Important Preliminary Inspections Before Beginning
Perform Diagnostic System Check - Engine Controls before using the symptom tables, and verify that all of the following are true
- The control module and malfunction indicator lamp (MIL) are operating correctly.
- There are no DTCs stored.
- The scan tool data is within the normal operating range, refer to «Scan Tool Data List»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-diagnostic-information-procedures__scan-tool-data-list) .
- Verify the customer concern and locate the correct symptom. Inspect the items indicated under that symptom.
- Several of the symptom procedures ask for a careful visual and physical inspection. This step is extremely important. The visual and physical inspection can lead to correcting a problem without further inspections, and can save valuable time.
- Inspect for improper installation of electrical components if an intermittent condition exists. Inspect for aftermarket theft deterrent devices, lights, and cellular phones. If you can not locate an intermittent condition, a cellular phone communication signal may cause the condition.
- If the intermittent condition exists as a start and then stall, test for DTCs relating to the vehicle theft deterrent system.
Use the following tables when diagnosing a symptom complaint
- «Hard Start»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__hard-start)
- «Surges/Chuggles»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__surgeschuggles)
- «Lack of Power, Sluggishness, or Sponginess»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__lack-of-power-sluggishness-or-sponginess)
- «Detonation/Spark Knock»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__detonationspark-knock)
- «Hesitation, Sag, Stumble»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__hesitation-sag-stumble)
- «Cuts Out, Misses»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__cuts-out-misses)
- «Poor Fuel Economy»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__poor-fuel-economy)
- «Poor Fuel Fill Quality»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__poor-fuel-fill-quality)
- «Rough, Unstable, or Incorrect Idle and Stalling»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__rough-unstable-or-incorrect-idle-and)
- «Dieseling, Run-On»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__dieseling-run-on)
- «Backfire»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__backfire)
Intermittent Conditions
| Inspections | Action |
|---|---|
| DEFINITION: The condition is not currently present but is indicated in the DTC history. OR There is a customer concern, but the symptom cannot currently be duplicated, if the condition is not DTC related. | |
| Preliminary | Refer to Important Preliminary Inspection Before Beginning in Symptoms - Engine Controls. The fault must be present to locate a problem using the DTC table. If a fault is intermittent, the use of DTC tables may result in the replacement of good parts. |
| Visual/Physical | This step is an important aid for locating a condition without extensive testing. Perform a thorough visual and physical inspection of the following components: Wiring harness for damage or cuts A misrouted harness that is too close to high voltage or high current devices such as the following: Secondary ignition components Motors Generators Vacuum hoses for the following conditions: Proper routing Proper connections Splits in the hose or the connections Kinks The control module and body grounds are clean and tight. Battery connections are clean and tight. Charging system for proper operation-Refer to Charging System Test (CS/AD/SI Generators) in Engine Electrical. |
| Harness/Connector Test | Many intermittent open or shorted circuits come and go with harness and connector movement caused by vibration, engine torque, bumps and rough pavement, etc. Test for this type of condition by performing the applicable procedure from the following list: Move the related connectors and wiring while monitoring the appropriate scan tool data. Move the related connectors and wiring with the component commanded ON and OFF, with the scan tool. Observe the components operation. With the engine running, move the related connectors and wiring while monitoring engine operation. If harness or connector movement affects the data displayed, the component and system operation, or the engine operation, inspect and repair the harness or connections as necessary. |
| Electrical Connections or Wiring | Poor electrical connections and terminal tension or wiring faults cause most intermittents. Perform a careful inspection of the suspected circuit for the following: Inspect for incorrect mating of the connector halves, or terminals not fully seated in the connector body, backed-out. Inspect for improperly formed or damaged terminals. Test for incorrect terminal tension. Inspect for poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body. Inspect for corrosion or water intrusion. Pierced or damaged insulation can allow 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 circuits. Inspect for wires that are broken inside the insulation. Inspect the harness for pinched, cut, or rubbed through wiring. Make sure the wiring does not come in contact with hot exhaust components. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. |
| Control Module Power and Grounds | Poor power or ground connections can cause widely varying symptoms. Test all control module power circuits. Many vehicles have multiple circuits supplying power to the control module. Inspect connections at the control module connectors, fuses, and any intermediate connections between the power source and the control module or component. A test lamp or a DMM may indicate that voltage is present, but neither tests a circuits ability to carry sufficient current. Ensure that the circuit can carry the current necessary to operate the component. Refer to Power Distribution Schematics in Wiring Systems. Test all control module ground and system ground circuits. The control module may have multiple ground circuits. Other components in the system may have separate grounds that may also need to be tested. Make sure the ground connections are clean and tight at the grounding point. Inspect the connections at the component and in splice packs, where applicable. Ensure that the circuit can carry the current necessary to operate the component. |
| Temperature Sensitivity | An intermittent condition may occur only when the component is cold, or only when the component is hot. The heat that affects the circuit can be engine generated or due to a poor connection in the circuit or a high electrical load. Information from the customer may help to determine if the trouble follows a pattern that is temperature related. The Freeze Frame/Failure Records or Snapshot data may help with this type of intermittent condition, where applicable. If the intermittent is related to heat, review the data for a relationship with the following: High ambient temperatures Underhood/engine generated heat Circuit generated heat due to a poor connection, or high electrical load Higher than normal load conditions (towing, etc.) If the intermittent is related to cold, review the data for the following: Low ambient temperatures-In extremely low temperatures, ice may form in a connection or component. Inspect for water intrusion. The condition only occurs on a cold start. The condition goes away when the vehicle warms up. |
| Electromagnetic Interference (EMI) and Electrical Noise | Some electrical components and circuits are sensitive to electromagnetic interference (EMI) or other types of electrical noise. Inspect for the following conditions: A misrouted harness that is too close to high voltage and high current devices such as secondary ignition components, motors, generator, etc. These components may induce electrical noise on a circuit that could interfere with normal circuit operation. Electrical system interference caused by a malfunctioning relay, control module driven solenoid, or switch. They can cause a sharp electrical surge. Normally, the problem will occur when the malfunctioning component is operating. Incorrect installation of non-factory, aftermarket, add-on accessories such as lights, 2-way radios, amplifiers, electric motors, remote starters, alarm systems, cell phones, etc. Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode or resistor. |
| Incorrect Control Module Programming | There are only a few situations where reprogramming a control module is appropriate: A new control module is installed. Revised software/calibration files have been released for this vehicle. IMPORTANT: DO NOT reprogram the control module with the SAME software/calibration files that are already present in the control module. This is not an effective repair for any type of driveability problem. Verify that the control module contains the correct software/calibration. If incorrect programming is found, reprogram the control module with the most current software/calibration. Refer to Service Programming System (SPS) in Programming and Setup. |
| Duplicating Failure Conditions | If the previous tests were not successful, attempt to duplicate and/or capture the failure conditions. Freeze Frame/Failure Records data, where applicable, contains the conditions that were present when the DTC set. Review and record the Freeze Frame/Failure Records data. Clear any DTCs with a scan tool. Turn OFF the key and wait 15 seconds. Operate the vehicle under the same conditions that were noted in Freeze Frame/Failure Records. The vehicle must also be operating within the Conditions For Running the DTC. Refer to Conditions for Running the DTC in the supporting text of the DTC being diagnosed. Monitor DTC status for the DTC being tested. The scan tool will indicate Ran when the enabling conditions have been satisfied long enough for the DTC to run. The scan tool will also indicate whether the DTC passed or failed. An alternate method is to drive the vehicle with a DMM connected to a suspected circuit. An abnormal reading on the DMM when the problem occurs may help you locate the problem. |
| Scan Tool Snapshot | The scan tool can be set up to take a snapshot of the parameters available via serial data. The Snapshot function records live data over a period of time. The recorded data can be played back and analyzed. The scan tool can also graph parameters singly or in combinations of parameters for comparison. The snapshot can be triggered manually at the time the symptom is noticed or set up in advance to trigger when a DTC sets. An abnormal value captured in the recorded data may point to a system or component that needs to be investigated further. Refer to the scan tool user instructions for more information on the Snapshot function. |
| IMPORTANT |
|---|
| DO NOT reprogram the control module with the SAME software/calibration files that are already present in the control module. This is not an effective repair for any type of driveability problem. |
Intermittent Conditions
Hard Start
| Inspection/Test | Action |
|---|---|
| DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies. | |
| Preliminary | Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls . Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Search for bulletins. Verify that the driver is using the correct starting procedure as described in the owners manual. |
| Sensor/System | Inspect the idle air control (IAC) system. Refer to Idle Air Control (IAC) System Diagnosis . Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature vs Resistance . Test for proper operation of the throttle position (TP) sensor. Refer to DTC P0121 . Test for proper operation of the manifold absolute pressure (MAP) sensor. Refer to DTC P0106 . |
| Fuel System | Verify there is adequate fuel. Inspect the fuel pump operation. The fuel pump should turn ON for 2 seconds when you turn ON the ignition. Refer to Fuel Pump Electrical Circuit Diagnosis . A faulty in-tank fuel pump check valve allows the fuel in the lines to drain back to the tank after the engine stops. Refer to Fuel System Diagnosis . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , and Fuel Injector Coil Test . Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . |
| Ignition System | In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement Remove spark plugs and inspect for the following: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Spark plugs are of the correct type. Inspect for proper secondary ignition voltage output with J 26792 HEI Spark Tester. An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect the distributor. Refer to Distributor Inspection . Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection . |
| Engine Mechanical | Inspect for the following conditions: Excessive oil in combustion chamber or leaking valve seals-Refer to Oil Consumption Diagnosis in Engine Mechanical. Low cylinder compression-Refer to Engine Compression Test in Engine Mechanical. Bent pushrods Improper valve timing Worn rocker arms Broken or worn valve springs Combustion chambers for excessive carbon buildup-Clean the chambers using top engine cleaner. Follow the instructions on the can. Incorrect, worn, or damaged basic engine parts-Inspect the following: The camshaft-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. The cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc.-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start and stall Erratic performance |
| Additional | Inspect for a restricted exhaust. Refer to Restricted Exhaust in Engine Exhaust. Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking. |
Hard Start
Surges/Chuggles
| Inspection/Tests | Action |
|---|---|
| DEFINITION: Engine power variation under steady throttle or cruise. Feels like the vehicle speeds up and slows down with no change in the accelerator pedal position. | |
| Preliminary | Refer to Important Preliminary Inspections Before beginning in Symptoms - Engine Controls . Search for bulletins. Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Verify the driver understands the operation of the transmission torque converter clutch (TCC) and A/C compressor operation as explained in the owners manual. |
| Sensor/System | NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature vs Resistance . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to DTC P0106 . |
| Fuel System | Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , Fuel Injector Coil Test . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Verify that each fuel injector harness is connected to the correct fuel injector or cylinder. Relocate the fuel injector harnesses as necessary. Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector Purging of a saturated evaporative emission (EVAP) canister Incorrect fuel pressure-Refer to Fuel System Diagnosis . A leaking fuel pressure regulator-Refer to Fuel System Diagnosis . Leaking fuel injectors-Refer to Fuel System Diagnosis . Manifold absolute pressure (MAP) sensor operation-Refer to DTC P0106 . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Proper MAP sensor operation-Refer to DTC P0106 . Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Balance Test with Tech 2 . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Ignition System | In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement . Inspect for proper secondary ignition voltage output with the J 26792 HEI Spark Tester. An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection . Monitor the Misfire Current Counters while driving the vehicle in the conditions that the symptom occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . |
