Engine Controls - System/component Tests: Other Geo Prizm II

TERMINOLOGY

Due to Federal government requirements, manufacturers may use names and acronyms for systems and components different than those used in previous years. The following table 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 (1)

COMPUTERIZED ENGINE CONTROLS

Note. Prizm LSi uses a Powertrain Control Module (PCM). All other models use an Engine Control Module (ECM). All references to ECM include PCM unless specified otherwise.

Ground Circuit Checks

1. Using an ohmmeter, check ground circuits to ECM for continuity to ground. See appropriate wiring diagram in WIRING DIAGRAMS article in this section to determine ECM ground terminals. Resistance to ground should be zero ohms. If reading is other than zero ohms, repair open circuit to ground.
2. 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 voltmeter reading is greater than one volt, check for open, corrosion or loose connection on ground lead.

Power Circuit Checks

1. Using a voltmeter, check for battery voltage between ECM constant battery power terminals and ground. See appropriate wiring diagram in WIRING DIAGRAMS article in this section to determine ECM power terminals. If battery voltage is not present, check ECM power supply fuse. If fuse is okay, check for open in power supply or ECM wiring.
2. Turn ignition switch to ON position. Using a voltmeter, check for battery voltage between ECM ignition power terminals and ground. If battery voltage is not present, check power supply fuse(s). If fuse is okay, check for an open in wiring between fuse and ECM, or check for a defective ignition switch.
3. Connect voltmeter between ground and ECM start (crank) signal terminal. Turn ignition switch to the START position. Battery voltage should be present between ECM start terminal and ground ONLY when ignition switch is in START position. If voltage is not present, check fuse(s). If fuse is okay, check for an open in wiring between fuse and ECM, or check for a defective ignition switch.

ENGINE SENSORS & SWITCHES

Note. For additional sensor testing specifications, see SENSOR RANGE CHARTS article in the ENGINE PERFORMANCE Section.

Camshaft Position Sensor

1. Ensure ignition is off. Remove rotor from distributor housing. Remove ignition coil dust cover and gasket from distributor housing. Remove 2 nuts and 4 wires from ignition coil terminals.
2. Remove 3 screws and 3 wires from igniter terminals. Remove 2 screws and igniter from distributor housing. Remove 2 connectors from harness retainer. Remove distributor wire from housing. Remove screw and noise suppressor condenser from housing.
3. Using ohmmeter, measure resistance of distributor connector C1, when cold (14-104°F; -10-50°C), between terminals No. 3 and 6. (Scheme 105) Camshaft Position (CMP) sensor resistance should be 185-275 ohms. If resistance is not as specified, replace distributor housing.
4. Measure resistance of distributor connector C1, when cold, between terminals No. 2 and 5. CMP sensor resistance should be 370-550 ohms. If resistance is not as specified, replace distributor housing.
5. Measure resistance of distributor connector C1, when hot (104-212°F; 50-100°C), between terminals No. 3 and 6. CMP sensor resistance should be 240-325 ohms. If resistance is not as specified, replace distributor housing.
6. Measure resistance of distributor connector C1, when hot, between terminals No. 2 and 5. CMP sensor resistance should be 475-650 ohms. If resistance is not as specified, replace distributor housing.
7. Measure air gap between signal rotor and camshaft position sensor. Air gap should be.008-.016" (.2-.4 mm). If air gap is not as specified, replace distributor housing. When testing is complete, reverse disassembly procedure.

Scheme 105

EGR Temperature Sensor

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

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

Electrical Load Sensor

For location of electrical load sensor, see illustrations. (Scheme 106) To test electrical load sensor circuit, see Diagnostic Chart C-1A under DIAGNOSTIC CHARTS in this article.

