Engine Controls - Basic Testing Oldsmobile Toronado Trofeo

INTRODUCTION

Note. This article contains general information on Basic Diagnostic Procedures on GM vehicles. The information in this article should not be used for a specific vehicle application.

The following diagnostic steps can help prevent overlooking simple problems. This is also the place to start diagnosis for a "NO-START" condition.

The first step in diagnosing any driveability problem is to verify the problem exists. This may be accomplished by test driving the vehicle under the conditions during which the problem reportedly occurs.

Prior to entering self-diagnostics, a careful and complete inspection of several systems is required. Most driveability or "no-start" problems are not related to computerized engine control systems, but are usually simple mechanical, electrical, fuel or vacuum problems. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged or misrouted vacuum hoses.

Before considering the computer system as a possible cause of problems, check ignition high tension wires, fuel supply, electrical connections and vacuum hoses. Failure to check these can result in improper diagnosis or lost diagnostic time.

Note. All voltage tests should be performed with a Digital Volt- Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in testing procedures.

VISUAL INSPECTION

Perform a visual inspection of all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Inspect electrical connectors and connections for tight fit and corrosion. Repair as necessary. Inspect all vacuum hoses for proper routing, cuts or pinches. If necessary, see VACUUM DIAGRAMS article to verify routing and connections. Repair as necessary. Inspect air induction system for possible vacuum leaks.

Compression

Check engine mechanical condition using a compression gauge, vacuum gauge, or an engine analyzer capable of performing a relative compression test. See engine analyzer instruction manual for availability and description of relative compression feature.

Exhaust System Backpressure

Before replacing any components, check exhaust system for restrictions. The exhaust system can be checked with a vacuum gauge or a 1-10 psi pressure gauge.

If a vacuum gauge is used, connect it to intake manifold vacuum and start engine. Observe gauge and hold throttle steady at 2000-2500 RPM. If vacuum gauge reading slowly drops after stabilizing, exhaust system may be restricted.

1. Check at AIR Pipe Remove rubber hose at exhaust manifold AIR pipe check valve and remove check valve. Install pressure gauge to hose and nipple via Propane Enrichment Device (J26911). Nipple should be inserted into exhaust manifold AIR pipe.
2. Check at O2 Sensor Remove O2 sensor. Install backpressure tester in place of O2 sensor. After test is completed, coat O2 sensor threads with anti-seize compound.
3. Diagnosis Start engine and bring to operating temperature. Increase engine speed to 2000-2500 RPM and note gauge. Reading should not exceed 1.25 psi (.09 kg/cm 2 ). Exhaust system is restricted if specification is exceeded. Check exhaust system for collapsed pipe, heat distress and possible internal muffler failure. If none of these conditions exist, check for restricted catalytic converter. Replace as required.

DEFINITION

No start is defined as engine cranks properly, but does not start. Engine may fire a few times.

NO START - ENGINE CRANKS OKAY (CARBURETED)

Note. Check battery, engine cranking speed and fuel supply before performing the following tests.

General Inspection

1. Ensure proper starting procedure is being used.
2. Check vacuum hoses for splits, kinks and proper connections, as shown on underhood Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both distributor cap and spark plugs.
3. Remove spark plugs. Check and replace as necessary. Remove distributor cap and check for moisture, dust, cracks, burns and arcing to ground through coil mounting screws or rotor.
4. Try to turn distributor shaft by hand. Drive gear pin may be broken.
5. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.

Ignition System

1. Disconnect tachometer wire at distributor (if equipped). A shorted tachometer will not allow vehicle to start.
2. Check for battery voltage at BAT terminal at distributor with ignition on. Repair as necessary.
3. Connect ST-125 spark tester to end of one plug wire and crank engine. (Scheme 1) If spark exists, check fuel delivery.
4. If spark does not exist, disconnect 4-wire EST connector at distributor. If spark now occurs, replace pick-up coil in distributor.
5. If spark does not occur, reconnect EST connector and check voltage at TACH terminal at distributor with ignition on.
6. If voltage is less than one volt, repair faulty coil connection or replace faulty coil. If voltage is 1-10 volts, replace ignition module and recheck for spark. If spark still does not occur, replace ignition coil.
7. If voltage reading at TACH terminal of distributor is greater than 10 volts, remove and invert distributor cap with wires connected. Fabricate an HEI coil spark tester by trimming a spark plug boot and connecting it to ST-125 spark tester. (Scheme 1) Crank engine.
8. If spark occurs, check cap for cracks, water or other defects. Check pick-up coil connector and ignition coil lead wire colors. Ignition coil with Yellow and Red wires should be used with Yellow pick-up coil connector. Ignition coil with White and Red wires should be used with Clear or Black pick-up coil connector.
9. If spark does not occur, turn ignition off and disconnect pick-up coil leads from module. Turn ignition on. With voltmeter connected to TACH terminal of distributor and fabricated coil spark tester connected, momentarily touch test light, connected to battery voltage, to terminal "P" of ignition module. DO NOT touch test light to terminal "P" for more than 5 seconds.
10. If voltage at TACH terminal does not drop, check ignition module ground and for open in ignition coil-to-module wires. If wiring is okay, replace ignition module.
11. If voltage at TACH terminal does drop, check for spark at spark tester as test light is removed from terminal "P". If spark occurs, check pick-up coil connections and check for 500-1500 ohms resistance at pick-up coil leads. Repair as necessary.
12. If spark does not occur, test ignition module with module tester. If module tests okay, check ignition coil wire. If module tester is not available, replace ignition coil and again touch terminal "P". If spark occurs, system is okay. If spark does not occur, reinstall original ignition coil and replace ignition module.

Fuel System

1. Remove air cleaner and check carburetor choke valve, vacuum break(s), linkage and unloader operation. Choke valve should move smoothly, be closed when cold and open when hot.
2. Check for presence of fuel by noting carburetor accelerator pump operation. Look for gasoline squirt in carburetor bore while quickly opening throttle lever. If no squirt occurs, check for fuel in tank, carburetor fuel inlet filter dirty or clogged and float needle for proper operation.
3. Check for proper fuel pump pressure and capacity. Check fuel pump vacuum. See «BASIC FUEL SYSTEM CHECKS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-basic-testing) in this article. If no problems are found, crank engine and check for flooding. If engine is not flooded, check ignition system. See «BASIC IGNITION SYSTEM CHECKS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-basic-testing) in this article.

Scheme 1

Scheme 2

NO START - ENGINE CRANKS OKAY (TBI WITH HEI)

Note. Check battery, engine cranking speed and fuel supply before performing the following tests.

1. Make sure proper starting procedure is being used.
2. Visually check vacuum hoses for splits, kinks and proper connections, as shown on underhood Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper 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. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.

1. Disconnect tachometer wire at distributor TACH terminal (if equipped). A shorted tachometer will not allow vehicle to start.
2. Check for battery voltage at BAT terminal at distributor with ignition on. Repair as necessary.
3. Connect ST-125 spark tester to end of one plug wire and crank engine. If spark occurs, check fuel delivery.
4. If spark does not occur, disconnect 4-wire EST connector at distributor. If spark now occurs, replace pick-up coil in distributor.
5. If spark does not occur, reconnect EST connector and check voltage at TACH terminal at distributor with ignition on.
6. If voltage is less than one volt, repair faulty coil connection or replace faulty coil. If voltage is 1-10 volts, replace ignition module and recheck for spark. If spark still does not occur, replace ignition coil.
7. If voltage reading at TACH terminal of distributor is greater than 10 volts, remove and invert distributor cap with wires connected. Fabricate an HEI coil spark tester by trimming a spark plug boot and connecting it to ST-125 spark tester. (Scheme 1) Crank engine.
8. If spark occurs, check cap for cracks, water or other defects. Check pick-up coil connector and ignition coil lead wire colors. Ignition coil with Yellow and Red wires should be used with a Yellow pick-up coil connector. Ignition coil with White and Red wires should be used with a Clear or Black pick-up coil connector.
9. If spark does not occur, turn ignition off and disconnect pick-up coil leads from module. Turn ignition on. With voltmeter connected to distributor TACH terminal and fabricated coil spark tester connected, momentarily touch test light, connected to a remote voltage source (1.5-8.0 volts), to ignition module terminal "P."
10. If voltage at TACH terminal does not drop, check ignition module ground and for open in wires from ignition coil to module. If all is okay, replace ignition module.
11. If voltage at TACH terminal does drop, check for spark at spark tester as test light is removed from terminal "P". If spark occurs, check pick-up coil connections and check for 500-1500 ohms resistance at pick-up coil leads. Repair as necessary.
12. If spark does not occur, test ignition module with module tester. If module tests okay, check ignition coil wire. If module tester is not available, replace ignition coil and again touch terminal "P." If spark occurs, system is okay. If spark does not occur, reinstall original ignition coil and replace ignition module.