| Engine Mechanical | Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start and stall Erratic performance |
| Additional Inspections | Visually and physically inspect vacuum hoses for splits, kinks, and proper connections and routing as shown on the Vehicle Emission Control Information label. Inspect the transmission torque converter clutch (TCC) for proper operation. Refer to Torque Converter Diagnosis Procedure in Automatic Transmission - 4L60-E/4L65-E. Inspect the exhaust system for possible restrictions. Refer to Restricted Exhaust in Engine Exhaust. |
| NOTE |
|---|
| Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Surges/Chuggles
Lack of Power, Sluggishness, or Sponginess
| Inspection/Tests | Action |
|---|---|
| DEFINITION: Engine delivers less than expected power. Little or no increase in speed when the accelerator pedal is pushed down part way. | |
| Preliminary Inspections | Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls . Search for bulletins. Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Remove the air filter element and inspect for dirt or for restrictions. Refer to Air Cleaner Element Replacement and replace as necessary. |
| Fuel System | Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , or Fuel Injector Coil Test . Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector Purging of a saturated evaporative emission (EVAP) canister Incorrect fuel pressure-Refer to Fuel System Diagnosis . A leaking fuel pressure regulator-Refer to Fuel System Diagnosis . Leaking fuel injectors-Refer to Fuel System Diagnosis . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted-Refer Air Cleaner Outlet Resonator Replacement . An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Balance Test with Tech 2 . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Sensor/System | Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Scan Tool Data List . |
| Ignition System | In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement Inspect for proper secondary ignition voltage output with J 26792 HEI Spark Tester. An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection . Monitor the Misfire Current Counters while driving the vehicle in the conditions that the symptom occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water. |
| Engine Mechanical | Inspect for incorrect camshaft timing. Inspect for excessive oil in the combustion chambers and leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical. Test the cylinder compression. Refer to Engine Compression Test in Engine Mechanical. Inspect for incorrect, worn, or damaged basic engine parts, including the following: The camshaft-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. The cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc.-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start and stall Erratic performance |
| Additional Inspections | Inspect the exhaust system for possible restrictions. Refer to Restricted Exhaust in Engine Exhaust. Inspect the exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or internal failure. Inspect the transmission torque converter clutch (TCC) for proper operation. Refer to Torque Converter Diagnosis Procedure in Automatic Transmission - 4L60-E/4L65-E. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Lack of Power, Sluggishness, or Sponginess
Detonation/Spark Knock
| Inspection/Tests | Action |
|---|---|
| DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening. | |
| Preliminary Inspections | Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls . Search for bulletins. Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . If there are no engine mechanical faults, 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 performance of the vehicle. |
| Fuel System | Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , or Fuel Injector Balance Test with Tech 2 . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Balance Test with Tech 2 . Inspect for proper operation of the manifold absolute pressure (MAP) sensor-Refer to DTC P0106 . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Sensor/System | Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature vs Resistance . |
| Ignition System | In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement Remove spark plugs and inspect for the following: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Verify that the spark plugs are of the correct type. Inspect for proper secondary ignition voltage output with J 26792 HEI Spark Tester. An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection . |
| Engine Cooling System | Inspect for obvious overheating problems: Low engine coolant-Refer to Loss of Coolant in Engine Cooling. Faulty thermostat- Refer to Thermostat Diagnosis in Engine Cooling. Restricted air flow to the radiator or restricted coolant flow through the radiator. Inoperative cooling fan-Refer to Fan Clutch Diagnosis in Engine Cooling. Proper tension on the drive belts-Refer to Drive Belt Tensioner Diagnosis in Engine Mechanical. Correct coolant solution should be a 50/50 mix. Refer to Cooling System Description and Operation in Engine Cooling |
| Engine Mechanical | Inspect for the following engine mechanical problems: Excessive oil in combustion chamber-Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical. High cylinder compression-Refer to Engine Compression Test in Engine Mechanical. Combustion chambers for excessive carbon buildup-Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can. Incorrect camshaft timing Inspect for incorrect, worn, or damaged basic engine parts. Inspect the following: The camshaft-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. The cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc.-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Refer to Symptoms - Engine Mechanical in Engine Mechanical. Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start and stall Erratic performance |
| Additional Inspections | Inspect the transmission torque converter clutch (TCC) operation. The TCC applying too soon can cause the engine to spark knock. Refer to Torque Converter Diagnosis Procedure in Automatic Transmission - 4L60-E/4L65-E. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Detonation/Spark Knock
Hesitation, Sag, Stumble
| Inspection/Tests | Action |
|---|---|
| DEFINITION: Momentary lack of response as the accelerator is pushed down. Can occur at any vehicle speed. Usually more pronounced when first trying to make the vehicle move from a stop. May cause the engine to stall if severe enough. | |
| Preliminary | Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls . Search for bulletins. Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . |
| Sensor/System | NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to DTC P0106 . Inspect for proper operation of the throttle position (TP) sensor. Refer to DTC P0121 . Verify that the engine coolant temperature (ECT) sensor has not shifted in value. Refer to Temperature vs Resistance . |
| Fuel System | Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Test the fuel injector Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , or Fuel Injector Coil Test . Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector Purging of a saturated evaporative emission (EVAP) canister Incorrect fuel pressure-Refer to Fuel System Diagnosis . A leaking fuel pressure regulator-Refer to Fuel System Diagnosis . Proper operation of the MAP sensor-Refer to DTC P0106 . Leaking fuel injectors-Refer to Fuel System Diagnosis . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted. An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Balance Test with Tech 2 . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Ignition System | In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement Inspect for proper secondary ignition voltage output with J 26792 HEI Spark Tester. An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection . Monitor the Misfire Current Counters while driving the vehicle in the conditions that the symptom occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water. |
| Engine Cooling System | Inspect the engine thermostat for proper operation and for correct heat range. Refer to Thermostat Diagnosis in Engine Cooling. |
| NOTE |
|---|
| Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Hesitation, Sag, Stumble
Cuts Out, Misses
| Inspections | Action |
|---|---|
| DEFINITION: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases. This condition is not normally felt above 1,500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle or low speed. | |
| Preliminary | Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls . Search for bulletins. Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Remove the air filter element and inspect for dirt and for restrictions. Refer to Air Cleaner Element Replacement . Replace as necessary. |
| Fuel System | Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , and Fuel Injector Coil Test . Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Inspect for the following conditions that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector Purging of a saturated evaporative emission (EVAP) canister Incorrect fuel pressure-Refer to Fuel System Diagnosis . A leaking fuel pressure regulator-Refer to Fuel System Diagnosis . Leaking fuel injectors-Refer to Fuel System Diagnosis . Proper operation of the manifold absolute pressure (MAP) sensor-Refer to DTC P0106 . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Balance Test with Tech 2 . Proper operation of the MAP sensor-Refer to DTC P0106 . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Sensor/System | Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature vs Resistance . Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Scan Tool Data List . Inspect for throttle body tampering, excessive deposits, or damage. Inspect for a vacuum leak. Inspect the crankcase ventilation system for proper operation. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. |
| Ignition System | In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement Inspect for proper secondary ignition voltage output with J 26792 HEI Spark Tester. Inspect the distributor cap and rotor. Refer to Distributor Inspection . An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection . Monitor the Misfire Current Counters while driving the vehicle in the conditions that the symptom occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water. |
| Engine Mechanical | Inspect engine mechanical for the following: Compression Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms Broken valve springs Excessive oil in combustion chamber or leaking valve seals. For more information, refer to one or more of the following procedures in Engine Mechanical: Engine Compression Test Symptoms - Engine Mechanical Oil Consumption Diagnosis For incorrect, worn, or damaged basic engine parts, inspect the following: The camshaft-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. The cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc.-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnosis procedures. Inspect for excessive end play that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions. A no start A start and stall Erratic performance |
| Additional Inspections | Inspect the exhaust system for possible restrictions. Inspect for the following: Inspect the exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or possible internal failure. Inspect for possible plugged catalytic converters. Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) can cause an engine misfire condition. A sudden increase in indicated RPM parameter with little change in actual engine RPM change indicates EMI is present. Inspect for high voltage components near ignition control circuits if a condition exists. Inspect the intake manifold and the exhaust manifold passages for casting flash. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Cuts Out, Misses
Poor Fuel Economy
| Inspections | Action |
|---|---|
| DEFINITION: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, fuel economy is noticeably lower than the economy was on this vehicle at one time, as previously shown by an actual road test. | |
| Preliminary | Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls . Search for bulletins. Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Discuss the following with the owner that may effect fuel economy: Is the A/C ON or the Defroster mode ON full time? Are the tires at the correct pressure? Are the wheels and tires the correct size? Are there excessively heavy loads being carried? Is the acceleration rate too much, too often? Remove the air filter element and inspect for dirt or for restrictions. Refer to Air Cleaner Element Replacement . Replace as necessary. |
| Fuel System | Discuss with the owner 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 (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Inspect the fuel injectors. Refer to Fuel Injector Coil Test , Fuel Injector Balance Test with Special Tool , and Fuel Injector Balance Test with Tech 2 . Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Inspect that each fuel injector harness is connected to the correct fuel injector and cylinder. Relocate the fuel injector harnesses as necessary. |
| Sensor/System | Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector Purging of a saturated evaporative emission (EVAP) canister Incorrect fuel pressure-Refer to Fuel System Diagnosis . A leaking fuel pressure regulator-Refer to Fuel System Diagnosis . Leaking fuel injectors-Refer to Fuel System Diagnosis . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect the air intake system and crankcase for air leaks. Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature vs Resistance . Inspect the crankcase ventilation system for proper operation. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. Inspect for an inaccurate speedometer. Refer to Symptoms - Instrument Panel, Gages and Console in Instrument Panel, Gages and Console. Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Scan Tool Data Definitions . |
| Ignition System | In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement Inspect for proper secondary ignition voltage output with the J 26792 HEI Spark Tester. An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection . Monitor the Misfire Current Counters while driving the vehicle in the conditions that the symptom occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . |
| Engine Cooling System | Inspect the engine coolant level for being low. Refer to Loss of Coolant in Engine Cooling. Inspect the engine thermostat for proper operation and for the correct heat range. Refer to Thermostat Diagnosis in Engine Cooling. |
| Engine Mechanical | Inspect engine mechanical for the following: Compression Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms Broken valve springs Excessive oil in combustion chamber or leaking valve seals. For more information, refer to one or more of the following procedures in Engine Mechanical: Engine Compression Test Symptoms - Engine Mechanical Oil Consumption Diagnosis For incorrect, worn, or damaged basic engine parts, inspect the following: The camshaft-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. The cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc.-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnosis procedures. |
