Engine Controls - System/component Tests: Other Geo Tracker I

TERMINOLOGY

Due to federal government requirements, manufacturers may use names and acronyms for systems and components different than those used in previous years. The SAE TERMINOLOGY will help eliminate confusion when dealing with these components and systems. Only relevant components and systems whose names have changed from current General Motors Corp. terminology have been listed.

SAE TERMINOLOGY CHART

Ground Circuit Checks

Check ground circuits to ECM for continuity to ground. Using a DVOM, touch negative voltmeter lead to a good ground. Touch positive voltmeter lead to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If volt-meter reading is greater than one volt, check for open, corrosion or loose connection on ground lead. To identify ECM ground terminals, see WIRING DIAGRAMS article in this section.

Power Circuit Checks

Using DVOM, check power circuits to ECM for opens or shorts. To identify ECM power terminals, see WIRING DIAGRAMS article in this section.

COOLANT TEMPERATURE SENSOR

1. Remove coolant temperature sensor. See «COOLANT TEMPERATURE SENSOR LOCATION»(ref-19482-S39674451872001010200000) .
2. Measure resistance of coolant temperature sensor at designated temperatures. Replace sensor if it is not within specification. See «COOLANT TEMPERATURE SENSOR RESISTANCE»(ref-19482-S25636654582001010200000) .

COOLANT TEMPERATURE SENSOR LOCATION

COOLANT TEMPERATURE SENSOR RESISTANCE

CRANK ANGLE SENSOR

1. Ensure ignition is off. Disconnect Yellow 24-pin connector from ECM, located under left side of instrument panel, near kick panel. (Scheme 50)
2. Connect voltmeter between White wire on 24-pin connector and Blue/Black wire on Green 17-pin connector. Remove distributor cap, rotor and shield cover. Ensure no metal particles exist on magnet area of crank angle sensor.
3. Turn ignition on. Rotate engine so signal rotor aligns with Hall Effect element, and note voltage reading. (Scheme 47) Voltage should be 0-1 volt. Rotate engine so signal rotor is not aligned with Hall Effect element. Battery voltage should now exist.
4. If battery voltage does not exist, check for defective wiring between distributor and ECM. If wiring is okay, replace crank angle sensor. Turn ignition off. Reconnect electrical connector on ECM. Install shield cover, rotor and distributor cap.

Scheme 47

EGR TEMPERATURE SENSOR

See EXHAUST GAS RECIRCULATION under EMISSIONS SYSTEMS & SUB-SYSTEMS.

Note. Electrical load sensor may be referred to as diode module.

INTAKE AIR TEMPERATURE (IAT) SENSOR

Note IAT sensor location. See IAT SENSOR LOCATION . Using ohmmeter, check resistance across IAT sensor terminals. Replace IAT sensor if resistance is not within specification. See IAT SENSOR RESISTANCE SPECIFICATIONS .

IAT SENSOR LOCATION

IAT SENSOR RESISTANCE SPECIFICATIONS

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR

1. MAP sensor is located on firewall. With ignition on, check supply voltage from ECM to MAP sensor on designated wire terminal. See «MAP SENSOR WIRE TERMINAL IDENTIFICATION»(ref-19482-S31441606042001010200000) . Reading should be about 5 volts.
2. Disconnect vacuum hose at MAP sensor. Install hand-held vacuum pump. Turn ignition on. Check signal voltage at designated wire terminal of MAP sensor. See «MAP SENSOR WIRE TERMINAL IDENTIFICATION»(ref-19482-S31441606042001010200000) .
3. Apply vacuum, and note change in signal voltage. As vacuum reading changes, signal voltage should change. Reading should be about 1-1 1/2 volts at high vacuum (idle position) to 4-4 1/2 volts at low vacuum (full throttle position).

MAP SENSOR WIRE TERMINAL IDENTIFICATION

PARK/NEUTRAL POSITION SWITCH CONTINUITY

PARK/NEUTRAL POSITION SWITCH

1. Disconnect negative battery cable. Disconnect switch connector located under intake manifold. Connector is round and contains 4 wires.
2. Using ohmmeter, check for continuity between specified wires with gearshift in proper position. See «PARK/NEUTRAL POSITION SWITCH CONTINUITY»(ref-19482-S22462200062001010200000) . Continuity should exist in these gears only.