1. Prior to checking fuel system for a no-start condition, check ignition for adequate spark. Check for proper fuel pump pressure (9-13 psi for all models except 2.8L W Body and 26-32 psi for 2.8L W Body) and capacity (one pint in 30 seconds). See «BASIC FUEL SYSTEM CHECKS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-basic-testing) in this article.
2. Crank engine and watch for injector spray. If injector spray occurs, go to step 5). If no spray occurs, disconnect injector harness and check for battery voltage at harness. Battery voltage should be present on one of the injector terminals. If battery voltage is not present, check for blown injector power fuse. If battery voltage is present on both terminals, check for wires shorted to one another.
3. If battery voltage is present on only one terminal, connect injector test light to injector harness. Crank engine and note light. If light flashes, check for stored ECM codes. If no codes are present, refer to HARD START symptom in «TESTS W/O CODES»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article. If light does not flash, momentarily touch test light from battery voltage to ECM RPM reference terminal (circuit No. 430).
4. Each time test light is removed from ECM RPM reference terminal, injector test light should flash. If test light does not flash, check for open in RPM reference wire, injector drive (ground) circuit, or replace faulty ECM.
5. If injector spray occurred while cranking engine, disconnect injector harness and crank engine. If injector spray or leakage occurs, this could cause a no-start condition due to excessive fuel being delivered during cranking. Repair faulty injector or injector seal. If no spray or leakage occurs, refer to HARD START symptom in appropriate «TESTS W/O CODES»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article.

Scheme 3

Scheme 4

Scheme 5

Scheme 6

NO START - ENGINE CRANKS OKAY (TBI WITH DIS)

Note. Check battery, engine cranking speed and fuel supply before performing the following tests.

1. Ensure proper starting procedure is being used.
2. 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.
3. Remove spark plugs. Check and replace as necessary.
4. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.

1. Disconnect tachometer wire (if equipped). A shorted tachometer will not allow vehicle to start.
2. With ignition on, check for battery voltage at Pink or Pink/Black wire of 2-wire connector at ignition module. Check for continuity to ground on Black/White wire of 2-wire connector. Repair as necessary.
3. Connect ST-125 spark tester to end of one plug wire and crank engine. Leave matching plug wire connected to spark plug. If spark occurs, check spark on matching wire. If spark occurs on both wires, check fuel system. If spark occurs on only one wire, go to step 5).
4. If spark does not occur on both wires, remove crankshaft sensor and check resistance. On 2.5L engine, it is necessary to remove ignition module in order to remove sensor. Resistance should be 800-900 ohms at room temperature. Lay a flat piece of metal on tip of sensor to determine if sensor is still magnetized. Replace if necessary. If sensor is okay, check wiring harness to and from ignition module for opens or shorts. If harness is okay, replace ignition module.
5. If spark occurred on only one wire in step 3), note which wire had no spark. Turn ignition off and remove ignition coils. Check for carbon tracking or faulty connections between coil and ignition module. Repair or replace as necessary. If no problems are noticeable, switch coil positions on module and recheck for spark.
6. If same plug wire has no spark, replace ignition module. If spark now occurs on plug wire which previously had no spark and no spark occurs on a different plug wire, replace defective ignition coil.

1. Prior to checking fuel system for a no-start condition, check ignition for adequate spark. Check for proper fuel pump pressure (9-13 psi for all models except 2.8L W Body and 26-32 psi for 2.8L W Body) and capacity (one pint in 30 seconds). See BASIC FUEL SYSTEM CHECKS in this article.
2. Crank engine and watch for injector spray. If injector spray occurs, go to step 5). If no spray occurs, disconnect injector harness and check for battery voltage at harness with ignition on. Battery voltage should be present on the Red or Pink/Black wire of the injector harness. If battery voltage is not present, check for blown injector power fuse. If battery voltage is present on both injector harness terminals, check for wires shorted to one another.
3. If battery voltage is present on only one terminal, connect injector test light to injector harness. Crank engine and note light. If light flashes, check for stored ECM codes. If no codes are present, refer to HARD START symptom in «TESTS W/O CODES»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article. If light does not flash, momentarily touch test light connected to battery voltage to ECM RPM reference terminal (circuit No. 430). (Scheme 7)-11.
4. Each time test light is removed from ECM RPM reference terminal, injector test light should flash. If test light does not flash, check for open in RPM reference wire, injector drive (ground) circuit, or replace faulty ECM.
5. If injector spray occurred while cranking engine, disconnect injector harness and crank engine. If injector spray or leakage occurs this could cause a no-start condition due to excessive fuel being delivered during cranking. Repair faulty injector or injector seal. If no spray or leakage occurs, refer to HARD START symptom in appropriate «TESTS W/O CODES»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article.

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

NO START - ENGINE CRANKS OKAY (PFI WITH HEI)

Note. Check battery, engine cranking speed and fuel supply before performing the following tests.

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

Ignition System (Remote Coil)

1. Disconnect tachometer wire at coil (if equipped). If tachometer lead is not used, it may be taped against harness near coil. A shorted tachometer will not allow vehicle to start.
2. Disconnect 2-wire connector at distributor. Turn ignition on. Check voltage on "C" and "+" terminals of harness. If voltage to "C" terminal only is less than 10 volts, check for open or ground in wire between terminal "C" at distributor and ignition coil. If wire is okay, fault is in ignition coil or ignition coil connector.
3. If voltage at both terminals is less than 10 volts, repair wire from module "+" terminal to ignition coil or repair primary circuit to ignition coil.
4. If voltage at both terminals is over 10 volts, reconnect 2-wire connector at distributor. Check voltage at tachometer terminal at coil with ignition on. Tachometer connector may be taped back against harness. If voltage is greater than 10 volts, go to step 5). If voltage is less than one volt, repair open in tachometer lead and repeat voltage check. If voltage is 1-10 volts, replace ignition module and check for spark from coil wire. If spark occurs, system is okay. If spark does not occur, replace ignition coil also.
5. Connect a test light from tach terminal to ground. Crank engine. If test light illuminates and does not flash, go to step 6). If test light flashes, replace ignition coil and recheck for spark with tester. If spark is still not present, replace ignition module and retest.
6. If test light was on steady in last step, turn ignition off and remove 4-wire connector at distributor. Remove distributor cap and disconnect pick-up coil leads from ignition module. Turn ignition on. With voltmeter connected to tachometer terminal of distributor, momentarily touch test light connected to a remote voltage source (1.5-8.0 volts) to terminal "P" of ignition module.
7. If voltage at tachometer terminal does not drop, check ignition module ground. If all is okay, replace ignition module.
8. If voltage at tachometer terminal does drop, check for spark at spark tester connected to coil wire. If spark occurs as test light is removed from terminal "P", check pick-up coil connections and check for 500-1500 ohms resistance at pick-up coil leads. Check if pole piece is still magnetized. Repair connections or replace pick-up coil as necessary.
9. If spark does not occur, test ignition module with module tester. If module tests okay, check ignition coil wire. If module tester is not available, replace ignition coil and again touch terminal "P". If spark occurs, system is okay. If spark does not occur, reinstall original ignition coil and replace ignition module.