| Additional Inspections | Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on the Vehicle Emission Control Information label. Inspect the transmission torque converter clutch (TCC) operation. The scan tool should indicate an RPM drop when the system commands the TCC ON. Inspect the exhaust system for a possible restriction. Inspect for the following: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure Possible plugged catalytic converter-Refer to Restricted Exhaust in Engine Exhaust. Inspect the brake system for dragging or improper operation. Refer to Brakes Drag in Hydraulic Brakes. Verify that the vehicle operator does not drive with a foot on the brake pedal. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Poor Fuel Economy
Poor Fuel Fill Quality
| Problem | Causes |
|---|---|
| Definition: During the fueling process a continual, occasional or no fuel nozzle shut-off condition has occurred. | |
| Difficult to fill | Fill limiter vent valve stuck closed Evaporative emission (EVAP) canister restricted EVAP vent valve stuck closed Restricted vapor lines High Reid vapor pressure or high fuel temperature Fuel filler hose is pinched or kinked Ignition switch ON, Vent Valve Closed |
| Over fill | Pressure relief valve is stuck open or leaking Fill limiter vent valve stuck open or leaking |
| Pre-mature shut-off of the fuel dispensing nozzle | Fill limiter vent valve stuck closed EVAP canister restricted EVAP vent valve stuck closed Restricted vapor lines High Reid vapor pressure or high fuel temperature Ignition switch ON, EVAP vent valve closed |
| Fuel Spitback | Restricted EVAP canister High Reid vapor pressure or high fuel temperature Ignition switch ON, EVAP vent valve closed |
Poor Fuel Fill Quality
Rough, Unstable, or Incorrect Idle and Stalling
| Inspections | Action |
|---|---|
| DEFINITION: Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary in RPM. Either condition may be severe enough to stall the engine. | |
| Preliminary Inspections | Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls . Search for bulletins. Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems. Remove and inspect the air filter element for dirt or for restrictions. Refer to Air Cleaner Element Replacement . Replace as necessary. |
| Fuel System | Inspect the fuel injectors. Refer to Fuel System Diagnosis . Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Inspect that each fuel injector harness is connected to the correct injector/cylinder. Relocate fuel injector harnesses as necessary. Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector Purging of a saturated evaporative emission (EVAP) canister Incorrect fuel pressure-Refer to Fuel System Diagnosis . A leaking fuel pressure regulator-Refer to Fuel System Diagnosis . Leaking fuel injectors-Refer to Fuel System Diagnosis . Vacuum hoses that are split, kinked, or improperly connected Proper operation of the manifold absolute pressure (MAP) sensor-Refer to DTC P0106 . An air intake duct that is collapsed or restricted An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Balance Test with Tech 2 . Proper operation of the MAP sensor-Refer to DTC P0106 Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Sensor/System | Test for conditions which cause an incorrect idle speed. Throttle body tampering, excessive deposits, or damage Restricted air intake system Large vacuum leak Inspect the crankcase ventilation system for proper operation. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. Inspect the IAC System. Refer to Idle Air Control (IAC) System Diagnosis . Inspect the throttle position (TP) sensor for proper operation. Refer to DTC P0121 . Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. |
| Ignition System | In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement Inspect for proper secondary ignition voltage output with the J 26792 HEI Spark Tester. An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection . Monitor the Misfire Current Counters while driving the vehicle in the conditions that the symptom occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . |
| Engine Mechanical | Inspect engine mechanical for the following: Compression Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms Broken valve springs Excessive oil in combustion chamber or leaking valve seals. For more information, refer to one or more of the following procedures in Engine Mechanical: Engine Compression Test Symptoms - Engine Mechanical Oil Consumption Diagnosis For incorrect, worn, or damaged basic engine parts, inspect the following: The camshaft-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. The cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc.-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnosis procedures. |
| Additional Inspections | Inspect the exhaust system for possible restrictions. Inspect for the following: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure Possible plugged catalytic converters -Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the reference circuit can cause an engine misfire condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM parameter with little change in actual engine RPM change indicates that EMI is present. If a condition exists, inspect routing of secondary ignition wires or high voltage components near the ignition control circuits. Inspect for faulty motor mounts. Refer to Engine Mount Inspection in Engine Mechanical. Inspect the intake manifold and the exhaust manifold passages for casting flash. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Rough, Unstable, or Incorrect Idle and Stalling
Dieseling, Run-On
| Inspections | Action |
|---|---|
| DEFINITION: Engine continues to run after key is turned OFF, but runs very rough. If the engine runs smooth, inspect the ignition switch and the ignition switch adjustment. | |
| Preliminary Inspections | Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls . Search for bulletins. Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . |
| Fuel System | Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , Fuel Injector Coil Test . |
Dieseling, Run-On
Backfire
| Inspections | Actions |
|---|---|
| DEFINITION: Fuel ignites in the intake manifold or in the exhaust system, making a loud popping noise. | |
| Preliminary Inspections | Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . |
| Fuel System | Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , or Fuel Injector Coil Test . Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary. |
| Sensor/System | Inspect the crankcase ventilation system for proper operation. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Scan Tool Data List . |
| Ignition System | In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement Remove spark plugs and inspect for the following: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Verify that the spark plugs are of the correct type. Inspect for proper ignition voltage output with J 26792 HEI Spark Tester. An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect for damaged or misaligned spark plug boots. Inspect the electronic ignition (EI) module for a proper ground connection. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the symptom occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water. |
| Engine Cooling System | Inspect the engine coolant level for being low. Refer to Loss of Coolant in Engine Cooling. Inspect the engine thermostat for proper operation and for the correct heat range. Refer to Thermostat Diagnosis in Engine Cooling. |
| Engine Mechanical | Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnosis procedures. Inspect engine mechanical for the following: Compression Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms Broken valve springs Excessive oil in combustion chamber or leaking valve seals. For more information, refer to one or more of the following procedures in Engine Mechanical: Engine Compression Test Symptoms - Engine Mechanical Oil Consumption Diagnosis For incorrect, worn, or damaged basic engine parts. Inspect the following: The camshaft-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. The cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc.-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. |
| Additional Inspections | Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on the Vehicle Emission Control Information label. Inspect the intake manifold and the exhaust manifold passages for casting flash. Inspect the exhaust system for possible restrictions. Inspect the following: Inspect the exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or possible internal failure. Inspect for possible plugged catalytic converter. Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) circuit can cause an engine misfire condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM parameter with little change in actual engine RPM change may indicate that EMI is present. If a problem exists, inspect for high voltage components near the ignition control circuits. |
Backfire
Circuit Description
Battery positive voltage is supplied directly to the malfunction indicator lamp (MIL). The powertrain control module (PCM) turns the MIL ON by grounding the MIL control circuit. There should be a steady MIL with the ignition ON and the engine OFF.
MIL Operation
The MIL is located on the instrument panel cluster (IPC).
MIL Function
- The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.
- The MIL illuminates during a bulb test and a system test.
- A DTC will be stored if a MIL is requested by the PCM.
MIL Illumination
- The MIL will illuminate with ignition switch ON and the engine not running.
- The MIL will turn OFF when the engine is started.
- The MIL will remain ON if the self-diagnostic system has detected a malfunction.
- The MIL may turn OFF if the malfunction is not present.
- If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the ignition switch is ON.
- If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.
Test Description
The number below refers to the step number on the diagnostic table.
- 4: This step tests for a short to voltage on the MIL control circuit. With the fuse removed there should be no voltage on the MIL control circuit.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check - Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Verify whether the instrument cluster is operational. If the instrument panel (I/P) is completely inoperative, refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gages and Console. Command the MIL ON and OFF with a scan tool. Does the MIL turn ON and OFF when commanded with a scan tool? | Go to Intermittent Conditions | Go to Step 3 | |
| 3 | Inspect the fuse that supplies battery positive voltage to the MIL. Is the fuse open? | Go to Step 10 | Go to Step 4 | |
| 4 | Turn OFF the ignition. Remove the fuse that supplies voltage to the MIL. Disconnect the powertrain control module (PCM). Turn ON the ignition with the engine OFF. Measure the voltage from the MIL control circuit in the PCM harness connector to a good ground. Is the voltage less than the specified value? | 0.3 V | Go to Step 5 | Go to Step 11 |
| 5 | Turn OFF the ignition. Install the fuse that supplies voltage to the MIL. Turn ON the ignition with the engine OFF. Connect a 3-amp fused jumper wire between the MIL control circuit in the PCM harness connector and a good ground. Is the MIL illuminated? | Go to Step 9 | Go to Step 6 | |
| 6 | Turn OFF the ignition. Remove the instrument panel cluster (IPC). Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Probe the MIL battery positive voltage circuit of the IPC harness connector with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 7 | Go to Step 12 | |
| 7 | Test the MIL control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct a condition? | Go to Step 15 | Go to Step 8 | |
| 8 | Test for an intermittent and for a poor connection at the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 13 | |
| 9 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 14 | |
| 10 | Repair the short to ground in the battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 15 | ||
| 11 | Repair the short to voltage in the MIL control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 15 | ||
| 12 | Repair the open in the MIL battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 15 | ||
| 13 | Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Did you complete the replacement? | Go to Step 15 | ||
| 14 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 15 | ||
| 15 | Turn OFF the ignition for 30 seconds. Does the vehicle operate correctly, without any MIL illumination and without any stored DTCs? | System OK | Go to Diagnostic Trouble Code (DTC) List | |
Malfunction Indicator Lamp (MIL) Inoperative
Battery positive voltage is supplied directly to the malfunction indicator lamp (MIL). The powertrain control module (PCM) turns the MIL ON by grounding the MIL control circuit.
The MIL is located on the instrument panel (IPC).
MIL Function
- The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.
- The MIL illuminates during a bulb test and a system test.
- A DTC will be stored if a MIL is requested by the diagnostic.
MIL Illumination
- The MIL will illuminate with ignition switch ON and the engine not running.
- The MIL will turn OFF when the engine is started.
- The MIL will remain ON if the self-diagnostic system has detected a malfunction.
- The MIL may turn OFF if the malfunction is not present.
- If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the ignition switch is ON.
- If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.
Diagnostic Aids
If the problem is intermittent, refer to Intermittent Conditions .
The number below refers to the step number on the diagnostic table.
- 2: This step determines if the condition is with the MIL control circuit or the PCM.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls |
| 2 | Turn OFF the ignition. Disconnect the PCM. Turn ON the ignition, with the engine OFF. Observe the MIL. Is the MIL illuminated? | Go to Step 3 | Go to Step 5 |
| 3 | Remove the instrument panel cluster (IPC). Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Test the MIL control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 4 |
| 4 | Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Did you complete the replacement? | Go to Step 6 | |
| 5 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 6 | |
| 6 | Turn the ignition OFF for 30 seconds. Start the engine. Does the vehicle operate correctly without any MIL illumination, and without any stored DTCs? | System OK | Go to Diagnostic System Check - Engine Controls |
Malfunction Indicator Lamp (MIL) Always On
Description
The Engine Cranks but Does Not Run diagnostic table is an organized approach to identifying a condition that prevents an engine from starting. The Engine Cranks but Does Not Run diagnostic table directs the service technician to the appropriate system diagnosis.
The Engine Cranks but Does Not Run diagnostic table assumes the following
- The battery is completely charged. Refer to «Battery Inspection/Test (Non-HP2)»(/chevrolet/chevy-express-g3500/1996-2012/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
- The cranking speed is acceptable. Refer to «Engine Cranks Slowly»(/chevrolet/chevy-express-g3500/1996-2012/remont/charging-system/#battery-charging-system-and-starting-system__engine-cranks-slowly) in Engine Electrical.
