Engine Controls - System/component Tests: Other Infiniti Q45 I

ELECTRONIC CONTROL UNIT (ECU)

Note. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section to identify ECU ground and power circuit terminals.

Ground Circuits

1. Using an ohmmeter, check for continuity to ground on ECU terminals No. 6, 13, 39, 48, 107, 108 and 116 on G20 or terminals No. 10, 20, 50, 60, 107, 108 and 116 on M30 and Q45. Resistance should be zero ohms. If reading is not zero ohms, repair open to ground.
2. Using a DVOM, touch negative lead of voltmeter to a good ground. Using positive lead of voltmeter, backprobe each ground terminal at ECU connector. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is greater than one volt, check for open, corrosion or loose connection on ground lead.

Power Circuits

1. Using a voltmeter, check for battery voltage between chassis ground and ECU terminals No. 46 and 109 on G20, or ECU terminal No. 58 on all other models. If battery voltage is not present, check fusible link. Fusible link also supplies power for fuel injectors.
2. Turn ignition switch to ON position. Using a voltmeter, check for battery voltage between chassis ground and ECU terminals No. 36, 38 and 47 on G20 or terminals No. 45, 49, 59 and 109 on M30 and Q45. If battery voltage is not present, check fusible link and fuse "G".
3. Connect voltmeter between chassis ground and ECU terminal No. 34 on G20 or terminal No. 43 on M30 and Q45. Turn ignition switch to START position. Battery voltage should be present only when ignition switch is in START position. If voltage is not present, check for blown fuse and defective ignition switch.

ENGINE SENSORS & SWITCHES

Note. Sensor resistance and/or voltage values (when available from manufacturer) can be found in SENSOR RANGE CHARTS article in the ENGINE PERFORMANCE Section.

Scheme 61

Scheme 62

Scheme 63

1. Ensure no dust or foreign material exists in hot wire air passage. Fold back airflow meter harness connector boot. Turn ignition on. Connect negative lead of voltmeter to ground. Using positive lead, backprobe airflow meter terminal No. 1 on Q45 or terminal "a" on G20 and M30. (Scheme 61)to 3. Voltmeter should read as specified. See «AIRFLOW METER VOLTAGE SPECIFICATIONS»(ref-17381-S40708941242000122900000) table.
2. Start engine, and allow it to warm to operating temperature. Recheck voltage reading. Voltage should be as specified. See AIRFLOW METER VOLTAGE SPECIFICATIONS table. Faults in airflow meter circuit should set a Code 12. If Code 12 is present, refer to TESTS W/CODES article in the ENGINE PERFORMANCE Section.

AIRFLOW METER VOLTAGE SPECIFICATIONS (1)

COOLANT (ENGINE) TEMPERATURE SENSOR

Disconnect coolant temperature sensor connector. Measure resistance across sensor terminals. See COOLANT TEMPERATURE SENSOR RESISTANCE TEST table. Replace sensor if it is not within specifications.

COOLANT TEMPERATURE SENSOR RESISTANCE TEST (1)

Scheme 64

Scheme 65

Scheme 66

1. On G20 and M30, crankshaft angle sensor is part of distributor. On Q45, crankshaft angle sensor is a self-contained unit located on left front of engine. If a fault is present in crankshaft angle sensor, Code 11 may set in ECU memory. If Code 11 is set, proceed to TESTS W/CODES article in the ENGINE PERFORMANCE Section.
2. To test crankshaft angle sensor, remove crankshaft angle sensor (Q45) or distributor (G20 and M30). Leave sensor wiring connected. Using a logic probe or DVOM with an analog bar graph function, touch negative lead to ground and positive lead to one-degree and 90/120/180-degree signal terminals of ECU. See CRANKSHAFT ANGLE SENSOR SIGNAL HARNESS TERMINALS table. (Scheme 64)to 6.
3. Rotate sensor by hand. On a DVOM, one-degree signals should measure about 2.3-2.8 peak volts with sensor rotating. 45/60-degree signal should measure about.1-.4 peak volt with sensor rotating. If either signal is not present, replace crank angle sensor. On Q45, also see SUB-CRANK ANGLE SENSOR (Q45).

Note. Crankshaft angle sensor voltage may be measured using a conventional DVOM without bar graph function; however, peak voltage signal may not easily be determined due to "averaging" of signal.

