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

CONNECTING TACHOMETER

Connect tachometer between chassis ground and terminal IG- of DLC No. 1. see scheme 17 See COMPONENT LOCATIONS.

ACIS SYSTEM CHECK

1. Connect vacuum gauge between IACV actuator and VSV. (Scheme 9) See «COMPONENT LOCATIONS»(ref-21748-S42748797422001010300000) under INTRODUCTION. 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 CIRCUITS test.

Scheme 9

ACIS CIRCUIT

1. Check ACIS Vacuum Switching Valve (VSV). (Scheme 9) See AC IS VACUUM SWITCHING VALVE (VSV). If VSV is okay, pull back the right front floor mat. Remove ECM protective cover. Connect Check Harness (09990-01000) between ECM and harness. See «USING CHECK HARNESS»(ref-21748-S23232169112001010300000) under INTRODUCTION. Turn ignition on.
2. Measure voltage between chassis ground and terminal No. 39 of ECM connector "B" (Brown/Red wire). To identify ECM connectors and terminals see scheme 1
3. If battery voltage is present, check for faulty vacuum tank or hoses. See «ACIS VACUUM TANK»(ref-21748-S10857381152001010300000). 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 9) 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)

Disconnect vacuum hoses and electrical connector from VSV. (Scheme 9) Remove VSV if necessary. Replace VSV if it does not operate as follows.

1. Ensure no continuity exists between VSV case (ground) and each terminal of VSV connector (this checks for an internal short).
2. Blow through port "E". (Scheme 10) Air comes out of filter, but not out of port "F".
3. Apply battery voltage across terminals. Blow through port "E". Air comes out of port "F".

ACIS VACUUM TANK

Disconnect vacuum hoses from vacuum tank. (Scheme 9) Replace vacuum tank if it does not operate as follows.

1. Blow through port "B". (Scheme 11) Air comes out of port "A".
2. Blow through port "A". Air does NOT come out of port "B".
3. Plug port "B". At port "A", apply 16 in. Hg. Vacuum holds for at least one minute.

Scheme 10

Scheme 11

ECM GROUND CIRCUITS

For ECM location, see COMPONENT LOCATIONS under INTRODUCTION. Measure resistance between engine (ground) and specified terminals of 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)

1. Check EFI fuse. See «COMPONENT LOCATIONS»(ref-21748-S42748797422001010300000) under INTRODUCTION. If EFI fuse is blown, repair circuit. If EFI fuse is okay, pull back the right front floor mat. Remove ECM protective cover. Connect Check Harness (09990-01000) between ECM and harness. See «USING CHECK HARNESS»(ref-21748-S23232169112001010300000) under INTRODUCTION.
2. Measure voltage between chassis ground and terminal No. 33 of ECM connector "A" (White/Blue wire). If battery voltage is not present, repair open circuit between ECM and EFI fuse, or between EFI fuse and battery.
3. If battery voltage is present, check to see if trouble codes remain stored in ECM memory after ignition is turned off. See appropriate «TESTS W/CODES»(ref-21749) article. If trouble codes remain stored, back-up (battery) power circuit is okay. If trouble codes do not remain stored, replace ECM.

ECM POWER SOURCE CIRCUIT (IGNITION KEYED)

1. Ensure ECM ground circuits are okay. See «ECM GROUND CIRCUITS»(ref-21748-S30878097502001010300000). Pull back the right front floor mat. Remove ECM protective cover. Connect Check Harness (09990-01000) between ECM and harness. See «USING CHECK HARNESS»(ref-21748-S23232169112001010300000) under INTRODUCTION. Turn ignition on.
2. Connect voltmeter negative lead to terminal No. 69 (Brown wire) of ECM connector "B". Connect voltmeter positive lead to terminal No. 31 (Black/Red wire) of ECM connector "A". To identify connectors and terminals see scheme 1
3. If battery voltage is present, ECM keyed (ignition) power circuit is okay. If battery voltage is not present, measure voltage between chassis ground and terminal No. 1 (Black/Orange wire) of ECM connector "A".
4. If battery voltage is present, go to step 6). If battery voltage is not present, check the following fuse. See «COMPONENT LOCATIONS»(ref-21748-S42748797422001010300000) under INTRODUCTION. AM2 fuse.
5. If fuse is blown, repair circuit. If fuse is okay, disconnect ignition switch connector. With ignition switch in ON position, check for continuity between White/Red and Black/Orange wire terminals of 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 of ECM connector "A" (Green/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-21748-S06101076972001010300000) under MODULES, MOTORS, RELAYS & SOLENOIDS. If EFI main relay is okay, check circuit between chassis ground and terminal No. 24 of ECM connector "A". If circuit is okay, repair circuit between battery and EFI fuse.

