Engine Controls - Basic Testing Cadillac Fleetwood II

INTRODUCTION

The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a no-start condition.

The first step in diagnosing any driveability problem is verifying the customer's complaint with a test drive under the conditions during which the problem reportedly occurred.

Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.

The following table provides the location of commonly used diagnostic information. These former "A" and "C" charts are now written in text and inserted into the appropriate location in the new Engine Performance workflow. To familiarize yourself with the Engine Performance workflow, see the article called AA - USING THIS SECTION (GENERAL HELP INFORMATION) in the ENGINE PERFORMANCE section.

GENERAL MOTORS A & C CHART REFERENCE

Note. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure.

VISUAL INSPECTION

Visually inspect all electrical wiring, looking 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. See VACUUM DIAGRAMS article in the ENGINE PERFORMANCE section to verify routing and connections (if necessary). Inspect air induction system for possible vacuum leaks.

Compression

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions. For compression specifications, see SPECIFICATIONS article in the ENGINE PERFORMANCE section.

Exhaust System Backpressure

Before replacing any components, check exhaust system for restrictions. The exhaust system can be checked with a vacuum gauge or a low pressure (0-5 psi) pressure gauge.

If a vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, exhaust system should be checked for a restriction. If using a low pressure gauge, connect gauge in one of the following manners

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(J-26911). Nipple should be inserted into exhaust manifold AIR pipe.
2. Check At Oxygen Sensor Remove oxygen sensor. Install backpressure tester in place of oxygen sensor. After test is completed, coat oxygen sensor threads with anti-seize compound.

Diagnosis

1. 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.
2. 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.

PCM REPLACEMENT CHECK

Many test procedures and test charts in ENGINE PERFORMANCE lead to conclusion that PCM is faulty. Before replacing PCM, check driven circuits and PCM Quad-Drivers (QDR) using following procedures and accompanying flow chart. See QDR diagnostic flow chart below.

1. Using a DVOM, backprobe PCM drive circuit in question and measure pin voltage with ignition on. If system voltage is present, go to next step. If system voltage is not present, turn ignition off. Disconnect PCM connector. Measure voltage on connector terminal for suspect circuit. If low voltage is measured, check circuit for an open or short to ground. Repair as necessary. If system voltage is measured, PCM is defective.
2. With DVOM still backprobing PCM at suspect circuit, ground DLC "test" terminal. Monitor voltage drop on circuit for at least 2 minutes. Voltage drop should not be greater than .5 volt. Some circuits may have low voltage until DLC "test" terminal is grounded. A "switching" operation should occur. Some Torque Converter Clutch (TCC) systems have pressure switches in series with TCC solenoid. On these applications, complete this circuit by disconnecting transmission/transaxle connector and using a test light in series between terminals "A" and "D" of transmission/transaxle connector.
3. If voltage drops and then floats back up, this occurs when QDR circuit is going into current limiting. Check the circuit current flow (.75 amp maximum, except as noted in QDR check chart). See QDR diagnostic flow chart below. NOTE: For PCM-equipped vehicles, transmission/transaxle functions can only be energized through use of the TECH 1 scan tester. Shift solenoids on these models will not energize when DLC is grounded.

Flowchart. Scheme 117

NO START DIAGNOSIS (A-3)

Note. Some vehicles are equipped with anti-theft systems (VATS or PASS-Key(R)) which will not allow vehicle to be started if improper starting procedures or improperly coded ignition keys are used. Both fuel injection and cranking systems will be disabled. Loss of fuel enable signal from anti-theft decoder module should set a trouble code in PCM memory.

Definition

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

General Inspection

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.