- There is adequate fuel in the fuel tank.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check - Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Turn ON the ignition, with the engine OFF. Observe the DTC information with a scan tool. Does the scan tool display DTC P0230, P0335, P0336, P0601, P0602, P0604, P1626, P1631, or P1683? | Go to Diagnostic Trouble Code (DTC) List | Go to Step 3 | |
| 3 | Does the scan tool display any body control module (BCM) vehicle theft deterrent (VTD) DTCs? | Go to Diagnostic System Check - Theft Deterrent in Theft Deterrent | Go to Step 4 | |
| 4 | Attempt to start the engine. Observe the Engine Speed parameter with a scan tool, while the engine is cranking. Does the engine speed increment? | Go to Step 5 | Go to Distributor Ignition (DI) System Diagnosis | |
| 5 | Monitor the Ignition 1 Signal Voltage parameter with a scan tool. Is the Ignition 1 Signal Voltage parameter at the specified value? | B+ | Go to Step 6 | Go to Step 11 |
| 6 | Command the fuel pump ON with a scan tool. Does the fuel pump turn ON? | Go to Step 7 | Go to Fuel Pump Electrical Circuit Diagnosis | |
| 7 | Turn OFF the ignition. Disconnect a spark plug wire. Install the J 26792 Spark Tester to the spark plug wire. Attempt to start the engine. Does the spark tester spark? | Go to Step 8 | Go to Distributor Ignition (DI) System Diagnosis | |
| 8 | Turn OFF the ignition. Install the J 34730-1A Fuel Pressure Gage. Refer to Fuel System Diagnosis . Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Is the fuel pressure within the specified range while the fuel pump is operating? | 379-427 kPa (55-62 psi) | Go to Step 9 | Go to Fuel System Diagnosis |
| 9 | Inspect for the following conditions: A collapsed air intake duct A restricted air filter element - Refer to Air Cleaner Element Replacement . The spark plugs for being gas or coolant fouled - Refer to Spark Plug Inspection . If the spark plugs are fouled, determine what caused the condition. Any engine mechanical condition, such as a worn timing chain, gears and low compression - Refer to Symptoms - Engine Mechanical in Engine Mechanical 4.3 L. A restricted exhaust system - Refer to Restricted Exhaust in Engine Exhaust. The engine coolant temperature (ECT) sensor is NOT close to the actual engine temperature. Refer to DTC P0125 . Compare manifold absolute pressure/barometric pressure (MAP/BARO) parameters to another vehicle. The parameters should be close in value. Refer to DTC P0106 . The throttle position (TP) sensor for being stuck in range - Refer to DTC P0121 . Did you complete the action? | Go to Step 13 | ||
| 10 | Test the ignition 1 signal voltage circuit for an open or for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Replace the fuse if necessary. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 | |
| 11 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 12 | |
| 12 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 14 | ||
| 13 | Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Attempt to start the engine. Does the engine start and continue to run? | Go to Step 14 | Go to Step 2 | |
| 14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List | System OK | |
Engine Cranks but Does Not Run
The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within two seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls |
| 2 | Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON and OFF with a scan tool. Repeat the commands as necessary. Does the fuel pump turn ON and OFF? | Go to Intermittent Conditions | Go to Step 3 |
| 3 | Command the fuel pump relay ON and OFF with a scan tool. Do you hear the fuel pump relay click when you command the fuel pump relay ON and OFF? | Go to Step 9 | Go to Step 4 |
| 4 | Turn OFF the ignition. Remove the fuel pump relay. Turn ON the ignition, with the engine OFF. Probe the control circuit of the fuel pump relay with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems. Command the fuel pump relay ON and OFF with a scan tool. Does the test lamp turn ON and OFF? | Go to Step 5 | Go to Step 6 |
| 5 | Connect a test lamp between the control circuit of the fuel pump relay and the ground circuit of the fuel pump relay. Command the fuel pump relay ON and OFF with a scan tool. Does the test lamp turn ON and OFF? | Go to Step 19 | Go to Step 22 |
| 6 | Does the test lamp remain illuminated with each command? | Go to Step 7 | Go to Step 8 |
| 7 | Test the control circuit of the fuel pump relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 26 |
| 8 | Test the control circuit of the fuel pump relay for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 20 |
| 9 | Turn ON the ignition, with the engine OFF. Does the fuel pump operate continuously? | Go to Step 10 | Go to Step 11 |
| 10 | Turn OFF the ignition. Remove the fuel pump relay. Turn ON the ignition, with the engine OFF. Does the fuel pump operate continuously? | Go to Step 21 | Go to Step 25 |
| 11 | Inspect the fuel pump fuse. Is the fuel pump fuse open? | Go to Step 12 | Go to Step 14 |
| 12 | Test the supply voltage circuit of the fuel pump for a short to ground between the fuel pump fuse and the fuel pump. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Replace the fuel pump fuse if necessary. Did you find and correct the condition? | Go to Step 27 | Go to Step 13 |
| 13 | Connect all disconnected electrical components. Install a new fuel pump fuse. Command the fuel pump relay ON with a scan tool. Inspect the fuel pump fuse. Is the fuel pump fuse open? | Go to Step 24 | Go to Intermittent Conditions |
| 14 | Turn OFF the ignition. Remove the fuel pump relay. Turn ON the ignition, with the engine OFF. Probe the ignition 1 voltage circuit of the fuel pump relay, switch side, with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate? | Go to Step 15 | Go to Step 23 |
| 15 | Connect a 20-amp fused jumper wire between the ignition 1 voltage circuit of the fuel pump relay and the supply voltage circuit of the fuel pump. Does the fuel pump operate? | Go to Step 19 | Go to Step 16 |
| 16 | Test the supply voltage circuit of the fuel pump for an open or high resistance between the fuel pump relay and the fuel pump. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 17 |
| 17 | IMPORTANT: Inspect the ground circuit for correct tightening, corrosion on the terminals, or damage to the wiring harness. Test the ground circuit of the fuel pump for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition? | Go to Step 27 | Go to Step 18 |
| 18 | Test for an intermittent and for a poor connection at the fuel sender cover. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 24 |
| 19 | Test for an intermittent and for a poor connection at the fuel pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 25 |
| 20 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 26 |
| 21 | Repair the short to voltage in the supply voltage circuit of the fuel pump. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 27 | |
| 22 | Repair the open or high resistance in the ground circuit of the fuel pump relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 27 | |
| 23 | Repair the open in the ignition 1 voltage circuit of the fuel pump relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 27 | |
| 24 | IMPORTANT: Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump. Replace the fuel sender. Refer to Fuel Sender Assembly Replacement . Replace the fuel pump fuse if necessary. Did you complete the replacement? | Go to Step 27 | |
| 25 | Replace the fuel pump relay. Did you complete the replacement? | Go to Step 27 | |
| 26 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 27 | |
| 27 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
| IMPORTANT |
|---|
| Inspect the ground circuit for correct tightening, corrosion on the terminals, or damage to the wiring harness. |
| IMPORTANT |
|---|
| Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump. |
Fuel Pump Electrical Circuit Diagnosis
System Description
The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within two seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within two seconds if ignition reference pulses cease to be detected and the ignition remains ON.
The fuel tank stores the fuel supply. The electric fuel pump supplies fuel through an in-line fuel filter to the fuel injection system. The pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pressure regulator maintains the correct fuel pressure to the fuel injection system. A separate pipe returns unused fuel to the fuel tank.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | IMPORTANT: Inspect the fuel system for damage or external leaks before proceeding with this diagnostic. Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON with a scan tool. Does the fuel pump operate? | Go to Step 3 | Go to Fuel Pump Electrical Circuit Diagnosis | |
| 3 | IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. IMPORTANT: The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. Command the fuel pump relay ON with a scan tool. Observe the fuel pressure gage with the fuel pump commanded ON. Is the fuel pressure within the specified range? | 379-427 kPa (55-62 psi) | Go to Step 4 | Go to Step 10 |
| 4 | IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gage for 1 minute.Does the fuel pressure decrease by more than the specified value? | 34 kPa (5 psi) | Go to Step 8 | Go to Step 5 |
| 5 | Relieve the fuel pressure to the first specified value. Monitor the fuel pressure gage for 5 minutes. Does the fuel pressure decrease by more than the second specified value? | 69 kPa (10 psi) 14 kPa (2 psi) | Go to Step 22 | Go to Step 6 |
| 6 | Turn ON the ignition, with the engine OFF. Monitor the fuel pressure gage. Start the engine. Does the fuel pressure decrease by the specified value when the engine is started? | 21-69 kPa (3-10 psi) | Go to Step 7 | Go to Step 21 |
| 7 | Operate the vehicle within the conditions of the customer's concern. Monitor the fuel related parameters with a scan tool. Do any of the scan tool parameters indicate a lean condition? | Go to Step 15 | Go to Symptoms - Engine Controls | |
| 8 | Turn OFF the ignition. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure . Remove the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement (Passenger/Cargo Van) or Evaporative Emission (EVAP) Canister Replacement (Cutaway Van) . Disconnect the rear fuel feed pipe and the rear fuel return pipe from the chassis fuel pipes. Refer to Quick Connect Fitting(s) Service (Plastic Collar) . Drain any remaining fuel into an approved gasoline container. Install the J 37287 fuel line shut-off adapters between the rear fuel pipes and the chassis fuel pipes. Open the valves on the fuel pipe shut-off adapters. Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON with a scan tool. Bleed the air from the fuel pressure gage. Command the fuel pump relay ON and then OFF with a scan tool. Close the fuel feed pipe shut-off valve. Monitor the fuel pressure gage for 1 minute. Does the fuel pressure remain constant? | Go to Step 17 | Go to Step 9 | |
| 9 | Turn OFF the ignition. Open the fuel feed pipe shut-off valve. Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON and then OFF with a scan tool. Close the fuel return pipe shut-off valve. Monitor the fuel pressure gage for 1 minute. Does the fuel pressure remain constant? | Go to Step 21 | Go to Step 18 | |
| 10 | Is the fuel pressure more than the specified value? | 427 kPa (62 psi) | Go to Step 12 | Go to Step 11 |
| 11 | Is the fuel pressure more than the specified value? | 0 kPa (0 psi) | Go to Step 14 | Go to Step 15 |
| 12 | Turn OFF the ignition. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure . Remove the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement (Passenger/Cargo Van) or Evaporative Emission (EVAP) Canister Replacement (Cutaway Van) . Disconnect the rear fuel return pipe from the chassis pipe. Refer to Quick Connect Fitting(s) Service (Plastic Collar) . Attach a length of flexible hose to the chassis fuel pipe. Place the open end of the flexible fuel hose into an approved gasoline container. Turn ON the ignition, with the engine OFF. Monitor the fuel pressure gage while the fuel pump is operating. Is the fuel pressure within the specified range? | 379-427 kPa (55-62 psi) | Go to Step 20 | Go to Step 13 |
| 13 | Inspect the engine fuel return pipe and the chassis fuel return pipe for a restriction. Did you find and correct the condition? | Go to Step 23 | Go to Step 21 | |
| 14 | Turn OFF the ignition. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure . Remove the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement (Passenger/Cargo Van) or Evaporative Emission (EVAP) Canister Replacement (Cutaway Van) . Disconnect the rear fuel return pipe from the chassis pipe. Refer to Quick Connect Fitting(s) Service (Plastic Collar) . Install the J 37287 between the rear fuel return pipe and the chassis fuel pipe. Open the valve in the fuel pipe shut-off adapter. Turn ON the ignition, with the engine OFF. Bleed the air from the fuel pressure gage. Monitor the fuel pressure gage. NOTE: DO NOT allow the fuel pressure to exceed 517 kPa (75 psi). Excessive pressure may damage the fuel system. Command the fuel pump relay ON with a scan tool. Slowly close the valve in the fuel return pipe shut-off adapter, while the fuel pump is operating. Does the fuel pressure increase to more than the specified value? | 427 kPa (62 psi) | Go to Step 21 | Go to Step 15 |
| 15 | Inspect the following components for a restriction: The fuel filter The fuel feed pipe Did you find and correct the condition? | Go to Step 23 | Go to Step 16 | |
| 16 | Inspect the harness connectors and the ground circuits of the fuel pump for poor connections. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 23 | Go to Step 17 | |
| 17 | Remove the fuel sender assembly. Refer to Fuel Sender Assembly Replacement . Inspect the following items: The fuel pump flex hose for damage The in-tank fuel pump harness connectors for poor connections The fuel strainer for a restriction The fuel tank for contaminants Did you find and correct the condition? | Go to Step 23 | Go to Step 22 | |
| 18 | Open the fuel return pipe shut-off valve. Remove the upper intake manifold. Refer to Intake Manifold Replacement - Upper in Engine Mechanical-4.3L. Install the engine compartment fuel feed and fuel return pipes to the fuel meter body. Turn ON the ignition, with the engine OFF. Inspect for a fuel leak from the fuel pressure regulator. Is the fuel pressure regulator leaking fuel? | Go to Step 21 | Go to Step 19 | |
| 19 | Remove the fuel injectors from the intake manifold in order to isolate the leaking fuel injector. Refer to Fuel Injector Replacement . Did you complete the replacement? | Go to Step 23 | ||
| 20 | Repair the restricted fuel return pipe between the chassis fuel pipe and the fuel tank. Did you complete the repair? | Go to Step 23 | ||
| 21 | IMPORTANT: Inspect for a missing or damaged O-ring seal before replacing the fuel pressure regulator. Replace the fuel pressure regulator. Refer to Fuel Pressure Regulator Replacement .Did you complete the replacement? | Go to Step 23 | ||
| 22 | Replace the fuel sender. Refer to Fuel Sender Assembly Replacement . Did you complete the replacement? | Go to Step 23 | ||
| 23 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
| IMPORTANT |
|---|
| Inspect the fuel system for damage or external leaks before proceeding with this diagnostic. |
| IMPORTANT |
|---|
| Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. |
| IMPORTANT |
|---|
| The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. |
| IMPORTANT |
|---|
| The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. |
| NOTE |
|---|
| DO NOT allow the fuel pressure to exceed 517 kPa (75 psi). Excessive pressure may damage the fuel system. |
| IMPORTANT |
|---|
| Inspect for a missing or damaged O-ring seal before replacing the fuel pressure regulator. |
Fuel System Diagnosis
The control module enables the appropriate fuel injector pulse for each cylinder. Ignition voltage is supplied directly to the fuel injectors. The control module controls each fuel injector by grounding the control circuit via a solid state device called a driver. A fuel injector coil winding resistance that is too high or too low will affect engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.
- Monitoring the misfire current counters, or misfire graph, may help to isolate the fuel injector that is causing the condition.
- Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.
