Engine Controls - Basic Testing 4.0L: Other Oldsmobile Aurora I

A & C CHART REFERENCE TABLE

Note. 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 HOW TO USE THE ENGINE PERFORMANCE SECTION in this 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.

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.

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.

DEFINITION

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

NO START - ENGINE CRANKS OKAY

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

Ignition System

1. Perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20281-S01061565852001010200000). After performing OBD system check, go to next step.
2. If Diagnostic Trouble Code (DTC) P0231, P0232, P0322, P0601, P1376, P1631, P1632 or P1634 is present, diagnose DTC(s) first. See TESTS W/CODES article. If DTC(s) are not present, go to next step.
3. Check all PCM ground points. Ground points are located on engine bracket on right front of engine, on DIS bracket, on right front cylinder head and on negative battery cable, under rear seat. Repair as necessary. After repairs, go to step 6). If ground circuits were okay, go to next step.
4. Check fuel system. Go to FUEL SYSTEM test or see «BASIC FUEL SYSTEM CHECKS (A-7)»(ref-20281-S19277959282001010200000). Repair as necessary. After repairs, go to step 6). If fuel system is okay, go to next step.
5. Diagnose DTC(s) present and cleared. See TESTS W/CODES article. Disconnect IC module connector terminal C3. (Scheme 2) Turn ignition on. Check voltage between IC module C3 connector and IC module terminal "C" (Pink wire). Voltage reading should be about 10 volts. If voltage reading is as specified, perform DTC P0322 diagnosis. If voltage reading is not as specified, check for open or short in Pink wire or faulty ignition feed fuse.
6. Start engine. If engine starts, perform OBD system check. If engine still does not start, go to next step.
7. Check engine mechanical condition causing a no-start condition. Check timing chain or valve timing. Repair as necessary. After repairs, perform OBD system check.

Scheme 2

Fuel System

1. Perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20281-S01061565852001010200000). After performing OBD system check, go to next step.
2. Check fuel system. See «BASIC FUEL SYSTEM CHECKS (A-7)»(ref-20281-S19277959282001010200000). After checking fuel system, go to next step.
3. Turn ignition off. Connect Fuel Pressure Gauge (J-34730-1A) and Fuel Injector Tester (J-39021). Install scan tool. Turn ignition on. Using scan tool, select MISC TEST and then OUTPUT TESTS and then FP RELAY to activate fuel pump. Note fuel pressure. Using fuel injector tester, select FUEL INJECTOR FLOW test and test injector No. 1. Subtract reading from fuel pressure prior to injector test. Repeat test on all injectors. If fuel pressure drops when each injector is tested, go to step 7). If fuel pressure does not drop when each injector is tested, go to next step.
4. If 2 or more injectors have no pressure drop, go to next step. If pressure drops on 2 or more injectors, go to step 11).
5. Turn ignition off. Check fuel injectors No. 1 and 2 fuse located in underdash fuse block. If fuses are okay, go to next step. If fuses are faulty, go to step 14).
6. Disconnect fuel rail harness connector. Turn ignition on. Using a DVOM, check voltage between harness connector terminals "N" and "P". (Scheme 3) If DVOM reads greater than 10 volts on both terminals, go to step 15). If voltage reading is not as specified, repair open in Pink wire between fuel rail harness connector and fuse block. (Scheme 3)
7. Using fuel injector tester, select COIL TEST and test all injectors. Reading should be about 9.5 volts. If voltage reading on any injector is greater than 9.5 volts, replace affected injector. If voltage reading on any injector is less than 9.5 volts, go to next step.
8. Subtract injector voltage reading from the specified voltage of 9.5 volts. If voltage difference of an injector is greater than.55 volt of highest voltage reading, replace affected injector. If injector voltage difference is less than.55 volt of highest voltage reading, go to next step.
9. If injectors have been replaced, duplicate conditions when problem occurred to verify proper operation. If injectors did not require replacement at this point, go to next step.
10. If fuel pressure drop is within 2 psi (.14 kg/cm 2 ), perform injector power balance test. See INJECTOR BALANCE TEST in SYSTEM/COMPONENT TESTS article. If fuel pressure drop is greater than as specified, replace affected injector.
11. Using fuel injector tester, select COIL TEST and test injector that did not show a fuel pressure drop. Coil test voltage should be 5.7-7.0 volts. If coil test voltage is as specified, go to next step. If coil test voltage is not as specified, go to step 13).
12. Turn ignition off. Reconnect fuel rail harness connector. Disconnect PCM connector C2. (Scheme 3) Turn ignition on. Using DVOM, check voltage between suspect injector PCM terminal and ground. Reading should be 10 volts or greater. If voltage is as specified, check PCM terminal contact. If contact is okay, replace PCM. If voltage is not as specified, repair open between fuel rail harness connector and suspect PCM terminal.
13. Check fuel rail harness connector for open or shorted circuit. If circuit is okay, replace injector. If circuit is open or shorted, repair as necessary.
14. Check Pink wires from injector fuel rail connector to underdash fuse block for short to ground. (Scheme 3) If circuit is shorted, repair as necessary, and then replace fuse. If circuit is okay, but fuse is faulty, replace fuse.
15. Using DVOM, check resistance between affected fuel injector terminal. Resistance should be 8-25 ohms. If resistance is not as specified, go to next step. If resistance is as specified, go to step 12).
16. Connect fuel injector tester to suspect injector. Select COIL TEST. Reading should be 5.7-7.0 volts. If voltage reading is as specified, check circuit in fuel rail harness connector to suspect injector. If voltage reading is not as specified, replace suspect injector.