Scheme 106

Engine Coolant Temperature (ECT) Sensor

1. A malfunction in the engine coolant temperature sensor circuit will set a related diagnostic trouble code. For testing procedures, see TESTS W/CODES article in this section. An out-of-calibration ECT sensor may not set a diagnostic trouble code. Use following procedure to test sensor calibration.
2. Remove engine coolant temperature sensor. Refer to the «ENGINE COOLANT TEMPERATURE (ECT) SENSOR LOCATION»(ref-19802-S16769855892001010200000) . Using ohmmeter, measure resistance of engine coolant temperature sensor at designated temperatures. Replace ECT sensor if resistance is not within specification. See «ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE»(ref-19802-S07011245422001010200000) .

ENGINE COOLANT TEMPERATURE (ECT) SENSOR LOCATION

ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE

Intake Air Temperature (IAT) Sensor

1. A malfunction in the intake air temperature sensor circuit will set a related diagnostic trouble code. For testing procedures, see TESTS W/CODES article in this section. An out-of-calibration IAT sensor may not set a diagnostic trouble code. Use following procedure to test sensor calibration.
2. Remove intake air temperature sensor. See «INTAKE AIR TEMPERATURE (IAT) SENSOR LOCATION»(ref-19802-S33724415612001010200000) . Using ohmmeter, measure resistance of intake air temperature sensor at designated temperatures. Replace IAT sensor if resistance is not within specification. See «INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE»(ref-19802-S05181192972001010200000) .

INTAKE AIR TEMPERATURE (IAT) SENSOR LOCATION

INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE

Knock Sensor (LSi)

1. A malfunction in the knock sensor circuit will set diagnostic trouble Code 52. For testing procedures, see TESTS W/CODES article in this section. Use the following procedure to diagnose knock sensor.
2. Check knock sensor resistance using ohmmeter. Measure resistance between knock sensor terminal and ground. Knock sensor, located on rear of engine block, has Black wire connector. Replace sensor if resistance is not one megohm or higher.
3. To check knock sensor operation, remove connector from knock sensor. Connect DVOM between knock sensor terminal and ground. Adjust voltmeter to 200 millivolts on AC scale. Tap on engine block near knock sensor, and note reading. Replace knock sensor if no reading is obtained.

Manifold Absolute Pressure (MAP) Sensor

1. A malfunction in the manifold absolute pressure sensor circuit will set diagnostic trouble Codes 31 and/or 32. For testing procedures, see TESTS W/CODES article in this section. Use the following procedure to diagnose MAP sensor. If driveability problems exist, MAP sensor failure is suspected and no Codes 31 and/or 32 is set, disconnect MAP sensor connector. If driveability improves, replace MAP sensor.
2. 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-19802-S40262661932001010200000) . Reading should be approximately 5 volts.
3. 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-19802-S40262661932001010200000) .
4. Apply vacuum, and note change in signal voltage. As vacuum reading changes, signal voltage should change. Reading should be about 1-1.5 volts at high vacuum (idle position) to 4-4.5 volts at low vacuum (full throttle position).

MAP SENSOR WIRE TERMINAL IDENTIFICATION

Oxygen (O2) Sensor

1. A malfunction in the oxygen sensor circuit will set a related diagnostic trouble code. For testing procedures, see TESTS W/CODES article in this section. Use following procedure to test oxygen sensor.
2. Start engine and warm to operating temperature. Disconnect oxygen sensor. Connect a DVOM between lead of oxygen sensor and ground. Place DVOM on the 2-volt scale. Voltmeter reading should increase to greater than .8 volt.
3. Using another DVOM on the 20-volt scale, connect voltmeter in series between the oxygen sensor wire from ECM and positive post of battery. Reading on voltmeter connected to oxygen sensor should decrease to a low voltage (less than .3 volt).
4. If a second DVOM is not available, install short jumper in oxygen sensor wire from ECM. Hold jumper in one hand and touch positive post of battery with other hand. This should cause oxygen sensor to produce less than .3 volt.

