Engine Controls - System/component Tests: Diagnosis Oldsmobile Silhouette I

A/C ON SWITCH/SYSTEM TEST

1. Turn ignition switch to RUN position. Move mode selector switch to OFF position. With A/C control assembly connected, measure voltage between mode selector switch Dark Green wire (Dark Green/White on "L", "M" & "U" Series) and ground. For wiring schematics, see mini-schematics in A/C CLUTCH under «MISCELLANEOUS ECM CONTROLS»(ref-10387-S40815329962001031200000) .
2. Battery voltage should be present. If battery voltage is present, mode selector switch is operating normally. If battery voltage is not present, check wire from selector switch to fuse for an open circuit. Also check A/C high and low pressure switches for open.
3. Check voltage between mode selector Dark Green or Dark Green/White wire and ground. Voltage should not be present. If voltage was present, replace mode selector switch.

PFI Injector Balance Test (C-2)

The injector balance test is used to pulse the injector for a precise amount of time, spraying a measured amount of fuel in the intake manifold. As each injector is pulsed, a drop in fuel rail pressure occurs. This pressure drop can be recorded and compared to other injectors. An injector with a pressure drop of 1.5 psi (.11 kg/cm 2 ) or more, greater than or less than other injectors, should be considered faulty.

Note. Allow engine to cool down to avoid irregular readings due to "hot soak" fuel boiling. To prevent flooding, the PFI INJECTOR BALANCE TEST should not be repeated more than once without starting and running engine.

1. With ignition off, connect Fuel Pressure Gauge (J-34730-1) to pressure tap. Unplug harness connector at all injectors. Connect Injector Tester (J-34730-3) to one of the injectors.
2. Follow manufacturer's instructions when installing adapter harness. Ignition should be turned off at least 10 seconds to complete ECM shutdown cycle.
3. Turn ignition on. Fuel pump should run at least 2 seconds after ignition is turned on. Bleed air from gauge and hose to ensure accurate gauge reading. Repeat this procedure until all air is bled from system. Turn ignition off for at least 10 seconds.
4. Turn ignition on again to bring fuel pressure to maximum. Record initial pressure reading. Energize tester one time and note pressure drop at lowest point.
5. Disregard any slight pressure drop after low point is reached. Subtracting second pressure reading from initial reading indicates amount of injector pressure drop.
6. Repeat step 4) on each injector and compare pressure drop. Recheck injectors not within pressure drop range. Replace injector(s) failing second check.
7. If injectors are all okay, plug in harness connectors and review SYMPTOMS in TESTS W/O CODES article.

Diagnostic Aids

A slow, unstable, or fast idle may be caused by a non-lAC system problem that cannot be overcome by the IAC valve. Out of control range, IAC Tech I "Scan" tool counts will be above 60 if idle is too low, and zero counts if idle is too high The following checks should be made to repair a non-lAC system problem.

PRELIMINARY GLOW PLUG DIAGNOSIS

1. If system does not operate as described in NORMAL GLOW PLUG CIRCUIT OPERATION, ensure glow plug system is correctly installed. Ensure all connectors are properly attached, clean and tight. Inspect engine harness ground connection. Ensure nut securing 4-wire connector at controller is tightened to 96 INCH lbs. (11 N.m), with connector fully seated and latched.
2. Ensure controller copper stud upper nuts are tightened to 96 INCH lbs (11 N.m). DO NOT tighten lower nuts. Ensure temperature switch connector in water crossover near front of engine is tightened to 48 INCH lbs. (5.4 N.m). Inspect WAIT light on instrument panel for tight connection and operation.

INJECTION PUMP HOUSING LEAKAGE TEST

1. Remove injection pump and drain all fuel. Connect an air supply line to fuel inlet fitting. Ensure air supply is clean and dry. Seal off return line fitting. Completely immerse pump assembly in a container of clean test oil.
2. Apply 20 psi (1.4 kg/cm 2 ) to pump. Leave pump immersed for 10 minutes to allow trapped air to escape. Watch for leaks after 10 minutes. If no leaks are observed after 10 minutes, reduce air pressure to 2 psi (.14 kg/cm 2 ) for 30 seconds.
3. If there are still no leaks, increase pressure to 20 psi (1.4 kg/cm 2 ) again. If no leaks are observed, pump is ready for use. If leaks are noticed, pump must be replaced.

