Engine Controls - System/component Tests 4.0L: Other Oldsmobile Aurora I

A & C CHART REFERENCE TABLE

GENERAL MOTORS A & C CHART REFERENCE

PCM POWER & GROUND CHECK

1. Perform On-Board Diagnostic (OBD) System Check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under BASIC TESTING article. After performing OBD system check, go to next step.
2. Ensure that battery is fully charged and tested. Using scan tool, store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connectors C1 and C2. Using DVOM, separately check voltage to ground at PCM harness connector C1 terminals No. 20 and 61. (Scheme 24) If voltage reading is greater than 10 volts, go to step 5). If voltage reading is 10 volts or less, go to next step.
3. If only one of the terminals measured greater than 10 volts, go to step 12). If both terminals measured 10 volts or less, go to next step.
4. Check PCM/VATS fuse in engine compartment fuse/relay block. If fuse is faulty, go to step 13). If fuse is okay, go to step 14).
5. Turn ignition on. Check voltage between ground and PCM harness connector C1 terminal No. 18. If voltage reading is greater than 10 volts, go to step 7). If voltage reading is 10 volts or less, go to next step.
6. Check PCM fuse in engine compartment fuse/relay block. If fuse is faulty, go to step 15). If fuse is okay, go to step 16).
7. Turn ignition on. Check voltage between ground and PCM harness connector C1 terminal No. 19 and PCM harness connector C2 terminal No. 37. If voltage reading is greater than 10 volts, go to step 9). If voltage reading is 10 volts or less, go to next step.
8. If only one of the terminals measured greater than 10 volts, go to step 17). If both terminals measured greater than 10 volts, go to step 18).
9. Turn ignition to LOCK position. Individually check resistance between ground and PCM harness connector C1 terminals No. 21 and 60, and C2 terminal No. 37. (Scheme 24) If resistance is less than 5 ohms, go to step 11). If resistance is 5 ohms or greater, go to next step.
10. If all terminals measured greater than 5 ohms, go to step 19). If not all terminals measured greater than 5 ohms, go to next step.
11. Check terminal contact at PCM harness connector C1 terminals No. 18, 19, 20, 21, 60 and 61, and C2 terminals No. 21 and 60. Repair as necessary. If terminal contacts are okay, fault is not present.
12. Repair open in circuit that measured less than 10 volts.
13. Repair short to ground in battery feed circuit. Replace fuse.
14. Repair open in battery feed circuit or cause of no voltage to PCM/VATS fuse.
15. Repair short to ground in ignition feed circuit. Replace PCM fuse.
16. Repair open in ignition feed circuit or cause of no voltage to PCM fuse.
17. Repair open in circuit that measured less than 10 volts.
18. Repair short to ground in either ignition feed circuit or PCM fuse.
19. Repair open in battery feed circuit between splice connections.
20. Repair open in battery feed circuit between PCM harness connector and splice on the circuit(s) that measured greater than 5 ohms.

Scheme 24

ENGINE SENSORS & SWITCHES

Note. For additional sensor testing specifications, see appropriate K - SENSOR RANGE CHARTS article.

A/C Pressure Sensor

A malfunction in A/C pressure sensor circuit will set a related diagnostic trouble code. For testing procedures, see TESTS W/CODES article. For wiring schematics, see appropriate WIRING DIAGRAMS article.

A/C Pressure Switch

1. Connect A/C pressure gauges to system and start engine. Note high and low pressure readings. If pressures are normal, go to next step. If pressures are less than normal, check system for leaks. Evacuate and recharge as necessary. If pressures are high, check for system overcharge, overheating or mechanical failure in refrigerant delivery system.
2. Disconnect high and low pressure switches. Install jumper across each switch harness connector to allow A/C system to function normally. Using an ohmmeter, check continuity between pressure switch terminals.
3. Continuity should be present on both high and low switches (if equipped). If continuity is not present, replace A/C pressure switch. For wiring schematics, see appropriate WIRING DIAGRAMS article.

Brake Switch

Disconnect brake switch harness connector. Using an ohmmeter, check continuity between brake switch terminals. Continuity should be present. Depress brake pedal to activate brake switch. Continuity should not be present.

Camshaft Position Sensor

A malfunction in the camshaft position sensor circuit will set a related diagnostic trouble code. See testing procedures in TESTS W/CODES article.