Sub-Oxygen Sensor (LSi California)

1. A malfunction in the sub-oxygen sensor circuit will set diagnostic trouble Code 27. For testing procedures, see TESTS W/CODES article in this section. Use following procedure to test sub-oxygen sensor.
2. Start engine and warm to operating temperature. Disconnect sub-oxygen sensor. Connect a DVOM between lead of sub-oxygen sensor and ground. Place DVOM on the 2-volt scale. Voltmeter reading should increase to greater than .8 volt.
3. Using another DVOM on the 20-volt scale, connect voltmeter in series between the sub-oxygen sensor wire from ECM and positive post of battery. Reading on voltmeter connected to sub-oxygen sensor should decrease to a low voltage (less than .3 volt).
4. If a second DVOM is not available, install short jumper in sub-oxygen sensor wire from ECM. Hold jumper in one hand and touch positive post of battery with other hand. This should cause sub-oxygen sensor to produce less than .3 volt.

Throttle Position (TP) Sensor

1. A malfunction in the throttle position sensor circuit will set diagnostic trouble Code 41. For testing and adjusting procedures, see THROTTLE POSITION (TP) SENSOR in ADJUSTMENTS article in this section. Use the following procedure to diagnose TP sensor.
2. Using ohmmeter, measure resistance or continuity of throttle position sensor between designated terminals with selected feeler gauge thickness between throttle lever and stop screw. (Scheme 107) Adjust or replace TP sensor if resistance is not within specification. See «THROTTLE POSITION (TP) SENSOR RESISTANCE»(ref-19802-S22546356362001010200000).

Scheme 107

THROTTLE POSITION (TP) SENSOR RESISTANCE

Vehicle Speed Sensor

Vehicle speed sensor is mounted on transaxle. A malfunction in the vehicle speed sensor circuit will set diagnostic trouble Code 42. For testing procedures, see TESTS W/CODES article in this section.

Diode Module Or Diode

Diode module or diode is also referred to as electrical load sensor. See ELECTRICAL LOAD SENSOR under ENGINE SENSORS & SWITCHES under COMPUTERIZED ENGINE CONTROLS.

Circuit Opening Relay

1. Circuit opening relay is located behind center of dash, near radio. To test circuit opening relay, see CHART A1-7A, FUEL SYSTEM DIAGNOSIS (CIRCUIT OPENING RELAY CHECK) diagnostic chart in BASIC TESTING article in this section.
2. To test circuit opening relay on LSi, see CHART A2-7A, FUEL SYSTEM DIAGNOSIS (CIRCUIT OPENING RELAY CHECK) diagnostic chart in BASIC TESTING article in this section. For identification of Data Link Connector (DLC) terminals, see illustration. (Scheme 108)

Scheme 108

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

EFI F-HTR Relay

1. EFI F-HTR relay is located in fuse/relay block in left front side of engine compartment, left of air cleaner. Remove EFI F-HTR relay from fuse/relay block. Using ohmmeter, ensure continuity exists between Black/Orange wire and White/Black wire terminals of EFI F-HTR relay.
2. Apply battery voltage to Black/Orange wire terminal and ground White/Black wire terminal. Continuity should exist between Black/Red wire and Red/White wire terminals of EFI F-HTR relay. Replace EFI F-HTR relay if continuity is not as specified.

A/C Solenoid Vacuum (SV) Valve

See IDLE CONTROL SYSTEM .

Exhaust Gas Recirculation Solenoid Vacuum (EGR SV) Valve

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

Fuel Injector

See FUEL CONTROL .

Throttle Opener Solenoid Vacuum (TO SV) Valve (Calif.)

See IDLE CONTROL SYSTEM .

FUEL DELIVERY

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

Fuel Pressure Regulator

To test fuel pressure regulator, see appropriate CHART A-7B, CHART A1-7B or CHART A2-7B, FUEL SYSTEM DIAGNOSIS (FUEL PRESSURE CHECK) diagnostic chart in BASIC TESTING article in this section.

