ENGINE CONTROLS - TESTS W/O CODES - ENGINE - 4.0L

• HEADINGS
  • INTRODUCTION
  • SYMPTOMS
    • SYMPTOMS DIAGNOSIS
    • NO CRANK
      • Preliminary Checks
      • Symptom Checks
    • HARD START/LONG CRANK
      • Preliminary Checks
      • Symptom Checks
    • STALLS AFTER START
      • Preliminary Checks
      • Symptom Checks
    • NO START/NORMAL CRANK
      • Preliminary Checks
      • Symptom Checks
    • SLOW RETURN TO IDLE
      • Preliminary Checks
      • Symptom Checks
    • ROUGH IDLE
      • Preliminary Checks
      • Symptom Checks
    • HIGH IDLE (DIESELS/RUNS ON)
      • Preliminary Checks
      • Symptom Checks
    • LOW IDLE (STALLS ON DECELERATION)
      • Preliminary Checks
      • Symptom Checks
    • HESITATES OR STALLS
      • Preliminary Checks
      • Symptom Checks
    • SURGE (ON ACCELERATION OR CRUISE)
      • Preliminary Checks
      • Symptom Checks
    • BACKFIRES
      • Preliminary Checks
      • Symptom Checks
    • LOSS OF POWER
      • Preliminary Checks
      • Symptom Checks
    • SPARK KNOCK
      • Preliminary Checks
      • Symptom Checks
    • POOR FUEL ECONOMY
      • Preliminary Checks
      • Symptom Checks
    • EMISSIONS COMPLIANCE
      • Preliminary Checks
      • Symptom Checks
    • WARNING INDICATOR LIGHTS
      • Symptom Checks
    • IMPROPER TRANSMISSION SHIFT
      • Preliminary Checks
      • Symptom Checks
    • HIGH OIL CONSUMPTION
      • Preliminary Checks
      • Symptom Checks
    • ENGINE RUNS HOT
      • Preliminary Checks
      • Symptom Checks
    • ENGINE RUNS COLD
      • Preliminary Checks
      • Symptom Checks
    • EXHAUST SMOKE
      • Black Smoke (Rich Mixture)
      • Blue Smoke (Burning Oil)
      • White Smoke (Water In Combustion)
    • FUEL PUMP ALWAYS ON
      • Symptom Checks
    • GAS SMELL
      • Preliminary Checks
      • Symptom Checks
    • SULFUR SMELL
      • Preliminary Checks
      • Symptom Checks
    • ENGINE NOISE
      • Squeal, Click Or Chirp
      • Rattle
      • Hiss
      • Snap
      • Rap Or Roar
      • Knock
    • VIBRATION
    • CLIMATE CONTROL (LACK OF COOLING)
      • Preliminary Checks
      • Symptom Checks
    • CLIMATE CONTROL (A/C ALWAYS ON)
      • Preliminary Checks
      • Symptom Checks
    • A/C DOES NOT GO OFF DURING WOT
      • Symptom Checks
  • INTERMITTENTS
    • INTERMITTENT PROBLEM DIAGNOSIS
• FIGURES
• TABLES

H - TESTS W/O CODES - 4.0L

1996 ENGINE PERFORMANCE Ford Motor Co. - Trouble Shooting - No Codes - (EEC-V)

INTRODUCTION

Before diagnosing symptoms or intermittent faults, perform BASIC DIAGNOSTIC PROCEDURES in the BASIC TESTING - 4.0L article and SELF-DIAGNOSTICS TESTS in the TESTS W/CODES - 4.0L article. Use this article to diagnose driveability problems existing when a hard fault code is not present.

NOTE:

Some driveability problems may have been corrected by manufacturer with a revised Powertrain Control Module (PCM). Check with manufacturer for latest PCM application.

Symptom checks can direct the technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component or system test and/or adjustment.

Use intermittent test procedures to locate driveability problems that DO NOT occur when the vehicle is being tested. These test procedures should also be used if a soft (intermittent) trouble code was present, but no problem was found during self-diagnostic testing.

NOTE:

For specific testing, see the TESTS W/CODES - 4.0L article. For specifications, see the ADJUSTMENTS - 4.0L or the SPECIFICATIONS - 4.0L article.

SYMPTOMS

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 - 4.0L and SELF-DIAGNOSTICS TESTS in the TESTS W/CODES - 4.0L articles 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

NO CRANK

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check battery connections. Check starter relay connections. Check all fuse links. On A/T models, ensure gearshift is in Park. On M/T models, ensure clutch is fully depressed. If vehicle is equipped with anti-theft devices, ensure system is deactivated.

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.

