Engine Controls - Basic Testing: Diagnosis Oldsmobile Silhouette I

VISUAL INSPECTION

Visually inspect all electrical wiring. Look for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and not pinched or cut. If necessary, see VACUUM DIAGRAMS article in this section to verify routing and connections. Inspect air induction system for possible vacuum leaks.

Diagnosis

1. Start engine, and bring to operating temperature. Increase engine speed to 2000-2500 RPM. Note gauge. Exhaust system is restricted if reading exceeds 1.25 psi (.09 kg/cm 2 ).
2. Check exhaust system for collapsed pipe, heat distress and possible internal muffler failure. If none of these conditions exists, check for restricted catalytic converter. Replace as required.

A-3, NO-START DIAGNOSIS

Note. For diesel information, see G - TESTS W/ CODES DIESEL and TESTS W/O CODES article in this Section.

General Inspection

1. Ensure proper starting procedure is being used.
2. Visually check vacuum hoses for splits, kinks and improper connections. See underhood emission control information label. Check ignition wires for cracking, hardness and improper connections at both distributor cap and spark plugs.
3. Remove spark plugs. Check and replace as necessary.
4. Remove distributor cap and check for moisture, dust, cracks, burns and arcing to ground through coil mounting screws or rotor.
5. Try to turn distributor shaft by hand. Drive gear pin may be broken.
6. If vehicle has been exposed to very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.

1. Ensure proper starting procedure is being used. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both coil pack and spark plugs.
2. Remove spark plugs. Check and replace as necessary. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.

Scheme 1

1. Ensure TPS scans less than 2.5 volts. If not, see Code 21 chart in appropriate «BASIC TESTING»(ref-10386) article in this section. Check for stored trouble codes. See appropriate «BASIC TESTING»(ref-10386) article in this section. If engine has not been started for at least 8 hours, MAT sensor scan temperature should be close to CTS scan temperature. Disconnect cam sensor and attempt to start engine. If engine starts, see Code 41 chart in appropriate «BASIC TESTING»(ref-10386) article in this section.
2. Reconnect cam sensor connector. Compare scanned CTS temperature with actual coolant temperature. If they are not close, replace coolant sensor. Depress accelerator pedal approximately 25 percent. Attempt to start engine. If engine does not start, go to next step. If engine starts, check IAC counts on scan tester. Check for stored Code 35. Check for blocked IAC passages.
3. Disconnect all injector connectors and install injector test light in each injector harness connector. All lights should be off and should blink as engine is cranked. If any injector lights are on, go to step 6). If lights do not blink at all while cranking, go to step 7). If all lights are off and they blink as engine is cranked, check for adequate spark using Spark Tester (ST-125). Check for spark on plug wires No. 1, 3 and 5 (one at a time). Leave matching plug wire connected while checking for spark. If spark jumped tester on all plug wires, check for fouled spark plugs or for fuel system as cause of no start. See «BASIC FUEL SYSTEM CHECKS (GASOLINE)»(ref-10386-S25668889412001010200000). If spark did not occur on any plug wire, ignition module connection is poor or ignition module is faulty.
4. If spark did not jump tester on all plug wires, verify that plug wire resistance is less than 30,000 ohms. Verify that ignition coils secondary resistance is 5000-6500 ohms at room temperature. Replace as necessary. If wires and coils are okay, remove coil that did not fire. Verify primary resistance of.3-.5 ohm. Replace coil if necessary. If coil is okay, connect a test light across ignition module terminals for problem coil.
5. Crank engine. If test light flashes, check for poor coil to module connections. If connections are okay, replace faulty coil. If test light does not flash, replace ignition module.
6. Turn ignition off. Disconnect PCM Black C-D connector. Turn ignition on. If all lights are now off, replace PCM. If any lights are still on, repair short to ground in that injector drive circuit.
7. Check ignition module power supply (20-amp INJ fuse and circuit). Repair as necessary. Disconnect fuel injector connector. Turn ignition on. With a test light connected to ground, check for battery voltage on Pink/Black wire of injector harness. If test light is on, go to next step. If test light is off, check injector harness between injector connectors and 20-amp INJ fuse. If fuse is blown, repair short to ground and replace fuse. If fuse is okay, check power supply to fuse and circuit between fuse and the injector harness connector.
8. Turn ignition off. Disconnect ignition module connector. Turn ignition on. Install injector test light in any injector harness connector. Connect test light to battery voltage, and repeatedly touch terminal "D" of ignition module harness connector. (Scheme 1) Injector test light should flash each time test light is touched to terminal "D". If injector test light flashes, go to step 10).
9. If injector test light does not flash, check injector drive circuit between PCM and injector harness connector for open or short to voltage. Repair as necessary. If injector drive circuit is okay, check for open, short to ground or short to voltage on fuel control circuit No. 430. If circuit is okay, problem is faulty connection at PCM fuel control terminal or faulty PCM.
10. Turn ignition off. Using proper jumper adaptor from Adaptor Kit (J 35616), connect a fused jumper between ignition module harness connector terminal "N" and battery voltage. Connect a second jumper between ignition module harness connector terminals "M" and ground. Connect DVOM between ignition module harness connector terminal "H" and battery voltage. Observe voltmeter while cranking engine. Voltmeter should read approximately 1.7 volts.
11. If voltage is high, check circuit No. 646 for open or short to ground. If open or short to ground is not present, replace faulty crank sensor. If voltage is low, check circuit No. 646 for an open or short to voltage, circuit No. 645 for an open and circuit No. 644 for an open or short to ground. If all circuits are okay, replace faulty crank sensor.
12. If voltage is approximately 1.7 volts, move DVOM lead from terminal "H" to terminal "G". Crank engine and once again monitor voltage. Voltmeter should read about 5.5 volts. If voltage is correct, go to next step. If voltage is less than 5.5 volts, check for open or short to voltage in circuit No. 643. If voltage is greater than 5.5 volts, check for a short to ground on circuit No. 643. If no problem is found, crank sensor is faulty.
13. If voltage is close to 5.5 volts, turn ignition on. Probe ignition module harness connector terminals "P" with a DVOM connected to ground. If battery voltage is not present, repair open in ignition module power supply circuit. If battery voltage is present, problem is poor ignition module connections or faulty ignition module.