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

FUEL INJECTOR RESISTANCE SPECIFICATIONS

IDLE-UP VACUUM SWITCHING VALVE (IVSV) (PRIZM)

1. IVSV is located on end of intake manifold on Prizm except LSi or below mass airflow sensor on Prizm LSi. IVSV by-passes air into intake manifold on Prizm except LSi or around throttle valve of mass airflow sensor on Prizm LSi when it is activated by ECM.
2. IVSV is energized whenever idle speed drops to less than desired RPM due to engine load (i.e., electrical, P/S, A/T in Drive, etc.). Other information is not available from manufacturer.

For testing and adjusting procedures, see THROTTLE OPENER in the ADJUSTMENTS article in this section.

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.

Electronic Ignition Timing Retard (LSi)

On LSi, a knock sensor, located in rear of cylinder block, sends a variable AC voltage signal to ECM depending on engine detonation. ECM uses this signal to determine if ignition timing should be retarded. Testing information is not supplied by manufacturer. If a fault occurs in retard circuit, a Code 52 will set in ECM memory. If a code is set, see TESTS W/CODES article in this section.

EGR Temperature Sensor (Calif.)

EGR temperature sensor is located on right rear of engine near firewall. If EGR temperature sensor fails, Code 71 will be set in ECM memory. See TESTS W/CODES article in this section.

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 solenoid vacuum valve, vacuum supply and hoses). Also, check ECM control of ground circuit to EGR solenoid vacuum valve and verify EGR solenoid vacuum 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 vacuum hoses from modulator. Plug modulator ports No. 2 and 3. (Scheme 109) Blow into port No. 4. Air should pass from filter.
2. Connect hand-held vacuum pump to port No. 5. Plug ports No. 2 and 3. Blow air into port No. 4. Vacuum pump should not obtain vacuum. Replace EGR modulator if defective.

Scheme 109

EGR Solenoid Vacuum (SV) Valve

1. With ignition off, disconnect vacuum hoses and wiring from solenoid. For SV location, see «EGR SOLENOID VACUUM (SV) VALVE LOCATION»(ref-19802-S39317317432001010200000). Using ohmmeter, ensure resistance between SV terminals is 33-39 ohms.
2. Blow air into port No. 1, ensuring air flows through filter only. (Scheme 110) Apply battery voltage and ground to SV terminals. With SV energized, blow air into port No. 1 to ensure air flows out port No. 2. Replace SV if defective.
3. Check ECM control of ground circuit to EGR SV valve. Ensure SV has voltage with ignition on. For wire colors and ECM terminal identification, see WIRING DIAGRAMS article in this section.

EGR SOLENOID VACUUM (SV) VALVE LOCATION

Scheme 110

Fuel Evaporation Canister Check Valve

1. With canister removed, blow into tank port of canister. Ensure air flows from purge port and air inlet (bottom of canister). (Scheme 111)
2. Blow into purge port. Air should not flow from any ports. Replace canister and check valve if they do not perform as indicated.
3. Apply 20 in. Hg of vacuum to vacuum signal line tube of canister valve while blowing air into purge tube. Air should come from throttle body tube. Replace canister if canister or check valve does not test as specified.

Scheme 111

Evaporation Emission Thermal Vacuum Valve (EVAP TVV)

1. Disconnect negative battery cable. Drain engine coolant. Disconnect 2 vacuum hoses from EVAP TVV. Remove EVAP TVV from intake manifold.
2. Cool EVAP TVV in water to 95° F (35° C). Ensure air does not flow from upper to lower port. If air flows from upper to lower port, replace EVAP TVV.
3. Heat EVAP TVV in water to 129° F (54° C). Ensure air flows from upper to lower port. If air does not flow, replace EVAP TVV.

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.

CHART C-1A, ELECTRICAL LOAD IDLE-UP DIODE CIRCUIT CHECK

ECM/PCM receives an idle-up signal from electrical load idle-up diode. This signal is present whenever one or more of the following systems is turned or operated.

1. Parklights.
2. Rear window defogger. NOTE: Test numbers refer to numbers on diagnostic chart.

1. Checks for electrical load idle-up signal to ECM/PCM.
2. Checks for open or short to voltage in Black wire, or faulty ECM/PCM or electrical load idle-up diode.