Ignition System (Integral Coil)

1. Disconnect tachometer wire at distributor (if equipped). A shorted tachometer will not allow vehicle to start.
2. Check for battery voltage at "BAT" terminal at distributor with ignition on. Repair as necessary.
3. Connect ST-125 spark tester to end of one plug wire and crank engine. Check for spark at several plug wires. If spark occurs, check fuel delivery system.
4. If spark does not occur, check voltage at distributor "BAT" terminal while cranking engine. If voltage is less than 7 volts, repair primary circuit to ignition switch. If voltage is greater than 7 volts, check voltage to distributor TACH terminal. If voltage is greater than 10 volts, go to step 6). If voltage is less than one volt, repair faulty ignition coil connection or replace defective ignition coil.
5. If voltage is 1-10 volts, replace ignition module and recheck for spark. If spark occurs, system is okay. If spark does not occur, replace ignition coil also.
6. If voltage reading at TACH terminal of distributor is greater than 10 volts, remove and invert distributor cap with wires connected. Fabricate an HEI coil spark tester by trimming a spark plug boot and connecting it to ST-125 spark tester. (Scheme 1) Crank engine.
7. If spark occurs, check cap for cracks, water or other defects. Check for rotor burn-through. Check pick-up coil connector and ignition coil lead wire colors. Ignition coil with Yellow and Red wires should be used with Yellow pick-up coil connector. Ignition coil with White and Red wires should be used with Clear or Black pick-up coil connector.
8. If spark does not occur, turn ignition off and disconnect pick-up coil leads from module. Turn ignition on. With voltmeter connected to TACH terminal of distributor and fabricated coil spark tester connected, momentarily touch test light, connected to battery voltage, to terminal "P" of ignition module. DO NOT touch test light to terminal "P" for more than 5 seconds.
9. If voltage at TACH terminal does not drop, check ignition module ground and for open in wires from ignition coil to module. If wiring is okay, replace ignition module.
10. If voltage at TACH terminal does drop, check for spark at spark tester as test light is removed from terminal "P". If spark occurs, check pick-up coil connections and check for 500-1500 ohms resistance at pick-up coil leads. Repair connections or replace pick-up coil as necessary.
11. If spark does not occur, test ignition module with module tester. If module tests okay, check ignition coil wire. If module tester is not available, replace ignition coil and again touch terminal "P". If spark occurs, system is okay. If spark does not occur, reinstall original ignition coil and replace ignition module.

1. Prior to checking fuel system for a no-start condition, check ignition for proper spark. Check for proper fuel pump pressure (approximately 40-47 psi) and capacity (one pint in 30 seconds). See «BASIC FUEL SYSTEM CHECKS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-basic-testing) in this article.
2. Disconnect injector harness. Turn ignition on and check for battery voltage at each injector harness. see scheme 12-17. Battery voltage should be present on one side of each injector. If battery voltage is not present, check for blown injector power fuse. If battery voltage is present on both injector terminals, check for wires shorted together.
3. If battery voltage is present on only one terminal, connect injector test light to injector harness. Crank engine and note light. Repeat on other injector connectors. If light flashes, check for stored ECM codes. If no codes are present, refer to HARD START symptom in «TESTS W/O CODES»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article.
4. If light does not flash, disconnect distributor 4-wire (5-wire on Cadillac) connector. Momentarily touch test light from battery voltage to ECM RPM reference wire (circuit No. 430) of 4-wire connector. Each time test light is removed from ECM RPM reference terminal, injector test light should flash. If test light does not flash, check for open in RPM reference wire, injector drive (ground) circuit or replace faulty ECM.

Scheme 12

Scheme 13

Scheme 14

Scheme 15

Scheme 16

Scheme 17

NO START - ENGINE CRANKS OKAY (PFI WITH DIS)

Note. Check battery, engine cranking speed and fuel supply before performing the following tests.

1. Ensure proper starting procedure is being used.
2. 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.
3. Remove spark plugs. Check and replace as necessary.
4. In very cold temperatures, check oil is proper viscosity and not contaminated with gasoline.

1. Disconnect tachometer wire (if equipped). A shorted tachometer will not allow vehicle to start.
2. With ignition on, check for battery voltage at Pink/Black wire of 2-wire connector at ignition module. Check for continuity to ground on Black/White wire of 2-wire connector. Repair as necessary.
3. Connect ST-125 spark tester to end of one plug wire and crank engine. Leave matching plug wire connected to spark plug. If spark occurs, check spark on matching wire. If spark occurs on both wires, check fuel delivery. If spark occurs on only one wire, go to step 5).
4. If spark does not occur on either wire, remove crankshaft sensor and check resistance. Resistance should be 900-1200 ohms at room temperature. Lay a flat piece of metal on tip of sensor to determine if sensor is still magnetized. Replace if necessary. If sensor is okay, check wiring harness to and from ignition module for opens or shorts. If harness is okay, replace ignition module.
5. If spark occurred on only one wire in step 3), note which wire had no spark. Turn ignition off and remove ignition coils. Check for evidence of carbon tracking or faulty connections between coil and ignition module. Repair or replace as necessary. If no problems are noticeable, switch coil positions on module and recheck for spark.
6. If same plug wire has no spark, replace ignition module. If spark now occurs on plug wire which previously had no spark and no spark occurs on a different plug wire, replace defective ignition coil.

1. Prior to checking fuel system for a no-start condition, check ignition for adequate spark. Check for proper fuel pump pressure (approximately 40-47 psi) and capacity (one pint in 30 seconds). See «BASIC FUEL SYSTEM CHECKS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-basic-testing) in this article.
2. Disconnect injector harness. Turn ignition on and check for battery voltage at each injector harness terminal. Battery voltage should be present on one injector harness terminal at each injector. If battery voltage is not present, check for blown injector power fuse. If battery voltage is present on both terminals, check for wires shorted to one another.
3. If battery voltage is present on only one terminal, connect injector test light to injector harness. Crank engine and note light. Repeat on other injector connectors. If light flashes, check for stored ECM codes. If no codes are present, refer to HARD START symptom in «TESTS W/O CODES»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article.
4. If light does not flash, turn ignition off. Disconnect ignition module 6-wire connector. Turn ignition on. Momentarily touch test light from battery voltage to ECM RPM reference wire (circuit No. 430) of 6-wire connector. Each time test light is removed from ECM RPM reference terminal, injector test light should flash. If test light does not flash, check for open in RPM reference wire, injector drive (ground) circuit or replace faulty ECM.

Scheme 18

Scheme 19

Scheme 20

Scheme 21

NO START - ENGINE CRANKS OKAY (PFI WITH IDI)

Note. Check battery, engine cranking speed and fuel supply before performing the following tests.

1. Ensure proper starting procedure is being used.
2. 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.
3. Remove spark plugs. Check and replace as necessary.
4. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.

1. Disconnect tachometer wire from IDI module (if equipped). A shorted tachometer will not allow vehicle to start. Temporarily remove IDI assembly and install spark plug Jumper Wires (J 36012). Check for adequate spark with Spark Tester (ST-125). Check for spark on 2 adjacent plug wires (1-2 or 3-4, not 2-3). Leave matching plug wire connected while checking for spark. If spark jumps tester on both plug wires, check fuel system. If spark did not jump tester on either plug wire, go to step 4).
2. If spark jumped tester on only one plug wire, disconnect plug jumper wires and remove coil housing. Disconnect coil harness connector at module. Install test light between module terminal "A" and control terminal for coil which did not spark. (Scheme 20)-24.
3. Crank engine and note test light. If test light blinks at both test terminals, repair faulty harness, poor connection or replace faulty coil. If test light did not blink on both terminals, repair module connections or replace faulty module.
4. If spark did not occur on either plug wire in step 1), Turn ignition off. Disconnect 11-pin connector at module. Turn ignition on and connect test light between terminals "K" and "L" at harness. If test light is not on, repair open or short in module ground or power supply.
5. If test light is on in step 4), install injector test light in any injector. Connect a test light to battery voltage and repeatedly touch to IDI module terminal "H". Injector test light should flash. If test light flashes, go to step 6). If not, check injector drive circuits for open or short to voltage. If ground circuits are okay, check injector power supply. If power supply is okay, repair poor connections at ECM or replace faulty ECM.
6. Connect DVOM between terminals "B" and "C" of IDI module harness connector. Place DVOM on 2-volt AC scale. Crank engine and note voltage. Voltmeter should read greater than 20mV. If voltage is correct, replace IDI module. If voltage is not correct, remove crankshaft sensor from block. Measure sensor resistance. Resistance should be 500-900 ohms. Place a flat piece of metal on tip of sensor to verify sensor is still magnetized. Inspect sensor harness. Repair or replace as necessary.

1. Prior to checking fuel system for a no-start condition, check ignition for proper spark. Check for proper fuel pump pressure (40-47 psi) and capacity (one pint in 30 seconds). See «BASIC FUEL SYSTEM CHECKS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-basic-testing) in this article.
2. Disconnect injector harness. Turn ignition on and check for battery voltage at each injector harness. Battery voltage should be present on one of the injector terminals. If battery voltage is not present, check for blown injector power fuse. If battery voltage is present on both terminals, check for wires shorted to one another.
3. If battery voltage is present to each injector, connect injector test light to injector harness. Crank engine and note light. Repeat on other injector connectors. If light flashes, check for stored ECM codes. If no codes are present, refer to HARD START symptom in «TESTS W/O CODES»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article.
4. If light does not flash, access IDI ignition module harness connector. Disconnect connector and momentarily touch test light from battery voltage to ECM RPM reference wire (circuit No. 430) of module harness. Each time test light is removed from ECM RPM reference terminal, injector test light should flash. If test light does not flash, check for open in RPM reference wire, injector drive (ground) circuit or replace faulty ECM.

