove intake air temperature sensor. Place threaded end of intake air temperature sensor and thermometer in container of water. Attach ohmmeter between electrical terminals on intake air temperature sensor.
3. Heat water and note that resistance is within specification in relation to temperature. (Scheme 14) Replace intake air temperature sensor if resistance is not within specification.

KNOCK SENSOR

Note. Knock sensor may also be referred to as knock sensor No. 1.

1. Knock sensor is located on side of the cylinder block. (Scheme 15) Remove knock sensor from cylinder block before testing. See KNOCK SENSOR under ENGINE SENSORS & SWITCHES in «REMOVE/INSTALL/OVERHAUL - 2.4L»(ref-22464) article.
2. Using ohmmeter, check that no continuity exists between electrical terminal on knock sensor and body of knock sensor. Replace knock sensor if continuity exists.

Scheme 15

OXYGEN SENSOR

1. Two heated oxygen sensors are used. One heated oxygen sensor is on exhaust pipe before catalytic converter. This oxygen sensor is referred to as the No. 1 or front oxygen sensor. Another heated oxygen sensor is located on exhaust pipe behind catalytic converter. This oxygen sensor is referred to as the No. 2 oxygen sensor or the rear oxygen sensor.
2. If problem exists with heated oxygen sensor, a diagnostic trouble code will be stored in Engine Control Module (ECM). For diagnostic trouble code diagnosis, see «TESTS W/CODES - 2.4L»(ref-22461) article.
3. To test the heater on the oxygen sensor, disconnect electrical connector from appropriate oxygen sensor. Using ohmmeter, check resistance between terminals +B and HT. (Scheme 16)and (Scheme 17). Replace oxygen sensor if resistance is not 5-7 ohms at 68°F (20°C) on No. 1 oxygen sensor or 11-16 ohms at 68°F (20°C) on No. 2 oxygen sensor.

Scheme 16

Scheme 17

A/T

If problem exists with Park/Neutral Position (PNP) switch or circuit, a diagnostic trouble Code P1780 will be stored in the Engine Control Module (ECM). For diagnostic trouble code diagnosis, see TESTS W/CODES - 2.4L article.

1. Disconnect electrical connector from Park/Neutral Position (PNP) switch. The PNP switch is mounted on side of transmission/transaxle. Note terminal identification. (Scheme 18)
2. Using ohmmeter, check for continuity between specified terminals with shift lever in proper positions. See «PARK/NEUTRAL POSITION SWITCH SPECIFICATIONS»(ref-22458-S23979468272001010300000) table. If proper continuity does not exist, adjust or replace switch as necessary.

PARK/NEUTRAL POSITION SWITCH SPECIFICATIONS

Scheme 18

PICK-UP COILS

Pick-up coil may also be referred to as a camshaft position sensor. For checking of pick-up coil, see PICK-UP COIL RESISTANCE and PICK-UP COIL AIR GAP under IGNITION CHECKS (DISTRIBUTOR TYPE IGNITION SYSTEM) in BASIC TESTING - 2.4L article.

THROTTLE POSITION (TP) SENSOR

1. Ensure ignition is off. Disconnect electrical connector from TP sensor on throttle body. Note terminal identification on TP sensor. (Scheme 19)
2. Apply vacuum to throttle opener. Insert specified thickness feeler gauge between throttle stop screw and throttle lever, and check resistance or continuity. See «TP SENSOR RESISTANCE SPECIFICATIONS»(ref-22458-S00484283992001010300000) table. Replace or adjust throttle position sensor if not within specification.

TP SENSOR RESISTANCE SPECIFICATIONS

Scheme 19

VEHICLE SPEED SENSOR

1. Vehicle speed sensor is located on rear of combination meter in instrument cluster. Connect ohmmeter between terminals "A" and "B" on rear of instrument cluster. (Scheme 20)or (Scheme 21).
2. Rotate speedometer cable shaft and note reading. Ohmmeter should deflect from continuity to no continuity 4 times per speedometer cable shaft revolution. Replace speedometer if reading does not deflect as specified.

Scheme 20

Scheme 21

CIRCUIT OPENING RELAY

1. Ensure ignition is off. Remove circuit opening relay. See «CIRCUIT OPENING RELAY LOCATION»(ref-22458-S38193285082001010300000) table. (Scheme 22) CIRCUIT OPENING RELAY LOCATION Application Relay Location 2.4L Behind Lower Instrument Panel Cover, Next To Driver's Side Of Steering Column
2. To check circuit opening relay continuity, use ohmmeter to check continuity between specified terminals. (Scheme 23)
3. To check circuit opening relay operation, apply battery voltage and ground to relay and use ohmmeter to check continuity between specified terminals. (Scheme 23) Replace circuit opening relay if defective.