CRANKSHAFT ANGLE SENSOR SIGNAL HARNESS TERMINALS

KNOCK SENSOR

Using an ohmmeter capable of reading greater than 10-megohm, test for continuity between knock sensor terminal and chassis ground. If continuity exists, circuit is okay. If continuity does not exist, replace knock sensor. If a fault is present in detonation sensor circuit, a Code 34 will be set in ECM memory. If a Code 34 is set, proceed to appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section.

EXHAUST GAS OXYGEN SENSOR (G20 & M30)

1. Disconnect oxygen sensor harness connector. Turn ignition on. Using DVOM, check voltage signal on center terminal of computer side of oxygen sensor harness. Voltmeter should indicate about one volt.
2. If one volt is not present, check for open or short to ground in oxygen sensor harness White wire between oxygen sensor and terminal No. 19 (G20) or terminal No. 29 (M30) at ECU. Also see FEEDBACK SYSTEM under «FUEL CONTROL»(ref-17381-S35873058082000122900000) .

EXHAUST GAS OXYGEN SENSOR (Q45)

See FEEDBACK SYSTEM under FUEL CONTROL.

EXHAUST GAS OXYGEN SENSOR HEATER

1. Disconnect oxygen sensor connector at sensor. Using ohmmeter, check resistance between 2 outside terminals on sensor side of harness.
2. Resistance should be 3-1000 ohms. If not within specification, replace oxygen sensor. DO NOT touch ohmmeter to center terminal of sensor, as damage to oxygen sensor will result.
3. Turn ignition on. Using voltmeter, measure voltage across 2 outside terminals on computer side of oxygen sensor harness. If battery voltage is not indicated, check ground at engine block, check for blown fuse "W" in engine compartment fuse block and check for open in harness between ECU and oxygen sensor.

EXHAUST GAS TEMPERATURE SENSOR (CALIFORNIA)

1. Measure resistance across sensor terminals. Place exhaust gas temperature sensor in container of water. Sensor resistance should decrease as temperature increases.
2. Heat water until boiling temperature of 212°F (100°C) has been obtained. Resistance at 212°F (100°C) should be 76,770-93,830 ohms. If a fault is present in exhaust temperature sensor circuit, a Code 35 will be set in ECU memory. If a Code 35 is set, proceed to TESTS W/CODES article in the ENGINE PERFORMANCE Section.

FUEL TEMPERATURE SENSOR (M30 & Q45)

Disconnect temperature sensor connector. Measure resistance across sensor terminals. See FUEL TEMPERATURE SENSOR RESISTANCE TEST (M30 & Q45) table.

FUEL TEMPERATURE SENSOR RESISTANCE (M30 & Q45) (1)

NEUTRAL SWITCH (G20 M/T)

Disconnect neutral switch harness connector. Using a DVOM, check for continuity between terminals. Continuity should exist in Neutral only.

PARK/NEUTRAL INPUT (G20 & M30 A/T)

1. Backprobe ECU terminal No. 35 (G20) or 44 (M30) with positive lead of a 10-megohm DVOM. Connect negative lead to chassis ground. See appropriate WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section to identify ECU terminals.
2. With gear selector in any position except Park or Neutral, voltmeter should indicate 8-10 volts. With gear selector lever in Park or Neutral, voltmeter should indicate about zero volts. On G20, check for short circuit between ECU and transmission inhibitor switch if voltmeter always indicates zero volts. If wiring is okay, substitute a known good ECU.
3. On M30, check for short circuit between transmission control unit terminal No. 13 and ECU if voltmeter always indicates zero volts. If wiring is okay, check for inhibitor switch misadjustment or short to voltage between A/T inhibitor switch and transmission control unit.
4. If wiring and switch are okay, substitute a known good transmission control unit. If circuit still does not operate correctly, substitute a known good ECU.

PARK/NEUTRAL RELAY INPUT (Q45)

1. Backprobe ECU terminal No. 44 with positive lead of a 10-megohm DVOM. Connect negative lead to a good ground. See appropriate WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section to identify ECU terminals.
2. With gear selector in any position except Park or Neutral, voltmeter should indicate 8-10 volts. With gear selector lever in Park or Neutral, voltmeter should indicate about zero volts. To test park/neutral relay, see «RELAYS & SOLENOIDS»(ref-17381-S33720257322000122900000) .