Test Preparation

1. Remove injector nozzles from engine. Clean carbon from tip area of nozzle with soft brass wire brush. DO NOT use steel brush or motorized brush to clean nozzle tip. Damage to nozzle tip may result. CAUTION: Use Nozzle Socket (J-36142) to remove and replace injection nozzle. Attach socket to 30mm hex portion of nozzle. Failure to do so will result in damage to the injector nozzle.
2. Connect injector nozzle to injection nozzle tester. Place clear plastic tubing on both fuel return fittings to prevent bleed-off from being confused with leaks. Close tester shutoff valve to pressure gauge.
3. Fill tester with test fluid. Fill and flush nozzle assembly with test fluid by operating tester lever briskly and repeatedly. This purges air from injector nozzle and coats all parts with test fluid.

Opening Pressure Test

1. Open tester shutoff valve 1/4 turn from closed position. Slowly depress tester lever and observe gauge. Note pressure at which needle of pressure gauge stops. Some injector nozzles may pop while other injector nozzles may drip (this is not a leak).
2. Injector opening pressure should not fall to less than 1500 psi (105 kg/cm 2 ). Replace any injector nozzle that does not meet lowest acceptable pressure. Release tester pressure.

Leakage Test

1. Open tester shutoff valve 3/4 to 1 3/4 turns from closed position. Blow dry injector nozzle tip. Slowly depress tester lever until pressure gauge reads 1400 psi (98 kg/cm 2 ). Maintain pressure for 10 seconds and observe injector nozzle tip.
2. A drop may form on end of injector nozzle, but should not fall off within a 10 second period. Replace injector nozzle if a drop of test fluid falls from tip during the 10 second period. (Scheme 21) Release tester pressure.

Scheme 21

Chatter Test

Chatter for new and used injector nozzles may vary. With some used injector nozzles, chatter is difficult to detect during slow actuation of tester lever. Some injector nozzles may chatter louder than others. As long as there is chatter, the injector nozzle is acceptable.

1. Close tester shutoff lever at pressure gauge. Slowly depress lever and note whether chatter can be heard. If no chatter is heard, increase speed of lever movement until it reaches a point at which injector nozzle chatters.
2. At fast lever movement, injector nozzle may emit a "hissing" or "squealing" sound rather than normal chatter. This is acceptable. These sounds indicate that injector nozzle needle moves freely and injector nozzle seat, guide and pintle have no mechanical defects. Replace any injector nozzle assembly that does not chatter.

Spray Pattern Test

The injector nozzles used with this system have several features that make pattern testing difficult. These features include longer nozzle overlap, greater pintle-to-body clearances and an internal wave washer between injector nozzle nut and injector. Typical injector nozzle tester cannot deliver fuel with sufficient velocity to obtain proper spray patterns. DO NOT replace injector nozzle(s) based on spray pattern.

System Test

Start and run engine to normal operating temperature. With engine at idle, RPM should drop as EGR valve is opened by pushing up on underside of EGR diaphragm.

CHART C-10, A/C CLUTCH CONTROL CKT DIAGNOSIS 2.5/2.8L (1 Of 2)

The ECM controls the A/C clutch engagement to improve idle quality and performance by delaying A/C clutch engagement until idle speed is increased, disengages clutch when idle speed is too low, and smooths cycling of compressor by providing additional fuel the instant A/C clutch is engaged.

Note. Test numbers refer to test numbers on diagnostic charts.

1. Checks for low A/C refrigerant charge, causing A/C clutch not to engage.
2. This and the following tests checks for faulty A/C control relay.

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CHART C-10, A/C CLUTCH CONTROL CKT DIAGNOSIS 2.5/2.8L (2 Of 2)

The ECM controls the A/C clutch engagement to improve idle quality and performance by delaying clutch engagement until idle speed is increased, disengages clutch when idle speed is too low, and smooths cycling of compressor by providing additional fuel the instant clutch is applied.

Turning on A/C switch supplies battery voltage to clutch control relay terminal "B" and ECM terminal B8. After a delay of about .5 seconds, the ECM will ground ECM terminal A4, closing the control relay and engages A/C compressor clutch.

Note. Test numbers refer to test numbers on diagnostic charts.

1. 3) Checks for faulty cycling switch. Solenoids and relays are turned on and off by the ECM, using "drivers". Each driver is a part of a group of 4, called quad-drivers. Failure of one driver can damage any other driver in the set. Solenoid and relay coil resistance should be greater than 20 ohms.

Check resistance of each ECM controlled relay or solenoid coil before replacing ECM. See CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS. Replace any relay or solenoid with a resistance of less than 20 ohms.