- Perform the fuel injector coil test within the conditions of the customer's concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Observe the ECT Sensor parameter with a scan tool. Is the ECT Sensor parameter within the specified range? | 10-32°C (50-90°F) | Go to Step 3 | Go to Step 4 |
| 3 | Remove the engine cover. Refer to Engine Cover Replacement in Interior Trim. Disconnect the multi-way harness connector of the fuel injectors. Measure the resistance of each fuel injector between the ignition 1 circuit and the fuel injector control circuit, at the multi-way connector with a DMM. Refer to Testing for Continuity in Wiring Systems. Is the resistance within the specified range for each injector? | 11-14 ohm | Go to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 | Go to Step 6 |
| 4 | Remove the engine cover. Refer to Engine Cover Replacement in Interior Trim. Disconnect the multi-way harness connector of the fuel injectors. Measure the resistance of each fuel injector between the ignition 1 voltage circuit and the fuel injector control circuit, at the multi-way connector with a DMM. Refer to Testing for Continuity in Wiring Systems. Record each fuel injector resistance value. Subtract the lowest resistance value from the highest resistance value. Is the difference equal to, or less than, the specified value? | 3 ohm | Go to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 | Go to Step 5 |
| 5 | Add all of the fuel injector resistance values to obtain a total resistance value. Divide the total resistance value by the number of fuel injectors to obtain an average resistance value. Subtract the lowest individual fuel injector resistance value from the average resistance value. Compute the difference between the highest individual fuel injector resistance value and the average resistance value. Replace the fuel injector that displays the greatest resistance difference above or below the average. Refer to Fuel Injector Replacement . Did you complete the replacement? | Go to Step 7 | ||
| 6 | Replace the fuel injector or fuel injectors with resistance that is out of the specified range. Refer to Fuel Injector Replacement . Did you complete the replacement? | 11-14 ohm | Go to Step 7 | |
| 7 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 | |
Fuel Injector Coil Test
The scan tool is first used to energize the fuel pump relay. The fuel injector tester is then used to pulse each injector for a precise amount of time, allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.
| Cylinder | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| 1st Reading | 393 kPa (57 psi) | 393 kPa (57 psi) | 393 kPa (57 psi) | 393 kPa (57 psi) |
| 2nd Reading | 310 kPa (45 psi) | 296 kPa (43 psi) | 303 kPa (44 psi) | 324 kPa (47 psi) |
| Amount of Drop | 83 kPa (12 psi) | 97 kPa (14 psi) | 90 kPa (13 psi) | 69 kPa (10 psi) |
| Average Range: 75-95 kPa (10.9-13.8 psi) | Injector OK | Replace fuel injector - too much fuel pressure drop | Injector OK | Replace fuel injector - too little fuel pressure drop |
Fuel Injector Balance Test Example (Typical)
The number below refers to the step number on the diagnostic table.
- 3: The engine coolant temperature (ECT) must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Did you perform the Fuel Injector Coil Test? | Go to Step 3 | Go to Fuel Injector Coil Test | |
| 3 | IMPORTANT: DO NOT perform this test if the engine coolant temperature (ECT) is above 94°C (201°F). Observe the ECT Sensor parameter with a scan tool.Is the ECT Sensor parameter less than the specified value? | 94°C (201°F) | Go to Step 4 | |
| 4 | IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. IMPORTANT: The fuel pump relay may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure. DO NOT start the engine. Command the fuel pump relay ON with a scan tool. Observe the fuel pressure gage, with the fuel pump operating. Is the fuel pressure within the specified range? | 379-427 kPa (55-62 psi) | Go to Step 5 | Go to Fuel System Diagnosis |
| 5 | IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gage for 1 minute.Does the fuel pressure decrease by more than the specified value? | 34 kPa (5 psi) | Go to Fuel System Diagnosis | Go to Step 6 |
| 6 | NOTE: Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding. Disconnect the multi-way harness connector of the fuel injectors. Connect the J 39021 Fuel Injector Tester, J 39021 - 210 Injector Selector Switch Box, and the J 39021-301 Injector Test Adapter to the fuel meter body. Set the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 amp position. Command the fuel pump relay ON and then OFF with a scan tool. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the first pressure reading. IMPORTANT: The fuel pressure may rise after the fuel injector stops pulsing. Record the fuel pressure value immediately after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value. Energize the fuel injector by depressing the Push to Start Test button on the fuel injector tester. Record the fuel pressure indicated by the fuel pressure gage after the fuel injector has stopped pulsing. This is the second pressure reading. Repeat steps 4 through 7 for each fuel injector. Subtract the second pressure reading from the first pressure reading for one fuel injector. The result is the pressure drop value. Obtain a pressure drop value for each fuel injector. Add all of the individual pressure drop values. This is the total pressure drop. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop. Is the difference between any individual pressure drop and the average pressure drop more than the specified value? | 10 kPa (1.5 psi) | Go to Step 7 | Go to Symptoms - Engine Controls |
| 7 | Perform the Fuel Injector Cleaning Procedure . Did you complete the procedure? | Go to Step 8 | ||
| 8 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Symptoms - Engine Controls |
| IMPORTANT |
|---|
| DO NOT perform this test if the engine coolant temperature (ECT) is above 94°C (201°F). |
| IMPORTANT |
|---|
| Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. |
| IMPORTANT |
|---|
| The fuel pump relay may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure. DO NOT start the engine. |
| IMPORTANT |
|---|
| The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. |
| NOTE |
|---|
| Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding. |
| IMPORTANT |
|---|
| The fuel pressure may rise after the fuel injector stops pulsing. Record the fuel pressure value immediately after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value. |
Fuel Injector Balance Test with Special Tool
The scan tool is first used to energize the fuel pump relay. The scan tool is then used to pulse each injector for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.
| Cylinder | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| 1st Reading | 393 kPa (57 psi) | 393 kPa (57 psi) | 393 kPa (57 psi) | 393 kPa (57 psi) |
| 2nd Reading | 310 kPa (45 psi) | 296 kPa (43 psi) | 303 kPa (44 psi) | 324 kPa (47 psi) |
| Amount of Drop | 83 kPa (12 psi) | 97 kPa (14 psi) | 90 kPa (13 psi) | 69 kPa (10 psi) |
| Average Range: 75-95 kPa (10.9-13.8 psi) | Injector OK | Replace fuel injector - too much fuel pressure drop | Injector OK | Replace fuel injector - too little fuel pressure drop |
Fuel Injector Balance Test Example (Typical)
The number below refers to the step number on the diagnostic table.
- 3: The engine coolant temperature (ECT) must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Did you perform the Fuel Injector Coil Test? | Go to Step 3 | Go to Fuel Injector Coil Test | |
| 3 | IMPORTANT: DO NOT perform this test if the engine coolant temperature (ECT) is above 94°C (201°F). Observe the ECT Sensor parameter with a scan tool.Is the ECT Sensor parameter less than the specified value? | 94°C (201°F) | Go to Step 4 | |
| 4 | IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. IMPORTANT: The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. Command the fuel pump relay ON with a scan tool. Observe the fuel pressure gage, with the fuel pump operating. Is the fuel pressure within the specified value? | 379-427 kPa (55-62 psi) | Go to Step 5 | Go to Fuel System Diagnosis |
| 5 | IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gage for 1 minute.Does the fuel pressure decrease by more than the specified value? | 34 kPa (5 psi) | Go to Fuel System Diagnosis | Go to Step 6 |
| 6 | With a scan tool, select the Fuel Injector Balance Test function, within the Special Functions menu. Select an injector to be tested. Press Enter. This will prime the fuel system. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the 1st pressure reading. IMPORTANT: Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value. Energize the fuel injector by depressing the Pulse Injector button on the scan tool. This will energize the injector and decrease the fuel pressure. Record the fuel pressure indicated by the fuel pressure gage after the fuel injector has stopped pulsing. This is the 2nd pressure reading. Press Enter again to bring you back to the Select Injector screen. Repeat for each fuel injector. Subtract the 2nd pressure reading from the 1st pressure reading for one fuel injector. The result is the pressure drop value. Obtain a pressure drop value for each fuel injector. Add all of the individual pressure drop values. This is the total pressure drop. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop. Is the difference between any individual pressure drop and the average pressure drop more than the specified value? | 10 kPa (1.5 psi) | Go to Step 7 | Go to Symptoms - Engine Controls |
| 7 | Perform the Fuel Injector Cleaning Procedure . Did you complete the procedure? | Go to Step 8 | ||
| 8 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Symptoms - Engine Controls |
| IMPORTANT |
|---|
| DO NOT perform this test if the engine coolant temperature (ECT) is above 94°C (201°F). |
| IMPORTANT |
|---|
| Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. |
| IMPORTANT |
|---|
| The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. |
| IMPORTANT |
|---|
| The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. |
| IMPORTANT |
|---|
| Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value. |
Fuel Injector Balance Test with Tech 2
The fuel tank leak test is used to locate any fuel or fuel vapor escaping the fuel tank area. Fuel vapors escaping above the fuel level will be detected, if more than the calibrated amount, when the evaporative emission (EVAP) diagnostics complete one test cycle. The malfunction indicator lamp (MIL) will illuminate after the EVAP diagnostics have failed 2 test cycles.
- Operate the vehicle under the condition of the customer concern. Under high temperature conditions fuel vapors may increase to the point of EVAP canister vapor saturation. Fuel vapors would then be released into the atmosphere. Once the engine is running and EVAP purge is enabled, all fuel vapor release would be eliminated.
- Movement of the EVAP pipes or the fuel pipes may help find an intermittent condition.
- If the fuel level is low, a liquid fuel leak may not be evident.
The numbers below refer to the step numbers on the diagnostic table.
- 4: This step tests for fuel leaks below the fuel tank fuel level.
- 5: This step tests for fuel vapors escaping above the fuel level in the fuel tank.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check - Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls |
| 2 | CAUTION: Gasoline or gasoline vapors are highly flammable. A fire could occur if an ignition source is present. Never drain or store gasoline or diesel fuel in an open container, due to the possibility of fire or explosion. Have a dry chemical (Class B) fire extinguisher nearby. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information. Inspect the fuel tank and the fuel pipes for damage or external leaks. Did you find fuel leaking from the fuel tank? | Go to Step 6 | Go to Step 3 |
| 3 | Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON with a scan tool. Inspect for fuel leaking from the fuel pipes. Did fuel leak from the fuel pipes? | Go to Step 7 | Go to Step 4 |
| 4 | Turn OFF the ignition. Install the J 41413-200 Evaporative Emissions System Tester (EEST) and the J 41415-40 Fuel Tank Cap Adapter or the GE-41415-50 Interrupted Thread Fuel Tank Cap Adapter. IMPORTANT: If the floating indicator registers any flow after stabilizing, a leak is evident. Test for a fuel tank leak referring to the J 41413-210 Operation Manual. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information. Inspect for a fuel leak while the system is under pressure. Did fuel leak from the fuel tank? | Go to Step 6 | Go to Step 5 |
| 5 | Using the J 41413-200 and the J 41413-210, introduce smoke into the evaporative emission (EVAP) system. IMPORTANT: It may be necessary to partially lower the fuel tank. Refer to Fuel Tank Replacement (Cutaway Van Side Tank) or Fuel Tank Replacement (Passenger/Cargo Van) or Fuel Tank Replacement (Cutaway Van Rear Tank) . Inspect for leaks in any of the following locations: The fuel tank, fill limiter vent valve, pressure relief valve and the grade vent valves-Refer to Fuel Tank Replacement (Cutaway Van Side Tank) or Fuel Tank Replacement (Passenger/Cargo Van) or Fuel Tank Replacement (Cutaway Van Rear Tank) . The fuel sender housing and fuel sender seal-Refer to Fuel Sender Assembly Replacement . The fuel tank pressure (FTP) sensor seal-Refer to Fuel Tank Pressure Sensor Replacement . The EVAP pipes-Refer to Evaporative Emission (EVAP) Hoses/Pipes Replacement - Chassis/Canister . The fuel fill pipe and hose-Refer to Filler Tube Replacement (w/LH Door) or Filler Tube Replacement (w/o LH Door) or Filler Tube Replacement (w/Rear Tank) . Did you find and correct the condition? | Go to Step 8 | Go to Diagnostic Aids |
| 6 | Replace the fuel tank. Refer to Fuel Tank Replacement (Cutaway Van Side Tank) or Fuel Tank Replacement (Passenger/Cargo Van) or Fuel Tank Replacement (Cutaway Van Rear Tank) . Did you complete the repair? | Go to Step 8 | |
| 7 | Replace the leaking fuel pipe. Refer to Fuel Hoses/Pipes Replacement - Filter to Tank (Rear Tank) or Fuel Hoses/Pipes Replacement - Filter to Tank (Side Tank) or Fuel Hose/Pipes Assembly Replacement (Passenger/Cargo Van Fuel Tank Pipes) or Fuel Hose/Pipes Assembly Replacement (Cutaway Van Rear Tank Fuel Tank Pipe) . Did you complete the replacement? | Go to Step 8 | |
| 8 | Operate the system under the condition of the customer concern in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
| CAUTION |
|---|
| Gasoline or gasoline vapors are highly flammable. A fire could occur if an ignition source is present. Never drain or store gasoline or diesel fuel in an open container, due to the possibility of fire or explosion. Have a dry chemical (Class B) fire extinguisher nearby. |
| IMPORTANT |
|---|
| If the floating indicator registers any flow after stabilizing, a leak is evident. |
| IMPORTANT |
|---|
| It may be necessary to partially lower the fuel tank. Refer to Fuel Tank Replacement (Cutaway Van Side Tank) or Fuel Tank Replacement (Passenger/Cargo Van) or Fuel Tank Replacement (Cutaway Van Rear Tank) . |
Fuel Tank Leak Test
Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no start, or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel injection system and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the fuel system components for rust or deterioration.