HARD START/LONG CRANK

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check for vacuum leaks. Check fuel quality. Check air cleaner/air intake duct.

Symptom Checks

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.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check PCV system. See CIRCUIT TEST HG.
• Check Evaporative Emission (EVAP) sys. See CIRCUIT TEST HW.
• Check air intake system. See CIRCUIT TEST HU.

STALLS AFTER START

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check for vacuum leaks. Check fuel quality. Check for restricted air filter/air intake duct. Check wiring harness connectors.

Symptom Checks

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.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check ignition system. See CIRCUIT TEST JD.
• Check exhaust system for restriction. See CIRCUIT TEST HF.
• Check PCV system. See CIRCUIT TEST HG.
• Ensure transmission is functioning properly. If engine stalls during transmission engagement, check transmission solenoids. Go to CIRCUIT TEST TC.

NO START/NORMAL CRANK

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check fuel quality. Check Inertia Fuel Shutoff (IFS) switch. Check alarm/anti-theft devices. Check wiring harness connectors. Check for disconnected or restricted air intake duct. Check fuses and relays.

Symptom Checks

Check the following items:

• Check for restricted air intake duct.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check ignition system. See CIRCUIT TEST JD.
• Check engine compression and engine mechanical condition. Check intake manifold gasket and valve timing.

SLOW RETURN TO IDLE

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check for vacuum leaks. Check throttle linkage operation. Check air intake system. Check throttle body.

Symptom Checks

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.
• Check fuel delivery system. See CIRCUIT TEST HC.

ROUGH IDLE

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check for vacuum leaks. Check air intake duct. Check air filter. Check primary and secondary ignition wiring harness and components. Check for cracked or missing cooling fan blades.

Symptom Checks

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.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check ignition system. See CIRCUIT TEST JD.
• Check exhaust system for restriction. See CIRCUIT TEST HF.
• Check PCV system. See CIRCUIT TEST HG.
• Ensure transmission is functioning properly. If engine stalls during transmission engagement, check transmission solenoids. Go to CIRCUIT TEST TC.
• Check engine compression. Check engine mechanical condition. Check camshaft and valve train components.

HIGH IDLE (DIESELS/RUNS ON)

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

NOTE:

If engine is overheating, go to ENGINE RUNS HOT symptom. If engine runs cold, go to ENGINE RUNS COLD symptom.

Preliminary Checks

Check for vacuum leaks. Check for carbon build-up on throttle plate. Check throttle linkage operation. Check for binding/sticking cruise control chain. Check air intake duct. Check for leaking intake manifold gasket.

Symptom Checks

Check the following items:

• Check for restricted air intake duct.
• Check PCV system. See CIRCUIT TEST HG.
• Check air intake system. See CIRCUIT TEST HU.

LOW IDLE (STALLS ON DECELERATION)

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check Idle Air Control (IAC) wiring harness connector. Check base timing. Check engine mechanical condition.

Symptom Checks

Check the following items:

• Check idle speed. See IDLE SPEED in ADJUSTMENTS - 4.0L 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.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check air intake system. See CIRCUIT TEST HU.

HESITATES OR STALLS

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

NOTE:

The PCM is equipped with an over RPM/speed limit function. If programmed speed is exceeded, fuel delivery will shut off and DTC P1270 will be set in PCM memory.

Preliminary Checks

Check for vacuum leaks. Check fuel quality. Check for restricted air filter/air intake duct. Check wiring harness connectors.

Symptom Checks

Check the following items:

• Check air intake system. Also, ensure throttle plate and linkages operate properly.
• Check EGR system. See the TESTS W/CODES - 4.0L 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.
• Check PCV system. See CIRCUIT TEST HG.
• Check PCV system. See CIRCUIT TEST HG.
• Check ignition system. See CIRCUIT TEST JD.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check Evaporative Emission (EVAP) sys. See CIRCUIT TEST HW.
• Check exhaust system for restriction. See CIRCUIT TEST HF.
• Ensure transmission is functioning properly. If engine stalls during transmission engagement, check transmission solenoids. Go to CIRCUIT TEST TC.
• Check engine compression. Check engine mechanical condition. Check valve timing.

SURGE (ON ACCELERATION OR CRUISE)

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check for vacuum leaks. Check fuel quality. Check for restricted air filter/air intake duct. Check wiring harness connectors.

Symptom Checks

Check the following items:

• Check EGR system. See the TESTS W/CODES - 4.0L article.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check PCV system. See CIRCUIT TEST HG.
• Check Evaporative Emission (EVAP) sys. See CIRCUIT TEST HW.
• Check exhaust system for restriction. See CIRCUIT TEST HF.

