Important Preliminary Checks Before Starting
Perform Diagnostic System Check - Vehicle in Vehicle DTC Information and verify that all of the following are true before using the Symptom tables
- The powertrain control module (PCM) and the malfunction indicator lamp (MIL) are operating correctly.
- No DTCs are stored.
- The scan tool data is within a normal operating range.
- Verify the customer complaint and locate the correct symptom in the table of contents. Check the items indicated under that symptom.
Several of the symptom procedures call for a careful visual/physical check. DO NOT neglect to perform the visual/physical check. The visual/physical check is an important procedure that can lead to the correction of a concern without further diagnosis. The performance of the visual/physical check can save valuable time. The visual/physical check should include the following
- Inspect all the PCM grounds for secure and clean connections that are in the proper location.
- Check all vacuum hoses for splits, kinks, and proper connections, as shown on the Vehicle Emission Control Information label. Check the vacuum hoses thoroughly for any type of leak or restriction.
- Inspect the air inlet ducts for collapsed or restricted sections.
- Check for air leaks at throttle body mounting area and intake manifold sealing surfaces.
- Inspect the wiring harness for proper connections and damage.
For more symptom base diagnostics refer to the following tables
- «Hard Start»(ref-200108-S27548178992005102000000)
- «Surges/Chuggles»(ref-200108-S22528102712005102000000)
- «Lack of Power, Sluggishness, or Sponginess»(ref-200108-S14910274582005102000000)
- «Detonation/Spark Knock»(ref-200108-S09246657502005102000000)
- «Hesitation, Sag, Stumble»(ref-200108-S13804815122005102000000)
- «Cuts Out, Misses»(ref-200108-S12972325832005102000000)
- «Poor Fuel Economy»(ref-200108-S35395860692005102000000)
- «Poor Fuel Fill Quality»(ref-200108-S02328884382005102000000)
- «Rough, Unstable, or Incorrect Idle and Stalling»(ref-200108-S30476175522005102000000)
- «Dieseling, Run-On»(ref-200108-S25089356522005102000000)
- «Backfire»(ref-200108-S38358308932005102000000)
- «Restricted Exhaust»(ref-200084-S26273253152005102000000) in Engine Exhaust
- «Malfunction Indicator Lamp (MIL) Inoperative»(ref-200108-S17284245842005102000000)
- «Malfunction Indicator Lamp (MIL) Always On»(ref-200108-S28266449032005102000000)
Intermittent Conditions
| Checks | Action |
|---|---|
| DEFINITION: The problem may or may not turn ON the MIL or store a DTC. There is a customer concern, but the symptom can not currently be duplicated, or the DTC diagnostic table indicates the fault not present at this time. | |
| Preliminary Checks | Refer to Important Preliminary Checks in Symptoms - Engine Controls . The fault must be present in order to be diagnosed correctly with a DTC table. If the fault that set the DTC is intermittent, then the use of DTC tables may result in replacement of good parts. |
| Electrical Connections or Wiring | Electrical connections and wiring cause most intermittent conditions. Determine which circuit is suspected of having an intermittent condition. This may be indicated by DTCs with a fault not present. Check the suspect circuit for the following conditions: Any connectors that are poorly mated Any terminals that are not fully seated in the connector Any terminals that are not properly formed or damaged A poor male to female connection-Checking for proper terminal retention requires the use of the J-38125 Terminal Repair Kit. Any poor terminal-to-wire connections-Checking for poor terminal-to-wire connections requires removing the wire/terminal from the connector body. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Any wires that are broken inside the insulation A pierced or damaged insulation that allows water or moisture to enter the wiring - The conductor can corrode inside the insulation with little visible evidence. Look for swollen and stiff sections of wire in the suspect circuit. Refer to Wiring Repairs and to Connector Repairs in Wiring Systems for the proper procedures to use when making a circuit repair. |
| Road Test | The following tests should be performed with 2 people in order to ensure the safe operation of the vehicle. Drive the vehicle while monitoring the suspect circuit with a scan tool or a DMM connected to the circuit. Look for an abnormal reading or voltage when the malfunction occurs. An abnormal reading on the scan tool or an abnormal voltage on the DMM display is an indication that there may be a malfunction in the circuit that was being monitored. If the intermittent fault sets a DTC, the diagnostic that sets the DTC can be enhanced using Check Mode. Operating the vehicle while in Check Mode can enable certain DTC diagnostics to run faster. Check Mode also turns some B type DTCs to A type DTCs. Refer to Service Bay Test . Certain DTCs must run before I/M system status can be determined. Any DTC that affects the status of an I/M system can be monitored indirectly on the scan tool under the I/M System Information selection. In order to determine which DTCs are associated with a particular I/M system test, refer to Inspection/Maintenance (I/M) System DTC Table . If an intermittent DTC is associated with a particular I/M system, monitoring the I/M system test can indicate whether the diagnostic for that DTC has run. When the I/M system test displays a YES status, indicating that the system diagnostic is complete, check for the applicable DTC in the Last Test Failed screen of the scan tool. If the DTC is not displayed, the diagnostic for that DTC has run and passed, indicating that no malfunction was present this time. All DTCs MUST BE CLEARED in order to view the Current Status of the I/M system tests. Do not forget that the I/M System Information tests only indicate that the test has run, not if the test passed or failed. The Last Test Failed screen must be checked for related DTCs in order to determine the outcome of the diagnostic test involved. |