POWER STEERING OIL PRESSURE SWITCH (G20)

1. Switch is attached to power steering high pressure hose. Disconnect switch connector. With engine idling and steering wheel in straight-ahead position, check continuity across switch terminals. Turn steering wheel quickly left or right. Resistance should change from infinite to zero ohms.
2. Reconnect switch connector. Check harness and signal to ECU. With engine idling and steering wheel in straight-ahead position, check voltage between chassis ground and ECU terminal No. 43. Voltage reading should be 7-10 volts. Turn steering wheel quickly left or right. Voltage should change from 7-10 volts to zero volts.

POWER STEERING OIL PRESSURE SWITCH (Q45)

1. Switch is attached to power steering high pressure hose. Disconnect switch connector. With engine idling and steering wheel in straight-ahead position, check continuity across switch terminals. Turn steering wheel quickly left or right. Resistance should change from infinite to zero ohm.
2. Check harness and signal to ECU. With engine idling and steering wheel in straight-ahead position, check voltage between chassis ground and ECU terminal No. 40. Voltage should be zero. Turn steering wheel quickly left or right. Voltage should change from zero to battery voltage.

START (IGNITION SWITCH) SIGNAL

Backprobe ECU terminal No. 34 (G20) or terminal No. 43 (M30 & Q45) with positive lead of DVOM. Connect negative lead to chassis ground. Turn ignition switch to START position, battery voltage should exist at ECU terminal. If battery voltage does not exist, check for open in wire between ignition switch and ECU. If wire is okay, replace ignition switch.

SUB-CRANKSHAFT POSITION SENSOR (Q45)

Disconnect harness at sub-crankshaft position sensor. Remove sensor. Connect analog volt-ohmmeter test leads between terminals "a" and "b" of sensor. (Scheme 66) Place voltmeter on low (100 millivolt) AC volt scale. Turn sensor by hand. Voltmeter needle should deflect. If voltmeter does not indicate generated voltage signal, replace sensor.

Scheme 67

1. Throttle position sensor and idle switch are a combined assembly located on side of throttle body. Idle switch connector is located on sensor; TPS connector is a separate harness connected to sensor. Warm engine to operating temperature. On Q45, ensure fast idle cam is fully released. On all models, turn ignition off. Disconnect TPS at harness. Connect ohmmeter between terminals No. 5 and 6 on sensor side of harness. (Scheme 67)
2. On G20, resistance should be approximately 2000 ohms with throttle closed. With throttle completely open, resistance should be approximately 10,000 ohms. If sensor does not respond as indicated, adjust TPS. See ADJUSTMENTS article in the ENGINE PERFORMANCE Section.
3. On M30, resistance should be approximately 1000 ohms with throttle closed. With throttle completely open, resistance should be approximately 9000 ohms. If sensor does not respond as indicated, adjust TPS. See ADJUSTMENTS article in the ENGINE PERFORMANCE Section.
4. On Q45, resistance should be about 400 ohms with throttle closed. With throttle completely open, resistance should be about 5000 ohms.
5. As throttle angle is slowly changed, resistance should change smoothly, with no skips or sudden changes indicated on ohmmeter. If sensor does not respond as indicated, replace TPS.
6. On M30 and Q45, reconnect TPS harness connector. Disconnect idle switch connector at TPS. Connect ohmmeter leads between terminals No. 2 and 3 of idle switch harness to sensor.
7. With throttle fully closed, resistance should be zero ohms. With throttle slightly open, resistance should be infinite. If sensor does not respond as indicated, replace TPS.

VEHICLE SPEED SENSOR

Raise and support front of G20 or rear of J30 and Q45 on jackstands. Disconnect vehicle speed sensor connector at wheel. Using an ohmmeter, check continuity across speed sensor harness connectors while rotating one driving wheel. Resistance should fluctuate between zero and infinite ohms.

A/C Clutch Relay

See MISCELLANEOUS CONTROLS .