Crankshaft Position Sensor

A malfunction in the crankshaft position sensor circuit will set a related diagnostic trouble code. For testing procedures, see TESTS W/CODES article. To diagnose crankshaft position sensor, the following procedures can be used

1. If a scan tool is available, scan RPM parameter while cranking engine. If RPM is indicated, crankshaft position sensor is operating properly.
2. If scan tool is not available, disconnect crankshaft position sensor harness connector. Set ohmmeter to 2-k/ohm position, and measure resistance across sensor terminals. Resistance should be 800-1200 ohms.
3. On all engines, set voltmeter on the 2-volt AC scale. Crank engine and measure output voltage across sensor terminals. Voltmeter reading should be .8-1.4 volts. If resistance reading is not as specified or sensor does not produce the specified output voltage reading, repair faulty wiring or faulty crankshaft position sensor.

Engine Coolant Level Switch

1. If Diagnostic Trouble Code (DTC) is present, diagnose DTC(s) first. See TESTS W/CODES article. Ensure coolant level is at proper level and coolant temperature is greater than 72°F (22°C).
2. Turn ignition on, with engine off. Low coolant light should come on and then turn off. If low coolant light stays on, turn ignition off. Install Tech 1 scan tool. Disconnect coolant level switch connector.
3. Turn ignition on. Using a fused jumper wire, jumper coolant level switch harness connector terminals. If scan tool displays OK with jumper wire installed and LOW with jumper wire removed, check coolant level switch terminals. If terminals are okay, replace coolant level switch. If scan tool does not read as indicated, go to next step.
4. Jumper coolant level switch harness connector terminal "A" (Light Green wire) to ground. If scan tool displays OK when jumpered and LOW when jumper is removed, check for open in Black/White wire from coolant level switch to ground. If scan tool does not read as indicated, go to next step.
5. Using a fused jumper wire, jumper PCM terminal B16 (Light Green wire) and ground. If scan tool displays OK with jumper wire installed and LOW when jumper is removed, check for open or short in Light Green wire between PCM and coolant level switch. If scan tool does not read as indicated, check PCM terminal B16 (Light Green wire). If terminal is okay, replace PCM.

Engine Coolant Temperature (ECT) Sensor

If a coolant sensor-related diagnostic trouble code is present, see TESTS W/CODES article. An out-of-calibration sensor may not set a diagnostic trouble code. Use following procedure to test sensor calibration. Disconnect ECT sensor connector. Measure resistance between sensor terminals. Resistance should be high when engine is cold and drop as engine warms. See ECT SENSOR RESISTANCE VALUES table.

ECT SENSOR RESISTANCE VALUES (1)

Fuel Pump/Oil Pressure Sensor

A malfunction in fuel pump circuit will set a related diagnostic trouble code. For testing procedures, see TESTS W/CODES article.

Fuel Tank Vapor Pressure Sensor

Fuel tank vapor pressure sensor is located on fuel sending unit. Using DVOM, check resistance between sensor terminals. Resistance should be 90 ohms with fuel tank full or zero ohms with fuel tank empty.

Intake Air Temperature (IAT) Sensor

IAT sensor may also be referred to as a Manifold Air Temperature (MAT) sensor. If a IAT sensor related code is present, see TESTS W/CODES article. An out-of-calibration sensor may not set a diagnostic trouble code. Use following procedure to test calibration. Disconnect IAT sensor harness connector. Connect ohmmeter between sensor terminals. Sensor resistance should be as specified. See IAT SENSOR RESISTANCE VALUES table. After vehicle has sat overnight, IAT sensor and coolant sensor should have close to the same resistance reading.

IAT SENSOR RESISTANCE VALUES (1)

Knock Sensor (KS)

Disconnect knock sensor harness connector. Using an ohmmeter, measure knock sensor resistance between sensor terminal and engine block. Resistance should be 3300-4500 ohms. Connect DVOM between sensor terminal and ground. Set voltmeter to 2-volt AC scale. Start and idle engine. Tap on engine block near sensor. A signal should be indicated on voltmeter. If no signal is indicated, replace knock sensor. Also, see TIMING CONTROL SYSTEMS under IGNITION SYSTEM. If any trouble codes are present, see TESTS W/CODES article.

Manifold Absolute Pressure (MAP) Sensor (C-1)

1. A malfunction in the MAP sensor circuit should set a related Diagnostic Trouble Code (DTC) in PCM memory. If a DTC is present, see TESTS W/CODES article. An out-of-calibration sensor may not set DTC. Use following procedure to test sensor calibration. If driveability problems exist, MAP sensor failure is suspected and no MAP code is present, disconnect MAP sensor connector. (Scheme 25) If driveability condition improves, replace MAP sensor.
2. With ignition on and engine off, check MAP sensor parameter using a scan tool connected to Data Link Connector (DLC). Voltage should be as specified. See «MAP SENSOR VOLTAGE RANGE»(ref-20351-S33954860442001010200000) table. If MAP sensor voltage is as specified, go to step 3). If voltage is not as specified, check for 5-volt reference supplied to sensor. Check harness integrity. If no problems are evident, replace MAP sensor.
3. Using a hand-held vacuum pump, apply 10 in. Hg to MAP sensor, and note voltage change. Voltage should drop about 1.2-2.3 volts less than as specified in table. If voltage is not as specified or voltage reading does not immediately follow vacuum change, MAP sensor is faulty.

