Engine Controls - System/component Tests: Other Lexus SC I

CONNECTING TACHOMETER

Connect tachometer between chassis ground and terminal IG- at DLC No. 1. (Scheme 19) DLC No. 1 is located on front of air intake chamber.

Scheme 19

Scheme 20

ACIS SYSTEM CHECK

1. Connect vacuum gauge between IACV actuator and VSV. (Scheme 21) Start engine. With engine idling, gauge needle should indicate no vacuum.
2. While snapping throttle fully open and releasing it, IACV actuator rod should move, and gauge needle should quickly fluctuate to the following specification: About 10 in. Hg or more.
3. System is okay if it operates as specified. If system does not operate as specified, perform ACIS CIRCUIT test.

Scheme 21

ACIS CIRCUIT

1. Check ACIS Vacuum Switching Valve (VSV). See «ACIS VACUUM SWITCHING VALVE (VSV)»(ref-22039-S34826422392001010300000). If VSV is okay, pull back the right front floor mat. Remove ECM protective cover. Connect Check Harness (SST 09990-01000) between ECM and harness. See USING CHECK HARNESS under ENGINE/VIN ID. Turn ignition on.
2. Measure voltage between chassis ground and terminal No. 39 (Green/Red wire) at ECM "B" connector. (Scheme 20)
3. If battery voltage is present, check for faulty vacuum tank or hoses. See «ACIS VACUUM TANK»(ref-22039-S04359485942001010300000). If battery voltage is not present, check for open or shorted circuit between EFI main relay and ECM. If circuit is okay, replace ECM.

ACIS INTAKE AIR CONTROL VALVE (IACV)

1. Remove air intake chamber for access to intake air control valve (leave intake air connector and throttle body installed). (Scheme 21) Apply about 15 in. Hg to IACV actuator. If IACV actuator rod does not move, replace IACV actuator.
2. If IACV actuator rod moves, check to see if diaphragm holds vacuum for at least one minute. If diaphragm does not hold vacuum, replace actuator. If diaphragm holds vacuum, ensure IACV plate is fully closed. If IACV plate is not fully closed, turn adjusting screw as necessary.

ACIS VACUUM SWITCHING VALVE (VSV)

1. Disconnect vacuum hoses and electrical connector from VSV. (Scheme 21) Remove VSV if necessary. Measure resistance between VSV terminals. If resistance is 39-45 ohms, go to next step. If resistance is not as specified, replace VSV.
2. Check for continuity between VSV case and each terminal at VSV connector (this checks for an internal short). If continuity does not exist, go to next step. If continuity exists, replace VSV.
3. Blow air through port "E". (Scheme 22) Air should flow out of filter, but not out of port "F". Apply battery voltage to VSV terminals. Blow air through port "E". Air should flow out of port "F". If VSV does not function as specified, replace VSV.

ACIS VACUUM TANK

Disconnect vacuum hoses from vacuum tank. Vacuum tank is located on bottom of air intake chamber. (Scheme 21)and (Scheme 23). Replace vacuum tank if it does not operate as follows

1. Blow air through port "B". (Scheme 23) Air should flow out of port "A".
2. Blow air through port "A". Air should not flow out of port "B".
3. Plug port "B". At port "A", apply 16 in. Hg. Vacuum should hold for at least one minute.

Scheme 22

Scheme 23

ECM GROUND CIRCUITS

ECM is located underneath top of passenger-side carpet (behind glove box) and is mounted to floor panel. Measure resistance between engine (ground) and specified terminals at ECM connector. See ECM GROUND CIRCUITS table. If resistance is more than one ohm, repair ground circuit. If resistance is one ohm or less, ground circuit is okay (ECM may be faulty).

ECM GROUND CIRCUITS

ECM BACK-UP POWER CIRCUIT (BATTERY)

If circuit or components are faulty, a Diagnostic Trouble Code (DTC) should set. See TESTS W/CODES article.