CAMSHAFT SENSORS

Not equipped with camshaft sensors.

CRANKSHAFT SENSOR

Not equipped with crankshaft sensor.

EGR TEMPERATURE SENSOR

Turn ignition off. Disconnect negative battery cable. Remove EGR temperature sensor. See COMPONENT LOCATIONS under INTRODUCTION. With sensing portion of EGR temperature sensor submerged in hot oil, measure resistance between terminals. Replace EGR temperature sensor if resistance is not as specified. See EGR TEMPERATURE SENSOR RESISTANCE table.

EGR TEMPERATURE SENSOR RESISTANCE

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

Turn ignition off. Disconnect negative battery cable. Drain coolant. Remove ECT sensor. See COMPONENT LOCATIONS under INTRODUCTION. With sensing portion of ECT sensor submerged in water, measure resistance between terminals. Replace ECT sensor if resistance is not as specified. See ECT SENSOR RESISTANCE table.

ECT SENSOR RESISTANCE

INTAKE AIR TEMPERATURE (IAT) SENSOR

Note. IAT sensor is part of Volume Airflow (VAF) sensor.

IAT Sensor Resistance

Turn ignition off. Disconnect electrical connector from VAF sensor. See COMPONENT LOCATIONS under INTRODUCTION. Measure resistance between terminals THA and E2. (Scheme 13) Replace sensor if resistance is not as specified. See INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE table.

INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE

Scheme 12

KNOCK SENSOR

Remove knock sensor. See COMPONENT LOCATIONS under INTRODUCTION. Replace knock sensor if continuity exists between knock sensor connector terminal and knock sensor body (hex portion).

OXYGEN SENSOR HEATER RESISTANCE

Disconnect oxygen sensor connector. See COMPONENT LOCATIONS under INTRODUCTION. Measure resistance between terminals +B and HT of oxygen sensor connector. (Scheme 13) Replace oxygen sensor if resistance is not as specified. See OXYGEN SENSOR HEATER RESISTANCE table.