Scheme 25

MAP SENSOR VOLTAGE RANGE

Manifold Air Temperature (MAT) Sensor

MAT sensor may also be referred to as an Intake Air Temperature (IAT) sensor. See INTAKE AIR TEMPERATURE (IAT) SENSOR. A malfunction in the MAT sensor will set a related diagnostic trouble code. For testing procedures, see TESTS W/CODES article.

Oxygen Sensor (O2S)

1. 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.
2. Using another DVOM on the 20-volt scale, connect voltmeter in series between the oxygen sensor wire from PCM and positive post of battery. Reading on voltmeter connected to oxygen sensor should decrease to a low voltage (less than .3 volt).
3. If a second DVOM is not available, install short jumper in oxygen sensor wire from PCM. 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. For additional testing procedures, see TESTS W/CODES article.

Park/Neutral Position (PNP) Switch (C-1)

1. Disconnect PNP switch harness connector. Connect ohmmeter between the PNP switch terminals. (Scheme 26) Continuity should be present only when gear shift selector is in Park or Neutral. If continuity is present, go to next step. If continuity is not present, check PNP switch adjustment or replace defective PNP switch.
2. With PNP switch connector disconnected, turn ignition on. Check for 12 volts on the Orange/Black wire of PNP switch harness. If 12 volts are not present, check for open or short to ground between switch harness connector and PCM.

Scheme 26

Power Steering Pressure (PSP) Switch

1. Install Tech 1 scan tool. Start and operate engine at idle. If scan tool indicates "Normal", go to step 3). If scan tool does not indicate "Normal", go to next step.
2. Disconnect PSP switch connector. Using a jumper wire, jumper PSP switch terminals. If scan tool indicates "Normal", replace PSP switch. If scan tool does not indicate "Normal", check for poor connection or open in Orange/Black wire between PCM and PSP switch. If circuit and connection is okay, replace PCM.
3. Turn steering wheel against stop. If scan tool indicates "High Pressure", PSP switch circuit is okay. Check power steering hydraulic pressure. If scan tool does not indicate "High Pressure", go to next step.
4. Disconnect PSP switch connector. Scan tester should indicate "High Pressure". If scan tool indicates "High Pressure", check for faulty connection or faulty PSP switch. If scan tool does not indicate "High Pressure", check for shorted Orange/Black wire. If wire is okay, replace PCM.

Throttle Position (TP) Sensor

Install jumper wires to enable connection of a DVOM in parallel between TP sensor harness connectors. Connect DVOM positive lead to Dark Blue TP sensor signal wire terminal. Connect negative lead to Black, Black/Orange or Purple sensor ground wire terminal. (Scheme 27) Turn ignition on, with engine off. Signal voltage should gradually change from less than one volt at closed throttle to about 5.0 volts at wide open throttle position. If reading is not as specified, adjust or replace TP sensor. See appropriate ADJUSTMENTS article.

A malfunction in the TP sensor circuit should set a related Diagnostic Trouble Code (DTC). For further information, see TESTS W/CODES article.

Scheme 27

Vehicle Speed Sensor (PM Generator Type)

Disconnect vehicle speed sensor harness connector (located in transaxle). Place gear selector in Neutral. Raise vehicle drive wheels off the ground. Turn drive wheels by hand (greater than 3 MPH). Measure AC signal voltage between sensor terminals. Voltage reading should vary from 0.1-0.5 volt AC as the wheel is turned. If reading is not as specified, replace vehicle speed sensor.

Vehicle Speed Sensor (LED Type)

A speed sensor or buffer malfunction should set a related diagnostic trouble code in PCM memory. If a code is set, refer to TESTS W/CODES article for diagnosis.

Idle Air Control (IAC) Motor

See IDLE CONTROL SYSTEM (C-2) .

A/C Clutch Relay

See MISCELLANEOUS CONTROLS .

Electric AIR Pump Relay

See EMISSION SYSTEMS & SUB-SYSTEMS .

Fuel Pump Relay

See FUEL SYSTEM .

SOLENOIDS

Note. All PCM-controlled solenoids should have at least 20 ohms of resistance when checked with positive ohmmeter lead connected to power supply terminal of solenoid and negative ohmmeter lead connected to ground terminal of solenoid. Some solenoids are equipped with internal diodes. On these solenoids, resistance values will differ if ohmmeter test leads are reversed.