ECM POWER SOURCE CIRCUIT (IGNITION KEYED)

1. Access ECM behind glove box. Connect Check Harness (SST 09990-01000) between ECM and harness. See USING CHECK HARNESS under ENGINE/VIN ID . Turn ignition on.
2. Connect voltmeter negative lead to terminal No. 69 (Brown wire) at ECM "B" connector. Connect voltmeter positive lead to terminal No. 31 (Black/Red wire) at ECM "A" connector. If battery voltage is present, ECM keyed (ignition) power circuit is okay. If battery voltage is not present, go to next step.
3. Check for an open circuit in wiring harness between ground and terminal No. 69 at ECM "B" connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, go to next step.
4. Measure voltage between chassis ground and terminal No. 1 (Black/Orange wire) at ECM "A" connector. If battery voltage is present, go to step 6). If battery voltage is not present, check the following fuse. IGN fuse.
5. If fuse is blown, repair cause of blown fuse. If fuse is okay, disconnect ignition switch connector. With ignition switch in ON position, check for continuity between Black/Orange wire and White/Red wire) terminals at ignition switch. If continuity does not exist, replace ignition switch. If continuity exists, repair open circuit between battery and ignition switch, or between ignition switch and ECM.
6. Turn ignition on. Measure voltage between chassis ground and terminal No. 24 at ECM "A" connector (Black/Orange wire). If battery voltage is not present, replace ECM. If battery voltage is present, check EFI fuse. If EFI fuse is blown, repair circuit.
7. If fuse is okay, check EFI main relay. See «RELAYS»(ref-22039-S21818815732001010300000) under MODULES, MOTORS, RELAYS & SOLENOIDS. If EFI main relay is okay, check circuit between chassis ground and terminal No. 24 at ECM "A" connector. If circuit is okay, repair circuit between battery and EFI fuse.

CRANKSHAFT SENSOR

Turn ignition off. Disconnect crankshaft sensor connector. Sensor is located at front of engine, near crankshaft pulley. Measure resistance between crankshaft sensor terminals. Replace crankshaft sensor if resistance is not as specified. See CRANKSHAFT SENSOR RESISTANCE table.

CRANKSHAFT SENSOR RESISTANCE

EXHAUST GAS RECIRCULATION (EGR) TEMPERATURE SENSOR

Turn ignition off. Disconnect negative battery cable. Remove EGR temperature sensor. Sensor is located next to EGR valve, on EGR pipe. With sensing portion of EGR temperature sensor submerged in hot oil, measure resistance between terminals. (Scheme 24) Replace EGR temperature sensor if resistance is not as specified. See EGR TEMPERATURE SENSOR RESISTANCE table.

EGR TEMPERATURE SENSOR RESISTANCE

Scheme 24

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

1. Turn ignition off. Disconnect negative battery cable. Drain coolant. Remove ECT sensor. Sensor is located on left front of engine.
2. With sensing portion of ECT sensor submerged in water measure resistance between terminals. (Scheme 24) Replace ECT sensor if resistance is not as specified. See «ECT SENSOR RESISTANCE»(ref-22039-S24809234742001010300000) table.

ECT SENSOR RESISTANCE

IAT Sensor Resistance

IAT sensor is part of Mass Airflow (MAF) sensor. Turn ignition off. Disconnect MAF sensor connector. Measure resistance between terminals THA and E2. (Scheme 25) Replace MAF sensor if resistance is not as specified. See INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE table.

INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE

Scheme 25

KNOCK SENSOR

Remove knock sensor. Knock sensors are located on front and rear left side of cylinder block. Check for continuity between knock sensor terminal and knock sensor body (hex portion). If continuity exists, replace sensor.

MAF Sensor Voltage

Leave MAF sensor connector attached. Turn ignition on. Backprobing connector, connect voltmeter positive lead to VG terminal at MAF sensor connector. See MASS AIRFLOW METER (MAF) SENSOR TERMINALS table. Connect voltmeter negative lead to remaining terminal to be checked. If voltage does not fluctuate while blowing air through MAF sensor, replace MAF sensor.

MASS AIRFLOW METER (MAF) SENSOR TERMINALS

OXYGEN SENSOR HEATER RESISTANCE

Disconnect oxygen sensor connector. Measure resistance between terminals +B and HT of oxygen sensor connector. (Scheme 26) Replace oxygen sensor if resistance is not as specified. See OXYGEN SENSOR HEATER RESISTANCE table.