Ignition System

1. Check for stored trouble codes. If Codes 16, 18, 41, 42, 46 or 48 are set, use those code charts first. See TESTS W/CODES article in the ENGINE PERFORMANCE section. If engine has not been started for at least 8 hours, compare scanned CTS temperature with actual coolant temperature. If scanned value are not close, replace coolant temperature sensor. Ensure TP sensor scan is greater than 2.5 volts at closed throttle. If not, refer to Code 21 chart in TESTS W/CODES article in the ENGINE PERFORMANCE section.
2. Scan engine RPM during cranking. If RPM is indicated on scan tester, go to step 4). If RPM is not indicated on scan tester, turn ignition off. Disconnect distributor electrical connector. Turn ignition on. Probe terminal "C" (Red wire) of distributor harness connector (PCM side) with a test light connected to ground. If test light is on, go to next step. If test light is not on, problem is faulty PCM connection, open or grounded ignition feed circuit (Yellow wire) or a faulty PCM.
3. Turn ignition off. Check for continuity between ground and distributor harness connector terminal "D" (Pink/Black wire). (Scheme 118)and (Scheme 119). If continuity exists, problem is faulty distributor connector connection or faulty distributor. If continuity does not exist, problem is faulty PCM connection, open ground circuit (Pink/Black wire) between PCM and distributor harness connector or faulty PCM.
4. Install Spark Tester (ST-125). Crank engine and check for spark on at least 2 spark plug wires. If spark is not present, go to step 9). If spark is present, crank engine with injector test light connected to each injector harness connector (one at a time). If light is on steady at any injector harness connector, go to next step. If light does not come on at any injector harness connector, go to step 6). If light blinks dimly, injector(s) is most likely shorted. Ensure injectors have at least 10 ohms resistance. If light blinks brightly on all injector harness connectors, check fuel system pressure. See BASIC FUEL SYSTEM CHECKS.
5. If injector test light is on steady when connected to any injector harness connector, check injector drive circuit of affected injector for short to ground. If circuit is not shorted to ground, ensure injector resistance is at least 10 ohms (but not infinity). If circuit is okay and all injectors have at least 10 ohms resistance, PCM is faulty.
6. Turn ignition on. Using test light connected to ground, probe each injector connector terminal (Dark Green, Pink/Black and Dark Blue wires). Since injectors are wired in parallel, test light should light on both terminals of each injector. If test light is off at both terminals, repair open in injector power feed circuit. If test light is on at only one wire of an injector harness connector, problem is an open in tested harness.
7. If test light is on at both terminals of each injector harness connector, turn ignition off. Reconnect all injector connectors. Disconnect PCM connectors. Turn ignition on. Probe PCM harness connector terminals D10 and D11 with a test light connected to ground. If test light is on for both terminals, go to next step. If test light is off on either terminal, repair open in that circuit between PCM connector and injector harness connector.
8. Disconnect all injector connectors. Turn ignition on. Using a test light connected to ground, probe injector drive circuit Dark Blue and Dark Green wires on PCM side of injector harness. Test light should not glow. If light is on, repair short to voltage on that circuit of harness. If harness is okay, ensure injector resistance is greater than 10 ohms (but not infinity). Replace injectors as necessary. Inspect injector harness connectors terminals for loose or backed-out pins. If no problems are found in this step, replace PCM.
9. Check spark at coil wire using Spark Tester (ST-125). Leave spark tester connected to coil for remaining steps. If spark does not occur, go to next step. If spark occurs, inspect distributor cap for cranks. Inspect secondary wiring (plug wires) for opens, shorts or poor connections. If cap and wires are okay, replace distributor.
10. If spark did not occur at coil wire, check for open or shorted coil wire. If coil wire is okay, disconnect ignition coil driver connector. Turn ignition on. Using voltmeter, check voltage between terminals "A" and "D" of coil driver harness. If voltage on one terminal is less than 10 volts, check for open or short or faulty coil connection on that circuit. If circuit and connection are okay, coil is faulty.
11. If voltage on both terminals is less than 10 volts, check for faulty power feed circuit to coil or grounded external coil circuit. If external circuits and power feed are okay, coil is faulty.
12. If voltage on both terminals is 10 volts or greater, connect DVOM set on AC scale to ground and terminal "B" of coil driver harness. Crank engine. If voltage is not 1-4 volts, go to step 14). If voltage is 1-4 volts, probe coil driver connector terminal "C" with a test light connected to battery voltage.
13. If test light does not come on, coil driver ground circuit is open. If test light comes on, coil driver connection or coil driver is faulty.
14. Crank engine and monitor low resolution signal on scan tester. If low resolution signal is present, problem is faulty EST connection at PCM, open EST circuit or faulty PCM. If low resolution signal is not present, turn ignition off. Disconnect distributor electrical connector. Turn ignition on. Probe terminal "C" of distributor harness with a test light connected to ground. If test light is on, go to step 16).
15. If test light is off, problem is faulty PCM connection, open in ignition feed circuit between PCM and distributor harness connector terminal "C" or faulty PCM.
16. Turn ignition off. Check for continuity between ground and distributor harness connector terminal "D". If continuity exists, go to next step. If continuity does not exist, open ground circuit between PCM and distributor harness connector terminal "D", faulty PCM connection or faulty PCM.
17. Turn ignition on. Using DVOM set on AC scale, measure voltage on terminal "A" of distributor harness connector. If about 5 volts are present, go to next step. If voltage is not as specified, problem is open or short in low resolution circuit between PCM and distributor harness connector terminal "A", faulty PCM connection or faulty PCM.
18. Measure voltage on terminal "B" of distributor harness connector. If about 5 volts are present, distributor connection or distributor is faulty. If about 5 volts are not present, problem is open or short in high resolution circuit between PCM and distributor harness connector terminal "B", faulty PCM connection or faulty PCM.