| Scan Tool | The scan tool features that can be used to locate an intermittent conditions include the following: The scan tool Snapshot feature - The scan tool Snapshot feature can be triggered to capture and store engine parameters when a malfunction occurs. This stored information can be reviewed and compared to the Typical Scan Tool Data Values or to data values taken from a similarly equipped known-good vehicle. The Freeze Frame/Failure Records data feature - The Freeze Frame/Failure Records are stored when certain DTCs set. They typically include information to aid in reproducing the driving conditions that were present when a DTC is stored. In addition, the engine parameters are also stored. This stored information can be reviewed and compared to the typical Scan Tool Data List values or to data values taken from a similarly equipped known-good vehicle. The Freeze Frame/Failure Records data will be erased when DTC Information is cleared either with the scan tool or by disconnection of the control modules ECU, vehicle control module/powertrain control module (VCM/PCM), or engine control module (ECM) power supply. |
| Intermittent malfunction indicator lamp (MIL) | The following conditions may cause intermittent MIL operation with no DTCs stored: A defective relay, control module driven solenoid, or a switch that causes electrical system interference-Usually the symptom will occur when the faulty component is operating. Any ignition control (IC) wires routed near the generator or near the secondary ignition system wires and components An ignition system secondary voltage that is arcing and shorting to ground Any poor ignition control circuit or ignition module grounds A MIL control circuit that is intermittently shorting to ground Any faulty diodes in the generator or charging system circuits The improper installation of add-on electrical devices - These can include the following: Alarm systems 2-way radios Lighting systems Electrical motors |
| Loss of DTC Memory | In order to check for proper DTC Memory function, perform the following procedure: Observe the Conditions For Running The DTC for the throttle position (TP) sensor circuit low voltage DTC. Disconnect the TP sensor connector. Operate the vehicle within the Conditions for Running the DTC. The MIL should illuminate upon completion of all the Conditions for Running the DTC. Two key cycles or drive trips may be required. A TP sensor circuit low voltage DTC should be stored in the PCM and remain in memory when the ignition is turned OFF. A failure to store a DTC or failure of the DTC to remain in memory may indicate a faulty PCM. |
| Additional Checks | Check for faulty PCM grounds. Refer to Engine Controls Schematics . Check for open diodes (A/C clutch, charging system, etc.) that may cause electrical interference. The improper installation of add-on electrical devices - These can include the following: Alarm systems 2-way radios Lighting systems Electrical motors If the intermittent fault is believed to involve a particular sensor or component, observe the sensor or component display on a scan tool while moving the connectors and the wiring harnesses related to the sensor or the component. A change in the scan tool display can indicate the location of the fault. |
Intermittent Conditions
Hard Start
| Checks | Action |
|---|---|
| DEFINITION: The engine cranks OK, but does not start for a long time. The engine does eventually run, or may start but immediately dies. | |
| Preliminary Checks | Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. Refer to Symptoms - Engine Controls . Check that the driver is using the correct starting procedure. |
| Sensor Checks | Check the engine coolant temperature (ECT) sensor using a scan tool to compare the engine coolant temperature with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5°C (9°F) more or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit or in the sensor. Refer to Temperature vs Resistance . Check the throttle position (TP) sensor. A sticking throttle shaft or a binding throttle linkage will causes a high TP sensor voltage. Under these conditions the PCM may not control the idle. Monitor the TP sensor angle with the scan tool. The indicated angle should be approximately 9-11 percent with throttle closed. Inspect the mass air flow (MAF) sensor operation. Run the engine to normal operating temperature. Turn OFF all accessories and observe the MAF sensor at idle with a scan tool. If the MAF sensor reading is more than 3.5 g/s refer to DTC P0101 . Check the crankshaft position (CKP) sensor engine reference signal with a scan tool. Observe the Engine Speed parameter while cranking the engine. The scan tool should indicate a steady 200-300 RPM while cranking. If erratic values, such as sudden spikes in the engine speed are displayed, the engine reference signal is not stable enough for the engine to start and run properly. |
| Fuel System Checks | Check the fuel pump relay for correct operation. Observe the fuel pump relay operation on a scan tool while cranking the engine. Check the fuel pressure. Refer to Fuel System Diagnosis . Check for good quality fuel. Old or inferior quality fuel can cause poor starting. Check for water contamination in the fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . Check for no Crank Signal at the powertrain control module (PCM) connector C2 terminal 9 if the vehicle takes longer to start in cold weather. Observe the Starter Switch parameter on a scan tool while cranking the engine. The PCM provides slightly more fuel for engine start up when receiving the crank input. Check the fuel pump check valve. A faulty fuel pump check valve will allow the fuel in the lines to drain back into the tank after stopping the engine. This condition is especially troublesome on hot soak restarts. In order to check for this condition perform the following steps: Turn OFF the ignition. Install the fuel pressure gauge. Refer to Fuel Pressure Gage Installation and Removal . Pressurize the fuel rail by turning the ignition key ON and OFF a few times. Turn the ignition key ON and observe the fuel pressure. The fuel pressure has to remain more than 147 kPa (24 psi). |