OXYGEN SENSOR HEATER RESISTANCE

Scheme 13

Main Sensors

1. Run the engine at 2500 RPM for about 2 minutes to warm the oxygen sensor. See «CONNECTING TACHOMETER»(ref-21748-S35161899392001010300000) under INTRODUCTION.
2. Connect Jumper Wire (09843-18020) between terminals TE1 and E1 of DLC No. 1. see scheme 17 See «COMPONENT LOCATIONS»(ref-21748-S42748797422001010300000) under INTRODUCTION. Connect negative lead of analog voltmeter to terminal E1 of DLC No. 1. Connect positive lead to terminal VF1 (or VF2) of DLC No. 1. See «IDENTIFYING VF1 & VF2 TERMINALS»(ref-21748-S21866622702001010300000) table. Maintain engine speed at 2500 RPM. IDENTIFYING VF1 & VF2 TERMINALS (1) Application Oxygen Sensor VF1 Front VF2 Rear (1) Terminals of Data Link Connector (DLC) No. 1. see scheme 17
3. Count how many times the voltmeter needle fluctuates in 10 seconds. No fluctuations: go to step 8). 8 or more fluctuations: oxygen sensor is okay. Less than 8 fluctuations: go to next step.
4. Run the engine at 2500 RPM for about 2 minutes to warm the oxygen sensor. Maintain engine speed at 2500 RPM. Count how many times the voltmeter needle fluctuates in 10 seconds. No fluctuations: go to step 8). 8 or more fluctuations: oxygen sensor is okay. Less than 8 fluctuations: go to next step.
5. Disconnect jumper wire from DLC No. 1. With engine speed at 2500 RPM, measure voltage between terminals E1 and VF1 (or VF2). If more than zero volts is indicated, replace oxygen sensor. If no voltage is indicated, retrieve and record trouble codes in normal mode and test mode, then go to next step. See appropriate «TESTS W/CODES»(ref-21749) article.
6. In test mode, if trouble codes other than Codes 21, 25, 26 and 28 are retrieved, perform procedure in «TESTS W/CODES»(ref-21749) article. In normal mode, if Code 21, 25, 26 or 28 is retrieved, disconnect PCV hose. With engine speed at 2500 RPM, measure voltage between terminals E1 and VF1 (or VF2).
7. If no voltage is indicated, replace oxygen sensor. If more than zero volts is indicated, fuel mixture is rich. Repair as necessary.
8. Retrieve and record trouble codes in normal mode and test mode. See appropriate «TESTS W/CODES»(ref-21749) article. In test mode, if trouble codes other than Codes 21, 25, 26 and 28 are retrieved, perform appropriate procedure in appropriate «TESTS W/CODES»(ref-21749) article. In normal mode, if Code 21, 25, 26 or 28 is retrieved, disconnect jumper wire from DLC No. 1.
9. With engine speed at 2500 RPM, measure voltage between terminals E1 and VF1 (or VF2). If about 5 volts is indicated, go to next step. If no voltage is indicated, disconnect PCV hose. With engine speed at 2500 RPM, measure voltage between terminals E1 and VF1 (or VF2). If no voltage is indicated, replace oxygen sensor. If more than zero volts is indicated, fuel mixture is rich. Repair as necessary.
10. Disconnect ECT sensor connector. Connect a 4000-8000 ohm resistor across connector terminals. Connect jumper wire between terminals TE1 and E1 of DLC No. 1. Run the engine at 2500 RPM for about 2 minutes to warm the oxygen sensor.
11. With engine speed at 2500 RPM, measure voltage between terminals E1 and VF1 (or VF2). If no voltage is indicated, replace oxygen sensor. If about 5 volts is indicated, fuel mixture is lean. Repair as necessary.

Note. When testing main sensors, if voltmeter needle did not fluctuate in step 2) and you ended up replacing the oxygen sensor, repeat step 2). Then, count how many times the voltmeter needle fluctuates in 10 seconds. If voltmeter needle does not fluctuate again, replace ECM.

Sub-Sensor(s)

1. Clear trouble codes. See appropriate «TESTS W/CODES»(ref-21749) article. Warm engine to normal operating temperature.
2. With transmission in Drive, cruise at 50-55 MPH for 10 minutes or more. Stop vehicle and idle engine for 2 minutes or less. Accelerate vehicle to 50 MPH with throttle fully open. Turn ignition off. Retrieve trouble codes. If no codes are set, sub-sensor circuit is functioning properly. If any codes are set, repair as necessary. See appropriate «TESTS W/CODES»(ref-21749) article.

PARK/NEUTRAL POSITION (PNP) SWITCH

1. If PNP switch is out of adjustment, voltage signals may not be correctly applied to ECM, causing a trouble code to set. Before assuming PNP switch is faulty, adjust PNP switch. See PARK/NEUTRAL POSITION (PNP) SWITCH under MISCELLANEOUS CONTROLS in appropriate «ADJUSTMENTS»(ref-21740) article.
2. After switch adjustment is completed, recheck for trouble code. If trouble code does not reset, PNP switch is okay. If trouble code resets, remove PNP switch. Check for continuity between specified terminals of PNP switch. See «PNP SWITCH CONTINUITY»(ref-21748-S05458648342001010300000) table. (Scheme 14) If continuity is not as specified, replace PNP switch. If continuity is as specified, install and adjust PNP switch.