OXYGEN SENSOR HEATER RESISTANCE

Scheme 26

PARK/NEUTRAL POSITION (PNP) SWITCH

1. If PNP switch is out of adjustment, voltage signals may not be correctly applied to ECM, causing a Diagnostic Trouble Code (DTC) to set. Before assuming PNP switch is faulty, adjust PNP switch. See «PARK/NEUTRAL POSITION (PNP) SWITCH»(ref-22039-S17382175722001010300000) under MISCELLANEOUS CONTROLS in ADJUSTMENTS article.
2. After switch adjustment is completed, recheck for codes. If DTC does not reset, PNP switch is okay. If DTC resets, remove PNP switch. Check for continuity between specified terminals of PNP switch. See «PNP SWITCH CONTINUITY»(ref-22039-S07658258392001010300000) table. (Scheme 27) If continuity is not as specified, replace PNP switch. If continuity is as specified, install and adjust PNP switch.

PNP SWITCH CONTINUITY

Scheme 27

PARK/NEUTRAL POSITION (PNP) SWITCH CIRCUIT

If circuit or component is faulty, a Diagnostic Trouble Code (DTC) should set. Perform appropriate circuit test. See SELF-DIAGNOSTICS article.

SUB-THROTTLE POSITION (SUB-TP) SENSOR

Note. Vehicles with Traction Control System (TRAC) are equipped with a main TP sensor and a sub-TP sensor. The following procedure applies to sub-TP sensor. For main TP sensor, see THROTTLE POSITION (TP) SENSOR.

Disconnect sub-TP sensor connector. (Scheme 28) Measure resistance between sub-TP sensor terminals. See SUB-TP SENSOR RESISTANCE table. (Scheme 29) If resistance is not as specified, adjust sub-TP sensor. See SUB-THROTTLE POSITION (SUB-TP) SENSOR in ON-VEHICLE ADJUSTMENTS article. Recheck resistance. If resistance is still not as specified, replace sub-TP sensor.

SUB-TP SENSOR RESISTANCE

Scheme 28

Scheme 29

THROTTLE POSITION (TP) SENSOR

Note. Vehicles with Traction Control System (TRAC) are equipped with a main TP sensor and a sub-TP sensor. The following procedure applies to main TP sensor. For sub-TP sensor, see SUB-THROTTLE POSITION (SUB-TP) SENSOR.

Disconnect TP sensor connector. Measure resistance between specified terminals of TP sensor connector. See TP SENSOR RESISTANCE table. (Scheme 29) If resistance is not as specified, adjust TP sensor. See THROTTLE POSITION (TP) SENSOR in ADJUSTMENTS article. Recheck resistance. If resistance is still not as specified, replace TP sensor.

TP SENSOR RESISTANCE

VEHICLE SPEED SENSOR (VSS) NO. 1

1. If speedometer operates, VSS No. 1 is okay. If speedometer does not operate, disconnect electrical connector from VSS No. 1. Remove VSS No. 1 from transaxle/transmission. Connect battery positive lead to terminal No. 1 and negative lead to terminal No. 2. (Scheme 30)
2. While rotating gear, measure voltage between terminals No. 2 (negative lead) and No. 3 (positive lead). Replace VSS No. 1 if voltage does not alternate between zero and 12 volts, 4 times per revolution.

Scheme 30

VEHICLE SPEED SENSOR (VSS) NO. 1 CIRCUIT (SPEEDOMETER OPERATES)

1. If odometer does not operate, repair as necessary. See INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. If odometer operates, remove instrument cluster, but leave electrical connectors attached.
2. Raise and support vehicle with rear wheels off of ground. Turn ignition on. Backprobing connector, connect voltmeter between ground and terminal No. 14 (Pink wire) at instrument cluster 23-pin connector. (Scheme 31) Rotate drive shaft.
3. If voltage does not alternate between zero and 5 or more volts for each revolution of drive shaft, replace printed circuit and retest. If voltage alternates between zero and 5 or more volts, check for faulty wire (Pink wire) between instrument cluster and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If wire is okay, replace ECM.

Scheme 31

VEHICLE SPEED SENSOR (VSS) NO. 1 CIRCUIT (SPEEDOMETER DOES NOT OPERATE)