| Ignition System Checks | Check for the proper secondary voltage output with a J 26792 Spark Tester or equivalent. See Special Tools . Refer to Electronic Ignition (EI) System Diagnosis . Inspect the spark plugs for correct operation and good ignition system performance. Refer to Spark Plug Inspection . Check for bare or shorted ignition system wiring. Check for loose ignition coil connections. |
| Additional Checks | An idle air control (IAC) system that is malfunctioning can cause a hard start condition. Hold the throttle open slightly while starting the engine. After the vehicle is started the scan tool can be used to check the operation of the IAC valve. Operate the IAC valve with the scan tool while checking for a smooth increase and decrease in engine speed. If engine speed can be controlled, the IAC system is functioning normally. If engine speed can not be controlled with the scan tool refer to Diagnostic Aids in DTC P0505 . If the engine stalls after starting inspect for a fault in the CMP Actuator System or the Rocker Arm Oil Control System. A stuck ON control solenoid can cause the engine to stall at idle speeds. Refer to DTC P0012 and DTC P2647 . Check the Service Bulletins for any updates. |
Hard Start
Surges/Chuggles
| Checks | Action |
|---|---|
| DEFINITION: The engine has a power variation under a steady throttle or cruise. There is a feeling as if the vehicle speeds up and slows down with no change in the accelerator pedal. | |
| Preliminary Checks | Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. Refer to Symptoms - Engine Controls . Be sure the driver understands the A/C compressor operation. Use a scan tool to make sure the reading of the vehicle speed sensor (VSS) matches the reading of the instrument panel speedometer. Transmission performance can be affected by incorrect VSS readings. If accuracy of the VSS is a concern, refer to Speedometer and/or Odometer Inaccurate or Inoperative in Instrument Panel, Gages, and Console. |
| Sensor Checks | Check the heated oxygen sensors (HO2S) 1 and HO2S 2 performance. Refer to the Diagnostic Aids for DTC P0130 . Inspect the mass air flow (MAF) sensor operation. Run the engine to normal operating temperature. Turn OFF all accessories and observe the MAF sensor at idle with a scan tool. If the MAF sensor reading is more than 3.5 g/s refer to DTC P0101 . Check for correct operation of the engine coolant temperature (ECT) sensor. A fixed or inaccurate ECT sensor reading can cause the engine to surge, especially at low speeds and at stops. |
| Fuel System Checks | Determine if a rich or lean system can cause the condition. Drive the vehicle at the speed of the complaint. Monitoring the Fuel Trim may help identify the problem. Lean - The Long Term Fuel Trim will be more than 20 percent. Refer to Diagnostic Aids in DTC P0171 . Rich - The Long Term Fuel Trim will be less than -20 percent. Refer to Diagnostic Aids in DTC P0172 . Check the fuel injectors. Perform the following procedures: The Fuel Injector Coil Test. Refer to Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Between 10-35 Degrees C (50-95 Degrees F) or Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Outside 10-35 Degrees C (50-95 Degrees F) . The Fuel Injector Balance Test - Refer to Fuel Injector Balance Test with Special Tool . Check the fuel pressure while the condition exists. Refer to Fuel System Diagnosis . |
| Ignition System Checks | Check for the proper secondary voltage output with a J 26792 Spark Tester. Inspect the spark plugs for correct operation and good ignition system performance. Refer to Spark Plug Inspection . |
| Additional Checks | Check the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics . Inspect the positive crankcase ventilation (PCV) valve for correct operation and the correct part. Refer to Crankcase Ventilation System Inspection/Diagnosis . Check the generator for the correct output voltage. Check the vacuum lines and hoses for leaks or incorrect routing. |
Surges and/or Chuggles Symptom
Lack of Power, Sluggishness, or Sponginess
| Checks | Action |
|---|---|
| DEFINITION: The engine delivers less than expected power. There is little or no increase in speed when partially applying the accelerator pedal. | |
| Preliminary Checks | Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. Refer to Symptoms - Engine Controls . Compare the customers vehicle with a similar unit in order to determine if the customer has an actual problem. Remove the air filter element and check for dirt or restrictions. Check the air inlet duct for any blockage or restrictions. Check the transmission shift pattern and down-shift operation. |
| Sensor/System | Inspect the mass air flow (MAF) sensor operation. Run the engine to normal operating temperature. Turn OFF all accessories and observe the MAF sensor at idle with a scan tool. If the MAF sensor reading is more than 3.5 g/s refer to DTC P0101 . |