AIR By-Pass Valve Solenoid

See EMISSION SYSTEMS & SUB-SYSTEMS .

Canister Purge Solenoid

See EMISSION SYSTEMS & SUB-SYSTEMS .

Cruise Control Vent Solenoid

A malfunction in the cruise control vent solenoid circuit will set a related diagnostic trouble code. See TESTS W/CODES article.

EGR Control Solenoid

See EMISSION SYSTEMS & SUB-SYSTEMS .

Transaxle Pressure Control Solenoid

A malfunction in the transaxle pressure control solenoid circuit will set a related diagnostic trouble code. See TESTS W/CODES article.

Transaxle Shift Solenoids

A malfunction in the transaxle shift solenoids ("A" & "B") circuit should set a related diagnostic trouble code. For further information, see TESTS W/CODES article.

FUEL DELIVERY

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

Fuel Pressure Regulator

1. Install fuel pressure gauge to fuel rail fuel pressure test fitting. Remove vacuum hose from fuel pressure regulator. Turn ignition on and note fuel pressure on gauge.
2. Start engine. Check for manifold vacuum at pressure regulator vacuum hose. If vacuum is not present, repair as necessary. Reconnect vacuum hose to pressure regulator and note fuel pressure on gauge. Compare first and second reading.
3. Fuel pressure reading should be 4-7 psi (.28-.49 kg/cm 2 ) less with vacuum hose installed. Fuel pressure should decrease as vacuum increases. If results are not as specified, replace fuel pressure regulator.

Note. For further fuel pump circuit diagnosis, refer to appropriate FUEL SYSTEM test under NO-START DIAGNOSIS (A-3) in BASIC TESTING article.

Fuel Pump Relay (A-5)

1. Disconnect fuel pump relay connector. See «COMPONENT LOCATIONS»(ref-20351-S18434770622001010200000) to locate fuel pump relay. Apply battery voltage and ground to fuel pump relay winding terminals. To identify fuel pump relay terminals, see appropriate wiring diagram in WIRING DIAGRAMS article.
2. Using an ohmmeter, check for continuity between fuel pump relay power supply terminal and fuel pump drive terminal. Continuity should exist ONLY with relay energized. If relay does not test as indicated, replace relay.
3. To by-pass fuel pump relay (to test fuel pump and wiring when fuel pump is not energizing), see FUEL PUMP RELAY BY-PASS PROCEDURE.

Fuel Pump Relay By-Pass Procedure

1. If fuel pump will not energize, relay may be by-passed to test fuel pump and related wiring. (Scheme 28) Turn ignition off. Disconnect fuel pump relay connector.
2. Using a fused jumper wire, apply battery voltage to fuel pump test connector (located in engine compartment). For fuel pump test connector location, see «COMPONENT LOCATIONS»(ref-20351-S18434770622001010200000). see scheme 10
3. If fuel pump runs and relay tests okay, check for faulty connections at relay. If fuel pump does not run, check for faulty wiring between relay and fuel pump or replace defective fuel pump.

Scheme 28

Oil Pressure Switch Fuel Pump Back-Up

With engine idling, disconnect fuel pump relay. Engine should continue to run through oil pressure switch back-up circuit. If engine stalls, check oil pressure switch and related wiring.

Fuel Injector(s)

Disconnect fuel injector harness connector. Measure resistance across injector terminals at each injector. Resistance should be as specified. See INJECTOR RESISTANCE SPECIFICATIONS table.

INJECTOR RESISTANCE SPECIFICATIONS (1)

Note. If injectors are dirty, they should be cleaned using approved injector cleaning procedure before performing INJECTOR BALANCE TEST.

Oxygen Sensor

See ENGINE SENSORS & SWITCHES .

1. Disconnect harness connector to motor. Check resistance across IAC coil terminals "A" and "B" (coil "B") and "C" and "D" (coil "A"). (Scheme 29) Resistance should be 40-80 ohms. If resistance is as specified, go to next step. If resistance is not as specified, replace IAC motor.
2. Check resistance between IAC terminals "B" to "C" and "A" to "D". Resistance should be infinite. If resistance is not as specified, replace IAC motor.

Note. Additional testing of Idle Air Control (IAC) motor requires an IAC motor actuator and noid light, or a scan tool capable of cycling PCM output devices (General Motors Tech 1).