PNP SWITCH CONTINUITY

Scheme 14

PARK/NEUTRAL POSITION (PNP) SWITCH CIRCUIT

1. Connect Jumper Wire (09843-18020) between terminals TE2 and E1 of DLC No. 1. see scheme 17 See «COMPONENT LOCATIONS»(ref-21748-S42748797422001010300000) under INTRODUCTION. Turn ignition on. Momentarily crank engine. Connect another jumper wire between terminals TE1 and E1 of DLC No. 1.
2. With transmission in Park, MIL should flash normal code (steady flashing). With transmission in Drive, MIL should flash Code 51. This indicates PNP switch circuit is okay. Code 51 In Park & Drive Check harness between PNP switch and ECM. If harness is okay, replace ECM. Normal Code In Park & Drive Check PNP switch. See «PARK/NEUTRAL POSITION (PNP) SWITCH»(ref-21748-S40114331922001010300000). If PNP switch is okay, replace ECM.

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. Measure resistance across specified terminals of sub-TP sensor connector. See SUB-TP SENSOR RESISTANCE table. (Scheme 15) If resistance is not as specified, adjust sub-TP sensor. See SUB-THROTTLE POSITION (SUB-TP) SENSOR.

1. If PNP switch is out of adjustment, voltage signals may not be correctly applied to ECM, causing a trouble code to set. Before assuming PNP switch is faulty, adjust PNP switch. See PARK/NEUTRAL POSITION (PNP) SWITCH under MISCELLANEOUS CONTROLS in appropriate «ADJUSTMENTS»(ref-21740) article. Recheck resistance. If resistance is still not as specified, replace sub-TP sensor.

SUB-TP SENSOR RESISTANCE

Scheme 15

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 across specified terminals of TP sensor connector. See TP SENSOR RESISTANCE table. (Scheme 15) If resistance is not as specified, adjust TP sensor. See THROTTLE POSITION (TP) SENSOR under MISCELLANEOUS CONTROLS in appropriate ADJUSTMENTS article.

1. If PNP switch is out of adjustment, voltage signals may not be correctly applied to ECM, causing a trouble code to set. Before assuming PNP switch is faulty, adjust PNP switch. See «PARK/NEUTRAL POSITION (PNP) SWITCH»(ref-21748-S40114331922001010300000) under MISCELLANEOUS CONTROLS in appropriate «ADJUSTMENTS»(ref-21740) 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. See «COMPONENT LOCATIONS»(ref-21748-S42748797422001010300000) under INTRODUCTION. Remove VSS No. 1. Connect battery positive lead to terminal No. 1 and negative lead to terminal No. 2. (Scheme 16)
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 16

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

1. If odometer does not operate, repair as necessary. See the INSTRUMENT PANEL article in the ACCESSORIES/SAFETY EQUIPMENT section. If odometer operates, remove instrument cluster, but leave electrical connectors attached. Raise and support vehicle with rear wheels off of ground. Turn ignition on. Connect voltmeter between chassis ground and terminal No. 14 (Violet/White wire) of instrument cluster center connector. Rotate drive shaft.
2. If voltage does not alternate between zero and 5 or more volts for each revolution of drive shaft, replace printed circuit. If voltage alternates between zero and 5 or more volts, check for faulty wire (Violet/White) between instrument cluster and ECM. See «COMPONENT LOCATIONS»(ref-21748-S42748797422001010300000) under INTRODUCTION. If wire is okay, replace ECM.

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 (13-pin), connect voltmeter between terminals No. 15 (Blue/Black wire). 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»(ref-21748-S21040205522001010300000) . 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 connector. At middle connector (harness side), connect one end of a jumper wire to terminal No. 1 (Red/Blue 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 (Blue/Black 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. Rotate drive shaft. If voltage alternates between zero and 11 or more volts for each revolution of drive shaft, replace speedometer. If voltage does not alternate between zero and 11 or more volts, replace printed circuit.

VOLUME AIRFLOW (VAF) SENSOR

Note. If circuit or component is faulty, a trouble code should set. See appropriate TESTS W/CODES article. VAF sensor contains the intake air temperature sensor. See INTAKE AIR TEMPERATURE (IAT) SENSOR.