1. If odometer does not operate, go to next step. If odometer operates, check trip meter operation. If trip meter does not operate, go to step 4). If trip meter operates, replace speedometer.
2. Remove instrument cluster, but leave electrical connectors attached. Raise and support vehicle with rear wheels off of ground. Turn ignition on. At instrument cluster middle connector (23-pin), connect voltmeter between terminals No. 13 (Blue/Red wire) and No. 15 (Red wire). (Scheme 31) Rotate drive shaft.
3. If voltage alternates between zero and 11 or more volts for each revolution of drive shaft, replace printed circuit. If voltage does not alternate between zero and 11 or more volts, check VSS No. 1. See VEHICLE SPEED SENSOR (VSS) NO. 1. If VSS No. 1 is okay, repair circuit between VSS No. 1 and instrument cluster.
4. Remove instrument cluster, leaving all connectors attached except middle 23-pin connector. At middle connector (harness side), connect one end of a jumper wire to terminal No. 1 (Yellow wire). Connect other end of jumper wire to corresponding terminal on instrument cluster. Use same procedure for the following terminals. This simulates an attached middle connector, but with only 4 wires connected. No. 13 (Blue/Red wire). No. 15 (Red wire). No. 23 (White/Black wire).
5. Raise and support vehicle with rear wheels off of ground. Turn ignition on. Connect voltmeter between terminals No. 13 and 15 of middle connector. (Scheme 31) Rotate drive shaft. If voltage alternates between zero and 11 or more volts for each revolution of drive shaft, replace speedometer and retest. If voltage does not alternate between zero and 11 or more volts, replace printed circuit plate and retest. (Scheme 32)

Scheme 32

Fuel Pump ECU

If circuit or component is faulty, a Diagnostic Trouble Code should set. Perform appropriate circuit test. See TESTS W/CODES article.

Ignitor

See SPARK TEST under IGNITION CHECKS in BASIC TESTING article.

Idle Air Control (IAC) Valve

See IDLE CONTROL SYSTEM .

Sub-Throttle Actuator Motor (Vehicles With Traction Control) - Disconnect electrical connector from sub-throttle actuator motor. (Scheme 33) Replace sub-throttle actuator motor if resistance across the following terminals is not 0.5-1.0 ohm.

1. ACM and "A".
2. ACM and "A-".
3. BCM and "B".
4. BCM and "B-".

Scheme 33

RELAYS

Note. Cooling fan is driven by accessory drive belt.

Preliminary Information

Remove relay from engine compartment relay box. Determine which one of the following test procedures to perform. See RELAY TYPE & TEST PROCEDURE NUMBER table. see scheme 17-21. Replace relay if it does not test as specified.

See ACOUSTIC CONTROL INDUCTION SYSTEM (ACIS) .

EGR Vacuum Switching Valve (VSV)

See EXHAUST GAS RECIRCULATION (EGR) VACUUM SWITCHING VALVE (VSV) under EMISSION SYSTEMS & SUB-SYSTEMS.

EVAP (Charcoal) Canister Purge Vacuum Switching Valve (VSV)

See FUEL EVAPORATION under EMISSION SYSTEMS & SUB-SYSTEMS.

Fuel Injectors

See FUEL SYSTEM .

Fuel Pressure Regulator Vacuum Switching Valve (VSV)

See FUEL PRESSURE REGULATOR VACUUM SWITCHING VALVE (VSV) under FUEL SYSTEM.

Vapor Pressure Sensor Vacuum Switching Valve (VSV)

See FUEL EVAPORATION under EMISSION SYSTEMS & SUB-SYSTEMS.

FUEL INJECTOR CIRCUIT

If circuit or component is faulty, a Diagnostic Trouble Code (DTC) should set. Perform appropriate circuit test. See TESTS W/CODES article.

FUEL INJECTOR RESISTANCE

Turn ignition off. Disconnect injector connector. Measure resistance between injector terminals. Resistance should be about 13.8-14.2 ohms. If resistance is not about 13.8-14.2 ohms, replace injector.

Scheme 34

1. Remove fuel injector. See REMOVE/INSTALL/OVERHAUL article. Connect Injection Measuring Tool Set (9268-41045). (Scheme 34) Attach a piece of vinyl tubing to bottom of fuel injector to prevent fuel splash. Put vinyl tubing into a graduated measuring cylinder.
2. If Lexus scan tester is not available, go to next. If using a Lexus scan tester, remove instrument panel fuse box cover and connect scan tester to Data Link Connector (DLC) No. 3. Turn ignition on. DO NOT start engine. Using scan tester manufacturer's instructions, activate electric fuel pump. Go to step 4).
3. Remove trunk floor mat. Remove trunk trim panel. Disconnect fuel pump connector. Connect battery voltage to specified terminals on fuel pump connector to activate fuel pump. (Scheme 35) Go to next step.
4. Turn ignition on, engine off. Connect EFI Inspection Wiring (09842-30070) between fuel injector and a 12-volt battery for 15 seconds. Compare measured volume with specified volume. See «FUEL INJECTOR VOLUME (15 SECONDS)»(ref-22039-S42466870042001010300000) table. Replace injector if one or more of the following conditions exists: Volume is not within specification. Difference in volume between injectors exceeds specification. More than one drop leaks from injector within one minute of disconnecting EFI inspection wiring from battery.