Scheme 22

Scheme 23

Scheme 24

NO START - ENGINE CRANKS OKAY (PFI WITH C(3)I)

Note. Before performing following tests, check battery condition, engine cranking speed, and for adequate fuel in the tank.

1. Ensure proper starting procedure is being used.
2. 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.
3. Remove spark plugs. Check and replace as necessary.
4. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.

Ignition System (3.3L)

1. Disconnect tachometer wire (if equipped). A shorted tachometer will not allow vehicle to start. Check for adequate spark with 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 fuel system. If spark did not occur on any plug wire, go to step 4). If spark did not jump tester on all plug wires, verify plug wire resistance is less than 30,000 ohms. Replace as necessary. If wires are okay, go to next step.
2. If spark jumped tester on one, but not all plug wires, remove 2 fasteners holding effected coil assembly. Remove coil from module. Connect a test light to 2 exposed terminals on the module. Crank engine. If test light flashes, check for poor coil to module connections. If connections are okay, replace faulty coil.
3. If test light does not flash, replace ignition module. Also, check primary coil resistance (.5-.9 ohm). Replace coil if necessary.
4. Turn ignition off. Disconnect ignition module connector. Turn ignition on. Check for battery voltage on terminal "M" of ignition module harness. (Scheme 23)and (Scheme 24). Repair open or short, or replace ignition fuse as necessary. If battery voltage is present, turn ignition off and disconnect fuel pump relay. Install injector test light in injector harness connector. Connect test light to battery voltage and repeatedly touch to terminal "C" of the ignition module harness connector.
5. Injector test light should flash each time test light is touched to terminal "C". If injector test light flashes, go to step 7). If not, backprobe ECM injector drive terminals (BC11 and BC12) with a test light to ground. If light is off, check for loss of power to fuel injector harness or open between injectors and drive terminals. If test light is on, disconnect ALL injectors. With test light connected to ground, check for voltage on both terminals of each injector harness.
6. If voltage is present on both wires of any or all injectors, check for short to voltage on injector drive circuit. If battery voltage is present on only one wire of each injector harness, check for open or shorted circuit No. 430 (RPM reference high), poor connections at ECM terminals BC11 and BC12 or a faulty ECM.
7. Turn ignition off and reconnect ignition module connector. Disconnect dual crank (combination) sensor. Turn ignition on. Using a DVOM, measure voltage between sensor harness terminals "C" and "D." If 10-12 volts are not present, check for poor connections at ignition module, open or short in combination sensor harness or replace faulty ignition module.
8. If 10-12 volts are present at combination sensor connector, turn ignition off. Disconnect No. 6 spark plug wire from coil tower. NEVER crank engine with a spark plug wire off coil. Damage to coil or ignition module may occur. Attach Spark Tester (ST-125) to coil tower. Install injector test light in any injector harness.
9. Turn ignition on. Jumper dual crank sensor connector terminal "A" to terminal "B". Using a test light connected to ground, momentarily touch terminal "A". If injector test light flashes and spark tester sparks, check for poor connections at dual crank sensor. If connections are okay, replace faulty dual crank sensor. Inspect dual crank sensor and pulley for signs of rubbing.
10. If spark did not occur and injector test light did not flash, check for poor connections at ignition module or replace faulty ignition module.

Ignition System (3.8L)

1. Ensure that fuel quantity and quality is okay. Turn ignition on with throttle closed. Service engine soon light should be ON. (If not see SERVICE ENGINE SOON LIGHT INOPERATIVE). Connect scan tool according to manufacturer's instructions. TPS should scan less than 2.5 volts (2500 ma). (If not see CODE 21 chart in appropriate TESTS W/CODES article.) Disconnect cam sensor and crank engine. If it starts, see CODE 41 chart in appropriate TESTS W/CODES article. If not, continue. On a cold engine (not run for 8 hours) MAT should be close to CTS value. If not, compare scan value of coolant temperature sensor to actual coolant temperature. Values should be close. If not, replace coolant temperature sensor.
2. Reconnect cam sensor. Depress throttle to approximately 1/4 position. attempt to start engine. If engine starts, check Idle Air Control system. If engine does not start, disconnect all injector connectors and install injector test light J 34730-2 or equivalent in each injector harness connector. Test lights should be off. If test lights are on, go to step 3. If test lights are off, Crank engine and observe if test lights blink. If test lights do not blink, go to step 3. If test lights blink, go to step 4).
3. If light is glowing steadily, disconnect ECM gray connector. If light does not turn off, repair short to ground in injector wiring. If light turns off, ECM is faulty. If test light is off, check INJ fuse. If fuse is not okay, repair short to ground in CKT 839 and replace fuse. If fuse is okay, remove injector test light. Probe injector harness CKT 839 at each injector terminal "A" with a test light to ground. If test light is off, check circuit from ignition feed for an open circuit. If test light is on, go to step 6). NOTE: If an injector driver circuit has been continuously grounded check oil for fuel contamination and exhaust system restriction.
4. Turn ignition off, install fuel pressure gauge and note pressure after ignition is turned ON for 2 seconds, pressure should be 40-47 psi (280-325 kpa) and holding. If no pressure is read, go to FUEL SYSTEM below. If pressure is incorrect, go to FUEL PRESSURE CHECK (PFI). If pressure is correct, go to step 4).
5. Check for spark with spark tester (ST-125) J 26792, or equivalent on plug wires 1, 3 & 5 one at a time while cranking, with remaining plug wires still connected. If there is spark on all wires, check for fouled spark plugs. Clean or replace as necessary, then check Idle Air Control system. No spark on all wires, check for faulty ignition module connection or module. If there is no spark on one or more wires, check the following: Verify that plug wire resistance is less than 30k ohms. If resistance is not as specified, replace wire. Verify coil secondary resistance is 5000-6500 ohms at approximately. 70°F. If resistance is not as specified, replace coil. Remove coil for cylinder(s) that did not fire. Verify coil primary resistance is .3 -.5 ohms. If resistance is not as specified, replace coil. Connect a test light between ignition module terminals for problem coil. The test light should blink while cranking engine. If test light does not blink, the ignition module is faulty. If test light does blink, the ignition coil connection or coil is faulty.
6. Turn ignition off. Disconnect 14 pin harness connector from ignition module. Install an injector test light in any injector harness connector. Turn ignition ON, connect a test light to 12 volts and repeatedly touch to ignition module harness terminal "D". Injector test light should blink. If test light blinks, go to step 7). If test light does not blink, Check injector driver circuit from ECM for an open or short to voltage. If circuit is okay, check CKT 430 for open or short to ground or to voltage. If circuit is ok, check for poor connection at ECM terminal "G9" or faulty ECM. If circuit is not okay, repair injector driver circuit.
7. Turn ignition off. Using appropriate jumper adaptor from connector test adaptor kit J 35616, connect a fused jumper between ignition module harness connector terminal "N" (CKT 644) and B+. Connect a second jumper between ignition module harness connector terminal "M" (CKT 645) and ground. Connect test light between ignition module harness connector terminal "H" (CKT 646) and B+. Test light should flash ON and OFF as starter is bumped. If test light does flash, go to step 8). If test light is on all the time, check CKT 646 for a short to ground. If circuit is okay, check for a faulty crank sensor. If test light is never on, check CKT 646 for an open or short to voltage, CKT 645 for an open, and CKT 644 for an open or short to ground. If circuit is okay, check for a faulty crank sensor.
8. Connect test light between ignition module harness connector terminal "G" (CKT 643) and B+. Observe test light while repeatedly bumping starter. Test light should flicker as starter is bumped. If test light flickers, go to step 9). If test light is on all the time, check CKT 643 for a short to ground. If okay, check for a faulty crank sensor. If test light is never on, Check CKT 643 for an open or short to voltage. If okay, it's a faulty crank sensor.
9. Turn ignition on. Probe ignition module harness connector terminal "P" (CKT 839) with a test light to ground. If test light is on, check for poor connections at ignition module or faulty ignition module. If test light is not on, repair open CKT 839 to ignition module.