Scheme 118

Scheme 119

BASIC FUEL SYSTEM CHECKS (A-7)

Fuel Pressure Relief (MFI)

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. Turn ignition off. Reconnect rear body connector.
2. Install Fuel Pressure Gauge(J-34730-1) on fuel pressure connector 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 (MFI)

1. Relieve fuel pressure as previously described in FUEL PRESSURE RELIEF (MFI). Connect Fuel Pressure Gauge (J-34730-1) to fuel pressure fitting on fuel rail. With gauge installed, turn ignition on and engine off, fuel pressure should read within specification. See FUEL PRESSURE (MFI) table. If no fuel pressure is present, go to step 5).
2. Start engine. Pressure should drop 3-10 psi (.2-.7 kg/cm 2 ). Turn ignition off. Pressure should hold. If pressure does not hold, check for leaking injectors or fittings. If injectors or fittings are not leaking, replace pressure regulator.
3. If pressure is present but less than specification, check for restricted delivery line or fuel filter. Repair as necessary. If no restriction is evident, apply battery voltage to fuel pump test connector using a 10-amp fused jumper wire. For location of fuel pump test connector, see COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.
4. Gradually pinch off fuel return line between gauge and fuel tank. If fuel pressure increases to within specification, replace fuel pressure regulator. If fuel pressure does not increase with line pinched, check for faulty in-tank fuel pump or partially blocked fuel strainer.
5. Apply battery voltage to fuel pump test connector using a 10-amp fused jumper wire. For location of fuel pump test connector, see COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section. Observe fuel pressure reading. If fuel pressure is still not present, 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. See SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

FUEL PRESSURE (MFI)

Fuel Pump Relay

See MOTORS, RELAYS & SOLENOIDS in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

Fuel Pump Relay By-Pass Procedure

See FUEL DELIVERY in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

FIELD SERVICE MODE CHECK

Note. Field service mode check can only be performed on vehicles equipped with 12-pin DLC with a wire present in test terminal "B". See DATA LINK CONNECTOR (DLC) TEST TERMINALS table.

Note. Oxygen sensor may 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.

Field service mode check 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.

Scheme 120

1. Start engine. With engine running, ground DLC terminal "B". (Scheme 120) In "closed loop" mode, Malfunction Indicator Light (MIL) will flash once a second.
2. In "open loop", MIL will flash 2.5 times a second. If MIL is off most of the time, a lean exhaust is indicated. If MIL is on most of the time, a rich exhaust is indicated. DATA LINK CONNECTOR (DLC) TEST TERMINALS Application Ground/Test 12-Pin DLC 5.7L (VIN P) "A" & "B"

HEI-EST DISTRIBUTOR

Note. The only adjustments that can be made to HEI/EST ignition system are basic ignition timing (on distributor-type ignitions) and spark plug gap.

Spark

1. If factory tachometer is connected at 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 less than 30,000 ohms.

Ignition Coil Power Source

1. Turn ignition on. Using voltmeter, check voltage between terminal "+" 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 battery voltage does not exist, check for open circuit, blown ignition fuse or defective ignition switch.

Ignition Coil Resistance

1. Turn ignition off. Remove distributor cap and coil assembly. Invert cap. (Scheme 121) Set ohmmeter to low scale. Connect leads to coil BAT and TACH terminals. Resistance should be zero or nearly zero. If resistance is not zero or nearly zero ohms, replace ignition coil.
2. Set ohmmeter on high scale. Connect one lead to coil secondary terminal and other lead to ground terminal. If resistance reading is infinite, replace ignition coil.

Scheme 121

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

1. Connect a scan tester to the ALDL diagnostic connector. RPM should be indicated on tester when engine is cranked or running. If scan tester is unavailable, tach pulse (RPM reference from ignition module) will be indicated as a voltage signal on a DVOM (with a minimum 10-megohm input impedance) when DVOM is touched to circuit No. 430 PCM terminal with engine cranking.
2. A tach pulse signal may be simulated (to test PCM response) by connecting a test light in series between battery and circuit No. 430 PCM terminal. Each time test light is touched to and removed from circuit No. 430, PCM will see this as a tach signal. For circuit and terminal reference, see appropriate schematic under NO START - ENGINE CRANKS OKAY.

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 more than one plug wire. 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 coil. If battery voltage is not present, check for blown 10-amp COIL fuse. If fuse is okay, check for open between fuse and ignition coil.

Information is not available from manufacturer.