Scheme 22

Scheme 23

EFI MAIN RELAY

Note. EFI main relay may also be referred to as EFI relay.

1. Ensure ignition is off. Remove EFI main relay. See «EFI MAIN RELAY LOCATION»(ref-22458-S12300965922001010300000) table. NOTE: The EFI main relay may also be identified using appropriate illustration in «THEORY/OPERATION - 2.4L»(ref-22459) article. EFI MAIN RELAY LOCATION Application Location 2.4L In Fuse/Relay Box Near Driver's Side Front Corner Of Engine Compartment, Just Behind The Battery
2. To check EFI main relay continuity, use ohmmeter to check continuity between specified terminals. (Scheme 24)
3. To check EFI main relay operation, apply battery voltage and ground to relay and use ohmmeter to check continuity between specified terminals. (Scheme 24) Replace EFI main relay if defective.

Scheme 24

See CIRCUIT OPENING RELAY under RELAYS.

See EFI MAIN RELAY under RELAYS.

Fuel Pump Pressure

For fuel pump pressure testing, see BASIC TESTING - 2.4L article.

Fuel Injectors

1. Ensure ignition is off. Disconnect electrical connector at fuel injector. Using ohmmeter, check resistance between electrical terminals on fuel injector. Replace fuel injector if resistance is not within specification. See «FUEL INJECTOR RESISTANCE»(ref-22458-S04007303142001010300000) table.
2. To check fuel injector volume, remove fuel injector. See FUEL RAILS & FUEL INJECTORS under FUEL SYSTEM in «REMOVE/INSTALL/OVERHAUL - 2.4L»(ref-22464) article. Disconnect fuel hose from fuel filter and use Delivery Hose (09268-41046) to install fuel injector on fuel filter. (Scheme 25) NOTE: Fuel injector is connected between fuel pressure regulator on the delivery pipe and the fuel filter.
3. Place fuel injector into a clean graduated container. Place vinyl tube on end of fuel injector to prevent fuel spillage.
4. Use scan tool to operate the fuel pump to pressurize the fuel system. See FUEL PRESSURE under FUEL SYSTEM in «BASIC TESTING - 2.4L»(ref-22456) article. NOTE: Fuel pump may also be operated to pressurize fuel system by applying battery voltage to electrical terminals on fuel pump. For operating of fuel pump, see FUEL PUMP RESISTANCE & OPERATION under «FUEL DELIVERY»(ref-22458-S04549108892001010300000) under FUEL SYSTEM.
5. Connect Fuel Injector Tester (09842-30070) to fuel injector for 15 seconds. (Scheme 26) Measure fuel injector volume. Test each fuel injector 2-3 times. Replace fuel injector if fuel injector volume is not within specification. See «FUEL INJECTOR VOLUME SPECIFICATIONS»(ref-22458-S35202716532001010300000) table. NOTE: Ensure difference between fuel injector volume on all fuel injectors is within specification. See «FUEL INJECTOR VOLUME SPECIFICATIONS»(ref-22458-S35202716532001010300000) table.
6. Disconnect fuel injector tester. Ensure fuel leakage from end of fuel injector is one drop or less in specified time. See «FUEL INJECTOR LEAKAGE SPECIFICATIONS»(ref-22458-S27749959242001010300000) table. Replace fuel injector if leakage exceeds specified amount.

FUEL INJECTOR RESISTANCE - Ohms @ 68°F (20°C)

FUEL INJECTOR VOLUME SPECIFICATIONS

FUEL INJECTOR LEAKAGE SPECIFICATIONS

Scheme 25

Scheme 26

Fuel Cut System

1. When testing fuel cut system, engine RPM must be monitored using scan tool. Connect scan tool to data link connector No. 3 for monitoring engine RPM. For connecting of scan tool, see appropriate application under IDLE SPEED & MIXTURE in «ADJUSTMENTS - 2.4L»(ref-22457) article.
2. Start and warm engine to normal operating temperature. Ensure the A/C and all accessories are off. Gradually increase engine RPM to maintain at least specified engine speed. See «FUEL CUT SYSTEM TESTING SPECIFICATIONS»(ref-22458-S11432368382001010300000) table. FUEL CUT SYSTEM TESTING SPECIFICATIONS Application Engine RPM 2.4L 3500
3. Using stethoscope, check for fuel injector operating sound. Ensure when throttle lever is released, fuel injector stops operating momentarily and then resumes operating (fuel return RPM).
4. Ensure fuel return RPM is within specification. See «FUEL CUT SYSTEM SPECIFICATIONS»(ref-22458-S38830690072001010300000) table. Shut engine off. Remove test equipment.