1. Before checking fuel system for a no-start condition, check ignition for proper spark. Check for proper fuel pump pressure (40-44 psi 3.3L or 40-47 psi 3.8L) and capacity (one pint in 30 seconds). See «BASIC FUEL SYSTEM CHECKS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-basic-testing) in this article.
2. Disconnect injector harness. Turn ignition on and check for battery voltage at each injector harness. Battery voltage should be present on one of the injector terminals. If battery voltage is not present, check for blown injector power fuse. If battery voltage is present on both terminals, check for injector drive circuit shorted to voltage.
3. If battery voltage is present to each injector, connect injector test light to injector harness. Turn ignition on. DO NOT crank engine. If light is off, go to step 4). If injector test light illuminates without cranking engine, turn ignition off. Disconnect ECM C-D connector. If light is off, replace faulty ECM. If light is still on, check for short to ground in injector drive circuit.
4. Crank engine and note light. Repeat on other injector connectors. If light flashes, check for stored ECM codes. If no codes are present, refer to HARD START symptom in «TESTS W/O CODES»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article.
5. If light does not flash, disconnect ignition module connector and momentarily touch test light from battery voltage to ECM RPM reference wire (circuit No. 430) of module harness. Each time test light is removed from ECM RPM reference terminal, injector test light should flash. If test light does not flash, check for open in RPM reference wire, injector drive (ground) circuit, or replace faulty ECM.

Scheme 25

Scheme 26

ALTERNATE WIRING COLORS "A" & "N" BODY CARS (1)

Scheme 27

Scheme 28

Scheme 29

Scheme 30

FUEL PUMP TESTS (CARBURETED)

Note. Cover fuel line fittings with a shop rag to prevent fuel spillage when releasing fuel lines.

Fuel Pump Test 1

Connect a section of hose to fuel pump outlet line. Place end of hose into a unbreakable graduated container. Start engine and idle for 15 seconds. Fuel pump should deliver 1/2 pint of fuel in 15 seconds.

Fuel Pump Test 2

Connect a short section of hose and a vacuum gauge to fuel pump inlet side. Start or crank engine until maximum vacuum reading is obtained. Vacuum reading should be 15 in. Hg.

Note. If fuel pump fails both Tests 1 and 2, replace fuel pump. If fuel pump failed Test 1 and passes Test 2, check fuel hoses and replace as necessary. If pump and hoses are okay and fuel delivery is still insufficient, remove fuel tank and inspect fuel tank strainer.

Fuel Pump Test 3

Connect a 8-10" hose and a pressure gauge to fuel pump outlet line. Hold gauge so it is about 16" above fuel pump. If equipped, pinch off fuel return line. Start engine and idle on fuel in carburetor. Fuel pressure should be 5.5-6.5 psi (.39-.46 kg/cm 2 ). If pressure is too low, too high or varies greatly with RPM change, replace fuel pump.

FUEL SYSTEM PRESSURE TEST (EFI)

Fuel Pressure Relief (Throttle Body Injection)

Disconnect negative battery cable. Remove fuel filler cap. Since these TBI units contain an internal bleed-down feature, after a short time, system fuel pressure should dissipate.

Fuel Pressure Relief (PFI)

Fuel system is under pressure. Pressure must be relieved prior to servicing fuel system. Fuel pressure may be relieved by using one of the following methods.

1. Disconnect fuel pump at rear body connector. Start engine and run engine until it stalls. Crank starter for 3 seconds to remove remaining fuel from fuel lines. Reconnect rear body connector.
2. Install Fuel Pressure Gauge (J-34730-1) on fuel pressure connection of fuel rail. Wrap shop towel around pressure connection when installing fuel pressure gauge to absorb fuel leakage. Install gauge bleed hose in container. Open bleed valve to bleed fuel pressure.

Fuel Pressure Check (Throttle Body Injection)

1. Relieve fuel pressure (if necessary). Remove air cleaner and plug thermal vacuum port on throttle body. When removing fuel line, always use 2 wrenches. Install Fuel Pressure Gauge (J-29658B or BT-8205) and Adapter (J-29658-85) in fuel line between steel line and flexible hose. NOTE: DO NOT pinch off fuel return line completely. DO NOT exceed pressure build-up of more than 32 psi (2.0 kg/cm 2 ) on 2.5L "W" Body or 13 psi (.9 kg/cm 2 ) on all other models as regulator may be damaged.
2. Turn ignition on and observe fuel pressure reading. Fuel pressure should read 26-32 psi (1.8-2.2 kg/cm 2 ) on 2.5L "W" Body (VIN R) or 9-13 psi (.6-.9 kg/cm 2 ) on all other models . If no fuel pressure is indicated, go to step 5). If fuel pressure is okay but engine will not start, proceed to NO START DIAGNOSIS. If fuel pressure is present but is too high, go to step 4). If fuel pressure is present but is too low, gradually pinch off fuel return line to fuel tank.
3. If fuel pressure remains low, check for plugged fuel filter or restriction in fuel delivery line. If filter is okay and no restrictions are present, replace fuel pump. If fuel pressure increases when return line is pinched, replace fuel pressure regulator.
4. If fuel pressure is present but is higher than specification, check for restriction in fuel return line. If return line is not restricted, replace fuel pressure regulator.
5. If no fuel pressure is observed, turn ignition off. Apply battery voltage to fuel pump test connector using a 10-amp fused jumper wire. For location of fuel pump test connector, refer to COMPONENT LOCATIONS in appropriate «SYSTEM/COMPONENT TESTS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article. Observe fuel pressure reading. If fuel pressure is still not evident, check wiring between test connector and fuel pump. If wiring is okay, replace fuel pump.
6. If fuel pressure is present with voltage applied to test connector, test fuel pump relay and voltage supply to relay. Refer to the appropriate «SYSTEM/COMPONENT TESTS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article.
7. After all repairs, allow fuel pressure to dissipate. Remove fuel pressure gauge and reconnect fuel line. Start engine and watch for fuel system leaks. For further details on fuel pressure testing, proceed to the appropriate «SYSTEM/COMPONENT TESTS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article.

Fuel Pressure Check (PFI)

1. Relieve fuel pressure as previously described in FUEL PRESSURE RELIEF (PFI). Connect Fuel Pressure Gauge (J-34730-1) to fuel pressure fitting on fuel rail.
2. With gauge installed at fuel rail connector, turn ignition on. With ignition on and engine off, pressure should read within specification. See «SPECIFICATIONS - 4-CYL»(ref-10110) article (for 4-cylinder models), See «SPECIFICATIONS - V6»(ref-10111) article (for V6 models),See «SPECIFICATIONS - V8»(ref-10112) article (for V8 models). Start engine. Pressure should drop 3-10 psi (.2-7 kg/cm 2 ). For more details on fuel system pressure testing, see «SYSTEM/COMPONENT TESTS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article.

Fuel Pump Relay

See RELAYS, SOLENOIDS, MOTORS & MODULES in SYSTEM/COMPONENT TESTS article.

Fuel Pump Relay By-Pass Procedure

See FUEL DELIVERY in SYSTEM/COMPONENT TESTS article.

SYSTEM PERFORMANCE CHECK (CARBURETED)

This verifies the computerized engine control system is functioning correctly and should always be made after any repair of computerized engine control system. Ensure parking brake is engaged and DRIVE wheels are blocked. Parking brake on FWD models does NOT hold drive wheels.

Note. On some engines, oxygen sensor will cool off after a short time while engine is idling. This will cause system to go into "open loop". To restore "closed loop" mode, run engine at part throttle for several minutes and accelerate from idle to part throttle several times.