POWER STEERING PRESSURE SWITCH

1. Power steering pressure switch is located on power steering pump. With wheels in straight-ahead position, disconnect Blue/Orange wire at power steering pressure switch.
2. With ignition on, ensure battery voltage exists on Blue/Orange wire. If battery voltage does not exist, check for open circuit in Blue/Orange wire between ECM and power steering pressure switch. ECM is located under left side of instrument panel, near kick panel. NOTE: If power steering pressure switch fails to close, or open circuit in wiring exists between ECM and pressure switch, engine may stall when wheels are turned. If power steering pressure switch fails to open or short to ground exists in wiring between ECM and pressure switch, idle quality will be affected.
3. Connect ohmmeter across switch terminals. Start engine. Check for continuity to ground while turning wheels from straight-ahead position to full turn. Switch should close and continuity should exist when wheels are in a full turn position. Replace switch if defective.

THROTTLE POSITION (TP) SENSOR RESISTANCE

THROTTLE POSITION (TP) SENSOR

Disconnect TP sensor electrical connection. Install proper thickness feeler gauge between stop screw and lever. Using ohmmeter, check continuity or resistance between designated terminals. Adjust or replace TP sensor if it is not within specification. See THROTTLE POSITION (TP) SENSOR RESISTANCE. (Scheme 48)for terminal identification.

Scheme 48

VEHICLE SPEED SENSOR

1. Following procedure applies if Code 24 is stored in ECM or incorrect input from vehicle speed sensor is suspected. Check speedometer operation. If speedometer operates correctly, go to next step. Repair or replace speedometer if it is not operating properly.
2. Disconnect 12-pin connector from instrument cluster. Using ohmmeter, measure resistance between Black/Yellow wire of connector and ground. If resistance is less than.3 ohm, go to next step. If resistance is greater than.3 ohm, repair Black/Yellow wire between instrument cluster and ground connection, located behind instrument panel (above fuse block).
3. Turn ignition on. Using voltmeter, measure voltage between Yellow wire of instrument cluster 12-pin connector and ground. If voltage is less than 5 volts, go to next step. If voltage is greater than 5 volts, go to step 6).
4. Turn ignition off. Disconnect 24-pin connector from ECM, located under left side of instrument panel, near kick panel. Using ohmmeter, measure resistance between Yellow wire of ECM connector and instrument cluster connector. If resistance is greater than.3 ohm, repair open circuit in Yellow wire. If resistance is less than.3 ohm, go to next step.
5. Connect ohmmeter between Yellow wire of 18-pin ECM connector and ground. If continuity exists, repair short to ground in Yellow wire. If continuity does not exist, replace ECM.
6. Disconnect speedometer cable from speedometer. Connect ohmmeter across vehicle speed sensor terminals at speedometer head. (Scheme 49) Measure resistance while rotating speedometer head. If resistance decreases to less than 5 ohms 4 times per revolution, replace ECM. If resistance does not decrease to less than 5 ohms, replace speedometer.

Scheme 49

EFI Main Relay

1. EFI main relay is mounted on ECM, located under left side of instrument panel, near kick panel. (Scheme 50) Disconnect electrical connector from EFI main relay.
2. Using ohmmeter, ensure continuity exists between Black/White and Blue wire terminals of EFI main relay. Apply battery voltage to Black/White wire terminal. Ground Blue wire terminal. Continuity should exist between Black/Red and Blue/Black wire terminals. Replace EFI main relay if continuity is not as specified.

Scheme 50

Idle Speed Control Solenoid

See IDLE CONTROL SYSTEM .

FUEL DELIVERY

Note. For fuel system pressure testing, see BASIC TESTING article in this section.

Fuel Injector

Check resistance across fuel injector terminals. Replace fuel injector if resistance is not within specification. See FUEL INJECTOR RESISTANCE SPECIFICATIONS .

FUEL INJECTOR RESISTANCE SPECIFICATIONS

Oxygen Sensor Heater

1. With ignition off, disconnect electrical connector at oxygen sensor. Turn ignition on with engine off. Using voltmeter, check for battery voltage on Black/White wire at connector. If battery voltage exists, go to step 3).
2. If battery voltage does not exist, check for open circuit in Black/White wire between oxygen sensor and 15-amp ignition/coil fuse. Fuse is located in fuse block on left side of steering column.
3. Turn ignition off. Connect test light to battery voltage. Backprobe Pink wire at oxygen heater jumper connector and note if voltage exists. Jumper connector is taped to wiring harness near ECM, located under left side of instrument panel, near kick panel.
4. If voltage exists, go to next step. If voltage does not exist, check for open circuit in Pink or Black wire to ground or defective Black wire in jumper connector.
5. Using ohmmeter, measure oxygen sensor heater resistance between Pink and Black/White wire terminals of oxygen sensor. Resistance should be 3.7-5.1 ohms at 73°F (23°C).
6. If resistance is as specified, heater portion of oxygen sensor is okay. Replace oxygen sensor if resistance is not as specified.