ECCS, Fuel Pump & Ignition Coil Relays

Relays are Green. For relay location, see RELAY LOCATION & IDENTIFICATION table. With battery voltage and ground applied to terminals No. 1 and 2 of relay, continuity should exist between terminals No. 3 and 5. (Scheme 68)

RELAY LOCATION & IDENTIFICATION

Scheme 68

Park/Neutral Relay (Q45)

Remove park/neutral relay (Gray), located in relay box in right front corner of engine compartment. With battery voltage and ground applied to terminals No. 1 and 2 of relay, continuity should exist between terminals No. 3 and 4. (Scheme 69)

Scheme 69

Safety Relay (M30)

1. Safety relay (Orange) is located at right kick panel. Remove relay from vehicle. Connect battery voltage to terminal No. 1 of relay. (Scheme 70)
2. Connect terminal No. 2 of relay to ground. Using ohmmeter, ensure continuity does not exist between terminals No. 2 and 3.
3. Reverse voltmeter power and ground leads. Continuity should now exist. If relay does not respond as indicated, replace relay.

Scheme 70

Air Induction Valve (AIV) Control Solenoid

See AIR INDUCTION (G20) under EMISSION SYSTEMS & SUB-SYSTEMS .

Auxiliary Air Control (AAC) Solenoid

See IDLE CONTROL SYSTEM .

EGR Solenoid Valve

See EXHAUST GAS RECIRCULATION (EGR) under EMISSION SYSTEMS & SUB-SYSTEMS .

Fuel Injector

See FUEL CONTROL under FUEL SYSTEM .

Fuel Pressure Regulator Solenoid (M30)

See FUEL DELIVERY under FUEL SYSTEM .

Canister Purge Solenoid Valve (G20 & Q45)

See FUEL EVAPORATION under EMISSION SYSTEMS & SUB-SYSTEMS

Variable Valve Timing Solenoid (Q45)

See MISCELLANEOUS CONTROLS .

Relieving Fuel Pressure

Remove fuel pump fuse, start engine and allow engine to run until it stalls due to lack of fuel. Crank engine an additional 2-3 times to verify all pressure has dissipated.

Fuel Pressure

For basic fuel pressure procedures and specifications, see FUEL PRESSURE under FUEL SYSTEM in BASIC TESTING article in the ENGINE PERFORMANCE Section.

Fuel Pressure Regulator

1. Relieve fuel pressure from system. Connect fuel pressure gauge between fuel filter and fuel tube. Remove hose from fuel pressure regulator and plug hose. Jump fuel pump relay. Connect hand-held vacuum pump to pressure regulator. Turn ignition on.
2. Gradually apply vacuum to regulator. Fuel pressure should decrease as vacuum increases. Compare values to FUEL PRESSURE table in BASIC TESTING article in the ENGINE PERFORMANCE Section. If results are unsatisfactory, replace fuel pressure regulator.

1. Remove vacuum lines and electrical connector from solenoid. Remove solenoid from vehicle. Apply battery voltage to White/Black wire terminal of solenoid. Apply ground to Purple wire terminal of solenoid. Blow into vacuum port "A" on end of solenoid. (Scheme 71)
2. As battery voltage is applied, air should pass out of right angle vacuum port "B". With power and ground removed from solenoid, air should pass out of port "C". Port "C" may be covered by a filter.

Scheme 71

Fuel Pump

Remove fuel tank filler cap. Turn ignition on. Listen for fuel pump operating noise. If noise is not present, check fuel pump relay and wiring harness between relay and pump. On Q45, check operation of fuel pump control unit. If fuel pump control unit is okay, disconnect fuel pump/sending unit connector at fuel tank and check resistance across fuel pump winding terminals. See FUEL PUMP WINDING IDENTIFICATION table. Ohmmeter should indicate .5 ohm. If resistance is not correct, replace fuel pump.

FUEL PUMP WINDING IDENTIFICATION

Fuel Pump Control Unit (Q45)

1. Disconnect fuel pump control unit connector, located above fuel tank at rear of vehicle. Install 3 jumper wires from unit side of harness, terminals No. 5, 6 and 7, to ECU side of harness, terminals "e", "f" and "g" respectively. (Scheme 72)
2. Connect one, then 2 and finally 3 jumper wires as indicated in illustration. Using a DVOM, check voltage between terminals No. 4 and 7 as each jumper wire is connected. (Scheme 72) If voltage readings are not as indicated, replace fuel pump control unit.

Scheme 72

Fuel Pump Relay

See RELAYS under RELAYS & SOLENOIDS.