| Fuel System Checks | Check for a restricted fuel filter or incorrect fuel pressure. Check the fuel injectors. Perform the following procedures: The Fuel Injector Coil Test - Refer to Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Between 10-35 Degrees C (50-95 Degrees F) or to Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Outside 10-35 Degrees C (50-95 Degrees F) . The Fuel Injector Balance Test - Refer to Fuel Injector Balance Test with Special Tool . Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . |
| Ignition System Checks | Check for the proper ignition voltage output with a J 26792 Spark Tester. See Special Tools . Inspect the spark plugs for correct operation and good ignition system performance. Refer to Spark Plug Inspection . Check the knock sensor (KS) and the sensor circuit shielding. A faulty knock sensor or signal interference could cause excessive retard of the ignition timing advance. Observe the spark parameter on a scan tool and compare with a known good vehicle. A typical value at 98 km/h (60 mph) with all engine accessories off is 26-32 degrees. |
| Exhaust System Checks | Check the exhaust system for a possible restriction. Refer to Restricted Exhaust in Engine Exhaust. Inspect the exhaust system for damaged or collapsed pipes. Inspect the muffler for heat distress or a possible internal failure. |
| Engine Mechanical Check | Check for any of the following engine mechanical problems: A low compression An incorrect valve timing An incorrect or worn camshaft Refer to Diagnostic Starting Point - Engine Mechanical in Engine Mechanical - 1.8L (LNK). |
| Additional Checks | If the loss of power is great above 6,000 RPM, inspect for the correct operation of the Rocker Arm Oil Control system. Refer to DTC P2647 . If there is a slight loss of power at wide open throttle (WOT), inspect for the correct operation of the Auxiliary Intake Air Control system. Refer to Auxiliary Intake Air System Diagnosis . Check the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics . Check the generator output voltage. |
Lack Of Power, Sluggishness, Or Sponginess
Detonation/Spark Knock
| Checks | Action |
|---|---|
| DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening. | |
| Preliminary Checks | Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. Refer to Symptoms - Engine Controls . Road test the vehicle and determine the severity of the complaint. |
| Cooling System Checks | Check for any obvious overheating problems. Refer to Engine Overheating in Engine Cooling. Check for a low engine coolant level. Refer to Loss of Coolant in Engine Cooling. Check for a loose water pump belt. Check for restricted air flow through the radiator, or a restricted coolant flow. Check for a faulty or incorrect thermostat. Refer to Thermostat Diagnosis in Engine Cooling. Check for a correct coolant solution. The solution should be a 50/50 mix of anti-freeze and water. Refer to Draining and Filling Cooling System in Engine Cooling. |
| Sensor Check | Check for an engine coolant temperature (ECT) sensor that has a shifted value. Refer to Temperature vs Resistance . |
| Fuel System Checks | Check to determine if a lean system causes the condition. Drive the vehicle at the speed of the complaint. Monitoring the Fuel Trim will help identify the problem. If the system is lean, the Long Term Fuel Trim will be more than 20 percent. Check the fuel pressure. Refer to Fuel System Diagnosis . Check the fuel injectors. Perform the Fuel Injector Coil Test procedure and the Fuel Injector Balance Test procedure. Refer to Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Between 10-35 Degrees C (50-95 Degrees F) and to Fuel Injector Balance Test with Special Tool . Check for inferior quality fuel and the proper octane rating. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . Fill the fuel tank with a known high quality fuel that meets the vehicles minimum octane requirements. Road test the vehicle and re-evaluate the vehicle performance. |
| Ignition System Checks | Check the spark plugs for the correct gap. Refer to Ignition System Specifications . Inspect the spark plugs for excessive deposits that can glow and pre-ignite the air/fuel mixture. Refer to Spark Plug Inspection . Check the spark plugs for the correct type and the correct heat range. Refer to Ignition System Specifications . |
| Engine Mechanical Checks | Check for carbon buildup. Remove the carbon with a top engine cleaner product. Follow the manufacturer instructions on the container. Check for excessive oil entering the combustion chamber. Refer to Symptoms - Engine Mechanical in Engine Mechanical. Check for incorrect basic engine parts such as the cam, the heads, the pistons, etc. |
| Additional Checks | Check for a dirty air filter or a restriction in the air induction system. Check for any Service Bulletins or updates. |
Detonation/Spark Knock
Hesitation, Sag, Stumble
| Checks | Action |
|---|---|
| DEFINITION: The vehicle has a momentary lack of response when pushing down on the accelerator. The condition can occur at any vehicle speed. The condition is usually most severe when trying to make the vehicle move, as from a stop sign. The condition may cause the engine to stall if severe enough. | |
| Preliminary Check | Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. Refer to Symptoms - Engine Controls . |
| Fuel System Checks | Check for a restricted fuel filter or incorrect fuel pressure. Refer to Fuel System Diagnosis . Check the fuel injectors. Perform the following procedures: The Fuel Injector Coil Test Procedure - Refer to Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Between 10-35 Degrees C (50-95 Degrees F) or Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Outside 10-35 Degrees C (50-95 Degrees F) . The Fuel Injector Balance Test Procedure - Refer to Fuel Injector Balance Test with Special Tool . Check for water or other fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . Check the throttle position (TP) sensor for binding or sticking. The voltage should increase at a steady rate as the throttle moves toward wide open throttle (WOT). Inspect the operation of the mass air flow (MAF) sensor. Run the engine to normal operating temperature. Turn OFF all accessories and observe the MAF sensor at idle with a scan tool. If the MAF sensor reading is more than 3.5 g/s refer to DTC P0101 . Check the evaporative emission (EVAP) control system. Refer to Evaporative Emission (EVAP) Control System Diagnosis . |