Scheme 29

A malfunction in the IAC circuit will set a diagnostic trouble code. For testing procedures, see TESTS W/CODES article. To check IAC for proper operation, perform the following

1. Install Tech 1 scan tool. Turn ignition on, with engine off. Check for stored Diagnostic Trouble Code(s) (DTCs). If any code(s) is present, diagnose trouble code first. If code(s) is not present, go to next step.
2. Start engine and let idle. Turn off all accessories. Using scan tool, enter "Misc Test" and select "IAC System". Command engine speed up to 1500 RPM and then to 500 RPM and back to 1500 RPM, while monitoring "Engine Speed" display on scan tool. If engine speed remains within 50 RPM for each RPM command, fault is not present. If engine speed is not as specified, go to next step.
3. Turn engine off. Disconnect IAC valve. Install Noid Light (J-37027). Start engine. Using scan tool, command engine speed up to 1500 RPM then to 500 RPM and back to 1500 RPM, while monitoring noid light. If noid light cycles from Red to Green, go to step 5). If noid light does not cycle from Red to Green, go to next step.
4. Check Light Green/Black, Light Blue/White and Light Green/White wires between IAC valve and PCM for open or shorted circuit. Repair as necessary. If circuit is okay, check terminal contact at PCM connector C1. Repair as necessary. If terminal contacts are okay, replace PCM and verify proper IAC valve operation.
5. Inspect throttle body for tampering, restriction in air intake system and throttle body for blockage or excessive deposits in IAC passage or throttle bore. Repair as necessary. If passages are okay, check for poor terminal contact at IAC harness connector. Repair as necessary. If connections are okay, replace IAC valve.

IGNITION SYSTEM

Note. For basic ignition system checks, see BASIC TESTING article.

Ignition Control (IC) Timing Advance System

1. A malfunction in the IC circuit (formerly referred to as the EST circuit) should set a related diagnostic trouble code. Start engine and warm to operating temperature. On vehicles equipped with a manual transmission, increase engine speed to about 2000 RPM. On vehicle equipped with an automatic transmission, slightly increase idle speed.
2. Ground DLC "test" terminal "B" (not applicable to all models). A noticeable change in engine speed should occur. If no change occurs, see DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING article.

Knock Sensor (KS) System Without KS Controller (C-5)

1. An open or short circuit on the KS wire to the PCM will set a related diagnostic trouble code. A false detonation signal will not cause PCM to set a code.
2. If a scan tool is available, connect it to the DLC. Tap on engine next to knock sensor and note "knock" parameter. Knock should be indicated on scan tool.
3. If a scan tool is not available, connect tachometer to engine. Start engine and hold RPM above idle. Using a metal object, tap on engine close to knock sensor. A noticeable decrease in engine RPM should occur. If no RPM decrease occurred, check knock sensor-to-PCM circuit.
4. On vehicles equipped with automatic transmission, it may be necessary to place transmission in Drive for timing change to occur. Also, see KNOCK SENSOR (KS) under «ENGINE SENSORS & SWITCHES»(ref-20351-S25812477572001010200000) .

Knock Sensor (KS) System With KS Controller (C-5)

1. An open or short circuit on KS wire to PCM will cause a loss of 12-volt KS controller signal. This will cause PCM to fully retard ignition timing.
2. If scan tool is available, connect it to the DLC. Tap on engine next to knock sensor and note "knock" parameter. Knock should be indicated on scan tool.
3. If scan tool is not available, connect a DVOM to PCM ESC signal terminal. With engine idling, 12 volts should be present at this terminal. Using a metal object, tap on engine close to knock sensor. Voltage signal at PCM terminal should drop to zero volts, and return when knock signal ceases.
4. If signal does not respond as described, check knock sensor signal to KS controller. On vehicles equipped with automatic transmission, it may be necessary to place transmission in Drive for timing change to occur. Also, see KNOCK SENSOR (KS) under «ENGINE SENSORS & SWITCHES»(ref-20351-S25812477572001010200000) .

AIR Pump (Belt-Driven)

Accelerate engine to approximately 1500 RPM and observe airflow from hoses. If airflow increases as engine is accelerated, pump is working properly. If airflow does not increase, check hoses, pump belt tension, leaky valves or defective air injection pump.

Check Valve

Detach check valve and blow through valve in direction of check valve flow (to cylinder head). Attempt to suck air back. Replace valve if airflow is allowed against the direction of flow.

EXHAUST GAS RECIRCULATION (C-7)

There are 3 types of EGR systems used: pulse width modulated backpressure (positive and negative) EGR with a control solenoid, pulse width modulated backpressure (positive and negative) EGR without a control solenoid, digital and linear EGR. See EGR SYSTEM IDENTIFICATION table.