FUEL INJECTOR VOLUME (15 SECONDS)

Scheme 35

FUEL PUMP RESISTANCE

Remove trim cover from behind rear seat in luggage compartment. Disconnect 2-pin fuel pump connector (NOT the sending unit connector). Measure resistance between female terminals of fuel pump connector. Replace fuel pump if resistance is not 0.2-3.0 ohms at 68°F (20°C).

FUEL PUMP CONTROL CIRCUIT

If circuit or component is faulty, a Diagnostic Trouble Code (DTC) should set. Perform appropriate circuit test. See TESTS W/CODES article.

FUEL PUMP PRESSURE

To check fuel pump pressure, see FUEL SYSTEM in BASIC TESTING article.

FUEL PRESSURE REGULATOR

To check fuel pressure regulator, perform FUEL PRESSURE test under FUEL SYSTEM in BASIC TESTING article.

1. Disconnect electrical connector and vacuum hoses from fuel pressure regulator VSV. See «FUEL PRESSURE REGULATOR VSV LOCATION»(ref-22039-S26365544282001010300000) table. Measure resistance between VSV terminals. If resistance is 33-39 ohms, go to next step. If resistance is not as specified, replace VSV.
2. Check for continuity between VSV case and each terminal of VSV (this checks for an internal short). If continuity does not exist, go to next step. If continuity exists, replace VSV.
3. Blow air through port "E" of VSV. Air should flow out of port "G". Apply battery voltage across VSV terminals. Blow air through port "E". Air should flow out of filter. If VSV does not operate as specified, replace VSV.

FUEL PRESSURE REGULATOR VSV LOCATION

FUEL PRESSURE REGULATOR VSV CONTROL CIRCUIT

1. Check fuel pressure regulator VSV. See «FUEL PRESSURE REGULATOR VACUUM SWITCHING VALVE (VSV)»(ref-22039-S38826291222001010300000). Replace VSV as necessary. If VSV is okay, access ECM connectors behind glove box. Connect a Check Harness (09990-01000) between ECM and harness. See USING CHECK HARNESS under ENGINE/VIN ID. Turn ignition on.
2. Measure voltage between ground and ECM "B" connector terminal No. 36 (Green/Red wire). (Scheme 20)
3. If battery voltage is not present, repair circuit between EFI main relay and ECM. If battery voltage is present, check fuel pressure regulator by performing FUEL PRESSURE test under FUEL SYSTEM in BASIC TESTING article. If fuel pressure regulator is okay, replace ECM and retest.

FUEL SYSTEM PRESSURE

To check fuel system pressure, see FUEL SYSTEM in BASIC TESTING article.

A/C IDLE-UP SYSTEM

See appropriate A/C IDLE-UP SYSTEM under MISCELLANEOUS CONTROLS.

IAC System Circuit

Perform IAC valve resistance and operation tests. If IAC valve resistance and operation are okay, check for open or shorted circuit between EFI main relay and IAC valve, and between IAC valve and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If circuits are okay, IAC system circuit is okay.

IAC Valve Resistance

Remove IAC valve from throttle body. Measure resistance between the following terminals of IAC valve connector. see scheme 24

1. Terminals B1 and S1.
2. Terminals B1 and S3.
3. Terminals B2 and S2.
4. Terminals B2 and S4.

If resistance is not as specified, replace IAC valve. See IAC VALVE RESISTANCE table.

IAC VALVE RESISTANCE

IGNITION SYSTEM

Note. For basic ignition checks, see IGNITION CHECKS in BASIC TESTING article.

DISTRIBUTOR PICK-UP COIL AIR GAP

See IGNITION CHECKS in BASIC TESTING article.

Pick-Up Coil

Measure resistance between specified terminals of distributor connector. See DISTRIBUTOR PICK-UP COIL RESISTANCE table. (Scheme 36) If resistance is not as specified, replace distributor housing assembly.

