SYMPTOMS DIAGNOSIS
Symptom checks cannot be used properly unless problem occurs while vehicle is being tested. To reduce diagnostic time, ensure basic diagnostic procedures in the BASIC TESTING article and self-diagnostic steps in the TESTS W/CODES article were performed before diagnosing a symptom. Symptom checks are listed in order of probability, ease of accomplishment, and accessibility. Symptoms available for diagnosis are as follows
- No Crank
- Hard Start/Long Crank
- Stalls After Start
- No Start/Normal Crank
- Slow Return To Idle
- Rough Idle
- High Idle (Diesels/Runs On)
- Low Idle (Stalls On Deceleration)
- Hesitates Or Stalls
- Surge (On Acceleration Or Cruise)
- Backfires
- Loss Of Power
- Spark Knock
- Poor Fuel Economy
- Emissions Compliance
- Warning Indicator Lights
- Improper Transmission Shift
- High Oil Consumption
- Engine Runs Hot
- Engine Runs Cold
- Exhaust Smoke
- Fuel Pump Always On
- Gas Smell
- Sulfur Smell
- Engine Noise
- Vibration
- Climate Control (Lack Of Cooling)
- Climate Control (A/C Always On)
- A/C Does Not Go Off During WOT
Symptom Checks
Check the following items
- Check starter relay.
- Check starter circuit.
- Check charging circuit.
- Check for defective flywheel.
- Check ignition switch.
- Check for seized/hydro-locked engine.
- Check transmission linkage adjustment.
Check the following items
- Check starting system.
- Check EGR system.
- Check for contaminated MAF sensor.
- Check cooling system for overheating (hard hot start only).
- Check ignition system. See CIRCUIT TEST JD in TESTS W/CODES article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check PCV system. See CIRCUIT TEST HG in TESTS W/CODES article.
- Check Evaporative Emission (EVAP) system. See CIRCUIT TEST HW in TESTS W/CODES article.
- Check air intake system. See CIRCUIT TEST HU in TESTS W/CODES article.
Check the following items
- Check for restricted air intake duct.
- Check engine compression and engine mechanical condition.
- Ensure Idle Air Control (IAC) solenoid controls idle speed. If IAC solenoid does not control idle speed, check IAC valve assembly. See CIRCUIT TEST KE in TESTS W/CODES article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check ignition system. See CIRCUIT TEST JD in TESTS W/CODES article.
- Check exhaust system for restriction. See step 7) of CIRCUIT TEST HF in TESTS W/CODES article.
- Check PCV system. See CIRCUIT TEST HG in TESTS W/CODES article.
- Ensure transmission is functioning properly. If engine stalls during transmission engagement, check transmission solenoids. See TRANSMISSION SERVICING - A/T in the AUTOMATIC TRANS SERVICE section.
Check the following items
- Check for restricted air intake duct.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check ignition system. See CIRCUIT TEST JD in TESTS W/CODES article.
- Check engine compression and engine mechanical condition. Check intake manifold gasket and valve timing.
Check the following items
- Check for throttle body contamination. Check for carbon build-up around throttle plate.
- Ensure Idle Air Control (IAC) solenoid controls idle speed. If IAC solenoid does not control idle speed, check IAC valve assembly. See CIRCUIT TEST KE in TESTS W/CODES article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
Check the following items
- Check for throttle body contamination. Check for carbon build-up around throttle plate.
- Ensure Idle Air Control (IAC) solenoid controls idle speed. If IAC solenoid does not control idle speed, check IAC valve assembly. See CIRCUIT TEST KE in TESTS W/CODES article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check ignition system. See CIRCUIT TEST JD in TESTS W/CODES article.
- Check exhaust system for restriction. See step 7) of CIRCUIT TEST HF in TESTS W/CODES article.
- Check PCV system. See CIRCUIT TEST HG in TESTS W/CODES article.