Fuel Pump ECU

If circuit or component is faulty, a trouble code should set. See appropriate 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 17) 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 17

RELAYS

Note. For cooling fan relay testing, see ENGINE COOLING FAN article in ENGINE COOLING section.

Preliminary Information

Remove relay. See COMPONENT LOCATIONS under INTRODUCTION. Determine which one of the following test procedures to perform. See RELAY CONNECTOR TYPE & TEST PROCEDURE NUMBER table. see scheme 11-15. 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.

FUEL INJECTOR CIRCUIT

1. Turn ignition off. Pull back the right front floor mat. Remove ECM protective cover. Connect a Check Harness (09990-01000) between ECM and harness. See «USING CHECK HARNESS»(ref-21748-S23232169112001010300000) under INTRODUCTION. Turn ignition on.
2. Measure voltage between chassis ground and terminals No. 15-20 of ECM connector "B". To identify ECM connectors and terminals see scheme 1
3. If battery voltage is present at all terminals, go to next step. If battery voltage is not present at all terminals, check IG2 (ignition main) relay. See «RELAYS»(ref-21748-S06101076972001010300000) under MODULES, MOTORS, RELAYS & SOLENOIDS. If IG2 relay is okay, repair harness between IG2 relay and battery.
4. Check for continuity between chassis ground and terminals No. 79 and 80 (White/Black wires) of ECM connector "B". If continuity does not exist, repair open White/Black wires. If continuity exists, check for open circuits between IG2 relay and injectors, and between injectors and ECM.
5. If circuits are okay, measure injector resistance and volume. See «FUEL INJECTOR RESISTANCE»(ref-21748-S29250800662001010300000) and FUEL INJECTOR VOLUME. If resistance and volume are as specified, replace ECM.

FUEL INJECTOR RESISTANCE

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

FUEL INJECTOR VOLUME

1. Remove fuel injector. Connect Injection Measuring Tool Set (9268-41045). (Scheme 18) Attach a piece of vinyl tubing to bottom of fuel injector to prevent fuel splash. Put vinyl tubing into a graduated measuring cylinder.
2. Connect Jumper Wire (00843-18020) between terminals +B and FG of DLC No. 1. see scheme 17 Reconnect negative battery cable. Turn ignition on, engine off. Connect EFI Inspection Wiring (09842-30070) between fuel injector and a 12-volt battery for 15 seconds.
3. Compare measured volume with specified volume. See «FUEL INJECTOR VOLUME (15 SECONDS)»(ref-21748-S27288466892001010300000) 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 18

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

Note. If circuit or component is faulty, a trouble code should set. See appropriate TESTS W/CODES article.

FUEL PUMP PRESSURE

Note. See FUEL SYSTEM in BASIC TESTING article.

FUEL PRESSURE REGULATOR

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

Disconnect electrical connector and vacuum hoses from fuel pressure regulator VSV. See COMPONENT LOCATIONS under INTRODUCTION. Replace VSV if it does not operate as follows

1. At 68°F (20°C), resistance across terminals should be 33-39 ohms.
2. There is no continuity between VSV case (ground) and each terminal of VSV connector (this checks for an internal short).
3. Blow through port "E". (Scheme 19) Air comes out of port "G".
4. Apply battery voltage across terminals. Blow air through port "E". Air comes out of filter.

Scheme 19

FUEL PRESSURE REGULATOR VSV CONTROL CIRCUIT

1. Check fuel pressure regulator VSV. See «FUEL PRESSURE REGULATOR VACUUM SWITCHING VALVE (VSV)»(ref-21748-S04842181402001010300000) . If VSV is okay, pull back the right front floor mat. Remove ECM protective cover. Connect a Check Harness (09990-01000) between ECM and harness. See «USING CHECK HARNESS»(ref-21748-S23232169112001010300000) under INTRODUCTION. Turn ignition on.
2. Measure voltage between chassis ground and terminal No. 36 (Green/Red wire) of ECM connector "B". If battery voltage is present, VSV circuit is okay. If battery voltage is not present, check circuit between ECM and VSV, and between VSV and EFI main relay. If circuit is okay, replace ECM.