EGR SYSTEM IDENTIFICATION

EGR Control Solenoid (Normally Closed)

1. Disconnect EGR solenoid electrical harness connector and vacuum hoses. Connect a hand-held vacuum pump to solenoid vacuum source port. Connect vacuum gauge to solenoid EGR port. Pump up vacuum pump. Vacuum should not be present at port to EGR valve.
2. Activate EGR solenoid with a 12-volt power supply. Vacuum should now be present or registered at vacuum gauge. If vacuum is not present, check EGR solenoid resistance. Solenoid should have at least 20 ohms of resistance.

EGR Control Solenoid (Normally Open)

1. Disconnect solenoid harness connector. Install vacuum pump to vacuum source side of solenoid. Apply vacuum to solenoid. Vacuum should pass through when solenoid connector is disconnected.
2. Apply battery voltage and ground to solenoid terminals. With solenoid energized, apply vacuum to solenoid. Vacuum should not pass through solenoid. If results are not as specified, check EGR solenoid resistance. Solenoid should have at least 20 ohms of resistance.

Linear EGR Valve

A malfunction in the EGR circuit will set a related diagnostic trouble code, see TESTS W/CODES article.

Negative Backpressure EGR Valve

With engine off, disconnect vacuum hose to EGR valve. Connect vacuum pump to EGR and apply 10 in. Hg. EGR diaphragm should move up and stay up for 20 seconds. If valve does not operate as indicated, replace EGR valve.

Positive Backpressure EGR Valve

1. Place transmission in Park or Neutral. Set parking brake and block drive wheels. Connect tachometer. With engine running at normal operating temperature, run engine at 2000 RPM.
2. Disconnect vacuum hose from EGR valve and plug hose. EGR valve diaphragm should move down and engine RPM should increase. NOTE: On some engines with PCM-controlled solenoid, EGR vacuum is locked out in Park/Neutral and solenoid must be by-passed with vacuum supply hose.
3. Reconnect vacuum hose. EGR diaphragm should move up and engine RPM should decrease. A slight vibration of diaphragm plate may be noticed in backpressure EGR valves.
4. If engine RPM did not change and EGR diaphragm moved, the EGR valve is functioning properly. If engine RPM did not change and diaphragm did not move, remove EGR valve and apply 10 in. Hg to EGR vacuum signal port. EGR valve should not open.
5. If EGR valve opens, replace EGR valve. With vacuum still applied, direct a stream of air (15 psi maximum) into valve seat. EGR valve should open completely.
6. If air is not available, connect a short piece of hose over EGR valve seat. Connect vacuum pump to signal port. With thumb plugging intake port of EGR valve, operate vacuum pump while alternately blowing through hose and pausing.
7. With vacuum present at signal port, EGR valve should open while pressure is applied and should close when no vacuum is present.

Canister Purge Solenoid (Normally Closed)

1. Disconnect canister purge solenoid harness connector and vacuum hose. Apply 10 in. Hg to ported intake manifold vacuum side of solenoid valve. If vacuum holds, go to next step. If vacuum does not hold, replace canister purge solenoid.
2. Using a 12-volt power source, energize canister purge solenoid. Vacuum should release. If vacuum does not release, replace canister purge solenoid. Solenoid resistance should be at least 20 ohms.

Fuel Tank Pressure Control Valve

Apply approximately 15 in. Hg to fuel tank pressure control valve. The diaphragm should hold vacuum for at least 20 seconds. If fuel tank pressure control valve does not hold vacuum, replace tank pressure control valve.

Required Service

The PCV system may require service for obstructions if any of the following conditions exist

1. Rough idle.
2. Stalling or slow idle speed.
3. Oil leaks.
4. Oil in air cleaner.
5. Sludge in engine.

A leaking PCV valve or hose could cause

1. Rough idle.
2. Stalling.
3. High idle speed.

If engine idles roughly, check for clogged PCV valve or plugged or broken hoses BEFORE adjusting idle. Check PCV valve application to ensure the correct valve is fitted. Replace PCV valve if required.

Checking PCV Valve Function

1. Remove PCV valve from rocker cover. Run engine at idle. Place thumb over open end of valve to check for vacuum. If there is no vacuum at valve, check for obstruction in manifold port, hoses or PCV valve. Repair or replace as necessary.
2. Turn engine off. Remove PCV valve. Shake valve and listen for rattle of check valve inside. If a clear rattle is not heard, replace PCV valve.
3. Visually inspect valve for varnish or deposits which may make PCV valve operation sticky or restricted, or cause incomplete seating of valve. Replace if necessary.
4. An engine must be sealed for the PCV system to function as designed. If leakage, sludging or dilution of oil is noted and the PCV system is functioning properly, check engine for cause and repair as required to ensure PCV system will continue to function properly.
5. An engine operating without any crankcase ventilation can be damaged, so it is important to replace PCV valve and air cleaner breather (if equipped) at regular intervals (at least every 30,000 miles). Check all hoses and clamps for failure or deterioration.