- Ensure transmission is functioning properly. If engine stalls during transmission engagement, check transmission solenoids. See TRANSMISSION SERVICING - A/T article in the AUTOMATIC TRANS SERVICE section.manual.
- Check engine compression. Check engine mechanical condition. Check camshaft and valve train components.
Check the following items
- Check for restricted air intake duct.
- Check PCV system. See CIRCUIT TEST HG in TESTS W/CODES article.
- Check air intake system. See CIRCUIT TEST HU in TESTS W/CODES article.
Check the following items
- Check idle speed. See IDLE SPEED in ADJUSTMENTS article.
- Ensure Idle Air Control (IAC) solenoid controls idle speed. If IAC solenoid does not control idle speed, check IAC valve assembly. See CIRCUIT TEST KE in TESTS W/CODES article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check air intake system. See CIRCUIT TEST HU in TESTS W/CODES article.
Check the following items
- Check air intake system. Also, ensure throttle plate and linkages operate properly.
- Check EGR system. See SYSTEM/COMPONENT TESTS article.
- Ensure Idle Air Control (IAC) solenoid controls idle speed. If IAC solenoid does not control idle speed, check IAC valve assembly. See CIRCUIT TEST KE in TESTS W/CODES article.
- Check PCV system. See CIRCUIT TEST HG in TESTS W/CODES article.
- Check PCV system. See CIRCUIT TEST HG in TESTS W/CODES article.
- Check ignition system. See CIRCUIT TEST JD in TESTS W/CODES article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check Evaporative Emission (EVAP) system. See CIRCUIT TEST HW in TESTS W/CODES article.
- Check exhaust system for restriction. See step 7) of CIRCUIT TEST HF in TESTS W/CODES article.
- Ensure transmission is functioning properly. If engine stalls during transmission engagement, check transmission solenoids. See TRANSMISSION SERVICING - A/T article in the AUTOMATIC TRANS SERVICE section.
- Check engine compression. Check engine mechanical condition. Check valve timing.
Check the following items
- Check EGR system. See SYSTEM/COMPONENT TESTS article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check PCV system. See CIRCUIT TEST HG in TESTS W/CODES article.
- Check Evaporative Emission (EVAP) system. See CIRCUIT TEST HW in TESTS W/CODES article.
- Check exhaust system for restriction. See step 7) of CIRCUIT TEST HF in TESTS W/CODES article.
Check the following items
- Check ignition system. See CIRCUIT TEST JD in TESTS W/CODES article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check exhaust system for restriction. See step 7) of CIRCUIT TEST HF in TESTS W/CODES article.
- Check engine compression and valve timing. Check engine mechanical condition.
Check the following items
- Check ignition system. See CIRCUIT TEST JD in TESTS W/CODES article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check exhaust system. See step 7) of CIRCUIT TEST HF in TESTS W/CODES article.
- Check engine compression. Check engine mechanical condition. Check intake manifold gasket, camshaft and valves.
- Ensure transmission is functioning properly. If engine stalls during transmission engagement, check transmission solenoids. See TRANSMISSION SERVICING - A/T article in the AUTOMATIC TRANS SERVICE section.
- Check for binding/dragging brakes.
- Ensure A/C turns off during Wide Open Throttle (WOT). If A/C does not turn off during WOT, go to step 130) of CIRCUIT TEST X in the TESTS W/CODES article.
Check the following items
- Check cooling system for overheating. If cooling system is overheating, go to ENGINE RUNS HOT symptom.
- Check ignition timing. See ADJUSTMENTS article.
- Check EGR system. See SYSTEM/COMPONENT TESTS article.
- Check ignition system. See CIRCUIT TEST JD in TESTS W/CODES article.
- Check engine compression. Check engine mechanical condition. Check intake manifold gasket, camshaft and valves.
- Check octane adjust system. See CIRCUIT TEST FG in TESTS W/CODES article. If available, check Technical Service Bulletins (TSBs) for OCT ADJ information.