DISTRIBUTOR PICK-UP COIL RESISTANCE

Scheme 36

See BASIC TESTING article (ignitor is checked by performing SPARK TEST under IGNITION CHECKS).

IGNITION COIL RESISTANCE

1. Disconnect electrical connector and distributor wire from ignition coil. To measure primary resistance, measure resistance between terminals of ignition coil.
2. To measure secondary resistance, measure resistance between positive wire terminal at ignition coil and coil secondary tower. See «IGNITION COIL POSITIVE TERMINAL IDENTIFICATION»(ref-22039-S20867988952001010300000) table. If resistance is not as specified, replace ignition coil. See «IGNITION COIL RESISTANCE»(ref-22039-S28773269672001010300000) table.

IGNITION COIL POSITIVE TERMINAL IDENTIFICATION

IGNITION COIL RESISTANCE - Ohms

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

Note. DO NOT warm the engine until specified. Some testing must be performed when engine is cold.

1. Remove cap and filter from top of EGR vacuum modulator. EGR vacuum modulator is mounted next to EGR valve. Clean filter with compressed air. Install filter with coarse side facing upward. Install cap.
2. Using a vacuum "T", connect a vacuum gauge in hose between EGR valve and EGR vacuum modulator. To ensure EGR valve is seating, start engine and check idle quality.
3. If idle is smooth, go to next step. If idle is rough, disconnect vacuum hose from EGR valve. If idle is smooth, check for problems in EGR vacuum control system. If idle is still rough, EGR valve is not seating. Replace EGR valve.
4. Ensure engine coolant is less than 113°F (45°C). Run engine at 2500 RPM. See CONNECTING TACHOMETER under ENGINE/VIN ID article. There should be no vacuum indicated (no EGR occurs). If any vacuum is indicated, check EGR system components.
5. If no vacuum is indicated, warm engine to 122°F (50°C). Check vacuum with engine running at 2500 RPM. If no vacuum or high vacuum is indicated, check EGR system components. If low vacuum (partial EGR) is indicated, disconnect vacuum hose from port "R" of EGR vacuum modulator.
6. Connect a separate hose between port "R" and intake manifold. With engine running at 3500 RPM, high vacuum should be indicated (as EGR volume increases, engine should start to misfire). If no vacuum or low vacuum is indicated, check EGR system components. If high vacuum is indicated, disconnect vacuum gauge.
7. Reconnect all vacuum hoses. Disconnect vacuum hose from EGR valve. Apply vacuum directly to EGR valve. If engine runs rough or stalls, system is okay. If engine does not run rough or stall, replace EGR valve.

EXHAUST GAS RECIRCULATION (EGR) VACUUM MODULATOR

1. Turn engine off. Label and disconnect all vacuum hoses from EGR vacuum modulator. EGR vacuum modulator is mounted next to EGR valve. Block ports "P" and "R" with finger.
2. Blow air through port "Q". If air flows out of filter side freely, go to next step. If air does not flow out of filter side freely, replace EGR vacuum modulator.
3. Start and raise engine speed to 2500 RPM. See CONNECTING TACHOMETER under ENGINE/VIN ID article. Block ports "P" and "R" with finger. Blow air through port "Q". There should be a strong resistance to airflow out of filter. Replace EGR vacuum modulator is it does not operate as specified.

EXHAUST GAS RECIRCULATION (EGR) VACUUM SWITCHING VALVE (VSV)

1. Disconnect vacuum hoses and electrical connector from VSV. See appropriate illustration in VACUUM DIAGRAMS article. Measure resistance between VSV terminals. If resistance is 39-45 ohms at 68°F (20°C), go to next step. If resistance is not 39-45 ohms, replace VSV.
2. Check for continuity between VSV case and each terminal of VSV connector (this checks for an internal short). If no continuity exists, go to next step. If continuity exist, replace VSV.
3. Blow air through port "E". (Scheme 37) If air does not flow out of port "G", go to next step. If air flows out of port "G", replace VSV.
4. Apply battery voltage across VSV terminals. Blow air through port "E". If air flows out of port "G", VSV is functioning properly. If air does not flow out of port "G", replace VSV.

Scheme 37

EXHAUST GAS RECIRCULATION (EGR) VALVE

Start engine and allow it to idle. Disconnect and plug vacuum hose to EGR valve. Connect a vacuum pump to EGR valve. Apply vacuum. If engine idles rough or stalls, EGR valve is functioning properly. If engine does not idle rough or stall, check for plugged EGR port or defective EGR valve. Repair as necessary.