Scheme 3

BASIC FUEL SYSTEM CHECKS (A-7)

Fuel Pressure Relief

Fuel system is under pressure. Pressure must be relieved prior to servicing fuel system. Disconnect negative battery terminal. Loosen fuel filler cap. 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

1. Relieve fuel pressure as previously described in FUEL PRESSURE RELIEF. Connect Fuel Pressure Gauge (J-34730-1) to fuel pressure fitting on fuel rail. With gauge installed, turn ignition on. With ignition on and engine off, fuel pressure should read within specification. See «FUEL PRESSURE»(ref-20281-S24317707792001010200000) 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 fuel pressure is less than specification, check for restricted fuel 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.
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. 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.

FUEL PRESSURE

Fuel Pump Relay

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

Fuel Pump Relay By-Pass Procedure

See FUEL DELIVERY in SYSTEM/COMPONENT TESTS article.

SPARK

1. If factory tachometer is connected to coil tachometer terminal, disconnect tachometer 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 other wires connected while checking for spark. Check spark plug wire resistance on suspect wires. Resistance should be about 30,000 ohms.

IGNITION COIL POWER SOURCE

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

IGNITION COIL RESISTANCE

If ignition coil is suspected of causing misfire or no-spark condition, switch coil locations on DIS module. If problem follows questionable coil, check ignition coil resistance or replace original coil. For ignition coil resistance, see IGNITION COIL RESISTANCE table.

IGNITION COIL RESISTANCE

CRANKSHAFT POSITION (CKP) SENSOR PICK-UP COIL SHORT & RESISTANCE CHECKS

1. Set DVOM on 2000-ohm scale position. Connect DVOM leads to CKP sensor connector, located on side of engine block. Turn ignition off. Disconnect ignition module connectors. Check resistance between CKP sensor terminals at ignition module connector.
2. CKP sensor resistance should be within specification range listed in «CRANKSHAFT SENSOR RESISTANCE»(ref-20281-S07353973762001010200000) table. If resistance is not as specified, replace CKP sensor. If sensor is within specification, go to next step.
3. With CKP sensor installed in block, connect one ohmmeter lead to either sensor terminal at ignition module. Touch other lead of ohmmeter to engine block. No continuity should exist. If continuity exists, sensor or harness is shorted to ground and must be repaired or replaced.

CRANKSHAFT SENSOR RESISTANCE (1)

CRANKSHAFT SENSOR OUTPUT SIGNAL

Set DVOM on 2-volt AC scale. Connect voltmeter leads to crankshaft sensor installed in side of engine block. 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 at high cranking speed. With engine running, voltage signal will be much greater.

TACH PULSE (RPM) SIGNAL

Connect scan tool to DLC. 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 used to backprobe RPM "high reference" circuit. 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.

THE OBD SYSTEM 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. 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 TESTS W/CODES article.

1. Turn ignition on with engine off. Observe Malfunction Indicator Light (MIL). If MIL illuminates, go to next step. If MIL does not illuminate, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20281-S01061565852001010200000) .
2. Turn ignition off. Install Tech 1 scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to A-2/A-4, DLC DIAGNOSIS OR NO SCAN TOOL DATA.
3. Attempt to start engine. If engine start and runs, go to next step. If engine does not start or starts and dies, go to «NO START DIAGNOSIS (A-3)»(ref-20281-S21020378672001010200000) .
4. Using scan tool, observe DTC statuses; MIL REQUEST, FAIL THIS IGN, LAST TST FAIL and HISTORY. If any of these DTC status are present, refer to affected DTC to diagnose problem. If DTC(s) are not present, check related circuit or component(s). See SYSTEM/COMPONENT TESTS article.

Scheme 4

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, no trouble codes (or only intermittent ones) were found while performing ON-BOARD DIAGNOSTIC SYSTEM 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 diagnostic procedures.