BACKFIRES

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check vacuum hose routing. Check spark plug wiring for incorrect firing order.

Symptom Checks

Check the following items:

• Check ignition system. See CIRCUIT TEST JD.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check exhaust system for restriction. See CIRCUIT TEST HF.
• Check engine compression and valve timing. Check engine mechanical condition.

LOSS OF POWER

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

NOTE:

The PCM is equipped with an over RPM/speed limit function. If programmed speed is exceeded, fuel delivery will shut off and DTC P1270 will be set in PCM memory.

Preliminary Checks

Verify symptom is reported under normal driving conditions without engine under excessive load conditions. Check vacuum hose routing. Check for restricted air filter. Check wiring harness connectors. Check for obstructed radiator. Check transmission fluid.

Symptom Checks

Check the following items:

• Check ignition system. See CIRCUIT TEST JD.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check exhaust system. See CIRCUIT TEST HF.
• 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. Go to CIRCUIT TEST TC.
• 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.

SPARK KNOCK

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check vacuum hose routing. Check for restricted air intake system. Check engine oil and fuel quality.

Symptom Checks

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 - 4.0L article.
• Check EGR system. See the TESTS W/CODES - 4.0L article.
• Check ignition system. See CIRCUIT TEST JD.
• Check engine compression. Check engine mechanical condition. Check intake manifold gasket, camshaft and valves.
• Check octane adjust system. See CIRCUIT TEST FG. If available, check Technical Service Bulletins (TSBs) for OCT ADJ information.

POOR FUEL ECONOMY

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

NOTE:

Fuel consumption will increases during stop-and-go driving, trailer towing, short-run operation, extended winter warm-up periods, etc. Determine if these factors are the cause of poor fuel mileage before proceeding with diagnostic procedure.

Preliminary Checks

Check for restricted air filter/air intake duct. Check transmission fluid level. Check fuel quality.

Symptom Checks

Check the following items:

• Check ignition system. See CIRCUIT TEST JD.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check exhaust system. See CIRCUIT TEST HF.
• 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.

EMISSIONS COMPLIANCE

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Canada and some states or metropolitan areas in the United States require periodic idle emission tests. All Ford products have been designed to pass these tests. If a Ford product fails an idle Emission test, it is probable that the engine temperature was not warm and stabilized prior to the test or the vehicle had idled excessively long prior to the test. Before starting any services, verify complaints of idle emission test failure.

The following encompasses most of the emissions measurement modes of current state idle test procedures:

• Ensure engine is at normal operating temperature and all accessories are turned off.
• Check emissions at idle.
• Operate engine at 2200-2800 RPM.
• Check emissions within 30 seconds.
• Return engine speed to idle.
• Check emissions within 30 seconds.

If any emission component is changed, Keep-Alive Memory (KAM) should be cleared before repeating state emission test procedure. See the TESTS W/CODES - 4.0L article. To relearn adaptive strategy, operate engine at 2500 RPM for one minute. Operate engine at idle speed for 2 minutes.

Preliminary Checks

Check for vacuum leaks/blockage. Check wiring harness connectors.

Symptom Checks

Check the following items:

• Check idle speed. See IDLE SPEED in ADJUSTMENTS - 4.0L article.
• Check PCV system. See CIRCUIT TEST HG.
• Check ignition system. See CIRCUIT TEST JD.
• Check fuel delivery system. See CIRCUIT TEST HC.
• Check Evaporative Emission (EVAP) sys. See CIRCUIT TEST HW.
• Check exhaust system for restriction. See CIRCUIT TEST HF.
• Check air intake system. See CIRCUIT TEST HU.
• Check exhaust system. See CIRCUIT TEST HF.
• 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 the TESTS W/CODES - 4.0L article.
• Check engine compression. Check engine mechanical condition. Check intake manifold gasket, camshaft and valves.

WARNING INDICATOR LIGHTS

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Symptom Checks

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.
• 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.

IMPROPER TRANSMISSION SHIFT

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check transmission fluid level and condition. Check for transmission leaks. Check wiring harness connectors. Check for vehicle modifications. Check for electronic add-on items. Check for misadjusted shift linkage.

Symptom Checks

Check the following items:

• Perform QUICK TEST. If code is present, perform appropriate CIRCUIT TEST. If code is not present, check transmission mechanical components.

HIGH OIL CONSUMPTION

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check for external engine oil leaks. Check for proper oil dipstick. Check for proper oil viscosity.

Symptom Checks

Check the following items:

• Check PCV system. See CIRCUIT TEST HG.
• Check engine mechanical condition. Check valves, valve guides, valve stem oil seals, intake manifold gaskets, cylinder head oil drain passages and piston rings.

ENGINE RUNS HOT

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check coolant level. Check for coolant leaks. Check fan belt. Check radiator fan connectors. Check water/anti-freeze mixture. Check radiator condition. Check for collapsed/restricted radiator hose. Check radiator cap. Check overflow system.

Symptom Checks

Check the following items:

• Check radiator cooling fan operation.
• Check base timing. See the ADJUSTMENTS - 4.0L article.
• Check gauges/senders.
• Check for brake drag.
• Check transmission for overheating.

ENGINE RUNS COLD

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check radiator cooling fan operation.

Symptom Checks

Check the following items:

• Check cooling system operation.
• Check temperature gauge and sender.

EXHAUST SMOKE

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Black Smoke (Rich Mixture)

• Check for restricted air cleaner/air intake duct.
• Check for restricted fuel return hoses.
• Check ignition system. See CIRCUIT TEST JD.
• Check fuel delivery system. See CIRCUIT TEST HC.

Blue Smoke (Burning Oil)

• Check PCV system. See CIRCUIT TEST HG.
• Check engine mechanical condition. Check valve guides, valve stems, valve seals, oil drain passages in cylinder heads (Blue smoke on start-up), piston rings and cylinder bores.

White Smoke (Water In Combustion)

• Check for cylinder head gasket leaks, intake manifold gasket leaks and cracked engine block.

FUEL PUMP ALWAYS ON

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Symptom Checks

Check the following items:

• Perform QUICK TEST. If code is present, perform appropriate CIRCUIT TEST. If code is not present, go to step 171) of CIRCUIT TEST X.

GAS SMELL

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check fuel system and EVAP system for leaks.

Symptom Checks

Check the following items:

• Check fuel delivery system. See CIRCUIT TEST HC.
• Check Evaporative Emission (EVAP) sys. See CIRCUIT TEST HW.

SULFUR SMELL

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check fuel system and EVAP system for leaks.

Symptom Checks

Check the following items:

• Check fuel delivery system. See CIRCUIT TEST HC.
• Check Evaporative Emission (EVAP) sys. See CIRCUIT TEST HW.

ENGINE NOISE

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Squeal, Click Or Chirp

• Check for low oil level.
• Check valve train components.
• Check drive belts.
• Check EEC-V solenoids.

Rattle

• Check for loose components.

Hiss

• Check for cooling system leaks.
• Check for vacuum leaks.
• Check for loose spark plugs.
• Check for air intake leaks.
• Check for secondary air injection leaks.
• Check for Evaporative Emission (EVAP) system leaks.

Snap

• Perform a visual/audible check of secondary ignition system.

Rap Or Roar

• Check for exhaust leak.
• Check for secondary air injection leaks.

Knock

• Check for worn rod/main bearings.
• Check for loose piston pins.
• Check piston to cylinder bore clearance.
• Knock (Detonation) - See SPARK KNOCK under SYMPTOMS .

VIBRATION

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

• Check radiator cooling fan.
• Check drive belt.
• Check engine mounts.
• Check crankshaft vibration damper.
• Check transmission.
• Check tires and wheels.
• Check driveline components.

CLIMATE CONTROL (LACK OF COOLING)

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Perform a visual inspection of A/C system. Check A/C switches. Check fuses.

Symptom Checks

Check the following items:

• Perform QUICK TEST. If code is present, perform appropriate CIRCUIT TEST. If no codes are present, go to step 110) of CIRCUIT TEST X
• Check voltage at A/C clutch.
• Connect A/C manifold gauges and perform A/C system function test.

CLIMATE CONTROL (A/C ALWAYS ON)

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Preliminary Checks

Check for shorted A/C wiring. Check A/C heater control. Check A/C compressor.

Symptom Checks

Check the following items:

• Ensure that voltage at A/C clutch is less than 2 volts with A/C switch off. If voltage is 1.0 volt or more, go to step 105) of CIRCUIT TEST X.

A/C DOES NOT GO OFF DURING WOT

NOTE:

For CIRCUIT TESTS and QUICK TEST referenced in this article, see the TESTS W/CODES - 4.0L article.

Symptom Checks

Check the following items:

• Perform QUICK TEST. If code is present, perform appropriate CIRCUIT TEST. If no codes are present, go to step 130) of CIRCUIT TEST X.

INTERMITTENTS

INTERMITTENT PROBLEM DIAGNOSIS

Intermittent fault testing requires duplicating circuit or component failure to identify the problem. These procedures may lead to the PCM setting fault code, which may help in diagnosis. If fault code not present, go to CIRCUIT TEST Z in TESTS W/CODES - 4.0L article.

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