1. Start engine and warm to operating temperature. Run engine at 2000 RPM for one minute to ensure O2 sensor is warm. Connect tachometer to engine. Ground diagnostic test terminal "B". see scheme 32 Disconnect mixture control solenoid and ground Green mixture control dwell lead. Increase engine speed to 3000 RPM and hold throttle held steady, while reconnecting mixture control solenoid. Note RPM change. This checks carburetor's ability to change air/fuel mixture. Disconnecting M/C solenoid makes carburetor run full rich. Reconnecting it with dwell lead grounded makes carburetor run full lean. RPM normally drops 300-1000 RPM as solenoid is reconnected. If RPM drops as described, go to step 3). Remove ground from dwell lead before returning to idle.
2. If RPM dropped less than 300 RPM or RPM increased in step 1), check evaporative canister and related valves for fuel saturation. If plugging PCV, purge or bowl vent hose causes RPM to drop more than 300 RPM, the hose that caused the RPM to change will lead to source of problem. If RPM increases as M/C solenoid is connected, system is running extremely rich. If no faults are found during system checks, service carburetor.
3. Connect dwell meter (on 6-cylinder scale) to Green mixture control solenoid dwell lead. Set carburetor on highest step of fast idle cam. Run for one minute or until dwell begins to vary, whichever happens first. Allow engine to idle and note dwell. This checks for proper control of idle circuit. Normal dwell will vary between 10 and 50 degrees, indicating "closed loop" operation. If dwell does NOT vary between 10 and 50 degrees, see appropriate heading: Dwell Fixed Less Than 10 Degrees Dwell Fixed Between 10 & 50 Degrees Dwell Fixed Greater Than 50 Degrees
4. If dwell is varying between 10 and 50 degrees, observe dwell at 3000 RPM to check for proper control of main metering system. RPM must be at least 3000 RPM to enter main metering system operation. Normal response is varying between 10 and 50 degrees. If dwell is less than 10 degrees, check air injection system for valve supplying air to exhaust manifold at 3000 RPM. A missing "O" ring between the switching valve solenoid and valve, or a defective valve, may cause air to leak into the exhaust ports at higher RPM only. If air is not being supplied to exhaust or dwell at 3000 RPM is greater than 50 degrees, service internal carburetor problems.

Dwell Fixed Less Than 10 Degrees

This indicates a full rich command from the ECM to the carburetor, caused by one of the following

1. Severe engine misfire.
2. False lean O2 sensor signal caused by grounded or open O2 sensor circuit.
3. High TPS signal voltage caused by open in ECM ground circuit No. 452 or sticking TPS.
4. False cold engine signal caused by open in coolant temperature sensor circuit. Ensure vehicle is at operating temperature. With dwell meter still connected to Green dwell lead, increase engine speed to 2000 RPM. Choke engine and note dwell (allow one minute for maximum change). This determines if problem is computer or engine related. Dwell should start increasing as soon as engine is choked and increase until it is greater than 50 degrees. If dwell responds, problem is a lean signal from the oxygen sensor. Check for air or vacuum leaks, including air injection system and deceleration valve (if equipped). Check for exhaust leaks near oxygen sensor. Check for proper vacuum hose routing. Check for proper EGR valve operation. If dwell does not respond when choking engine at 2000 RPM, disconnect oxygen sensor. Connect a DVOM (minimum 10-megohm input impedance) set on the 20-volt scale between the Purple oxygen sensor lead to the ECM and the positive post of the battery. This checks ECM response to input to O2 sensor circuit. The voltmeter is used to put a voltage signal on the O2 sensor circuit to simulate a rich condition. Dwell should increase (lean command) if ECM and harness are good. If dwell increases, check for on open oxygen sensor ground circuit (terminal No. 14 of ECM) or replace faulty oxygen sensor. If dwell does not increase, check coolant temperature using a "Scan" tester. This checks for a normal coolant sensor circuit condition. Temperature on a hot engine should be greater than 167°F (75°C). If reading is less than specified, check for an open in the coolant temperature sensor circuit or an out-of-calibration sensor. See «SYSTEM/COMPONENT TESTS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article for testing of the coolant temperature sensor. If coolant temperature scans 167°F (75°C) or greater, check for grounded or open oxygen sensor circuits. If circuits are okay, scan throttle position sensor voltage. If TPS is greater than 1.1 volts, adjust or replace TPS as necessary. If TPS scans less than 1.1 volts, check for faulty connection at ECM terminal No. 14. If connection is okay, replace ECM.

Dwell Fixed Between 10 & 50 Degrees

This indicates an "open loop" condition caused by one of the following

1. Open O2 sensor circuit or bad sensor.
2. Open coolant temperature sensor circuit.
3. Open circuit No. 413 from ECM terminal No. 14 to ground. Run engine at 2000 RPM for one minute to ensure normal operating temperature. Idle engine and check mixture control solenoid dwell. Disconnect oxygen sensor and jumper ECM harness terminal (not sensor) to ground. Grounding O2 sensor input checks ECM response to a "lean" signal. Normal response is dwell decreasing to full rich command. If dwell does not change as indicated, go to step 4). If dwell decreases with oxygen sensor ECM harness terminal grounded, check for open in oxygen sensor ground circuit (ECM terminal No. 14). On some ECMs, an open circuit to terminal No. 14 can cause "open loop". Repair as necessary. If circuit is not open, leave oxygen sensor lead to ECM grounded. Connect a DVOM (minimum 10-megohm input impedance) set on the 2-volt scale to the oxygen sensor Purple lead. This checks O2 sensor output with full rich command from ECM caused by grounding O2 sensor input circuit. Normal response is O2 sensor voltage reading greater than .8 volt. If DVOM does not read greater than .8 volt, replace oxygen sensor. If DVOM does read greater than .8 volt, repair faulty connections at oxygen sensor. If dwell did not change when oxygen sensor lead to ECM was grounded, jumper ECM terminal No. 9 to terminal No. 14. This grounds O2 sensor circuit at ECM to check for open in wiring to ECM terminal No. 9. Normal response to "lean" signal is a decrease in dwell. If dwell decreases, check for open in circuit No. 412 (Purple wire of oxygen sensor). If there is no change in dwell when terminal No. 9 is jumpered to terminal No. 14, turn ignition off. Turn ignition on with engine off. Using a "Scan" tester, check coolant temperature sensor parameter. This checks coolant sensor input. Normal reading on a warm engine is greater than 167°F (75°C). An open coolant sensor signal or ground circuit would cause a reading of approximately 77°F (25°C). If this is the indicated reading, check coolant sensor harness for opens. Also, check coolant sensor for an being out of calibration. See «SYSTEM/COMPONENT TESTS»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article. If coolant temperature scans greater than 167°F (75°C), check for faulty connections to ECM terminals No. 9 or No. 14. If connections are okay, replace ECM.

Dwell Fixed Greater Than 50 Degrees

This indicates a full lean command from the ECM to the carburetor caused by one of the following

1. M/C solenoid wires reversed.
2. Leaking bowl vent valve, excessive fuel in vapor canister or fuel in crankcase.
3. Faulty carburetor calibration or carburetor.
4. Silicone-contaminated O2 sensor. Run engine at fast idle for at least 2 minutes to ensure vehicle has reached normal operating temperature. Allow engine to idle. Monitor mixture control solenoid dwell while creating a large vacuum leak. This determines if problem is related to engine or electronics. Normal response is dwell decrease. If dwell decreases, this indicates O2 sensor, harness and ECM are okay. Problem is a rich engine condition. If engine is very rich, a large air leak may be required to lean mixture. When mixture is lean enough, engine will begin to run rough and dwell will drop at least 20 degrees. If dwell drops at least 20 degrees, check evaporative canister for being loaded with fuel. Check related purge and vent valves. If plugging PCV or bowl vent vacuum hose causes dwell to decrease, that hose leads to source of problem. Also check for fuel in crankcase. If no problems are found, service carburetor, including checking float level. If dwell did not drop at least 20 degrees when vacuum leak was created, disconnect oxygen sensor harness connector and ground ECM side of harness (not sensor). This checks ECM response to a "lean" O2 signal. Normal response is drop in dwell. No dwell change indicates a defective ECM. This test also eliminates the possibility of an open sensor wire. An open wire would cause "open loop" operation and may set Code 13. If dwell drops to less than 10 degrees when ECM side of oxygen sensor harness is grounded, turn ignition off. Turn ignition on with engine off. Remove ground from ECM side of oxygen sensor harness. Using a DVOM, check voltage on ECM side of harness. If reading is less than .55 volt, replace oxygen sensor. If reading is .55 volt or greater, check for short to voltage on harness. If short to voltage is not present, replace ECM.

FIELD SERVICE MODE CHECK (FUEL INJECTED)

Note. On some engines, oxygen sensor will cool off while engine is idling. This causes system to go into "open loop". To restore "closed loop" mode, run engine at part throttle several minutes and accelerate from idle to part throttle several times.

This confirms proper fuel system operation and verifies "closed loop" operation. Clear codes and perform this test after any repair is completed. When performing this check, always engage parking brake and block DRIVE wheels. Parking brake on FWD models does NOT hold drive wheels.