Ethanol concentrations of greater than 10 percent can cause driveability conditions and fuel system deterioration. Fuel with more than 10 percent ethanol could result in driveability conditions such as hesitation, lack of power, stalling, or no start. Excessive concentrations of ethanol used in vehicles not designed for it may cause fuel system corrosion, deterioration of rubber components, and fuel filter restriction.
Alcohol in Fuel Testing Procedure
The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be detected. The sample should be bright and clear. If alcohol contamination is suspected then use the following procedure to test the fuel quality.
- Using a 100 ml (3.38 oz) specified cylinder with 1 ml (0.034 oz) graduation marks, fill the cylinder with fuel to the 90 ml (3.04 oz) mark.
- Add 10 ml (0.34 oz) of water in order to bring the total fluid volume to 100 ml (3.38 oz) and install a stopper.
- Shake the cylinder vigorously for 10-15 seconds.
- Carefully loosen the stopper in order to release the pressure.
- Re-install the stopper and shake the cylinder vigorously again for 10-15 seconds.
- Put the cylinder on a level surface for approximately 5 minutes in order to allow adequate liquid separation.
If alcohol is present in the fuel, the volume of the lower layer, which would now contain both alcohol and water, will be more than 10 ml (0.34 oz). For example, if the volume of the lower layer is increased to 15 ml (0.51 oz), this indicates at least 5 percent alcohol in the fuel. The actual amount of alcohol may be somewhat more because this procedure does not extract all of the alcohol from the fuel.
Particulate Contaminants in Fuel Testing Procedure
The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be detected. The sample should be bright and clear. If the sample appears cloudy, or contaminated with water, as indicated by a water layer at the bottom of the sample, use the following procedure to diagnose the fuel.
- Using an approved fuel container, draw approximately 0.5 liter (0.53 qt) of fuel.
- Place the container on a level surface for approximately 5 minutes in order to allow settling of the particulate contamination. Particulate contamination will show up in various shapes and colors. Sand will typically be identified by a white or light brown crystals. Rubber will appear as black and irregular particles.
- Observe the fuel sample. If any physical contaminants or water are present, clean the fuel system. Refer to «Fuel System Cleaning»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-introduction__fuel-system-cleaning) .
Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no start, or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel injection system, and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the fuel system components for rust or deterioration.
Ethanol concentrations of greater than 10 percent can cause driveability conditions and fuel system deterioration. Fuel with more than 10 percent ethanol could result in driveability conditions such as hesitation, lack of power, stalling, or no start. Excessive concentrations of ethanol used in vehicles not designed for it may cause fuel system corrosion, deterioration of rubber components, and fuel filter restriction.
Test Procedure
- Test the fuel composition using J 44175 Fuel Composition Tester and J44175-3 Instruction Manual.
- If water appears in the fuel sample, perform the following steps: Clean the fuel system. Refer to «Fuel System Cleaning»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-introduction__fuel-system-cleaning) . Replace the fuel filter. Refer to «Fuel Filter Replacement (Passenger/Cargo Van)»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-introduction) or «Fuel Filter Replacement (Cutaway Van)»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-introduction) .
- Subtract 50 from the reading on the DMM in order to obtain the percentage of alcohol in the fuel sample. Refer to the examples in the Fuel Composition Test Examples table.
- If the fuel sample contains more than 15 percent ethanol, add fresh, regular gasoline to the vehicle's fuel tank.
- Test the fuel composition.
- If testing shows the ethanol percentage is still more than 15 percent, replace the fuel in the vehicle. Refer to «Fuel System Cleaning»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-introduction__fuel-system-cleaning) .
| Frequency (Hz) | Subtract 50 | Ethanol Percent | |
|---|---|---|---|
| Example A | 50 Hz | 50 | 0 |
| Example B | 65 Hz | 50 | 15 |
| Example C | 129 Hz | 50 | 79 |
Fuel Composition Test Examples
The engine idle speed is controlled by the idle air control (IAC) valve. The IAC valve is on the throttle body. The IAC valve pintle moves in and out of an idle air passage bore to control air flow around the throttle plate. The IAC valve consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. The stepper motor is capable of highly accurate rotation, or of movement, called steps. The stepper motor has 2 separate windings that are called coils. Each coil is supplied current by 2 circuits from the powertrain control module (PCM). When the PCM changes polarity of a coil, the stepper motor moves one step. The PCM uses a predetermined number of counts to determine the IAC pintle position. Observe IAC counts with a scan tool. The IAC counts will increment up or down as the PCM attempts to change the IAC valve pintle position. An IAC Reset will occur when the ignition key is turned OFF. First, the PCM will seat the IAC pintle in the idle air passage bore. Second, the PCM will retract the pintle a predetermined number of counts to allow for efficient engine start-up. If the engine idle speed is out of range for a calibrated period of time, an idle speed diagnostic trouble code (DTC) sets.
Inspect for the following conditions
- High resistance in an IAC valve control circuit
- The correct positive crankcase ventilation (PCV) valve, properly installed and proper operation of the PCV valve
- Proper operation and installation of all air intake components
- Proper installation and operation of the mass air flow (MAF) sensor, if equipped
- A tampered with or damaged throttle stop screw
- A tampered with or damaged throttle plate, throttle shaft, throttle linkage, or cruise control linkage, if equipped
- A skewed high throttle position (TP) sensor
- Excessive deposits in the IAC passage or on the IAC pintle
- Excessive deposits in the throttle bore or on the throttle plate
- Vacuum leaks
- A high or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve. Refer to «Symptoms - Engine Controls»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting) .
- If the problem is determined to be intermittent, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g3500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .
The numbers below refer to the step numbers on the diagnostic table.
- 5: This test will determine the ability of the PCM and IAC valve control circuits to control the IAC valve.
- 7: This test will determine the ability of the PCM to provide the IAC control valve circuits with a ground. On a normally operating system, the test lamp should not flash while the IAC Counts are incrementing.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls |
| 2 | IMPORTANT: Ensure that the Engine Speed parameter stabilizes with each Commanded RPM change to determine if the engine speed stays within 100 RPM less than the Commanded RPM or within 200 RPM more than the Commanded RPM. Set the parking brake and block the drive wheels. Start the engine. Turn OFF all accessories. Slowly increment the engine speed to 1,700 RPM, then to 600 RPM, then to 1,700 RPM with the scan tool RPM Control function. Exit the RPM Control function. Did the Engine Speed parameter stabilize within 100 RPM less than the commanded engine speed or within 200 RPM above the Commanded RPM? | Go to Diagnostic Aids | Go to Step 3 |
| 3 | Turn OFF the ignition. Disconnect the IAC valve. Connect an J 37027-1A IAC Motor Driver to the IAC valve. Start the engine. Command the IAC valve in until 600 RPM is reached with the J 37027-1A . Command the IAC valve out until 1,700 RPM is reached with the J 37027-1A . Return the engine speed to the Desired Idle Speed parameter. Did the Engine Speed parameter steadily decrease to 600 RPM and steadily increase to 1,700 RPM when the IAC valve was commanded in and out? | Go to Step 5 | Go to Step 4 |
| 4 | Did you observe an excessively high idle condition that could not be controlled with the IAC motor driver? | Go to Step 11 | Go to Step 12 |
| 5 | Connect a test lamp between one of the IAC valve control circuits and a good ground. Start the engine. Observe the IAC Counts parameter with a scan tool. Command high RPM with the J 37027-1A until the IAC Counts parameter starts to increment. Command low RPM with the J 37027-1A until the IAC Counts parameter starts to increment. Return the Engine Speed to the Desired Idle Speed parameter. Repeat the above procedure for the other three IAC valve control circuits. Did the test lamp remain ON, never flashing, while the IAC Counts were incrementing for any of the IAC valve control circuits? | Go to Step 10 | Go to Step 6 |
| 6 | Did the test lamp remain OFF, never flashing, while the IAC Counts were incrementing for any of the IAC valve control circuits? | Go to Step 9 | Go to Step 7 |
| 7 | Connect a test lamp between the IAC coil A low control circuit and the IAC coil A high control circuit. Observe the IAC Counts parameter with a scan tool and the test lamp. Command high RPM with the J 37027-1A until the IAC Counts parameter starts to increment. Command low RPM with the J 37027-1A until the IAC Counts parameter starts to increment. Return the Engine Speed parameter to the Desired Idle Speed parameter. Repeat the above procedure with the test lamp connected between the IAC coil B low control circuit and the IAC coil B high control circuit. Did the test lamp stay illuminated, never flashing, while the IAC Counts were incrementing? | Go to Step 8 | Go to Step 17 |
| 8 | Test for an intermittent and for a poor connection at the IAC valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 13 |
| 9 | Turn OFF the ignition. Disconnect the PCM. Test the circuit where the test lamp remained OFF for the following conditions: An open circuit A short to ground A short to another IAC valve control circuit-Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 13 |
| 10 | Turn ON the ignition. Test the IAC valve control circuit where the test lamp remained illuminated for the following conditions: A short to voltage A short to another IAC valve control circuit- Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 13 |
| 11 | Inspect for the following: Throttle body damage and tampering Skewed TP sensor signal Throttle lever screw tampering, if equipped Vacuum leaks Faulty, incorrectly installed PCV valve and hose, if equipped Throttle shaft binding Throttle linkage or cruise control linkage binding, if equipped Remove the IAC valve. Refer to Idle Air Control (IAC) Valve Replacement . Inspect for the following conditions: Debris in the IAC passage Excessive deposits on the throttle plate Excessive deposits in the throttle bore Excessive deposits on IAC valve pintle Did you find and correct the condition? | Go to Step 18 | Go to Step 15 |
| 12 | Inspect for the following conditions: Throttle body damage and tampering Throttle lever screw tampering, if equipped Excessive deposits on the throttle plate Restricted air intake system-Inspect the following conditions: A possible collapsed or clogged air intake duct, before and after the air filter element A restricted air filter element Restriction at the throttle body intake screen, if equipped Remove the IAC valve. Refer to Idle Air Control (IAC) Valve Replacement . Inspect for excessive deposits on the IAC valve pintle and in the IAC valve passage. Did you find and correct the condition? | Go to Step 18 | Go to Step 15 |
| 13 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 14 |
| 14 | Disconnect the PCM. Test all IAC valve control circuits for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 17 |
| 15 | Test for an intermittent and for a poor connection at the IAC valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 16 |
| 16 | Replace the IAC valve. Refer to Idle Air Control (IAC) Valve Replacement . Did you complete the replacement? | Go to Step 18 | |
| 17 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 18 | |
| 18 | Reassemble the vehicle as necessary. Clear any DTCs with a scan tool. Start the engine. Operate the system to verify the repair. Did you correct the condition? | Go to Step 19 | Go to Step 2 |
| 19 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List | System OK |
| IMPORTANT |
|---|
| Ensure that the Engine Speed parameter stabilizes with each Commanded RPM change to determine if the engine speed stays within 100 RPM less than the Commanded RPM or within 200 RPM more than the Commanded RPM. |
Idle Air Control (IAC) System Diagnosis
This system includes the crankshaft position (CKP) sensor, the camshaft position (CMP) sensor, the ignition coil with the ignition control (IC) module, the secondary wires, the spark plugs, and the circuit conductors and connectors.
The powertrain control module (PCM) controls the ignition system. The PCM monitors the input signals from various engine sensors. The PCM controls the dwell of the ignition primary coil, computes the desired spark timing and firing of the ignition system via an IC timing control circuit to the ignition control module.
The Distributor Ignition (DI) System Diagnostic Table assumes the following conditions
- The battery is fully charged.