FUEL SYSTEM PRESSURE TEST

FUEL PUMP FLOW TEST

1. Disconnect fuel line at fuel filter inlet. Disconnect fuel injection pump electric shut-off solenoid wire (Pink).
2. Crank engine 15 seconds. If fuel pump does not supply approximately 1/2 pint of fuel in 15 seconds, go to FUEL SYSTEM PRESSURE TEST.

1. Turn engine off. Disconnect fuel line at inlet to fuel filter assembly. Install low pressure fuel gauge to fuel line.
2. Crank or run engine 10-15 seconds. If fuel pressure is not 5.8-8.7 psi (.41-.61 kg/cm 2 ), check fuel lines and fuel tank sending unit for restriction. If fuel lines and sending unit are okay, replace fuel pump.

Diagnostic Circuit Check determines

1. If SERVICE ENGINE SOON light works.
2. If ECM is operating and can recognize a fault.
3. If any codes are stored.

After performing basic diagnostic procedures listed under PRELIMINARY INSPECTION & ADJUSTMENTS, BASIC FUEL SYSTEM CHECKS (GASOLINE) and C-4, BASIC IGNITION SYSTEM CHECKS. use self-diagnostic system for determining computer-related problems. (Scheme 7)

After performing necessary tests in diagnostic circuit check and if no codes are indicated and driveability problems still exist, see TESTS W/O CODES article and SCAN TESTER USAGE in G - TESTS W/ CODES GASOLINE article in this section.

1. Check SERVICE ENGINE SOON light operation. Turn ignition on with Scan tester not connected, ALDL test terminal not grounded and engine not running. SERVICE ENGINE SOON light should be on steady. If light illuminates and stays on steady, go to next step. If light does not illuminate, go to A-1, SERVICE ENGINE SOON LIGHT INOPERATIVE. If light flashes, go to step 3).
2. Grounding ALDL diagnostic test terminal "B" now should cause SERVICE ENGINE SOON light to flash a Code 12, followed by any codes stored in ECM memory. If light goes from bright to dim or if light remains on and does not flash Code 12, see A-2, SERVICE ENGINE SOON LIGHT ALWAYS ON OR WON'T FLASH CODE 12.
3. If light begins to flash as soon as ignition is turned on, check for a short to ground on diagnostic test terminal wire between ALDL diagnostic terminal "B" and ECM terminal. (Scheme 2)- (Scheme 4). If circuit is okay, replace ECM.

Note. (Scheme 2) is Courtesy of General Motors Corp.

Fuel Injection Diagnostic Circuit Schematic (Except 4.3L Turbo & Models With 4L80-E Transmission). Scheme 2

Scheme 3

Scheme 4

DIAGNOSTIC CIRCUIT CHECK (DIESEL)

Note. The 6.2L model with light duty emissions is equipped with a self-diagnostic system. For information on diagnostic circuit check and retrieving codes, see G - TESTS W/ CODES DIESEL article in this section.

Preliminary Inspection

1. Check all vacuum hoses for incorrect routing, restrictions, cuts or other damage. Inspect hoses beneath air cleaner assembly and other engine components.
2. Inspect all wires in engine compartment for correct and good connections. Also check wires for pinched or chaffed spots, as well as contact with sharp edges or exhaust manifolds.
3. Perform preliminary inspection CAREFULLY and THOROUGHLY. A thorough inspection often leads to fixing a problem without further diagnosis.

Diagnostic Procedure

1. Ensure all engine systems not related to Diesel Electronic Control (DEC) system are operating properly. DO NOT proceed with testing unless all problems not related to DEC system have been repaired. DEC system diagnosis should always begin with DIAGNOSTIC CIRCUIT CHECK chart in G - TESTS W/ CODES DIESEL article in this section. Performing this check determines whether DEC system and ECM are working properly.
2. If trouble codes (other than Code 12) are displayed, determine whether codes are "hard" or "intermittent" trouble codes. A hard code remains until code-setting condition is repaired. Hard codes cause SERVICE ENGINE SOON light to come on.
3. An intermittent code does not reset itself and is not present when vehicle is repaired. An intermittent code is often caused by loose connections. SERVICE ENGINE SOON light goes out 10 seconds after fault goes away.

Note. Figures 13 & 14 are Courtesy of General Motors Corp.

Diesel Fuel Injection Diagnostic Circuit Schematic (Except Commercial Van & Van). Scheme 5

Diesel Fuel Injection Diagnostic Circuit Schematic (Commercial Van & Van). Scheme 6

Diagnostic Circuit Check & Work Flow. Scheme 7