FUEL SYSTEM PRESSURE

Note. See FUEL SYSTEM in BASIC TESTING S 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 COMPONENT LOCATIONS under INTRODUCTION. If circuits are okay, IAC system circuit is okay.

IAC Valve Resistance

Remove IAC valve. See COMPONENT LOCATIONS under INTRODUCTION. Measure resistance between the following terminals of IAC valve connector. see scheme 19 If resistance is not 10-30 ohms, replace IAC valve.

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

IGNITION SYSTEM

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

DISTRIBUTOR PICK-UP COIL AIR GAP

See IGNITION CHECKS in BASIC TESTING S article.

(Pick-Up Coil)

Measure resistance between specified terminals of distributor connector. See DISTRIBUTOR PICK-UP COIL RESISTANCE table. (Scheme 20) If resistance is not as specified, replace distributor housing assembly.

DISTRIBUTOR PICK-UP COIL RESISTANCE

Scheme 20

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

IGNITION COIL RESISTANCE

Disconnect electrical connector and distributor wire from ignition coil. To measure primary resistance, measure resistance between terminals of ignition coil electrical connector. See COMPONENT LOCATIONS under INTRODUCTION. To measure secondary resistance, measure resistance between Black/Orange wire terminal of ignition coil electrical connector and coil secondary tower. If resistance is not as specified, replace ignition coil. See IGNITION COIL RESISTANCE table.

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. See «COMPONENT LOCATIONS»(ref-21748-S42748797422001010300000) under INTRODUCTION. 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»(ref-21748-S35161899392001010300000) under INTRODUCTION. 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

Turn engine off. Label and disconnect all vacuum hoses from EGR vacuum modulator. See COMPONENT LOCATIONS under INTRODUCTION. Replace EGR vacuum modulator if it does not operate as follows

1. Block ports "P" and "R" with finger. Blow through port "Q". Air flows freely out of filter.
2. Start and run engine at 2500 RPM. See «CONNECTING TACHOMETER»(ref-21748-S35161899392001010300000) under INTRODUCTION. Block ports "P" and "R" with finger. Blow through port "Q". There is strong resistance to airflow out of filter.

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

Disconnect vacuum hoses and electrical connector from VSV. See COMPONENT LOCATIONS under INTRODUCTION. Replace VSV if it does not operate as follows

1. Resistance across terminals should be 39-45 ohms at 68°F (20°C).
2. There is no continuity between VSV case (ground) and each terminal of VSV connector (this checks for an internal short).
3. Blow through port "E". (Scheme 21) Air does NOT come out of port "G".
4. Apply battery voltage across terminals. Blow through port "E". Air comes out of port "G".

Scheme 21

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.

Check Valve For EVAP Vacuum Control Circuit

Remove check valve. See COMPONENT LOCATIONS under INTRODUCTION. 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 Blue port toward intake manifold.

PCV Valve

Remove PCV valve. See COMPONENT LOCATIONS under INTRODUCTION. 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 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 INTRODUCTION. Push dashpot rod all the way with a screwdriver and verify engine speed is 1800 RPM. 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 INTRODUCTION. 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.
2. Turn throttle opener adjustment screw as necessary.

THROTTLE OPENER SET SPEED SPECIFICATIONS

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.

Note. Compressor circuit may be faulty. See the A/C-HEATER SYSTEM article.

COOLING FAN SYSTEM

Note. Use the following procedure to check operation of cooling fan system. For all other cooling fan testing, see the ENGINE COOLING FAN article in the ENGINE COOLING section.

1. Ensure coolant temperature is less than 190°F (88°C). Turn ignition on. If cooling fan does not come on, go to next step. If cooling fan comes on, check for faulty cooling fan system components or wiring. See the ENGINE COOLING FAN article in the ENGINE COOLING section.
2. Ensure coolant temperature is greater than 207°F (97°C). If cooling fan comes on, system is okay. If cooling fan does not come on, check for faulty cooling fan system components or wiring. See the ENGINE COOLING FAN article in the ENGINE COOLING section.

TRANSMISSION

Note. For transmission diagnostic information, see the TRANSMISSION SERVICING article.