Tach Pulse (RPM Reference) Signal

Connect scan tester to DLC. Scan low and high resolution reference pulses. Both high and low pulses should be present when engine is cranking or running. If low resolution pulse is not present, engine will not start and PCM will set Code 16 in memory. If high resolution pulse is not present, vehicle will still run; however, PCM will set Code 36 in memory. For circuit and terminal reference, see appropriate schematic in NO START - ENGINE CRANKS OKAY.

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. For adjustment procedures, see ADJUSTMENTS article in the ENGINE PERFORMANCE section.

DIAGNOSTIC CIRCUIT CHECK

The Diagnostic Circuit Check determines

1. If Malfunction Indicator Light (MIL) works.
2. If PCM 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. (Scheme 122)and (Scheme 123). 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 article in the ENGINE PERFORMANCE section.

Note. On vehicles equipped with 16-pin DLC or 12-pin DLC without test terminal "B", use of Tech 1 scan tester is required to perform diagnostic circuit check. See DATA LINK CONNECTOR (DLC) TEST TERMINALS table.

1. Check operation of MIL. Turn ignition on with engine off. MIL should be on steady. If MIL illuminates and stays on steady, go to step 3). If MIL does not illuminate, go to A-1, MIL INOPERATIVE. If MIL flashes, go to step 4).
2. On vehicles equipped with 16-pin DLC or 12-pin DLC without test terminal "B", install Tech 1 scan tester and follow scan tester manufacturer's instructions to proceed with test. If MIL does not come on, go to A-1, MIL INOPERATIVE. If MIL comes on, check for diagnostic trouble codes and diagnose codes using appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section. On vehicles equipped with 12-pin DLC with test terminal "B", go to next step.
3. Grounding DLC terminal "B" at this time should cause MIL to flash a Code 12, followed by any codes stored in PCM memory. (Scheme 118)and (Scheme 119). MIL going from bright to dim is not considered a code. If MIL dims or remains on and does not flash Code 12, see A-2, MIL ON STEADY OR WON'T FLASH CODE 12. NOTE: On some models, as long as a 30-second pause may occur between code flashes. This is normal and does not indicate necessary component replacement.
4. If MIL begins to flash as soon as ignition is turned on, check for a short to ground on the diagnostic test terminal wire between DLC terminal "B" and PCM terminal No. 5. If circuit is okay, replace PCM.

Scheme 122

Scheme 123

A-1, MIL INOPERATIVE

1. If Malfunction Indicator Light (MIL) 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 PCM fuse. If fusible links or PCM fuse are blown, repair short to ground.
2. If fusible links and PCM fuse are okay, turn ignition on and check power circuits to PCM, including keep alive memory and ignition feed. See appropriate wiring diagram in WIRING DIAGRAMS section for power terminal identification. If power is not available to power terminals of PCM, check for opens in power circuits. If power is available to PCM power terminals, check for poor PCM ground circuits, or replace faulty PCM.
3. If engine starts and MIL does not illuminate, turn ignition off. Disconnect PCM connectors. Turn ignition on and jumper PCM light driver terminal to ground using a test light. See appropriate wiring diagram in WIRING DIAGRAMS section for power terminal identification.
4. If light is now on, repair light driver terminal connections at PCM or replace faulty PCM. 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 PCM and bulb, driver circuit shorted to voltage, or an open in the ignition feed to MIL.

A-2, MIL ON STEADY OR WON'T FLASH CODE 12

1. Start engine. Check MIL. If MIL is not flashing, go to next step. If MIL is flashing, turn ignition off. Disconnect PCM connector "D". Using test light connected to battery voltage, probe DLC test terminal "B". (Scheme 118)and (Scheme 119). If test light illuminated, output/field service enable circuit (12-pin DLC terminal "B") is shorted to ground. If test light did not illuminate, replace faulty PCM.
2. Connect DVOM between ground and DLC output/field service enable terminal (12-pin DLC terminal "B"). DVOM should read 5 volts. If reading is as specified, check for faulty PCM connection or faulty PCM. If reading is not as specified, go to next step.
3. Turn ignition off. Disconnect PCM connector"D". Using jumper wire, ground DLC test terminal "B". With test light connected to battery positive, probe PCM harness connector terminal D20 (White/Black wire). Test light should illuminate. If test light illuminated, check for faulty PCM connection or faulty PCM. If test light did not illuminate, DLC test terminal "B" circuit is open.

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, 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 in the ENGINE PERFORMANCE section for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.

PCM Wiring Diagram (Fleetwood - 1 Of 3). Scheme 124

PCM Wiring Diagram (Fleetwood - 2 Of 3). Scheme 125

PCM Wiring Diagram (Fleetwood - 3 Of 3). Scheme 126

See also:
• I - SYSTEM/COMPONENT TESTS