| Ignition System Checks | Inspect the spark plugs for correct operation and good ignition system performance. Refer to Spark Plug Inspection . |
| Additional Checks | Check the Service Bulletins for any updates. Check the generator output voltage. |
Hesitation, Sag, Stumble
Cuts Out, Misses
| Checks | Action |
|---|---|
| DEFINITION: A steady pulsation or jerking that follows engine speed, usually more pronounced as the engine load increases. The exhaust has a steady spitting sound at idle, low speed or on hard acceleration. | |
| Preliminary Checks | Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. Refer to Symptoms - Engine Controls . |
| Sensor Checks | Check the engine coolant temperature (ECT) sensor using a scan tool to compare the engine coolant temperature with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5°C (9°F) more or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit or in the sensor. Refer to Temperature vs Resistance . Inspect the mass air flow (MAF) sensor operation. Run the engine to normal operating temperature. Turn OFF all accessories and observe the MAF sensor at idle with a scan tool. If the MAF sensor reading is more than 3.5 g/s refer to DTC P0101 . |
| Fuel System Checks | Check for a restricted fuel filter or an incorrect fuel pressure. Refer to Fuel System Diagnosis . Check the fuel injectors. Perform the Fuel Injector Coil Test procedure and the Fuel Injector Balance Test procedure. Refer to Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Between 10-35 Degrees C (50-95 Degrees F) and Fuel Injector Balance Test with Special Tool . Check for water contamination of the fuel. |
| Ignition System Checks | Check for an ignition system misfire: IMPORTANT: Do not perform this test for more than 2 minutes in order to prevent damage to the catalytic converter. Start the engine. Remove one ignition coil at a time using insulated pliers. If there is an RPM drop on all cylinders (equal to within 50 RPM), refer to Rough, Unstable, or Incorrect Idle and Stalling . Check for spark on the suspected cylinders with a J 26792 Spark Tester or equivalent if there is no RPM drop on one or more cylinders. See Special Tools . If there is no spark, refer to Electronic Ignition (EI) System Diagnosis . If there is spark, inspect the spark plugs for correct operation and good ignition system performance. Refer to Spark Plug Inspection . Check the ignition system for moisture, dust, cracks, burns, etc. |
| Engine Mechanical Checks | Check for any of the following engine mechanical problems: Any faulty hydraulic lifter assemblies Any broken or weak valve springs An incorrect valve timing An incorrect or worn camshaft Check the intake and exhaust manifold passages for casting flash. Refer to the Diagnostic Starting Point - Engine Mechanical in Engine Mechanical. |
| Additional Checks | An engine miss condition can be caused by electromagnetic interference (EMI) on the reference circuit. EMI can usually be detected by monitoring the engine RPM with a scan tool. A sudden increase in RPM with little change in the actual engine RPM change indicates EMI is present. If a problem exists, check the routing of the secondary ignition wires and the high voltage components. Verify the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Engine Controls Schematics . |
| IMPORTANT |
|---|
| Do not perform this test for more than 2 minutes in order to prevent damage to the catalytic converter. |
Cuts Out, Misses Symptom
Poor Fuel Economy
| Checks | Action |
|---|---|
| DEFINITION: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, the economy is noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test. | |
| Preliminary Checks | Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. Refer to Symptoms - Engine Controls . Check the air cleaner element for dirt or restrictions. Visually and physically check the vacuum hoses for splits, kinks, and proper connections as shown on the Vehicle Emission Control Information label. Check the owners driving habits for any of the following: The A/C system defroster mode is ON all the time. The tires are improperly inflated. Heavy loads are frequently being carried. Heavy acceleration and high speeds are common. Frequent short trips Prolonged periods of idling Driving on unpaved or rough roads Suggest that the owner refill the fuel tank and recheck the fuel economy. |
| Fuel System Checks | Check the type, quality, and alcohol content of the fuel. Oxygenated fuels have lower energy and may deliver reduced fuel economy. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . Check for the correct fuel pressure. Refer to Fuel System Diagnosis . |
| Ignition System Checks | Inspect the spark plugs for correct operation and good ignition system performance. Refer to Spark Plug Inspection . Check the ignition coil boots for cracking, chafing, and loose connections. Observe the Spark parameter on the scan tool at idle, while operating the rear defogger, the A/C system, or the headlights. If the scan tool display remains fixed at 10 degrees, check for a short to ground in the Diagnostic Request circuit from the powertrain control module (PCM) connector C4 terminal 20 to the data link connector (DLC). Check the knock sensor (KS) and the sensor circuit shielding. A faulty knock sensor or signal interference could cause excessive retard of the ignition timing advance. Observe the Spark parameter on a scan tool and compare with a known good vehicle. A typical value at 98 km/h (60 mph) with all engine accessories off is 26-32 degrees. |