Scheme 24

CHART C-10, A/C CLUTCH CONTROL CIRCUIT DIAGNOSIS (FRONT A/C ONLY) 3.1L (1 of 2)

A/C clutch control circuit is ECM controlled to delay A/C clutch engagement approximately 8 seconds after engine is started. This allows the Idle Air Control Valve (IAC) to adjust engine RPM before A/C clutch engages. ECM also causes relay to disengage A/C clutch during Wide Open Throttle (WOT) operation or if engine is overheating.

A/C clutch control relay is energized when ECM provides a ground path for circuit No. 459. Low pressure switch will open if A/C pressure is less than 40 psi (2.8 kg/cm 2 ); high pressure switch will open if A/C pressure is approximately 440 psi (30.9 kg/cm 2 ).

Vehicles equipped with rear A/C option use a pressure cycling switch instead of a low pressure switch. A/C pressure cycling switch closes at pressure greater than 43-49 psi (3.0-3.4 kg/cm 2 ) and opens at pressure of less than 23-25 psi (1.6-1.8 kg/cm 2 ). An A/C refrigerant fan request switch opens to request fan(s) on, when A/C refrigerant pressure exceeds approximately 200 psi (14.1 kg/cm 2 ).

Note. Test numbers refer to test numbers on diagnostic charts.

1. ECM will only energize A/C relay when engine is running. This test determines if relay or circuit No. 459 is faulty.
2. A/C compressor clutch should apply if the following conditions are met: On front A/C option only, low and high pressure switch must be closed so A/C request (12 volts) will be present at ECM. On rear A/C option only, A/C mode is requested via high pressure and pressure cycling switches, 12 volts is supplied to relay coil through high pressure switch. As compressor reduces evaporator pressure to approximately 25 psi (1.8 kg/cm 2 ), pressure cycling switch will open and compressor clutch will disengage. As system equalizes and pressure cycling switch closes, compressor clutch will cycle on. This cycling continues and maintains evaporator discharge and temperature at approximately 33°F (1°C).
3. This step determines if signal is reaching ECM on circuit No. 66 from A/C control panel. Signal should only be present when A/C mode or defrost mode is selected.
4. With engine idling and A/C on, ECM should ground circuit No. 459, causing test light to illuminate.

If complaint was insufficient cooling, problem may be caused by inoperative cooling fan(s) or faulty A/C refrigerant fan request switch. Engine cooling fan(s) should turn on when A/C pressure exceeds a value to open switch, causing ECM to energize cooling fan relay(s). See CHART C-12 for cooling fan diagnosis. If fan operates correctly, ensure A/C system refrigerant charge is okay.

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CHART C-10, A/C CLUTCH CONTROL CIRCUIT DIAGNOSIS (REAR A/C ONLY) (2 OF 2) 3.1L

Note. Test number refers to test numbers on diagnostic charts.

1. Determines if signal is reaching ECM from A/C control panel. Signal should only be present when A/C mode or defrost mode is selected.

If complaint was insufficient cooling, problem may be caused by inoperative cooling fan(s) or A/C refrigerant fan request switch. Engine cooling fan(s) should turn on when A/C pressure exceeds a value to open switch, which causes ECM to energize cooling fan relay(s). See CHART C-12 for cooling fan diagnosis. If fan operates correctly, ensure A/C system refrigerant charge is okay.

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CHART C-10, A/C CONTROL DIAGNOSIS (A/T) (1 OF 2) 4.3L TURBO PFI

ECM controls operation of A/C clutch to improve idle quality and performance by

1. Delaying A/C clutch application until idle air rate is increased.
2. Releasing A/C clutch when idle speed is too low.
3. Releasing A/C clutch at wide open throttle operation.
4. Smooths cycling of compressor by providing additional fuel the instant A/C clutch is applied.

Turning on A/C supplies battery voltage to clutch relay (circuit No. 59) and ECM terminal BC9. After a time delay of .5 seconds, the ECM grounds terminal GF1 (circuit No. 459), and closes control relay. A/C compressor clutch then engages.

Note. Test numbers refer to test numbers on diagnostic charts.

1. Checks for low refrigerant as cause for no A/C.
2. This step and the steps that follow checks for faulty A/C control relay. QUAD-DRIVER CHECK is located under COMPUTERIZED ENGINE CONTROLS.

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CHART C-10, A/C CLUTCH CONTROL DIAGNOSIS (A/T) (2 OF 2) 4.3L TURBO PFI

Note. Test numbers refer to test numbers on diagnostic charts.