AIR VALVE

1. Air valve is located in lower body of throttle body. Remove air valve cap on throttle body. With engine temperature at 140°F (60°C) or less, ensure air valve is open. (Scheme 51)
2. Install air valve cap. Warm engine to normal operating temperature. Remove air valve cap. Inspect air valve. Air valve should be closed. Replace air valve if defective.

Scheme 51

IDLE AIR CONTROL VALVE

1. With ignition off, disconnect electrical connector from Idle Air Control (IAC) valve. IAC valve is located on throttle body and contains a Blue/Black and Light Green/Black wire connector.
2. Turn ignition on. Using voltmeter, check for battery voltage at Blue/Black wire of electrical connector. Battery voltage should exist.
3. If battery voltage exists, go to next step. If battery voltage does not exist, check for open circuit in Blue/Black wire between IAC valve and EFI main relay. EFI main relay is mounted on ECM, located under left side of instrument panel, near kick panel. (Scheme 50)
4. Turn ignition off. Connect test light to battery voltage. Probe Light Green/Black wire. Turn ignition on. Light should glow momentarily.
5. If test light glows momentarily, go to next step. If test light stays on, check for short to ground in Light Green/Black wire between IAC valve and ECM. ECM is located under left side of instrument panel, near kick panel. If test light does not glow momentarily, check for open circuit in Light Green/Black wire between IAC valve and ECM. If circuit is not open, replace ECM.
6. Turn ignition off. Using ohmmeter, measure resistance between IAC valve terminals. Resistance should be 11-14 ohms at 68°F (20°C). CAUTION: DO NOT apply battery voltage to IAC solenoid for more than one second. Allow 10 seconds between voltage applications to prevent valve damage.
7. If resistance is not as specified, replace IAC valve. If resistance is as specified, connect battery voltage to Blue/Black wire terminal and ground Light Green/Black wire terminal momentarily. A click should be heard to indicate valve operation. Replace IAC valve if a click is not heard. Reinstall electrical connector.

Note. Idle-up vacuum switching valve also may be referred to as Idle Speed Control (ISC) solenoid.

THROTTLE OPENER CONTROL SYSTEM

1. Disconnect electrical connector at throttle opener vacuum Switching Valve (SV), located in front of valve. SV contains a 2-pin connector with Light Green/White and Blue/Black wires.
2. Turn ignition on. Using test light connected to ground, probe Blue/Black wire at SV connector. If test light glows, go to next step. If test light does not glow, check for open circuit in Blue/Black wire between SV and EFI main relay. EFI main relay is mounted on ECM, located under left side of instrument panel, near kick panel. (Scheme 50)
3. With test light connected to battery voltage, probe Blue/Black wire of SV electrical connector. If test light does not come on, go to next step. If test light comes on, check for short to ground in Light Green/White wire between SV and ECM. ECM is located under left side of instrument panel, near kick panel. If wiring is okay, replace ECM.
4. With ignition off, remove vacuum hose from throttle opener port on SV. Connect a hand-held vacuum pump to hose, and apply vacuum. If throttle opener does not move, check hose for leaks and kinks. If hose is okay, replace throttle opener. If throttle opener moves, go to next step.
5. Reconnect vacuum hose to SV. Remove intake manifold-to-SV vacuum hose at intake manifold. Connect hand-held vacuum pump to hose, and apply vacuum. If throttle opener moves, go to next step. If throttle opener does not move, check hose for leaks and kinks. If hose is okay, replace SV.
6. Turn ignition off. Using test light connected to ground, backprobe Light Green/White wire at ECM. Turn ignition on. Apply vacuum to hose disconnected from intake manifold. Note if throttle opener moves. If throttle opener moves, replace SV. If throttle opener does not move, system is okay.

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING article in this section.

Electronic Ignition Timing Advance

Ignition timing is controlled by Electronic Control Module (ECM). Testing information is not supplied by manufacturer. If crank angle sensor fails, a trouble code may be set. See TESTS W/CODES article in this section.

EGR Temperature Sensor (Tracker California)

EGR temperature sensor is located near EGR valve. Remove EGR temperature sensor. Immerse sensing portion of EGR temperature sensor in water. Heat water, and note EGR temperature sensor resistance at specified temperatures. See EGR TEMPERATURE SENSOR RESISTANCE . Replace sensor if it is not within specification.