Start Signal

Start signal from ignition switch is used for ECU control of fuel pump and pressure regulator control solenoid. On Q45, start signal is used by ECU in controlling fuel pump control unit. See ENGINE SENSORS & SWITCHES .

FUEL CONTROL

ECU controls fuel system based upon sensor input signals. See FUEL CONTROL SYSTEM INPUT SIGNALS table. If feedback system does not function properly, check input signals before replacing ECU.

FUEL CONTROL SYSTEM INPUT SIGNALS

Feedback System

1. Start engine, and warm it to operating temperature. Ensure idle speed and timing are adjusted to specification. Increase engine speed to about 2000 RPM for 2 minutes under no-load condition. Using a small screwdriver, turn diagnostic mode selector screw on ECU.
2. With screwdriver turned fully clockwise for at least 2 seconds, inspection lights will begin to flash. Turn screwdriver fully counterclockwise. This switches ECU to Mode II which is used to monitor exhaust gas sensor feedback signals.
3. With engine speed at 2000 RPM for 2 minutes, LED should flash at least 5 times during a 10-second period. If sensor does not respond as indicated and no other faults which may affect air/fuel mixture are indicated by ECU self-diagnostic system, use a voltmeter to verify input signals to ECU are correct. If so, replace oxygen sensor. If still not correct, replace ECU.
4. Q45 uses 2 oxygen sensors. When Mode II is first entered, left bank oxygen sensor is being monitored. To change to right bank monitoring (with engine running), turn diagnostic mode selector on ECU fully clockwise. Wait at least 2 seconds. Turn selector lever fully counterclockwise. Repeat step 2).

1. With engine idling, individually disconnect injector harness connectors. Each injector should produce an equal RPM drop.
2. With engine cranking or while manually rotating crank angle sensor (harness connected with ignition on), listen for clicking or feel for vibration, indicating injectors are triggering. If injectors are not triggering, check power and ground circuits and crank angle sensor signal to ECU.
3. Disconnect fuel injector connector. Using ohmmeter, check across injector terminals for 10-14 ohms resistance. If 10-14 ohms is not indicated, replace fuel injector.
4. Check for injector leaks by removing injector fuel rail. Keep fuel hose and all injectors connected to rail. Turn ignition on. DO NOT start engine. Observe injector tips for leakage. If injectors drip, replace faulty injectors.

See ENGINE SENSORS & SWITCHES .

IDLE CONTROL SYSTEM

Idle speed is controlled by ECU through AAC valve and Fast Idle Control Device (FICD) valve on G20 and M30. ECU controls idle speed components based upon signals received from various input devices. If idle speed components test correctly but idle speed is not being regulated properly, check input signals to ECU. See IDLE SPEED SYSTEM INPUT SIGNALS table.

On Q45, fast idle is controlled by fast idle cam on non-traction control system equipped vehicles and air cut valve on traction control system equipped vehicles. Engine coolant temperature changes volume of wax element to control amount of air by-passing secondary throttle valve. As engine warms, by-pass air is reduced, reducing idle speed.

Note. On Q45, see ADJUSTMENTS article in the ENGINE PERFORMANCE Section for testing and adjustment of fast idle cam.

IDLE SPEED SYSTEM INPUT SIGNALS

AIR CUT VALVE (Q45 WITH TRACTION CONTROL SYSTEM)

1. Remove air cut valve. Place valve, gasket side up, in about one inch of 32°F (0°C) water. DO NOT wet gasket. Blow through air inlet. Air should pass easily.
2. Heat water to warmer than 122°F (50°C). Blow through air inlet. Almost no air should pass. If valve does not function as specified, replace valve.

AIR REGULATOR (G20 & M30)

Start engine. Pinch off large air line going to regulator. When engine is cold, RPM should drop. When engine is warmed up, RPM should not change. Disconnect air regulator connector. Check resistance across regulator terminals for 70-80 ohms.

1. Warm engine to operating temperature. Place transmission in Neutral. Ensure idle speed is within specification. If idle speed is not within specification, adjust it before proceeding. See ADJUSTMENTS article in the ENGINE PERFORMANCE Section. If idle speed cannot be adjusted, check idle speed screw passage for blockage.
2. With engine idling at specified RPM, disconnect AAC solenoid connector. RPM should drop. If RPM drops, AAC is functioning correctly.
3. If RPM does not drop, turn ignition off. Disconnect electrical connector from AAC solenoid. Using ohmmeter, ensure resistance of solenoid windings is 10 ohms. Remove AAC valve, and check for plunger seizing or sticking. Check for broken tension spring. If no faults are found, check AAC power and ground circuits. Check ECU input signals used to control AAC solenoid.