1. Start engine. With engine running, ground "test" terminal "B" of the ALDL diagnostic connector. (Scheme 33) In "closed loop" mode, SERVICE ENGINE SOON light will flash once a second.
2. In "open loop", light will flash 2.5 times a second. If light is off most of the time, a lean exhaust is indicated. If light is on most of the time, a rich exhaust is indicated.

HEI-EST DISTRIBUTOR

Note. The only adjustments that can be made to HEI/EST ignition system are basic ignition timing and spark plug gap.

Spark

1. If factory tachometer is connected to ignition coil tachometer terminal, disconnect it before performing tests. When removing spark plug wire from spark plug, twist and pull on boot, NOT on wire.
2. Using Spark Tester (ST-125), check for spark at coil wire (if applicable) and at each spark plug wire using spark tester. Check spark plug wire resistance on suspect wires. Resistance should be no greater than 30,000 ohms.

Ignition Coil Power Source

1. Turn ignition on. Using voltmeter, check voltage between terminal "B" of ignition coil and ground on models with remote-mounted coil.
2. On models equipped with integral ignition coil, check voltage between "BAT" terminal and ground at distributor. Battery voltage should exist. If not, check for open circuit, blown ignition fuse or defective ignition switch.

Ignition Coil Resistance (Externally Mounted)

1. Remove coil connectors and secondary coil wire. In test "A", use high ohmmeter scale. (Scheme 31) Resistance value should be very high (infinite). If not, replace coil.
2. In test "B", use low ohmmeter scale. Reading should be approximately zero ohms or replace coil. In test "C", use high ohmmeter scale. If there is no continuity, replace coil.

Scheme 31

Ignition Coil Resistance (Internally Mounted)

1. Turn ignition off. Remove the distributor cap and coil assembly. Turn cap upside down. (Scheme 32) Set ohmmeter to low scale. Connect leads to coil BAT and TACH terminals. If resistance is more than zero, replace ignition coil.
2. Set ohmmeter on high scale. Connect one lead to coil secondary terminal and other lead first to TACH terminal and then to ground terminal. If resistance reading in BOTH instances is infinite, replace ignition coil.

Scheme 32

Distributor Pick-up Coil Short & Resistance Checks

1. Disconnect pick-up coil leads from HEI/EST module terminals "N" and "P". Set ohmmeter to middle scale. Connect one ohmmeter lead to either pick-up coil lead and the other lead to distributor housing. Flex pick-up coil leads by hand to check for intermittent shorts to ground. Reading should be infinity at all times. If resistance is not infinite, replace pick-up coil.
2. Connect ohmmeter between both pick-up coil leads. Check for intermittent opens by flexing wires and connectors. Resistance should be 500-1500 ohms. If resistance is not as specified, replace pick-up coil.

Tach Pulse (RPM) Signal

Connect a "Scan" tester to the ALDL diagnostic connector. RPM should be indicated on tester when engine is cranked or running. Tach pulse (RPM reference will be indicated as a voltage signal when a DVOM (minimum 10-megohm input impedance) is touched to circuit No. 430 ECM terminal. For circuit and terminal reference, see appropriate schematic in NO START - ENGINE CRANKS OKAY in this article.

1. If factory tachometer is connected to ignition coil tachometer terminal, disconnect it before performing tests. When removing spark plug wire from spark plug, twist and pull on boot, NOT on wire.
2. Using Spark Tester (ST-125), check for spark at each spark plug wire using spark tester. Leave opposed firing plug connected while checking for spark. Check spark plug wire resistance on suspect wires. Resistance should be no greater than 30,000 ohms.

Turn ignition on and check Pink or Pink/Black wire of ignition module for battery voltage. If battery voltage is not present, check ignition/ECM fuse. If fuse is not blown, check for open between fuse and ignition module.

Ignition Coil Resistance

1. Disconnect leads from ignition coil. Using an ohmmeter, check secondary ignition coil resistance. See «DIS SECONDARY COIL RESISTANCE»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-basic-testing) table.
2. Primary resistance and secondary resistance values on models not listed in «DIS SECONDARY COIL RESISTANCE»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-basic-testing) table are not supplied by manufacturer.

DIS SECONDARY COIL RESISTANCE

Crankshaft Sensor Pick-Up Coil Short & Resistance Checks

1. Set DVOM on the 2000-ohm scale. Connect leads to crank angle sensor, located on side of engine block. On 2.5L models, it will be necessary to remove ignition module. Crankshaft sensor resistance should be within specification in «CRANKSHAFT SENSOR RESISTANCE»(/oldsmobile/toronado-trofeo/1990-1990/remont/testing-diagnostics/#engine-controls-basic-testing) table. If resistance is not as specified, replace sensor.
2. Connect one ohmmeter lead to either sensor terminal. Touch other lead of ohmmeter to engine block. No continuity should exist. If continuity exists, sensor is shorted to ground and must be replaced.

CRANKSHAFT SENSOR RESISTANCE (OHMS)

Crank Angle Sensor Signal

Set DVOM on the 2-volt AC scale. Connect voltmeter leads to crank angle sensor installed in side of engine block. On 2.5L models it will be necessary to remove ignition module. Crank engine and observe voltmeter reading. Crank angle sensor should generate a voltage signal of about .05 volt at slow cranking speed to greater than .1 volt (100 mV) at high cranking speed.

Connect "Scan" tester to ALDL diagnostic connector. RPM should be indicated on tester when engine is cranked or running. Tach pulse (RPM reference will be indicated as a voltage signal when a DVOM (minimum 10-megohm input impedance) is touched to circuit No. 430 ECM terminal. For circuit and terminal reference, see appropriate schematic in NO START - ENGINE CRANKS OKAY in this article.

Disconnect tachometer wire from IDI module (if equipped). A shorted tachometer will not allow vehicle to start. Temporarily remove IDI assembly and install spark plug Jumper Wires (J 36012). Check for adequate spark with Spark Tester (ST-125). Check for spark on 2 adjacent plug wires (1-2 or 3-4, not 2-3). Leave matching plug wire connected while checking for spark. When removing spark plug wire from spark plug, twist and pull on boot. DO NOT pull on wire.

Turn ignition on. Check for battery voltage on Pink/Black wire to ignition module. If battery voltage is not present, check for blown ignition fuse. If fuse is not blown, check for open between fuse and ignition module.

Disconnect leads from ignition coil. Using an ohmmeter, check ignition coil secondary resistance. Secondary resistance should be less than 10,000 ohms on all models.

1. Set DVOM on the 2000-ohm scale. Connect leads to crank angle sensor installed in side of engine block. Crankshaft sensor resistance should be 500-900 ohms on all models. If resistance is not as specified, replace sensor.
2. Connect one ohmmeter lead to either sensor terminal. Touch other ohmmeter lead to engine block. No continuity should exist. If continuity exists, sensor is shorted to ground and must be replaced.

Set DVOM on the 2-volt AC scale. Connect voltmeter leads to crank angle sensor, located on side of engine block. Crank engine and observe voltmeter reading. Crank angle sensor should generate a voltage signal of about .01 volt at slow cranking speed to greater than .02 volt (20 mV) at high cranking speed.

Connect "Scan" tester to ALDL diagnostic connector. RPM should be indicated on tester when engine is cranked or running. Tach pulse (RPM reference will be indicated as a voltage signal when a DVOM with a minimum 10-megohm input impedance) is touched to circuit No. 430 ECM terminal. For circuit and terminal reference, see appropriate schematic in NO START - ENGINE CRANKS OKAY in this article.

Disconnect tachometer wire (if equipped). A shorted tachometer will not allow vehicle to start. Disconnect cam sensor and attempt to start engine. If engine starts, see cam sensor trouble code in appropriate SELF-DIAGNOSTICS article. Check for adequate spark with 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. When removing spark plug wire from spark plug, twist and pull on boot. DO NOT pull on wire.

Turn ignition on. Check for battery voltage on Pink/Black wire to ignition module. If battery voltage is not present, check for blown ignition fuse. If fuse is not blown, check for open between fuse and ignition module.

Disconnect ignition coil leads. Use an ohmmeter to check ignition coil resistance. Primary resistance should be .5-.9 ohm. Secondary resistance should be 5000-10,000 ohms. Replace ignition coil if not within specification.

Tach Pulse (RPM Reference) Signal

Connect "Scan" tester to ALDL diagnostic connector. RPM should be indicated on tester when engine is cranked or running. Tach pulse (RPM reference will be indicated as a voltage signal when a DVOM with a minimum 10-megohm input impedance) is touched to circuit No. 430 ECM terminal. For circuit and terminal reference, see appropriate schematic in NO START - ENGINE CRANKS OKAY in this article.