| Cooling System Checks | Check for the correct engine coolant level. Check the engine thermostat for always being open or for the wrong heat range. Refer to Thermostat Diagnosis in Engine Cooling. |
| Additional Checks | Check the clutch adjustment in vehicles equipped with a manual transmission. Refer to Clutch Slipping in Clutch. Check the transmission shift pattern and the torque converter clutch (TCC) operation in vehicles equipped with an automatic transmission. Refer to Symptoms - Automatic Transmission in Automatic Transmission. Check for dragging brakes. Refer to Brakes Drag in Hydraulic Brakes. Check for uneven or premature tire wear. A suspension misalignment can cause reduced fuel economy. Refer to Measuring Wheel Alignment in Wheel Alignment. Verify that the tires and wheels are similar to OEM. Wide performance tires create more drag and taller tires can cause odometer discrepancies. Check for the speedometer for proper calibration. Refer to Speedometer and/or Odometer Inaccurate or Inoperative in Instrument Panel, Gages, and Console. Check for a green engine. Fuel economy may not be near expected levels until the engine has had 5 000-8 000 km (3,000-5,000 miles) to break in. Check for add-on equipment like luggage racks and carriers. Wind resistance can lower fuel economy. Check the Service Bulletins for any updates or information. |
Poor Fuel Economy
Poor Fuel Fill Quality
| Concern | Causes |
|---|---|
| DEFINITION: Difficulty when refueling the vehicle. | |
| Difficult to fill | The fuel filler pipe check valve is stuck closed. The fill limiter vent valve (FLVV) on the evaporative emission (EVAP) canister is stuck closed. The EVAP canister air filter is restricted or dirty. Any restricted vapor lines or hoses The EVAP canister has an internal blockage or restriction. A fuel with high Reid vapor pressure characteristics. A high fuel temperature The fuel filler hose/pipe is pinched, kinked, or blocked. |
| Over fill | The pressure relief valve in the fill limiter vent valve (FLVV) is stuck open. The pressure relief valve in the FLVV is leaking. The FLVV is stuck open. The FLVV is leaking. |
| Premature shut-off of the fuel dispensing nozzle | The fill limiter vent valve (FLVV) is stuck closed. The EVAP canister air filter is restricted or dirty. Any restricted vapor lines or hoses The EVAP canister has an internal blockage or restriction. A fuel with high Reid vapor pressure characteristics A high fuel temperature |
| Fuel spitback | The fuel filler pipe check valve is stuck open. The filler pipe check valve is stuck closed. The filler pipe check valve is leaking. A fuel with high Reid vapor pressure characteristics. A high fuel temperature |
| Liquid fuel in the EVAP canister | The fill limiter vent valve is stuck open. The fill limiter vent valve is leaking. |
| Liquid fuel leak | The pressure relief valve in the fill limiter vent valve (FLVV) is stuck open. The pressure relief valve in the FLVV is leaking. The fuel filler hose is loose or torn. The FLVV is stuck open. |
| Fuel odor | The pressure relief valve in the fuel limiter vent valve (FLVV) is stuck open. The pressure relief valve in the FLVV is leaking. The EVAP canister is saturated with fuel. |
Poor Fuel Fill Quality
Rough, Unstable, or Incorrect Idle and Stalling
| Checks | Action |
|---|---|
| DEFINITION: The engine runs unevenly at idle. If severe enough, the engine or vehicle may shake. The engine idle speed may vary in RPM. Either condition may be severe enough to stall the engine. The engine idles at an incorrect speed. | |
| Preliminary Check | Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. Refer to Symptoms - Engine Controls . |
| Sensor Checks | Inspect the heated oxygen sensors (HO2S) 1 and HO2S 2 for a condition that can affect sensor activity and response. Refer to Diagnostic Aids for the following DTCs: DTC P0130 DTC P0134 DTC P0031 DTC P0032 Inspect the throttle position (TP) sensor. A sticking throttle shaft or a binding throttle linkage will causes a high TP sensor voltage. Under these conditions the powertrain control module (PCM) may not control the idle. Monitor the TP sensor angle with the scan tool. The indicated angle should be approximately 11 percent with the throttle closed. Inspect the engine coolant temperature (ECT) sensor. A fixed or inaccurate ECT sensor reading can cause the engine idle to surge or race. Using the scan tool, compare the ECT with the ambient air temperature on a cold engine. If the engine coolant is 5°C (9°F) more than or 5°C (9°F) less than the ambient air temperature, inspect the resistance of the coolant sensor. Refer to Temperature vs Resistance . If the ECT is significantly less than the ambient air temperature, inspect the coolant sensor electrical circuit for high resistance. Inspect the mass air flow (MAF) sensor operation. Run the engine to normal operating temperature. Turn OFF all accessories and observe the MAF sensor at idle with a scan tool. If the MAF sensor reading is more than 3.5 g/s refer to DTC P0101 . If the MAF sensor reading is less than 1.0 g/s, inspect for a vacuum leak between the MAF sensor and the engine. |
| Fuel System Checks | Inspect the operation of the fuel system for rich or lean condition. Operate the vehicle under the conditions that caused the concern. Monitor the Fuel Trim parameter on a scan tool in order to identify the problem. Lean - The Long Term Fuel Trim will be more than 20 percent. Refer to Diagnostic Aids in DTC P0171 . Rich - The Long Term Fuel Trim will be less than -20 percent. Refer to Diagnostic Aids in DTC P0172 . Test the fuel pressure while the condition exists. Refer to Fuel System Diagnosis . Inspect the evaporative emission (EVAP) control system. Refer to Electronic Ignition (EI) System Diagnosis . Test the fuel injectors for leaking. Refer to Fuel Injector Balance Test with Special Tool . |