FAST IDLE CONTROL DEVICE (FICD) SOLENOID (G20 & M30)

Disconnect FICD solenoid connector. Briefly apply ground and battery voltage to solenoid. Solenoid should click as it is energized. If solenoid does not click, remove FICD and check for seizing or sticking plunger. Check for broken tension spring.

Ignition Coil

See IGNITION CHECKS in BASIC TESTING article in the ENGINE PERFORMANCE Section.

Power Transistor

See IGNITION CHECKS in BASIC TESTING article in the ENGINE PERFORMANCE Section.

Crankshaft Angle Sensor

ECU depends upon crankshaft angle sensor for RPM signals. ECU uses signals to determine triggering of power transistors and fuel injectors. See CRANKSHAFT ANGLE SENSOR and SUB-CRANK ANGLE SENSOR under ENGINE SENSORS & SWITCHES .

See IGNITION CHECKS in BASIC TESTING article in the ENGINE PERFORMANCE Section.

See IGNITION CHECKS in BASIC TESTING article in the ENGINE PERFORMANCE Section.

ECU depends upon crankshaft angle sensor for RPM signals. Signals are used by ECU to determine triggering of power transistor and fuel injectors. See CRANKSHAFT ANGLE SENSOR under ENGINE SENSORS & SWITCHES .

Timing Advance System

ECU controls ignition timing advance based upon sensor input signals that reflect ignition timing needs. If timing problems are experienced, inspect input signals for proper operation. See TIMING ADVANCE SYSTEM INPUT SIGNALS table. To check input signals, see ENGINE SENSORS & SWITCHES or ECU pin voltage charts in PIN VOLTAGE CHART S article in the ENGINE PERFORMANCE Section.

TIMING ADVANCE SYSTEM INPUT SIGNALS

AIR INDUCTION (G20)

Air induction is controlled by Air Induction Valve (AIV) and AIV control solenoid. AIV sends secondary air to exhaust manifold using vacuum created by exhaust pulsation. Reed valves prevent secondary air from being sent back to air cleaner when exhaust pressure is greater than atmospheric pressure.

AIV control solenoid provides vacuum to open AIV at idle and on deceleration. During acceleration, solenoid is energized, preventing vacuum from opening AIV.

Air Induction Valve (AIV)

Start engine, and bring it to full operating temperature. With engine at idle, AIV should operate. Raise engine speed to greater than 2000 RPM, and then allow it to return to idle. AIV should not operate during acceleration and should operate on deceleration. If AIV does not operate as specified, check vacuum hoses and AIV control solenoid. See AIV CONTROL SOLENOID. If hoses and solenoid are okay, replace AIV.

AIV Control Solenoid

1. Remove vacuum lines and electrical connector from solenoid. Remove solenoid from vehicle. Apply battery voltage to White/Green wire terminal of solenoid. Apply ground to Gray wire terminal of solenoid. Blow into vacuum port "A" on end of solenoid.
2. As battery voltage is applied, air should pass out of right angle vacuum port "B". With power and ground removed from solenoid, air should pass out of port "C". Port "C" may be covered by a filter. (Scheme 71)

EXHAUST GAS RECIRCULATION (EGR)

ECU controls EGR through a EGR solenoid valve. ECU controls solenoid based upon input signals received from various input components. If EGR system components test okay and system fails to function properly due to ECU control of EGR solenoid, test input signals which ECU uses to determine control of EGR system. See EGR SYSTEM INPUT SIGNALS table.

EGR SYSTEM INPUT SIGNALS

EGR System Check

1. Warm engine to normal operating temperature. Disconnect vacuum line at EGR valve and connect vacuum gauge. Increase engine speed to 2000 RPM. Vacuum should be indicated on gauge.
2. If vacuum is not indicated, check backpressure transducer, EGR solenoid valve and input signals which ECU uses to control EGR system. See EGR SYSTEM INPUT SIGNALS table. Also check EGR solenoid power supply and harness between ECU and EGR solenoid for opens or shorts.