FUEL CUT SYSTEM SPECIFICATIONS (1)

IDLE AIR CONTROL (IAC) VALVE

1. Warm engine to normal operating temperature. Ensure idle speed is within specification. See IDLE SPEED & MIXTURE in «ADJUSTMENTS - 2.4L»(ref-22457) article.
2. Apply parking brake and place transmission/transaxle in Neutral. Install Jumper Wire (SST 09843-18020) between terminals TE1 and E1 on data link connector No. 1. (Scheme 27) Start engine and note RPM. NOTE: Data link connector No. 1 is located in engine compartment. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 2) to step 4). No test procedures have been omitted.
3. Engine RPM should increase to specified RPM for 5 seconds, and then return to idle. See «IAC VALVE ENGINE SPEED TESTING SPECIFICATIONS»(ref-22458-S41378006962001010300000) table. IAC VALVE ENGINE SPEED TESTING SPECIFICATIONS Application Engine RPM 2.4L 1000-1500
4. If engine RPM is not as specified, test IAC valve resistance and operation. If engine RPM is within specification, remove jumper wire. Turn ignition off.
5. To test IAC valve resistance, ensure ignition is off. Disconnect electrical connector from IAC valve. IAC valve is located on lower area of throttle body. Using ohmmeter, check resistance between terminal +B and each remaining terminal. (Scheme 28)
6. Replace IAC valve if resistance is not within specification. See «IAC VALVE RESISTANCE SPECIFICATIONS»(ref-22458-S31645595392001010300000) table. IAC VALVE RESISTANCE SPECIFICATIONS Application Ohms Cold (1) 17.0-24.5 Hot (2) 21.5-28.5 (1) Cold is with temperature of 14-122°F (-10 - 50°C). (2) Hot is with temperature of 122-212°F (50-100°C).
7. To test IAC valve operation, remove IAC valve from throttle body. Connect positive battery terminal to +B terminal on IAC valve. (Scheme 29) Connect negative battery cable to proper terminal and ensure valve opens and closes. (Scheme 29) Replace IAC valve if defective.
8. If IAC valve resistance is within specification and operates correctly, check wiring circuit between Engine Control Module (ECM) and IAC valve. See ECM LOCATION table. See appropriate wiring diagram in «WIRING DIAGRAMS - 2.4L»(ref-22460) article.

ECM LOCATION

Scheme 27

Scheme 28

Scheme 29

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING - 2.4L article.

See KNOCK SENSOR under ENGINE SENSORS & SWITCHES.

1. Remove EGR check valve. see scheme 21 Apply air pressure on Orange-colored side of EGR check valve. Air should flow through EGR check valve.
2. Apply air pressure on Black-colored side of EGR check valve. Air should not flow through EGR check valve. Replace EGR check valve if defective.

EGR (EXHAUST GAS RECIRCULATION) GAS TEMPERATURE SENSOR

See EGR GAS TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES.

EGR VACUUM MODULATOR

Note. When testing EGR vacuum modulator, it may be necessary to monitor engine RPM by using scan tool. For scan tool connections, see IDLE SPEED & MIXTURE in ADJUSTMENTS - 2.4L article.

1. Mark vacuum hose locations and disconnect vacuum hoses from EGR vacuum modulator. see scheme 21 Block ports "P" and "R" on EGR vacuum modulator. see scheme 19 NOTE: Ports "P" and "R" are the double ports on side of EGR vacuum modulator. Port "Q" is single port on side of EGR vacuum modulator.
2. Apply air pressure to port "Q". see scheme 19 Air should flow freely through air filter side of EGR vacuum modulator.
3. Start and operate engine at specified RPM. See «EGR VACUUM MODULATOR TESTING SPECIFICATIONS»(ref-22458-S05459859672001010300000) table. Repeat test procedures in steps 1) and 2). Strong resistance of airflow should be felt with engine at specified RPM. Replace EGR vacuum modulator if strong resistance is not felt. Reconnect vacuum hoses to proper locations.