| Ignition System Checks | Test for the proper secondary voltage output with a J 26792 Spark Tester. See Special Tools . Inspect the spark plugs for correct operation and good ignition system performance. Refer to Spark Plug Inspection . Inspect the ignition coil boots for damage. Observe the IAC Motor Command parameter on the scan tool at idle, while operating the rear defogger, the A/C system, or the headlights. The IAC Motor Command parameter should increase 2-7 percent when operating the engine loads. If the IAC Motor Command parameter remains fixed, check for a short to ground in the Diagnostic Request circuit from the PCM to terminal 13 of the data link connector (DLC) OBD II. Refer to Engine Controls Schematics . |
| Engine Mechanical Check | Inspect for the following engine mechanical conditions: Any faulty hydraulic lifter assemblies Any broken or weak valve springs A low compression An incorrect valve timing Any sticking or leaking valves An incorrect or worn camshaft Refer to the Diagnostic Starting Point - Engine Mechanical in Engine Mechanical - 1.8L (LNK). |
| Additional Checks | Inspect for vacuum leaks. Vacuum leaks can cause a higher than normal idle speed. Verify the PCM grounds are clean, tight, and in the proper locations. Refer to Engine Controls Schematics . Check the scan tool to determine if the PCM is receiving an A/C signal. The idle speed should be increased with the A/C ON. Refer to Electrical/Accessory Load Idle-Up Signal Diagnosis . Inspect the battery cables and the ground straps. They should be clean and secure. Inspect the A/C refrigerant pressure for being too high or for a faulty high pressure switch. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation, and Air Conditioning. Test for the proper operation of the IAC system. Refer to Idle Air Control (IAC) System Diagnosis . The engine will run rough and the engine can stall if the camshaft position (CMP) actuator solenoid is advancing camshaft timing at idle. Inspect for a fully energized or stuck CMP actuator solenoid. If the operation of the CMP actuator solenoid is suspect, refer to DTC P0012 . Inspect for the correct operation of the Rocker Arm Oil Control System. A stuck ON oil control solenoid can cause the engine to stall at idle speeds. Refer to DTC P2647 . Inspect the positive crankcase ventilation (PCV) valve for correct operation and the correct part. Refer to Crankcase Ventilation System Inspection/Diagnosis . Inspect that the idle speed is increasing for changes in electrical loads on the engine. Refer to Electrical/Accessory Load Idle-Up Signal Diagnosis . Verify that the PCM is increasing the idle speed when the P/S system pressure is increased on turns. Refer to Electrical/Accessory Load Idle-Up Signal Diagnosis . Inspect for broken or worn motor and transmission mounts. |
Rough, Unstable, or Incorrect Idle, Stalling
Dieseling, Run-On
| Checks | Action |
|---|---|
| DEFINITION: Engine continues to run when turning the ignition OFF, but runs very roughly. If the engine runs smoothly, check the ignition switch and adjustment. | |
| Preliminary Check | Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. Refer to Symptoms - Engine Controls . |
| Fuel System Checks | Check the evaporative emission (EVAP) control system. Refer to Evaporative Emission (EVAP) Control System Diagnosis . Check the fuel injectors for leaking. Refer to Fuel Injector Balance Test with Special Tool . |
Dieseling, Run-On
Backfire
| Checks | Action |
|---|---|
| DEFINITION: The fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise. | |
| Preliminary Check | Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. Refer to Symptoms - Engine Controls . |
| Ignition System Checks | Check for the proper ignition coil output voltage with a J 26792 Spark Tester or equivalent. See Special Tools . Inspect the spark plugs for correct operation and good ignition system performance. Refer to Spark Plug Inspection . Inspect the ignition coil boots for damage. |
| Engine Mechanical Checks | Check for any of the following engine mechanical problems: Any broken or weak valve springs A low compression Any sticking or leaking valves An incorrect valve timing An incorrect or worn camshaft Refer to Symptoms - Engine Mechanical in Engine Mechanical. Check the intake and the exhaust system for casting flash or other restrictions. |
Backfire
Tools Required
J 23738-A Hand Vacuum Pump. See Special Tools .
- Remove the vacuum check valve (1) from the auxiliary intake air system.
- Connect the J 23738-A or an equivalent hand vacuum pump to the intake manifold side of the vacuum check valve.
- Attempt to apply a vacuum of 34 kPa (254 mm Hg, 10 inches Hg) to the vacuum check valve.
- The check valve SHOULD NOT hold vacuum pressure.
- Disconnect the J 23738-A or an equivalent hand vacuum pump from the check valve.
- Connect the J 23738-A or an equivalent hand vacuum pump to the other side of the check valve.
- Apply a vacuum of 34 kPa (254 mm Hg, 10 inches Hg) to the vacuum check valve.
- The check valve SHOULD hold vacuum pressure.
- Replace the vacuum check valve if the valve failed either of the tests above.
- Install the vacuum check valve (1).
- Ensure that the check valve (1) is installed with the side that holds vacuum toward the intake air control solenoid (3).
J 23738-A Hand Vacuum Pump. See Special Tools .
- In order to view the operation of the auxiliary intake air door, remove the air cleaner cover and air cleaner element.
- Observe that the auxiliary intake air door is OPEN.