- There is adequate fuel in the fuel tank.
- The fuel delivery system is functional.
Engine mechanical conditions may prevent the distributor from rotating. Inspect the following if the distributor rotor does not rotate
- A broken distributor drive shaft
- A worn or broken distributor drive gear
- A worn or broken camshaft timing chain and gears
An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. If a repair is necessary, refer to Wiring Repairs in Wiring Systems.
The numbers below refer to the step numbers on the diagnostic table.
- 3: This step is testing for a crankshaft position sensor (CKP) signal to the PCM.
- 4: This step is testing for an internally shorted camshaft position sensor.
- 9: This step is testing for spark output at more than one spark plug wire. The J-26792 requires a minimum of 25,000 volts to operate.
- 10: This step determines if spark is being delivered to the distributor cap.
- 20: This test is testing if the PCM is providing a timing control signal to the ignition control module.
- 21: This test checks for a basic engine mechanical problem.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check - Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Test the fuse which supplies ignition 1 voltage to the ignition coil assembly and the ignition control module (ICM). Refer to Circuit Protection - Fuses in Wiring Systems. Is the fuse open? | Go to Step 32 | Go to Step 3 | |
| 3 | Observe the engine speed parameter with a scan tool. Crank the engine. Is the engine speed parameter more than the specified value? | 125 RPM | Go to Step 9 | Go to Step 4 |
| 4 | Turn OFF the ignition. Disconnect the camshaft position (CMP) sensor electrical connector. Attempt to start the engine. Does the engine start and continue to run? | Go to Step 26 | Go to Step 5 | |
| 5 | Turn ON the ignition with the engine OFF. Measure the voltage of the 12-volt reference circuit of the CMP sensor to a good ground with a DMM. Refer to Measuring Voltage in Wiring Systems. Is the voltage equal the specified value? | B+ | Go to Step 6 | Go to Step 8 |
| 6 | Turn OFF the ignition. Disconnect the crankshaft position (CKP) sensor electrical connector. Turn ON the ignition with the engine OFF Measure the voltage from the 12-volt reference circuit of the CKP sensor to a good ground with a DMM. Refer to Measuring Voltage in Wiring Systems Is the voltage equal the specified value? | B+ | Go to Step 27 | Go to Step 7 |
| 7 | Turn OFF the ignition. Test the CKP 12-volt reference circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 8 | |
| 8 | Turn OFF the ignition. Test the CMP 12-volt reference circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 30 | |
| 9 | Turn OFF the ignition. Disconnect a spark plug wire from a spark plug. Install the J 26792 Spark Tester into the spark plug wire end and attach the clamp end to a good engine ground. IMPORTANT: A few sparks then nothing is considered no spark. Observe the J 26792 . Crank the engine. If there is no spark on one wire, test a second wire. Does multiple spark events occur on both spark plug wires? | Go to Step 31 | Go to Step 10 | |
| 10 | Disconnect the ignition coil wire from the distributor cap. Install the J 26792 into the ignition coil wire end and clamp the spark tester to a good engine ground. Observe the J 26792 . Crank the engine. Does multiple spark events occur? | Go to Step 21 | Go to Step 11 | |
| 11 | Disconnect the ignition coil wire from the ignition coil. Measure the ignition coil wire resistance. Is the resistance less than the specified value? | 1,000 ohm/ft | Go to Step 12 | Go to Step 44 |
| 12 | Turn OFF the ignition. Disconnect the ignition coil electrical connector. Probe the ignition coil control circuit of the ignition coil with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Systems. Crank the engine. Does the test lamp flash while cranking the engine? | Go to Step 15 | Go to Step 13 | |
| 13 | Turn OFF the ignition. Probe the ignition coil control circuit of the ignition coil with a test lamp connected to battery voltage. Does the test lamp illuminate? | Go to Step 14 | Go to Step 16 | |
| 14 | Turn OFF the ignition. Disconnect the ignition control module electrical connector. Probe the ignition coil control circuit of the ignition coil with a test lamp connected to battery voltage. Does the test lamp illuminate? | Go to Step 40 | Go to Step 47 | |
| 15 | Turn ON the ignition with the engine OFF. Measure the voltage from the ignition 1 voltage circuit of the ignition coil to a good ground with a DMM. Is the voltage more than the specified value? | 10 V | Go to Step 29 | Go to Step 33 |
| 16 | Turn OFF the ignition. Disconnect the ignition control module electrical connector. Turn ON the ignition with the engine OFF. Probe the ignition coil control circuit of the ignition control module with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 39 | Go to Step 17 | |
| 17 | Turn OFF the ignition. Test the ignition coil control circuit between the ignition coil and the ignition module for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 18 | |
| 18 | Turn ON the ignition with the engine OFF. Measure the voltage from the ignition 1 voltage circuit of the ignition control module to a good ground with a DMM. Is the voltage more than the specified value? | 10 V | Go to Step 19 | Go to Step 34 |
| 19 | Probe the ground circuit of the ignition control module with a test lamp that is connected to battery voltage. Does the test lamp illuminate? | Go to Step 20 | Go to Step 35 | |
| 20 | Measure the voltage from the IC timing control circuit of the ignition control module to a good ground with a DMM. Observe the voltage on the DMM. Crank the engine. Is the voltage within the specified value? | 1-4 V | Go to Step 28 | Go to Step 23 |
| 21 | Remove the distributor cap. Inspect inside the distributor cap for damage or contamination. Refer to Distributor Inspection . Did you find a condition? | Go to Step 46 | Go to Step 22 | |
| 22 | Observe the distributor rotor. Crank the engine. Does the distributor rotor rotate when the engine cranks? | Go to Step 45 | Go to Diagnostic Aids | |
| 23 | Turn OFF the ignition. Disconnect the PCM electrical connectors. Test the IC timing control circuit for an open or a high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 24 | |
| 24 | Probe the IC timing control circuit of the PCM with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate? | Go to Step 37 | Go to Step 25 | |
| 25 | Turn ON the ignition with the engine OFF. Probe the IC timing control circuit of the PCM with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate? | Go to Step 38 | Go to Step 30 | |
| 26 | Test for an intermittent and for a poor connection at the CMP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 41 | |
| 27 | Test for an intermittent and for a poor connection at the CKP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 42 | |
| 28 | Test for an intermittent and for a poor connection at the ignition control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 47 | |
| 29 | Test for an intermittent and for a poor connection at the ignition coil. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 43 | |
| 30 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 48 | |
| 31 | Inspect the spark plugs for damage or contamination. Refer to Spark Plug Replacement and Spark Plug Inspection . Did you find and correct the condition? | Go to Step 50 | Go to Intermittent Conditions | |
| 32 | Repair the short to ground in the ignition 1 voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 49 | ||
| 33 | Repair the open or the high resistance in the ignition 1 voltage circuit between the underhood fuse block and the ignition coil. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 34 | Repair the open or the high resistance in the ignition 1 voltage circuit between the underhood fuse block and the ignition control module. Did you complete the repair? | Go to Step 50 | ||
| 35 | Repair the open or the high resistance in the ground circuit of the ignition control module. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 36 | Repair the open or the high resistance in the IC timing control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 37 | Repair the short to ground in the IC timing control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 38 | Repair the short to voltage in the IC timing control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 39 | Repair the short to voltage in the ignition coil control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 40 | Repair the short to ground in the ignition coil control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 41 | Replace the CMP sensor. Refer to Camshaft Position (CMP) Sensor Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 42 | Replace the CKP sensor. Refer to Crankshaft Position (CKP) Sensor Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 43 | Replace the ignition coil. Refer to Ignition Coil(s) Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 44 | Replace the ignition coil wire. Refer to Spark Plug Wire Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 45 | Replace the distributor rotor. Refer to Distributor Overhaul . Did you complete the replacement? | Go to Step 50 | ||
| 46 | Replace the distributor cap. Refer to Distributor Overhaul . Did you complete the replacement? | Go to Step 50 | ||
| 47 | Replace the ignition control module. Refer to Ignition Control Module Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 48 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 49 | Replace the fuse. Did you complete the replacement? | Go to Step 50 | ||
| 50 | Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle for 5 minutes. Does the vehicle operate normally with no malfunction indicator lamp (MIL) illumination and no stored DTCs? | System OK | Go to Diagnostic Trouble Code (DTC) List | |
| IMPORTANT |
|---|
| A few sparks then nothing is considered no spark. |
Distributor Ignition (DI) System Diagnosis
Several states require that a vehicle pass on-board diagnostic (OBD) system tests and the I/M emission inspection in order to renew license plates. This is accomplished by viewing the I/M System Status display on a scan tool. Using a scan tool, the technician can observe the I/M System Status in order to verify that the vehicle meets the criteria that comply with the local area requirements.
Conditions for Updating the I/M System Status
Each system monitor requires at least one, and sometimes several diagnostic tests. The result of each test is 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 when any one of the DTCs comprising the monitor has illuminated the malfunction indicator lamp (MIL). Once the system monitor is complete, the I/M System Status display will indicate YES in the Completed column.
For example, when the HO2S Heater Status indicates YES, either all of the oxygen sensor heater tests have passed or one of the tests has illuminated the MIL. If the vehicle has four heated oxygen sensors, either all four heater circuit tests have passed or one of the heater circuit tests has illuminated the MIL. 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.
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
- The air conditioning system
- The catalytic converter efficiency
- Comprehensive component monitoring-Emission related inputs and outputs
- The evaporative emissions (EVAP) system
- The EGR System
- The fuel delivery system
- Heated catalyst monitoring
- Misfire monitoring
- The oxygen sensor system (O2S or HO2S)
- The oxygen sensor heater system (HO2S heater)
- The AIR system
For the specific DTCs required for each system, refer to Inspection/Maintenance (I/M) System DTC Table . Systems such as fuel delivery, misfire, and comprehensive components may not be listed in a system status list. These tests run continuously and do not require an I/M System Status indicator.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Perform Diagnostic System Check - Engine Controls . IMPORTANT: Many DTC related repairs will instruct the technician to clear the DTC information. This procedure will reset ALL of the I/M System Status indicators to NO, and require performing the I/M Complete System Set Procedure. Repair any DTCs or driveability concerns that would prevent the I/M System Status tests from completing. Did you find and repair a DTC or driveability concern? | Go to Step 3 | Go to Step 2 |
| 2 | Review any service bulletins for software updates that may prevent I/M readiness. Perform any reprogramming or repairs indicated by the service bulletins. Was a reprogramming or repair service required? | Go to Inspection/Maintenance (I/M) Complete System Set Procedure | Go to Step 3 |
| 3 | Observe the I/M System Status display with a scan tool. Is more than one test indicating a NO status? | Go to Inspection/Maintenance (I/M) Complete System Set Procedure | Go to the I/M System Set Procedure for the indicated system that has not updated |
| IMPORTANT |
|---|
| Many DTC related repairs will instruct the technician to clear the DTC information. This procedure will reset ALL of the I/M System Status indicators to NO, and require performing the I/M Complete System Set Procedure. |
Inspection/Maintenance (I/M) System Check
The purpose of the I/M Complete System Set Procedure is to satisfy the enable criteria necessary to execute all of the I/M readiness diagnostics, and complete the trips for those particular diagnostics. When all diagnostic tests are completed, the I/M System Status indicators are set to YES. Perform this test when more than one of the I/M System Status indicators are set to NO.
Conditions for Running
Cold Start
- The barometric pressure (BARO) is more than 74 kPa.
- The engine coolant temperature (ECT) is below 30°C (86°F).
- The intake air temperature (IAT) is below 30°C (86°F).
- The difference between the intake air temperature (IAT) and the engine coolant temperature (ECT) is 8°C (14°F) or less.
- The battery voltage is between 9-18 volts.
- The fuel level is between 15-85 percent.
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step runs the HO2S Heater Tests and initiate the EVAP System Test. Preprogramming the scan tool will reduce the amount of time the oxygen sensor heaters operate while verifying the enable criteria.
- 3: This step runs the EVAP, AIR and the Oxygen Sensor Tests. The EVAP Test begins once the engine coolant reaches a calibrated temperature. The AIR Test, if equipped, begins shortly after Closed Loop and the indicated speed is achieved. The Oxygen Sensor Tests begin once the engine is at operating temperature, in Closed Loop Fuel Control, and a calibrated amount of time has elapsed.