EGR TEMPERATURE SENSOR RESISTANCE

EGR System Check

1. With engine cool, grasp top of EGR valve and check for looseness. If looseness is felt, replace EGR valve. WARNING: Wear gloves if EGR valve is hot.
2. Warm engine to normal operating temperature. Place finger on bottom of EGR valve diaphragm. Start engine. Increase engine speed. Note if EGR valve diaphragm moves. If diaphragm does not move, allow engine to idle. Disconnect vacuum hose from EGR valve. Apply 10 in. Hg of vacuum to valve. Vacuum should hold and engine should run rough or stall. If vacuum does not hold, go to step 4).
3. If engine ran rough or stalled and EGR valve held vacuum, check components controlling vacuum supply to EGR valve (i.e., EGR modulator, EGR vacuum switching valve, vacuum supply and hoses). Also, check ECM control of ground circuit to EGR vacuum switching valve and verify EGR vacuum switching valve has power when ignition is on. For wire colors and ECM terminal identification, see WIRING DIAGRAMS article in this section.
4. If EGR valve did not hold vacuum, replace EGR valve. If engine did not run rough or stall, remove EGR valve and check for plugged EGR valve or EGR passages in intake/exhaust system. Clean or replace as necessary.

EGR Vacuum Supply

Locate EGR vacuum supply port on throttle body or intake manifold. Disconnect vacuum supply hose. Connect vacuum gauge to port. Start engine. Increase engine speed to 2000 RPM, and note vacuum reading. At least 10 in. Hg of vacuum should be obtained. If vacuum is low, check vacuum supply port for restriction (carbon, dirt, etc.).

EGR Modulator

1. Remove EGR modulator. Plug one upper vacuum hose fitting while blowing air into other upper vacuum hose fitting. Air should pass through filter.
2. Connect vacuum pump to either upper vacuum hose fittings. Plug other upper vacuum hose fitting (exhaust gas pressure port). Blow air into bottom vacuum hose fitting while applying vacuum using vacuum pump. Vacuum should be obtained. Replace modulator if defective.

EGR VACUUM SWITCHING VALVE LOCATION

EGR Vacuum Switching Valve (SV)

1. With ignition off, disconnect Green connector from ECM, located under left side of instrument panel near kick panel.
2. Disconnect electrical connector and vacuum hoses from SV. See «EGR VACUUM SWITCHING VALVE LOCATION»(ref-19482-S20057558292001010200000). Turn ignition on. Using voltmeter, ensure battery voltage exists at terminal "A" of SV connector. (Scheme 52) If battery voltage does not exist, check for open circuit between SV and EFI main relay. EFI main relay is located near ECM. (Scheme 50)
3. Reconnect SV electrical connector. With ignition on, blow into port No. 1. Air should come out of port No. 2 only. If SV does not perform correctly, SV is defective or Light Green/Yellow wire is shorted to ground.
4. Turn ignition off. Using fused jumper wire, ground terminal G5 (Light Green/Yellow wire) on Green connector at ECM. Turn ignition on. With SV energized, blow air into port No. 1. Air should come out filter only. If air also comes out port No. 2, SV is defective or open circuit exists on Light Green/Yellow wire between ECM and SV.

Scheme 52

Canister Purge Vacuum Switching Valve

1. With ignition on and engine off, disconnect throttle body-to-canister purge vacuum Switching Valve (SV) hose at SV. SV is located on right side of engine compartment, near strut tower, and contains a Light Green/Red and Blue/Black wire connector.
2. Apply 10 in. Hg of vacuum on disconnected vacuum hose port on SV. SV should not hold vacuum.
3. If vacuum holds, go to next step. If vacuum does not hold, disconnect electrical connector at SV. Reapply vacuum to SV. If vacuum holds, replace SV. If vacuum does not hold, check for short to ground in Light Green/Red wire between SV and ECM. ECM is located under left side of instrument panel, near kick panel.
4. With vacuum applied, ground Light Green/Red wire at SV electrical connector. If vacuum decreases, go to step 6). If vacuum does not decrease, disconnect electrical connector at SV. Connect test light to ground. Probe Blue/Black wire at electrical connector.
5. If test light glows, replace SV. If test light does not glow, check for open circuit in Blue/Black wire between SV and EFI main relay. EFI main relay is located near ECM. (Scheme 50)
6. Install vacuum gauge on vacuum hose to SV from throttle body. Start engine, and operate it at 2500 RPM. Momentarily increase engine speed, and then allow engine to idle. Ensure 10 in. Hg of vacuum is obtained.
7. If vacuum is okay, system is operating correctly. If low vacuum exists, check for damaged vacuum hoses and plugged vacuum passages.

PCV Valve

Remove PCV valve from valve cover. Run engine at idle, placing thumb over end of hose to check for vacuum. If vacuum does not exist, check for plugged hoses or manifold port. Turn engine off. Remove PCV valve. Shake valve to ensure needle inside valve is free. Replace valve if needle is not free.

MISCELLANEOUS CONTROLS

Note. Although some controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

A/C CLUTCH SYSTEM CONTROLS

Note. When A/C is operated, ECM will supply a ground to compressor relay. Compressor relay then supplies voltage to A/C clutch.