1. 3) Checks for faulty cycling switch. Solenoids and relays are turned on and off by the ECM, using "drivers". Each driver is a part of a group of 4, called quad-drivers. Failure of one driver can damage any other driver in the set. Solenoid and relay coil resistance should be greater than 20 ohms.

Check resistance of each ECM controlled relay or solenoid before replacing ECM. See CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS. Replace any relay or solenoid that measures less than 20 ohms.

Scheme 31

CHART C-12, COOLING FAN CIRCUIT DIAGNOSIS (1 OF 2) 3.1L

ECM controls electric cooling fan(s) based on inputs from coolant temperature sensor, A/C request, refrigerant fan request switch and vehicle speed. ECM energizes fan(s) by grounding circuits No. 335 and No. 473, which closes cooling fan relay(s). Battery voltage is supplied to cooling fan(s) when energized by the ECM. ECM grounds circuit No. 335 (puller fan) when coolant temperature is approximately 223°F (106°C) or when A/C has been requested and refrigerant fan request switch opens with high A/C pressure, approximately 200 psi (14.1 kg/cm 2 ). Pusher fan relay is grounded when coolant temperature is approximately 217°F (103°C) and/or puller fan is energized for A/C pressure.

Note. Test numbers refer to test numbers on diagnostic charts.

1. With ALDL diagnostic terminal grounded, cooling fan driver closes and energizes fan control relay.
2. If A/C fan request switch or circuit is open, cooling fan operates whenever A/C is operating.
3. With A/C requested and 45 seconds after request is removed, A/C refrigerant fan request switch should open when A/C high pressure exceeds approximately 200 psi (14.1 kg/cm 2 ). This signal should cause ECM to energize fan control relays(s).
4. This test checks if cooling puller and pusher fan relay(s) (circuits No. 335 and 473) are shorted to ground. This condition would cause fans to be energized continuously.

If an overheating condition is suspected, verify if it is due to actual boilover. If gauge or light indicates an overheat condition and boilover is not evident, inspect gauge/light circuit for malfunction.

If vehicle is overheating and gauge or light indicates so, but cooling fan is not operating and scan tester indicates normal readings, coolant temperature sensor is out of calibration and should be replaced. If engine is overheating and cooling fan is on, check cooling system.

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CHART C-12, COOLING FAN CIRCUIT DIAGNOSIS (2 OF 2) 3.1L

Note. Test numbers refer to test numbers on diagnostic charts.

1. Battery voltage should be available at cooling fan relay terminals "A" and "D" when ignition switch is in the ON position.
2. This checks ECM's ability to ground circuits No. 335 and 473. SERVICE ENGINE SOON light should be flashing at this point. If SERVICE ENGINE SOON light is not flashing, refer to G - TESTS W/ CODES article.
3. This test checks if cooling puller and pusher fan relays (circuits No. 533 and 702) are open. Jumpering relay terminals "A" and "E" by-passes relay, which should cause fans to operate, if motors and wiring are okay.

Scheme 34

CHART C-12A, COOLING FAN CIRCUIT DIAGNOSIS (1 OF 4) 3.8L

Power for fan motor goes through a 40-amp fusible link to terminal "A" of fan relays. Fan relays are energized when a good ground circuit is completed through the Powertrain Control Module (PCM) quad-driver. PCM energizes puller relay through terminal "GC4", when coolant temperature reaches 212°F (100°C) or when A/C is requested. PCM energizes pusher relay if A/C refrigerant pressure reaches 210 psi (99°C) or coolant temperature reaches 226°F (108°C).

Note. Test numbers refer to test numbers on diagnostic charts.

1. Using Tech 1 miscellaneous tests, low speed fan control will cause PCM to ground circuit No. 335. Puller fan should operate.
2. Using Tech 1 miscellaneous tests, high speed fan allows control of circuit No. 473. Pusher fan should operate.
3. When jumpering coolant temperature sensor wires together, scan tester should display coolant temperature of 304°F (151°C). Both fans will operate when ignition is cycled from off to on.
4. Opening A/C pressure switch will cause pusher fan to operate.

An intermittent may be caused by a poor connection, rubbed-through wire insulation or a broken wire inside insulation. Check PCM harness connector for backed out terminals. Connect a DVOM between affected terminal and ground. Wiggle related wires and connectors while watching DVOM for voltage reading change. Ensure coolant temperature sensor is not mis-scaled. See Code 15 in G - TESTS W/ CODES article in this section. Ensure engine cooling system is operating normally.

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An intermittent TPS output will cause the ECM to receive a false output.

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