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. For adjustment procedures, see ON-VEHICLE ADJUSTMENTS article.

DIAGNOSTIC CIRCUIT CHECK (EXCEPT ECM/BCM EQUIPPED VEHICLES)

The 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 procedures in PRELIMINARY INSPECTION & ADJUSTMENTS, BASIC FUEL SYSTEM CHECKS and BASIC IGNITION SYSTEM CHECKS, this is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in the diagnostic circuit check, if no codes are indicated and driveability problems still exist, see TESTS W/O CODES article and SCAN TESTER USAGE in appropriate TESTS W/CODES - 3.8L PFI article.

CARBURETED

1. Check SERVICE ENGINE SOON light operation. With ignition on and engine off, light should be on steady. If light illuminates and stays on steady, go to next step. If light does not illuminate, go to SERVICE ENGINE SOON LIGHT INOPERATIVE. If light flashes, go to step 3).
2. Grounding the ALDL "test" terminal 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, this is not considered a code. If lights dims or remains on, see SERVICE ENGINE SOON LIGHT 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 the diagnostic test terminal wire between ALDL terminal "B" and ECM terminal No. 5. If circuit is okay, replace ECM.

SERVICE ENGINE SOON Light Inoperative

1. If the "SERVICE ENGINE SOON" light does not illuminate with ignition on and engine off, attempt to start engine. If engine starts, go to step 3). If engine does not start, check fusible links at battery and ECM fuse. If fusible links or ECM fuse are blown, repair short to ground.
2. If fusible links and ECM fuse are okay, turn ignition on and check power circuits to ECM, including keep alive memory and ignition feed. See the WIRING DIAGRAMS article in this section for power terminal identification. If power is not available to power terminals of ECM, check for opens in power circuits. If power is available to ECM power terminals, check for poor ECM ground circuits, or replace faulty ECM.
3. If engine starts and "SERVICE ENGINE SOON" light does not illuminate, turn ignition off. Disconnect ECM connectors. Turn ignition on and jumper ECM "SERVICE ENGINE SOON" light driver terminal to ground using a test light. See the appropriate WIRING DIAGRAMS article in this section for power terminal identification.
4. If light is now on, repair light driver terminal connections at ECM or replace faulty ECM. If light stays off when test light is used to ground light driver terminal, check for blown instrument panel fuse, faulty bulb, open in light driver circuit between ECM and bulb, driver circuit shorted to voltage, or an open in the ignition feed to the "SERVICE ENGINE SOON" light.

SERVICE ENGINE SOON Light On Or Won't Flash Code 12

1. Check for battery voltage at ECM terminals "C" and "R". Voltage must be greater than 11 volts. With ALDL "test" terminal not grounded, check voltage at lamp driver module terminal "C".
2. If voltage is 11 volts or greater, check for short to voltage on wire between terminal "C" of lamp driver module and ECM terminal "G". If voltage on terminal "C" of lamp driver module is less than 11 volts, ground lamp driver terminal "C" and note SERVICE ENGINE SOON light. If light is off, go to step 4).
3. If light is on, disconnect driver and note SERVICE ENGINE SOON LIGHT. If light is now on, repair short to ground in wire between lamp driver module terminal "E" and SERVICE ENGINE SOON light. If light is off, repair connection at lamp driver module or replace faulty lamp driver module.
4. If light is off with terminal "C" of driver grounded, ground ECM terminal "G" and note light. This should turn light off. If it does, go to next step. If light stays on, repair open in wire between terminal "C" of lamp driver module and terminal "G" of ECM.
5. If light goes off with terminal "G" of ECM grounded, ground ECM terminal No. 5. If light flashes Code 12, repair open in circuit between terminal No. 5 of ECM and ALDL "test" terminal "B". If Code 12 does not flash, check voltage from between ground and ECM terminal "U". This checks for bad ground in ECM. Terminals "A" and "U" are connected together inside ECM. If reading is one volt or greater, repair poor connections from ECM terminals "A" and "U" to ground.
6. If voltage from terminal "U" to ground is less than one volt, turn ignition off. Remove PROM from ECM. Turn ignition on. Wait 30 seconds and check for Code 51. This step distinguishes between a faulty ECM and PROM. Normal response is for Code 51 to flash even though PROM is not installed in ECM. If there is no Code 51, ECM is faulty. If Code 51 is present, check for proper PROM installation. If PROM was installed properly, install new PROM and repeat diagnostic circuit check. If Code 12 is not flashed, replace ECM.

Scheme 33

Scheme 34

FUEL INJECTED

1. Check operation of SERVICE ENGINE SOON light. Turn ignition on with engine off. (Scheme 33) 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 SERVICE ENGINE SOON LIGHT INOPERATIVE. If light flashes, go to step 3).
2. Grounding the ALDL "test" terminal at this time 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, this is not considered a code. If light dims or remains on, and does not flash Code 12, see SERVICE ENGINE SOON LIGHT ON STEADY 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 the diagnostic test terminal wire between ALDL terminal "B" and ECM terminal No. 5. If circuit is okay, replace ECM.

1. If SERVICE ENGINE SOON light does not illuminate with ignition on and engine off, attempt to start engine. If engine starts, go to step 3). If engine does not start, check fusible links at battery and ECM fuse. If fusible links or ECM fuse are blown, repair short to ground.
2. If fusible links and ECM fuse are okay, turn ignition on and check power circuits to ECM, including keep alive memory and ignition feed. See appropriate diagram in WIRING DIAGRAMS article for power terminal identification. If power is not available to power terminals of ECM, check for opens in power circuits. If power is available to ECM power terminals, check for poor ECM ground circuits, or replace faulty ECM.
3. If engine starts and SERVICE ENGINE SOON light does not illuminate, turn ignition off. Disconnect ECM connectors. Turn ignition on and jumper ECM SERVICE ENGINE SOON light driver terminal to ground using a test light. See appropriate diagram in WIRING DIAGRAMS article for power terminal identification.
4. If light is now on, repair light driver terminal connections at ECM or replace faulty ECM. If light stays off when test light is used to ground light driver terminal, check for blown instrument panel fuse, faulty bulb, open in light driver circuit between ECM and bulb, driver circuit shorted to voltage, or an open in the ignition feed to the SERVICE ENGINE SOON light.

SERVICE ENGINE SOON Light On All The Time Or Won't Flash Code 12

1. Turn ignition off. Disconnect ECM connectors. Turn ignition on. If SERVICE ENGINE SOON light is on, check for short to ground in light driver circuit between light and ECM driver terminal. See appropriate diagram in WIRING DIAGRAMS article for terminal identification.
2. If light is off with ECM connectors disconnected, turn ignition off. Reconnect ECM connectors. Turn ignition on with engine off. Using a DVOM, check voltage at ALDL "test" terminal "B". (Scheme 33) If voltage is greater than 9 volts, check for a short to voltage on ALDL terminal "B" wire between ECM and ALDL connector. If voltage is 5-6 volts, proceed to next step. If voltage is less than 5 volts, backprobe appropriate ECM terminal with DVOM. See appropriate diagram in WIRING DIAGRAMS article for terminal identification. If 5-6 volts is now present, repair open or short in wire between ECM and ALDL terminal "B".
3. If voltage at terminal "B" of ALDL connector is 5-6 volts, jumper that wire terminal at ECM to ground. If SERVICE ENGINE SOON light flashes a Code 12, and ALDL terminal "A" was used when grounding terminal "B", check terminal "A" for continuity to ground. If SERVICE ENGINE SOON light does not flash when ECM end of terminal "B" wire is jumpered to ground, check PROM/MEM-CAL for proper installation. If installed correctly, replace ECM, using original PROM/MEM-CAL. Repeat diagnostic circuit check. If Code 12 still does not flash, replace PROM/MEM-CAL. Replace PROM/MEM-CAL only after replacing ECM, as PROM/MEM-CAL is not likely to be at fault.

Scheme 35

SUMMARY

If no problems were found while performing BASIC TESTING , no trouble codes (or only intermittent ones) were found while performing DIAGNOSTIC CIRCUIT CHECK and driveability problems exist, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnosis procedures.

See also:
• TESTS W/O CODES
• SYSTEM/COMPONENT TESTS
• BASIC FUEL SYSTEM CHECKS