Diagnostic Procedures
- If QUICK TEST was not performed, go to QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed, go to next step.
- Visual Inspection
Visually inspect engine compartment to ensure all vacuum hoses and spark plug wires are properly routed and securely connected. Check all wiring harnesses and connectors for damaged, burned or overheated insulation and loose or broken conditions. Ensure battery is fully charged. All accessories must be off during diagnosis. If a problem is indicated, repair as necessaryNOTE: In order for diagnostic procedures to provide accurate results, it is essential that the calibration of the engine analyzer be maintained. Refer to equipment manual for procedure to calibrate engine analyzer. If equipment manual is not available, an estimate of the calibration can be made by connecting a Spark Tester (303-D037) to a properly operating ignition system and measuring the firing voltage of spark tester only. The spark tester firing voltage should be approximately 28KV. - Connect Engine Analyzer
Obtain Engine Analyzer (010-01060) or equivalent to diagnose concerns in secondary side of ignition system. After engine analyzer is connected to vehicle, go to next step. - Check For Ignition Pattern
Observe pattern on scope while cranking engine. Refer to Figure. If ignition pattern is not flat, go to next step. If ignition pattern is flat which indicates no spark on all cylinders, check condition of No. 19 STARTER fuse (40-amp) in under-hood battery junction box. If fuse is okay, repair open circuit. If fuse/fuse link is burned, check IGN START/RUN circuit for short to ground. See WIRING DIAGRAMS article. Repair as necessary. After repair, go to step 12.NOTE: Spark plugs are fired up to four strikes per firing. Multi-strike operating mode is dependent on PCM calibration and is limited to less than 2000 RPM. Above 2000 RPM, spark plugs are fired once per firing. - Check For Normal Ignition Pattern
Start engine. Check spark plug firing voltage average and evenness of patterns. Refer to Figure. If patterns are even and average value of spark plug firing voltage is 20KV or more with evenness of spark plug firing voltage of 8KV or less, proceed as follows:- If directed here from TROUBLE SHOOTING - NO CODES article, return to SYMPTOM DIAGNOSIS in TROUBLE SHOOTING - NO CODES article.
- If directed here from step 5) of IGNITION SCOPE TEST under SYSTEM TESTS return to step 11.
- All others, go to INTERMITTENT testing under SYSTEM TESTS .
If ignition pattern values are not normal as specified, go to next step.
- Check Pattern On Scope
Observe pattern on scope and look for anything unusual. Refer to Figure-Figure for unusual signal patterns. If ignition pattern appears normal, go to next step. If ignition pattern does not appear normal, inspect spark plug wires (if applicable). Measure resistance of spark plug wires. Replace spark plug wires if resistance reading is more than 7000 ohms per foot. If okay, go to step 10. - DTC P0301-P0310: Misfire On Cylinders 1-6
If any DTCs P0301-P0310 are present, go to next step. If DTCs P0301-P0310 are not present, go to step 9. - Check For Spark At Cylinder(s) Indicated By DTC(s)
Disable Inertia Fuel Shutoff (IFS) switch. Connect spark tester and check for spark at suspect cylinder while cranking engine. If a Bluish-White spark is present, go to step 10. If a Bluish-White spark is not present, check spark plugs at cylinder with miss. Measure resistance of spark plugs. Replace spark plugs if resistance reading is less than 2000 ohms or more than 20,000 ohms. After repair, go to step 12. - Check For Spark At All Cylinders
Disable Inertia Fuel Shutoff (IFS) switch. Using spark tester check for spark at each cylinder while cranking engine. If a Bluish-White spark is consistent between all cylinders, go to next step. If a Bluish-White spark is not present between all cylinders, measure resistance of spark plugs. Replace spark plugs if resistance reading is less than 2000 ohms or more than 20,000 ohms. After repair, go to step 12. - Check Spark Plugs
Remove and check plugs for damage, wear, carbon deposits and proper plug gap. If spark plugs are okay, go to next step. If spark plugs are not okay, adjust gap or replace spark plugs. After repair, go to step 12. - Check Spark Plug Resistance
Measure spark plug resistance. If resistance reading is less than 2000 ohms or more than 20,000 ohms, replace spark plugs and go to next step. If resistance reading is 2000-20,000 ohms, proceed as follows:- If directed here from TROUBLE SHOOTING - NO CODES article, return to SYMPTOM DIAGNOSIS in TROUBLE SHOOTING - NO CODES article.
- If directed here from step 5) of IGNITION SCOPE TEST under SYSTEM TESTS return to step 11.
All others, go to INTERMITTENT testing under SYSTEM TESTS .
- Drive Cycle
Reconnect all disconnected connectors. Clear DTCs from PCM memory using scan tool. See CLEARING CODES under SELF DIAGNOSTICS. Perform Misfire Monitor Drive Cycle. See MONITOR REPAIR VERIFICATION DRIVE CYCLES under DRIVE CYCLE PROCEDURES. Retrieve pending code. If same DTC is present, replace PCM. After repair, go to next step. If same DTC is not present, go to next step. - Verify Trouble Shooting Of DTCs Completed
Perform PCM Quick Test. If any DTC is present, go to applicable procedure for other DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are set, trouble shooting is complete.