MISCELLANEOUS CONTROLS

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

HOT LIGHT OR COOLANT TEMPERATURE LIGHT

Note. These checks assume vehicle is not overheating. Verify proper operation of cooling system prior to diagnosing hot light. The coolant temperature sensor, in rare cases, may fail to indicate correct coolant temperature without setting a Diagnostic Trouble Code (DTC). This could result in hot light turning on without having an overheating condition. It could also result in engine overheating without hot light turning on. Check coolant sensor temperature-to-resistance values in K - SENSOR RANGE CHARTS article.

Hot light is powered by the 10-amp INDIC or GAGES fuse. Light will turn on when PCM provides a ground for the circuit. If circuit grounds between light and PCM, light will illuminate any time ignition is turned on.

1. Turn ignition on, with engine off (bulb test position). If hot light illuminates, go to step 3). If hot light does not illuminate, check the following and proceed to next step: 10-amp INDIC or GAGES fuse. Faulty instrument cluster bulb. Open circuit between fuse and hot light.
2. Backprobe PCM hot light driver terminal with a test light to battery voltage. Turn ignition on. If test light does not illuminate, PCM terminal connection is bad or PCM is faulty. If test light illuminates, turn ignition off. Disconnect PCM connectors. Jumper PCM hot light driver harness terminal to ground. Turn ignition on. If hot light does not illuminate, check for open circuit between hot light and PCM. If all circuits are okay and power is available to light, replace instrument cluster.
3. Start engine. If hot light goes off, no problem is evident. If hot light is on, turn ignition off. Disconnect PCM connector. Probe PCM hot light driver harness terminal with a test light to battery voltage. If test light does not illuminate, replace PCM. If test light illuminates, repair short to ground in hot light driver circuit. If circuit is okay, replace instrument cluster.

Converter Clutch Solenoid

Disconnect harness connector to Torque Converter Clutch (TCC) solenoid. Solenoid resistance should be 10-15 ohms. On all other models, measure resistance between appropriate TCC solenoid terminals. (Scheme 30) Solenoid resistance should be greater than 20 ohms.

Note. Some solenoids have an internal pressure switch in series with the solenoid winding and will not show continuity until that pressure switch is applied by transmission hydraulic pressure. (Scheme 30)

Converter Lock-Up Signal At Transmission

1. Warm engine to operating temperature. Raise vehicle and support drive wheels. Support suspension where necessary to prevent damage to drive axles.
2. Disconnect converter clutch connector at transmission. Connect a test light across appropriate converter clutch harness terminals. Start engine and place transmission in Drive. Accelerate vehicle to 45 MPH and note test light.
3. If test light is off, check solenoid power supply wire of harness for open or short to ground. Check ground circuit for open between harness connector and PCM. If harness is okay, see CONVERTER LOCK-UP SIGNAL FROM PCM.

Converter Lock-Up Signal From PCM

1. Warm engine to operating temperature. Raise vehicle and support drive wheels. Support suspension where necessary to prevent damage to drive axles.
2. Connect a test light to battery voltage. Touch TCC control driver terminal with test light. On some vehicles, this is terminal "F" of Data Link Connector (DLC). (Scheme 30) Accelerate vehicle to 45 MPH and note test light. If test light does not illuminate, problem is a faulty PCM connector or PCM.

Converter Clutch Schematic. Scheme 30

A/C CLUTCH (C-10)

Note. For specific A/C clutch system diagnosis, see C-10 & C-12 DIAGNOSTIC TESTS .

1. Disconnect A/C clutch relay harness connector. See «A/C COMPRESSOR CLUTCH RELAY LOCATION»(ref-20351-S31430820512001010200000) table. Using proper wiring diagram and an ohmmeter, check continuity between A/C clutch relay winding terminals. See appropriate WIRING DIAGRAMS article. Continuity should exist. Check continuity between clutch drive circuit terminals of relay. Continuity should not exist.
2. Using jumper wires, apply ground and battery voltage to relay winding of relay. Continuity should now exist between clutch drive circuit terminals of relay. Replace A/C clutch relay if readings are not as specified.

A/C COMPRESSOR CLUTCH RELAY LOCATION

ELECTRIC COOLING FAN (C-12)

Note. For specific A/C clutch system diagnosis, see C-10 & C-12 DIAGNOSTIC TESTS .

Cooling Fan System

1. Connect a test light to battery voltage. Probe test light to cooling fan control driver terminal of PCM. (Scheme 31) Disconnect coolant temperature sensor. This should set a code, causing PCM to engage cooling fan through relay. On some models, it may be necessary to jumper the coolant temperature sensor harness connectors. On some models, grounding the DLC with ignition on and engine off will cause PCM to activate cooling fan control driver (ground circuit).
2. If test light illuminates and cooling fan does not come on, check cooling fan relay, power circuits, cooling fan motor, and relay and fan motor ground circuits. If test light does not illuminate, problem is a faulty PCM connector or PCM. Clear diagnostic trouble code(s) from PCM memory after testing.
3. If cooling fan functions normally during testing but fails to operate under normal conditions, check PCM monitored inputs which affect cooling fan operation. These include the following: coolant temperature sensor, A/C request signal from A/C control switch and A/C pressure sensor, or pressure/temperature switch signals (if equipped).

Cooling Fan Relay

1. Disconnect cooling fan relay harness connector. See «COOLING FAN RELAY LOCATION»(ref-20351-S37277273652001010200000) table for specific vehicle relay location. Using an ohmmeter, check continuity of relay winding. See WIRING DIAGRAMS . Continuity should exist. Check continuity across power delivery terminals of relay. With relay not energized, no continuity should exist.
2. With ohmmeter still attached to power delivery terminals of relay, apply battery voltage and ground to energize relay winding. Continuity should now be present between cooling fan relay power delivery terminals. Replace cooling fan relay if readings are not as specified.

Cooling Fan Motor

Disconnect cooling fan motor harness connector. Apply battery voltage to one of the fan motor terminals and jumper the other terminal to ground. Fan motor should activate. If fan motor does not activate, replace faulty fan motor.

COOLING FAN RELAY LOCATION

Cooling Fan Circuit Wiring Diagram. Scheme 31

Cooling Fan Functional Check

1. Perform On-Board Diagnostics (OBD) System check. See BASIC TESTING article. After performing OBD system check, go to next step.
2. Ensure engine coolant temperature is between 41-212°F (5-100°C). Turn A/C controls off. Start and idle engine. Using scan tool, select OUTPUT TESTS function, then FAN RELAYS, and command all relays on for about 15 minutes. In DTC INFO on scan tool, select FAIL THIS IGN. If DTC P1660 failed this ignition, perform diagnosis for this code. See TESTS W/CODES article. If DTC P1660 did not fail, go to next step.
3. With engine idling, turn A/C on to maximum cooling. If any other DTCs have failed this ignition, see TESTS W/CODES article. If no DTCs have failed this ignition, go to next step.
4. Turn engine off, key on. Ensure engine coolant temperature is less than 212°F (100°C). Observe fan operation while individually commanding FAN RELAY NO. 1 on, then all relays on, then all relays off. With FAN RELAY NO. 1 commanded on, both fans should operate at low speed. With all relays commanded on, both fans should operate at high speed. With all relays commanded off, both fans should not operate (unless PCM detects a fault or high temperature condition). If both cooling fans operate as commanded, system is operating normally at this time. If both cooling fans do not operate as commanded, go to next step.
5. If only cooling fan No. 1 operates with FAN RELAY NO. 1 commanded on, then both fans operate when all relays are commanded on, go to next step. If cooling fan No. 1 does not operate with FAN RELAY NO. 1 commanded on, or both fans do not operate when all relays are commanded on, go to step 7).
6. Repair short to ground in White wire. Go to step 4).
7. If neither cooling fan operates with FAN RELAY No. 1 commanded on, then only cooling fan No. 2 operates with all relays commanded on, go to COOLING FAN SYMPTOM CHECK NO. 1. If system does not operate as specified, go to next step.
8. If neither cooling fan operates with FAN RELAY No. 1 commanded on, then only cooling fan No. 1 operates with all relays commanded on, go to COOLING FAN SYMPTOM CHECK NO. 2. If system does not operate as specified, go to next step.
9. If both cooling fans operate with FAN RELAY No. 1 commanded on, then only cooling fan No. 2 operates with all relays commanded on, go to COOLING FAN SYMPTOM CHECK NO. 3. If system does not operate as specified, go to next step.
10. If both cooling fans operate with FAN RELAY No. 1 commanded on, then only cooling fan No. 1 operates with all relays commanded on, go to COOLING FAN SYMPTOM CHECK NO. 4. If system does not operate as specified, go to next step.
11. If neither cooling fan operates with FAN RELAY No. 1 commanded on, and also when all relays is commanded on, go to COOLING FAN SYMPTOM CHECK NO. 5. If system does not operate as specified, go to next step.
12. If either cooling fan operates when all relays are commanded off, go to DIAGNOSTIC AIDS. If system does not operate as specified, go to step 4).