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

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 to verify routing and connections (if necessary). Inspect air induction system for possible vacuum leaks.

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.

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.

General Inspection

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. In very cold temperatures, ensure oil is of proper viscosity and not contaminated with gasoline.

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK

Note. Tech 1 scan tool is required to perform OBD system check.

A-2/A-4, DLC DIAGNOSIS OR NO SCAN TOOL DATA

1. Perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20281-S01061565852001010200000) . After performing OBD system check, go to next step.
2. Turn ignition on with engine off. Connect a test light between DLC terminal No. 16 (Orange wire) and DLC terminal No. 4 (Black/White or Black wire). If test light illuminates, go to step 4). If test light does not illuminate, go to next step.
3. Connect test light to ground. Using test light, probe DLC terminal No. 16 (Orange wire). If test light illuminates, go to next step 9). If test light does not illuminate, go to step 10).
4. Turn ignition on with engine off. Using DVOM, check voltage between ground and DLC terminal No. 2 (Purple wire). DVOM should read zero volts. If voltage is as specified, go to next step. If voltage is not as specified, go to step 7).
5. Turn ignition off. Disconnect PCM harness connector. Turn ignition on with engine off. Connect DVOM between battery voltage and DLC terminal No. 2 (Purple wire). DVOM should read zero volts. If voltage is as specified, go to next step. If voltage is not as specified, go to step 8).
6. Check for open in circuit (Purple wire) between DLC and PCM connector. If circuit is open, repair as necessary. After repairs, perform OBD system check. If circuit is okay, go to step 11).
7. Check for short to voltage in circuit (Purple wire) between DLC and PCM connector. If circuit is shorted, repair as necessary. After repairs, perform OBD system check. If circuit is okay, go to step 11).
8. Check for short to ground in circuit (Purple wire) between DLC and PCM connector. If circuit is shorted, repair as necessary. After repairs, perform OBD system check.
9. Locate and repair open in DLC ground circuit (Black wire). After repairs, perform OBD system check.
10. Locate and repair open or short to ground in DLC terminal No. 16 (Orange wire). After repairs, perform OBD system check.
11. Replace PCM. Perform PCM relearn procedures and then perform OBD system check.