Check the following items
- Check ignition system. See CIRCUIT TEST JD in TESTS W/CODES article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check exhaust system. See step 7) of CIRCUIT TEST HF in TESTS W/CODES article.
- Check engine compression. Check engine mechanical condition. Check intake manifold gasket, camshaft and valves.
- Ensure engine operates at normal operating temperature.
- Ensure transmission operates properly.
- Check for dragging brakes.
Check the following items
- Check idle speed. See IDLE SPEED in ADJUSTMENTS article.
- Check PCV system. See CIRCUIT TEST HG in TESTS W/CODES article.
- Check ignition system. See CIRCUIT TEST JD in TESTS W/CODES article.
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check Evaporative Emission (EVAP) system. See CIRCUIT TEST HW in TESTS W/CODES article.
- Check exhaust system for restriction. See step 7) of CIRCUIT TEST HF in TESTS W/CODES article.
- Check air intake system. See CIRCUIT TEST HU in TESTS W/CODES article.
- Check engine compression. Check engine mechanical condition. Check intake manifold gasket, camshaft and valves.
- Ensure engine operates at normal operating temperature.
- Check EGR system. See SYSTEM/COMPONENT TESTS article.
- Check engine compression. Check engine mechanical condition. Check intake manifold gasket, camshaft and valves.
Check the following items
- If Malfunction Indicator Light (MIL) is always on, go to step 1) of CIRCUIT TEST NB.
- If Malfunction Indicator Light (MIL) does not come on, go to step 2) of CIRCUIT TEST NB in TESTS W/CODES article.
- If Transmission Control Indicator (TCIL) does not come on, go to step 6) of CIRCUIT TEST TB.
- If engine does not start, go to CIRCUIT TEST A in TESTS W/CODES article.
Check the following items
- Perform QUICK TEST. See TESTS W/CODES article. If code is present, perform appropriate CIRCUIT TEST. If code is not present, check transmission mechanical components.
Check the following items
- Check PCV system. See CIRCUIT TEST HG in TESTS W/CODES article.
- Check engine mechanical condition. Check valves, valve guides, valve stem oil seals, intake manifold gaskets, cylinder head oil drain passages and piston rings.
Check the following items
- Check radiator cooling fan operation.
- Check base timing. See ADJUSTMENTS article.
- Check gauges/senders.
- Check for brake drag.
- Check transmission for overheating.
Check the following items
- Check cooling system operation.
- Check temperature gauge and sender.
Check the following items
- Perform QUICK TEST. See TESTS W/CODES article. If any DTCs are present, perform appropriate CIRCUIT TEST. If DTCs are not present, go to step 171) of CIRCUIT TEST X in the TESTS W/CODES article.
Check the following items
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check Evaporative Emission (EVAP) system. See CIRCUIT TEST HW in TESTS W/CODES article.
Check the following items
- Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
- Check Evaporative Emission (EVAP) system. See CIRCUIT TEST HW in TESTS W/CODES article.
Check the following items
- Perform QUICK TEST. See TESTS W/CODES article. If code is present, perform appropriate CIRCUIT TEST. If no codes are present, go to step 110) of CIRCUIT TEST X in the TESTS W/CODES article.
- Check voltage at A/C clutch.
- Connect A/C manifold gauges and perform A/C system function test.
Check the following items
- Ensure that voltage at A/C clutch is less than 1.0 volt with A/C switch off. If voltage is 1.0 volt or more, go to step 106) of CIRCUIT TEST X in the TESTS W/CODES article.
Check the following items
- Perform QUICK TEST. See TESTS W/CODES article. If code is present, perform appropriate CIRCUIT TEST. If no codes are present, go to step 130) of CIRCUIT TEST X in the TESTS W/CODES article.
INTERMITTENT PROBLEM DIAGNOSIS
Intermittent fault testing requires duplicating circuit or component failure to identify the problem. These procedures may lead to the PCM setting a fault code, which may help in diagnosis. If fault code is not present, go to CIRCUIT TEST Z. See TESTS W/CODES article.