For EGR temperature sensor testing, see EXHAUST GAS RECIRCULATION (EGR) TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES.

EVAP Canister

1. Visually inspect EVAP canister and hoses for cracks and damage. Disconnect all hoses from canister. Remove check valve (if equipped) from hose that is connected to bottom of canister. Connect a clean hose to fuel tank port "A" on top of canister. (Scheme 38) Blow 0.68 psi (0.05 kg/cm 2 ) of air through clean hose. Air should flow from all other ports, including port(s) on bottom of canister.
2. Blow air into canister purge port "B" on top of canister. If air flows from any other port, replace canister. If air does not flow from any other port, hold finger over port "B". Blow a maximum of 43 psi (3 kg/cm 2 ) of compressed air through port "A" to clean canister filter. No charcoal should come out. DO NOT try to clean canister filter by washing canister.

Scheme 38

EVAP Vacuum Switching Valve (VSV)

1. Disconnect electrical connector and vacuum hoses from VSV. See appropriate illustration in VACUUM DIAGRAMS article. Measure resistance between VSV terminals. If resistance is 27-30 ohms at 68°F (20°C), go to next step. If resistance is not as specified, replace VSV.
2. Check for continuity between VSV case and each terminal of VSV connector (this checks for an internal short). If continuity does not exist, go to next step. If continuity exists, replace VSV.
3. Blow air through port "E". (Scheme 37)If air does not flow out of port "G", go to next step. If air flows out of port "G", replace VSV.
4. Apply battery voltage across VSV terminals. Blow air through port "E". If air flows out of port "G", VSV is functioning properly. If air does not flow out of port "G", replace VSV.

Check Valve For EVAP Canister

Remove check valve. Check valve is mounted to side of EVAP canister. Air should flow from Yellow port to Black port. Air should not flow from Black port to Yellow port. Replace check valve if it does not operate as specified. Install check valve with Black port toward canister.

Check Valve For EVAP Vacuum Control Circuit

Remove check valve. Check valve is located underneath air intake chamber. Air should flow from Blue port to Black port. Air should not flow from Black port to Blue port. Replace check valve if it does not operate as specified. Install check valve with Black port toward throttle body.

Vapor Pressure Sensor Vacuum Switch Valve (VSV)

1. Disconnect vapor pressure sensor VSV vacuum hoses. VSV is mounted on top of EVAP charcoal canister. Apply air pressure to VSV port "E". (Scheme 39) If air flows from port "G", go to next step. If air does not flow from port "G", replace VSV.
2. Apply battery voltage across VSV terminals. Blow air through port "E". If air flows out of port "F", VSV is functioning properly. If air does not flow from port "F", replace VSV.

Scheme 39

PCV Valve

Remove PCV valve from valve cover. Inspect PCV hoses, connections and gaskets for leaks and damage. Blow air through cylinder head side of PCV valve. Air should pass freely through PCV valve. Blow air through intake manifold side of PCV valve. Air should not pass freely through PCV valve. Clean or replace PCV valve if air does not flow as specified.

DASHPOT

Shift transmission into Neutral. Run engine at operating temperature. Ensure idle speed is 650-750 RPM. See CONNECTING TACHOMETER under ENGINE/VIN ID article. Push dashpot rod all the way with a screwdriver and verify engine speed is 1800 RPM (2600 RPM on M/T). If engine speed is not as specified, turn dashpot adjusting screw as necessary.

THROTTLE OPENER

Run engine at operating temperature. Ensure idle speed is 650-750 RPM. See CONNECTING TACHOMETER under ENGINE/VIN ID article. Disconnect vacuum hose from throttle opener, and plug hose end. Run engine at 2500 RPM, then release throttle. Compare actual engine speed with specified engine speed. See THROTTLE OPENER SET SPEED SPECIFICATIONS table. If engine speed is not as specified

1. Replace throttle body.

THROTTLE OPENER SET SPEED SPECIFICATIONS

Scheme 40

MISCELLANEOUS CONTROLS

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect drive-ability if they malfunction.

COOLING FAN SYSTEM

Note. Cooling fan is driven by accessory drive belt.

TRANSMISSION

Note. For transmission diagnostic information, see appropriate AUTO TRANS DIAGNOSIS - A-340 (W/OBD-II) article.