EGR Backpressure Transducer

1. Remove vacuum and exhaust lines from transducer. Plug one upper vacuum port of EGR transducer. Connect hand-held vacuum pump to remaining EGR vacuum port. (Scheme 73) Apply vacuum. Vacuum should not hold. If vacuum holds, replace transducer.
2. Blow into exhaust pressure port. Apply vacuum to EGR vacuum port again. Vacuum should hold only when air pressure is applied to transducer pressure port. If vacuum is not as specified, replace transducer.

Scheme 73

EGR Valve

1. With engine idling, disconnect EGR vacuum line. Apply vacuum to EGR valve. Engine speed should decrease or engine should stall. If engine does not respond in this manner, go to step 2). Vacuum should hold on gauge. If vacuum does not hold, replace EGR valve.
2. Manually compress EGR valve diaphragm from underside. If engine speed does not decrease or engine does not stall, remove EGR valve and inspect EGR passages for plugging. If engine speed decreases or engine stalls, replace EGR valve.

1. Remove vacuum lines and electrical connector from solenoid. Remove solenoid from vehicle. Using jumper wires, connect battery voltage and ground to appropriate terminal of solenoid. See EGR SOLENOID TERMINAL IDENTIFICATION table. Blow into vacuum port "A" on end of solenoid. EGR SOLENOID TERMINAL IDENTIFICATION Application Power Ground G20 White/Green Purple M30 White/Black Light Green Q45 Red Blue/Red
2. As battery voltage is applied, air should pass out of right angle vacuum port "B". With power and ground removed from solenoid, air should pass out of port "C". Port "C" may be covered by a filter. (Scheme 71)

Exhaust Gas Temperature Sensor

Check sensor resistance with sensor immersed in a coolant solution heated to 212°F (100°C). Resistance across sensor terminals should be 77,000-94,000 ohms. Resistance should also decrease in response to temperature increase. If resistance is not as indicated, replace sensor.

Carbon Canister & Purge Control Valve

Remove hoses from canister. Blow through port "C" of canister. Air should pass freely out of bottom of canister. Blow through port "B" of canister. A low volume of air should pass into canister. Apply vacuum to port "A" of canister. Volume of air blown into port "B" should increase. (Scheme 74)

Scheme 74

1. Remove vacuum lines and electrical connector from solenoid. Remove solenoid from vehicle. Using jumper wires, connect battery voltage and ground to appropriate terminal of solenoid. See CANISTER PURGE SOLENOID TERMINAL IDENTIFICATION table. Blow into vacuum port "A" on end of solenoid. CANISTER PURGE SOLENOID TERMINAL IDENTIFICATION Application Power Ground G20 White/Green Purple Q45 Red Green/Yellow
2. As battery voltage is applied, air should pass out of right angle vacuum port "B". With power and ground removed from solenoid, air should pass out of port "C". Port "C" may be covered by a filter. (Scheme 71)

Vacuum Relief Filler Cap

Wipe cap clean. Apply vacuum from tank side. Slight resistance should be felt and cap should make distinct clicking noises. As vacuum increases, resistance should decrease and clicking noise should go away. If valve is plugged or no resistance is felt, replace cap as an assembly.

POSITIVE CRANKCASE VENTILATION

Run engine at idle. Remove ventilation hose from PCV valve; hissing noise should be heard from hose and a strong vacuum should be felt immediately when finger is placed over valve inlet. If vacuum is not felt, check hose and hose connections for leaks and obstructions. Check PCV valve. Service or replace as necessary.

1. A/C clutch relay is controlled by ECU. Under normal conditions, ECU will engage clutch relay by providing a ground circuit for relay windings. If ECU receives a wide open throttle signal from throttle position sensor while it is also receiving a A/C on signal from A/C Auto Amplifier, ECU will disengage relay.
2. A/C clutch relay (Blue or Green) is located in relay box on right side of engine compartment. On G20, relay is in foremost position. On M30, relay is second from rear. On Q45, relay is in rearmost position.
3. Remove relay from relay box. Apply ground to terminal No. 2 of relay. see scheme 15 Apply battery voltage to terminal No. 1. With relay energized, continuity should exist between terminals No. 3 and 5. No continuity should exist with relay de-energized.

Remove solenoid from front of engine. Apply battery voltage across solenoid terminals. (Scheme 75) If solenoid does not energize, replace solenoid.

Scheme 75