Diagnostic Procedures
- If powertrain diagnostic system check has already been performed, go to next step. If powertrain diagnostic system check has not been performed, go to POWERTRAIN DIAGNOSTIC SYSTEM CHECK under DIAGNOSTIC SYSTEM CHECKS.
- Start engine and allow it to idle. Ensure engine is at normal operating temperature. Using scan tool, record LONG TERM FUEL TRIM data. Turn ignition off. Turn ignition on. Using scan tool, review FREEZE FRAME RECORDS and/or FAILURE RECORDS and record data. If long term fuel trim is more than 23 percent, go to next step. If long term fuel trim is 23 percent or less, see DIAGNOSTIC AIDS .
- Start engine and allow it to idle. Using scan tool, observe HO2S voltage. If voltage is 200-800 millivolts and fluctuating, go to next step. If voltage is not 200-800 millivolts or is not fluctuating, go to step 5.
- Turn ignition off. Check vacuum hoses for splits, kinks and proper routing. Check for contaminated fuel. Ensure fuel tank has enough fuel. Check fuel pressure. See appropriate BASIC DIAGNOSTIC PROCEDURES article. Fuel pressure that is too low can cause a lean condition. If any problems are found, repair as necessary. After repairs, go to step 7. If no problems are found, go to step 6.
- Turn ignition off. Ensure HO2S is installed correctly and wiring harness is not touching exhaust. Disconnect HO2S 1 connector. HO2S 1 is located in right (rear) exhaust manifold. See Figure. Disconnect PCM connectors. PCM is located in left front corner of engine compartment, inside air filter housing. Check for continuity between terminal "A" (Black wire) and terminal "B" (Purple/White wire) at HO2S 1 harness connector. See Figure. If continuity exists, Black and Purple/White wires are shorted together. Repair wiring as necessary. After repairs, go to step 7. If continuity does not exist, diagnose fuel system. See FUEL SYSTEMS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
- Operate engine at idle. Check for missing, loose, or leaking exhaust components. Check for vacuum leaks at intake manifold, throttle body and injector "O" rings. Check air induction system and air intake ducts for leaks. Check crankcase ventilation system for leaks. If any problems are found, repair as necessary. After repairs, go to next step. If no problems are found, check engine mechanical condition and repair as necessary.
- After repairs, using scan tool fuel trim reset function, reset long term fuel trim. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions for running the DTC as specified in code enable criteria. If DTC runs and passes, go to next step. If DTC resets, go to step 2.
- Using scan tool, check for any other DTCs that are set. If no other DTCs are set, test is complete. If any other DTCs are set, repair DTCs as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .