SYMPTOMS
| CAUTION | When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. Before disconnecting battery, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. |
SYMPTOM DIAGNOSIS
Symptom checks cannot be used properly unless problem occurs while vehicle is being tested. To reduce diagnostic time, ensure steps in appropriate BASIC DIAGNOSTIC PROCEDURES article and SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV 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
- «ROUGH OR ROLLING IDLE, STALLS, MISSES, HESITATION OR SURGE»(ref-138152-S05982670332002032500000)
- «HARD START/LONG CRANK OR ERRATIC START/CRANK»(ref-138152-S03885603022002032500000)
- «NO START/NORMAL CRANK»(ref-138152-S22957405572002032500000)
- «SLOW RETURN TO IDLE»(ref-138152-S13639249672002032500000)
- «FAST IDLE OR DIESELS/RUNS ON»(ref-138152-S06802595302002032500000)
- «LOW IDLE (STALLS ON DECELERATION)»(ref-138152-S41247426102002032500000)
- «BACKFIRES»(ref-138152-S18444083572002032500000)
- «LACK/LOSS OF POWER»(ref-138152-S30484476772002032500000)
- «SPARK KNOCK»(ref-138152-S06165233012002032500000)
- «POOR FUEL ECONOMY»(ref-138152-S22891796842002032500000)
- «VEHICLE FAILS EMISSIONS/EMISSIONS COMPLIANCE»(ref-138152-S16381010882002032500000)
- «HISSING SOUND WHEN REMOVING FUEL CAP»(ref-138152-S10104532982002032500000)
- «EXCESSIVE FUEL ODOR»(ref-138152-S38110365042002032500000)
- «UNABLE TO REFUEL VEHICLE»(ref-138152-S11236372522002032500000)
- «WARNING INDICATOR LIGHTS»(ref-138152-S03843874762002032500000)
- «AUTOMATIC TRANSMISSION DOWN OR UPSHIFT, OR ENGAGEMENT»(ref-138152-S26739352592002032500000)
- «SPEEDOMETER OR TACHOMETER INOPERATIVE»(ref-138152-S24126454662002032500000)
- «HIGH OIL CONSUMPTION»(ref-138152-S18237694062002032500000)
- «ELECTRIC COOLING FAN INOPERATIVE AT LOW, MEDIUM &/OR HIGH SPEED, OR HYDRAULIC COOLING FAN INOPERATIVE (LS)»(ref-138152-S03351355482002032500000)
- «ELECTRIC OR HYDRAULIC COOLING FAN(S) ALWAYS ON»(ref-138152-S13131083132002032500000)
- «EXHAUST SMOKE»(ref-138152-S09847200982002032500000)
- «FUEL ODOR»(ref-138152-S27521440532002032500000)
- «ENGINE NOISE»(ref-138152-S38872993192002032500000)
- «CLIMATE CONTROL (LACK OF A/C COOLING, A/C ALWAYS ON OR A/C INOPERATIVE)»(ref-138152-S09336514472002032500000)
- «EXHAUST ODOR (SULFUR SMELL)»(ref-138152-S25497264102002032500000)
Symptom Checks Using Scan Tool PIDs
Check and compare the following PID values to PID specifications in appropriate PIN VOLTAGE/PID VALUE CHARTS article.
Note. On some models, DPFEGR PID may not be available.
- DPFEGR If DPFEGR HOT IDLE PID is not within .15 volt of KOEO value, go to TEST HE, step 100) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
- LONGFT1 &/Or LONGFT2 If LONGFT1 or LONGFT2 PID is low (-20 percent or less), concentrate checks in areas that would cause engine to run rich. If LONGFT1 or LONGFT2 PID is high (+20 percent or more), concentrate checks in areas that would cause engine to run lean.
- VPWR VPWR PID voltage should be 10.5-17.0 volts and within .5 volt of battery voltage. If VPWR PID voltage is not 10.5-17.0 volts, check and repair charging system as necessary. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If VPWR PID voltage is 10.5-17.0 volts but not within .5 volt of battery voltage, check B+ circuit to PCM power relay (or CCRM), VPWR circuit between PCM and PCM power relay or CCRM, and PWR GND circuits. See WIRING DIAGRAMS article.
Additional Intermittent Testing
Go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Check and compare the following PID values to PID specifications in appropriate PIN VOLTAGE/PID VALUE CHARTS article.
Note. On some models, DPFEGR PID may not be available.
- DPFEGR If DPFEGR HOT IDLE PID is not within .15 volt of KOEO value, go to TEST HE, step 100) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
- LONGFT1 &/Or LONGFT2 If LONGFT1 or LONGFT2 PID is low (-20 percent or less), concentrate checks in areas that would cause engine to run rich. If LONGFT1 or LONGFT2 PID is high (+20 percent or more), concentrate checks in areas that would cause engine to run lean.
- IMTVF (Econoline & Pickup 4.6L, & Blackwood & Navigator 5.4L (4V) Only Ensure transmission is in Park or Neutral. Record IMTVF PID value when ignition switch is turned to OFF position. Then start engine and raise engine speed to 3000 RPM. IMTVF PID value should indicate NO (no fault) in both situations. If IMTVF PID value indicates YES (fault is present) during either situation, go to TEST HU, step 65) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Check and compare the following PID values to PID specifications in appropriate PIN VOLTAGE/PID VALUE CHARTS article.
Note. On some models, DPFEGR PID may not be available.
- DPFEGR If DPFEGR HOT IDLE PID is not within .15 volt of KOEO value, go to TEST HE, step 100) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
- LONGFT1 &/Or LONGFT2 If LONGFT1 or LONGFT2 PID is low (-20 percent or less), concentrate checks in areas that would cause engine to run rich. If LONGFT1 or LONGFT2 PID is high (+20 percent or more), concentrate checks in areas that would cause engine to run lean.
- VPWR VPWR PID voltage should be 10.5-17.0 volts and within .5 volt of battery voltage. If VPWR PID voltage is not 10.5-17.0 volts, check and repair charging system as necessary. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If VPWR PID voltage is 10.5-17.0 volts but not within .5 volt of battery voltage, check B+ circuit to PCM power relay (or CCRM), VPWR circuit between PCM and PCM power relay or CCRM, and PWR GND circuits. See WIRING DIAGRAMS article.
Go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Symptom Checks
Check the following
- On Natural Gas models, check fuel delivery system for leaks. Go to TEST HB, step 16) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
- On all models, check EVAP emission system for leaks. See EXCESSIVE FUEL ODOR under SYSTEM TESTS (EVAPORATIVE EMISSIONS) in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
A snap noise may be due to secondary ignition arcing. On Coil On Plug (COP) models, check condition of spark plug boots. On all other models, check secondary ignition system. Go to TEST JB, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Check the following items
- Check fuel delivery system. Go to TEST HB, step 1) (Natural Gas models), or go to TEST HC, step 1) (all others) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
- Check EVAP emission system for leaks. See SYSTEM TESTS (EVAPORATIVE EMISSIONS) in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
- Sulfur content can vary in different fuels. Try a different fuel source.