- If the intake air door is closed test for a faulty intake air control solenoid.
- Disconnect the vacuum hose to the auxiliary intake air door motor.
- Observe that the auxiliary intake air door is OPEN.
- Replace the air cleaner assembly if the intake air door is closed. Refer to «Air Cleaner Assembly Replacement»(ref-200095-S32008618622005102000000) .
- Connect the J 23738-A or an equivalent hand vacuum pump to the intake air door motor.
- Apply a vacuum of 34 kPa (254 mm Hg, 10 inches Hg) to the intake air door motor.
- The intake air door motor should CLOSE and HOLD vacuum.
- Replace the air cleaner assembly if the intake air door fails the above test. Refer to «Air Cleaner Assembly Replacement»(ref-200095-S32008618622005102000000) .
- Connect the J 23738-A or an equivalent hand vacuum pump to the vacuum storage chamber on the air cleaner upper assembly.
- Apply a vacuum of 34 kPa (254 mm Hg, 10 inches Hg) to the storage chamber.
- The vacuum chamber should HOLD the vacuum pressure.
- Replace the air cleaner assembly if the vacuum storage chamber looses pressure. Refer to «Air Cleaner Assembly Replacement»(ref-200095-S32008618622005102000000) .
Conditions for Updating the I/M System Status
Each system requires at least one, and sometimes several, diagnostic tests. The results of these tests are reported by a diagnostic trouble code (DTC). A system monitor is complete when either all of the DTCs comprising the monitor have Run and Passed, or any one of the DTCs comprising the monitor have illuminated the malfunction indicator lamp (MIL). Once all of the tests are completed, the I/M System Status display will indicate YES in the Completed column. For example, when the HO2S Heater Test indicates YES, all of the oxygen sensor heaters have been diagnosed. If the vehicle has four heated oxygen sensors, all four heater circuits have been diagnosed. The I/M System Status will indicate NO under the Completed column when any of the required tests for that system have not run. The following is a list of conditions that would set the I/M System Status indicator to NO
- The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
- The battery has been disconnected or discharged below operating voltage.
- The control module power or ground has been interrupted.
- The control module has been reprogrammed.
- The control module DTCs have been cleared as part of a service procedure.
Monitored Emission Control Systems
The OBD II system monitors all emission control systems that are on-board. Not all vehicles have a full complement of emission control systems. For example, a vehicle may not be equipped with secondary air injection (AIR) or exhaust gas recirculation (EGR). The OBD II regulations require monitoring of the following
- Air conditioning system
- Catalytic converter efficiency
- Comprehensive component monitoring - Emission related inputs and outputs
- Evaporative emissions (EVAP) system
- Exhaust gas recirculation (EGR) system
- Fuel delivery system
- Heated catalyst monitoring
- Misfire monitoring
- Oxygen sensor system (O2S or HO2S)
- Oxygen sensor heater system (HO2S heater)
- Secondary air injection (AIR) system
For the specific DTCs required for each system, refer to systems such as fuel delivery, misfire, and comprehensive components may not be listed in a system status list. These tests run continuously on some vehicles and may not require an indicator.
Check Mode
Check Mode can be used to increase the ability of the powertrain control module (PCM) to detect engine control system malfunctions. The PCM can be requested to operate in Check Mode by using the Output Controls feature of the scan tool. While in Check Mode operation the PCM will turn ON the malfunction indicator lamp (MIL) and record Freeze Frame data even on the first failure of a B type DTC. Not all engine control system diagnostics will be enhanced by Check Mode operation. The Check Mode service bay test can be performed while driving the vehicle in order to duplicate the customer concern. Those diagnostics most commonly known to benefit from Check Mode operation will be specified in the diagnostic procedure.
In order to activate the enhanced diagnostics of Check Mode operation, perform the following procedure
| IMPORTANT | DO NOT turn OFF the ignition anytime during or after the operation of the vehicle in Check Mode. Observe and capture all Check Mode operation DTC and Freeze Frame information on the scan tool before turning OFF the ignition. Any DTC or Freeze Frame information that occurred during Check Mode operation will be cleared by the PCM when the ignition is turned OFF. |
- Capture or save any DTC or Freeze Frame information on the scan tool before entering Check Mode operation. All DTC and Freeze Frame information will be cleared by the PCM when Check Mode is entered.
- Turn ON the ignition, with the engine OFF.
- Enter Check Mode operation with the scan tool from the Special Functions selection. Verify that the MIL is flashing which indicates that the Check mode request was received and accepted.
- Return to the Data List selection on the scan tool.
- DO NOT turn OFF the ignition after requesting Check Mode operation with a scan tool. The PCM will return to Normal Mode operation when the ignition is cycled from ON to OFF to ON.
- Start the engine.
- Operate the vehicle within the conditions under which the original concern was noted or within the Freeze Frame conditions that set the DTC.
- The Diagnostic Mode parameter in the scan tool data list can be viewed at anytime in order to verify that the vehicle is still operating in Check Mode.
- If the MIL illuminates while in Check Mode, observe and capture all DTC and Freeze Frame information with the scan tool.
- Check Mode operation can be terminated by cycling the ignition switch, or commanding Normal Mode with the scan tool.