EGR VACUUM MODULATOR TESTING SPECIFICATIONS

EGR VACUUM SWITCHING VALVE (VSV)

Note. When testing EGR VSV, it may be necessary to use proper illustration to determine component location. see scheme 21

1. Disconnect electrical connector from EGR VSV. See «EGR VSV LOCATIONS»(ref-22458-S03963959202001010300000) table. Using ohmmeter, check that continuity exists between electrical terminals on EGR VSV and that resistance is within specification. See «EGR VSV RESISTANCE SPECIFICATIONS»(ref-22458-S32255523282001010300000) table. Replace EGR VSV if no continuity exists or resistance is not within specification.
2. Ensure no continuity exists between each electrical terminal and the body of EGR VSV body. Replace EGR VSV if continuity exists between electrical terminal and the body of EGR VSV.
3. To test EGR VSV operation, apply air pressure to port "E". Ensure no air flows from port "F". Perform STEP 1. (Scheme 30) Apply battery voltage and ground to electrical terminals on EGR VSV.
4. Apply air pressure to port "E". Ensure air flows from port "F". Perform STEP 2. (Scheme 30) Replace EGR VSV if defective. Reinstall EGR VSV.

EGR VSV LOCATIONS

EGR VSV RESISTANCE SPECIFICATIONS

Scheme 30

FUEL EVAPORATION SYSTEM

Note. Fuel evaporation systems contain different components depending on application. see scheme 21 When testing fuel evaporation system components, it may be necessary to use proper illustration to determine component location.

Charcoal Canister

1. Remove charcoal canister. Check for clogged filter and/or stuck check valve by applying light air pressure to port "A". (Scheme 31) Ensure air flows freely from other ports on charcoal canister.
2. Apply light air pressure to port "B". (Scheme 31) Ensure air does not flow from port "A", but flows freely from port "C". Replace charcoal canister if defective.
3. To clean charcoal canister filter, apply 43 psi (3 kg/cm 2 ) air pressure to port "A" while holding port "B" closed. Air should flow from port "C". Ensure no activated carbon comes out of charcoal canister. DO NOT attempt to wash out charcoal canister.

Scheme 31

EVAP Vacuum Switching Valve

1. Remove EVAP Vacuum Switching Valve (VSV). See «EVAP VSV LOCATION»(ref-22458-S40028086252001010300000) table. see scheme 21 EVAP VSV LOCATION Application Location 2.4L On Side Of Charcoal Canister NOTE: EVAP VSV may also be identified by wire colors. See appropriate wiring diagram in «WIRING DIAGRAMS - 2.4L»(ref-22460) article.
2. Using ohmmeter, ensure continuity exists between electrical terminals on EVAP VSV and resistance is 30-34 ohms at 68°F (20°C). Ensure no continuity exists between each electrical terminal and the body of the EVAP VSV. Replace EVAP VSV if continuity exists between electrical terminal and body of EVAP VSV.
3. To test EVAP VSV operation, apply air pressure to port "E". Ensure air does not flow from port "F". Perform STEP 1. (Scheme 32)
4. Apply battery voltage and ground to electrical terminals on EVAP VSV. Apply air pressure to port "E". Ensure air flows from port "F". Perform STEP 2. (Scheme 32) Replace EVAP VSV if defective.

Scheme 32

POSITIVE CRANKCASE VENTILATION (PCV)

1. Remove PCV valve. Apply air pressure to PCV valve at cylinder head side of PCV valve. Ensure air flows easily through PCV valve.
2. Apply air pressure to PCV valve at intake manifold side of PCV valve. Ensure air flows through PCV valve with some resistance. Replace PCV valve if valve does not function as described.

THROTTLE OPENER

1. Warm engine to normal operating temperature. Ensure idle speed is within specification. See IDLE SPEED & MIXTURE in «ADJUSTMENTS - 2.4L»(ref-22457) article.
2. Shut engine off. Disconnect and plug vacuum hose at throttle opener. Throttle opener is located on side of throttle body. Start engine and note engine speed. Engine speed should be within specification. See «THROTTLE OPENER SPECIFICATIONS»(ref-22458-S03720610282001010300000) table.
3. If engine speed is not within specification, replace throttle body. Shut engine off. Reinstall vacuum hose on throttle opener. Start engine and ensure engine returns to proper idle speed.

THROTTLE OPENER SPECIFICATIONS (1)