- 5: This step runs the Catalyst Tests. This test runs during the idle period immediately following a cruise period that meets a minimum calibrated RPM and time period.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| 1 | Did you perform the Inspection/Maintenance (I/M) System Check? | Go to Step 2 | Go to Inspection/Maintenance (I/M) System Check | |
| 2 | IMPORTANT: Whenever the ignition is turned ON, ignition positive voltage is supplied to the HO2S heaters. After verifying the enable criteria, turn OFF the ignition for approximately 5 minutes to allow the sensors to cool before continuing with the test. Once the engine is started, DO NOT turn the engine OFF for the remaining portion of the set procedure. Preprogram the scan tool with the vehicle information before the ignition is turned ON. Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Set the vehicle parking brake. Verify the transmission is in PARK for automatic transmissions. Start the engine. Allow the engine to idle for the specified time. Is the action complete? | 2 minutes | Go to Step 3 | |
| 3 | CAUTION: Refer to Road Test Caution in Cautions and Notices. In order for the next group of tests to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 90 km/h (55 mph) with this speed maintained until the engine reaches operating temperature. This may be up to 10 minutes depending on the start up coolant temperature. Continued operation under these conditions for an additional 6 minutes. Is the action complete? | Go to Step 4 | ||
| 4 | CAUTION: Refer to Road Test Caution in Cautions and Notices. In order for the next group of tests to run, the vehicle must operate in the following conditions: Vehicle speed reduced to 72 km/h (45 mph) with this speed maintained for one additional minute. Four decelerations of 25 seconds each from 72 km/h (45 mph) while the following criteria is maintained: Throttle is closed NO brake application NO manual downshift Vehicle speed remains above 40 km/h (25 mph). After each deceleration period, vehicle is returned to 72 km/h (45 mph) under part throttle acceleration and speed is maintained for 15 seconds. Is the action complete? | Go to Step 5 | ||
| 5 | CAUTION: Refer to Road Test Caution in Cautions and Notices. In order for the next group of tests to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 75-89 km/h (45-55 mph) with this speed maintained for 2 minutes Decelerate to 0 km/h (0 mph) Idle the engine for 2 minutes while the following criteria is maintained: Service brake is pressed. Automatic transmission is in DRIVE. Is the action complete? | Go to Step 6 | ||
| 6 | Observe the I/M System Status display with a scan tool. Did all of the I/M System Status indicators update to YES? | Go to Step 7 | Go to the I/M System Set Procedure for the indicated systems that have not updated | |
| 7 | Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set? | Go to Diagnostic Trouble Code (DTC) List | System OK |
| IMPORTANT |
|---|
| Whenever the ignition is turned ON, ignition positive voltage is supplied to the HO2S heaters. After verifying the enable criteria, turn OFF the ignition for approximately 5 minutes to allow the sensors to cool before continuing with the test. Once the engine is started, DO NOT turn the engine OFF for the remaining portion of the set procedure. |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
Inspection/Maintenance (I/M) Complete System Set Procedure
Inspection/Maintenance (I/M) System DTC Table
| System | DTCs Required to Set System Status to YES |
|---|---|
| Catalyst | DTC P0420 or P0430 |
| EVAP | DTC P0442 DTC P0446 DTC P0455 DTC P0496 |
| Oxygen Sensor | DTC P0133 or P0153 DTC P0136 or P0156 DTC P0140 or P0160 DTC P1133 or P1153 DTC P1134 or P1154 |
| Oxygen Sensor Heater | DTC P0135, P0141, P0155, or P0161 |
Inspection/Maintenance (I/M) System DTC Table
The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the Catalyst System. The test may be used to set the I/M System Status indicators to YES.
The I/M System Status Display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run.
- The barometric pressure is more than 74 kPa.
- Engine coolant is at operating temperature, 71-120°C (160-248°F).
- The intake air temperature (IAT) is between -15 to +75°C (5-167°F).
- The engine is in Closed Loop Fuel Control.
- The engine has run for 6-8 minutes off idle in order to initiate test.
- Battery voltage is between 11-18 volts.
The control module runs a maximum of 6 tests per trip until the Catalyst System Status updates to YES. If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.
If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Inspection/Maintenance (I/M) System Check? | Go to Step 2 | Go to Inspection/Maintenance (I/M) System Check |
| 2 | Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Start the engine. Allow the engine to idle for 2 minutes. CAUTION: Refer to Road Test Caution in Cautions and Notices. IMPORTANT: In order for this test to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 90 km/h (55 mph) with this speed maintained for 5 minutes. Decelerate to 0 km/h (0 mph) Idle the engine for 2 minutes while the following criteria is maintained: Service brake is pressed. Automatic transmission is in DRIVE. Manual transmission is in NEUTRAL with the clutch pedal pressed. Observe the I/M System Status display with a scan tool. Did the Catalyst System Status update to YES? | Go to Step 5 | Go to Step 3 |
| 3 | Observe the DTC Information with a scan tool. Does the scan tool indicate any failed DTCs? | Go to Diagnostic Trouble Code (DTC) List | Go to Step 4 |
| 4 | Refer to Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test. Observe the Not Ran Since Code Cleared display with a scan tool. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the Specific DTC menu of the scan tool. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. This may take up to 2 hours. Repeat steps 4-6 for any additional required DTCs that have not run. Observe the I/M System Status display with a scan tool. Did the Catalyst System Status update to YES? | Go to Step 5 | Go to Diagnostic Aids |
| 5 | Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set? | Go to Diagnostic Trouble Code (DTC) List | System OK |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
| IMPORTANT |
|---|
| In order for this test to run, the vehicle must operate in the following conditions |
Inspection/Maintenance (I/M) Catalyst System Set Procedure
The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the evaporative emission (EVAP) system. The test may be used to set the I/M System Status indicators to YES. The I/M System Status Display on the scan tool provides an indication of when the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run. Performing a visual inspection prior to running the EVAP test may prevent having to repeat the test. A failed or aborted test will require the vehicle to cool down in order to meet the enable criteria to run another test.
- DTCs P0442, P0446, P0455, P0496 are not set.
- The barometric pressure (BARO) is more than 75 kPa.
- The fuel level is between 1/4 and 3/4.
- The battery voltage is between 10-18 volts.
- The test will initiate only after a cold start. The control module considers the engine to be cold if the following conditions are met: The engine coolant temperature (ECT) is between 3.75-30°C (39-86°F). The intake air temperature (IAT) is between 3.75-30°C (39-86°F). The difference between the ECT and the IAT is less than 8°C (14°F).
If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as the cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Inspection/Maintenance (I/M) System Check? | Go to Step 2 | Go to Inspection/Maintenance (I/M) System Check |
| 2 | Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. IMPORTANT: Once the engine is started, DO NOT turn the engine OFF for the remainder of the procedure until the test is complete. Start the engine and idle. CAUTION: Refer to Road Test Caution in Cautions and Notices. IMPORTANT: In order for this test to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 72 km/h (45 mph) with this speed maintained until the engine reaches operating temperature. This may be up to 8-10 minutes depending on the start up coolant temperature. Continue the operating conditions for an additional 3 minutes after the engine reaches operating temperature. Decelerate to 0 km/h (0 mph). Idle the engine for 2 minutes. Turn OFF the ignition for 1 hour. After 1 hour, turn ON the ignition. Observe the EVAP System Status with the scan tool. Did the EVAP System Status update to YES? | Go to Step 5 | Go to Step 3 |
| 3 | Observe the DTC Information with a scan tool. Does the scan tool indicate any failed DTCs? | Go to Diagnostic Trouble Code (DTC) List | Go to Step 4 |
| 4 | Refer to Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test. Observe the Not Ran Since Code Cleared display with a scan tool. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the Specific DTC menu of the scan tool. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat steps 4-6 for any additional required DTCs that have not run. Observe the I/M System Status display with a scan tool. Did the EVAP System Status update to YES? | Go to Step 5 | Go to Diagnostic Aids |
| 5 | Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set? | Go to Diagnostic Trouble Code (DTC) List | System OK |
| IMPORTANT |
|---|
| Once the engine is started, DO NOT turn the engine OFF for the remainder of the procedure until the test is complete. |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
| IMPORTANT |
|---|
| In order for this test to run, the vehicle must operate in the following conditions |
Inspection/Maintenance (I/M) Evaporative Emission (EVAP) System Set Procedure
The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the Oxygen Sensor (O2S/HO2S) System. The test may be used to set the I/M System Status to YES.
The I/M System Status Display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run.
- The engine coolant temperature (ECT) is more than 57°C (135°F).
- The engine is running in Closed Loop Fuel Control.
- The engine has been running for more than 160 seconds.
- The battery voltage is between 9-18 volts.
If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.
If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Inspection/Maintenance (I/M) System Check? | Go to Step 2 | Go to Inspection/Maintenance (I/M) System Check |
| 2 | Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Start the engine. Allow the engine to idle for 2 minutes. CAUTION: Refer to Road Test Caution in Cautions and Notices. IMPORTANT: In order for this test to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 75-90 km/h (45-55 mph) with this speed maintained for 6 minutes or until the I/M System Status updates to YES. Manual transmissions, either 5 or 6 speed, may require operation in 4th or 5th gear respectively, in order for this test to run. Review the I/M System Status display with a scan tool. Did the HO2S/O2S System Status update to YES? | Go to Step 5 | Go to Step 3 |
| 3 | Observe the DTC Information with a scan tool. Does the scan tool indicate any failed DTCs? | Go to Diagnostic Trouble Code (DTC) List | Go to Step 4 |
| 4 | Refer to Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test. Observe the Not Ran Since Code Cleared display with a scan tool. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the Specific DTC menu of the scan tool. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. This may take up to 2 hours. Repeat steps 4-6 for any additional required DTCs that have not run. Observe the I/M System Status display with a scan tool. Did the HO2S/O2S System Status update to YES? | Go to Step 5 | Go to Diagnostic Aids |
| 5 | Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set? | Go to Diagnostic Trouble Code (DTC) List | System OK |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
| IMPORTANT |
|---|
| In order for this test to run, the vehicle must operate in the following conditions |
Inspection/Maintenance (I/M) Heated Oxygen Sensor/Oxygen Sensor (HO2S/O2S) System Set Procedure
The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the Heated Oxygen Sensor (HO2S) Heater System. The test may be used to set the I/M System Status to YES.
The I/M System Status Display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run.
- The start up engine coolant temperature (ECT) is less than 50°C (122°F).
- The start up intake air temperature (IAT) is less than 50°C (122°F).
- The difference between the IAT and the ECT is less than 8°C (14°F).
- The battery voltage is between 11-18 volts.
The HO2S Heater Tests will normally run within the 2 minutes allotted in the procedure. If there is an indeterminate condition, the test may take up to 8 minutes on some vehicles before a decision of pass or fail is made. If the test does not update to YES, the test may have failed or aborted due to the loss of enabling conditions. Extremely high ambient temperatures may prevent the HO2S Heater Test from initiating.
If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| 1 | Did you perform the Inspection/Maintenance (I/M) System Check? | Go to Step 2 | Go to Inspection/Maintenance (I/M) System Check | |
| 2 | IMPORTANT: Whenever the ignition is turned ON, ignition positive voltage is supplied to the HO2S heaters. After verifying the enable criteria, turn OFF the ignition for approximately 5 minutes to allow the sensors to cool before continuing with the test. Preprogram the scan tool with the vehicle information before the ignition is turned ON. Ensure the vehicle is within the Conditions for Running specified in the supporting text. Set the vehicle parking brake. Verify the transmission is in PARK for automatic transmissions and NEUTRAL for manual transmissions. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Start the engine. Allow the engine to idle for the specified time or until the I/M System Status indicator updates to YES. Did the HO2S Heater System Status update to YES? | 2 minutes | Go to Step 5 | Go to Step 3 |
| 3 | Observe the DTC information with a scan tool. Does the scan tool indicate any failed DTCs? | Go to Diagnostic Trouble Code (DTC) List | Go to Step 4 | |
| 4 | Refer to Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test. Observe the Not Ran Since Code Cleared display with a scan tool. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the Specific DTC menu of the scan tool. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. This may take up to 2 hours. Repeat steps 4-6 for any additional required DTCs that have not run. Observe the I/M System Status display with a scan tool. Did the HO2S Heater System Status update to YES? | Go to Step 5 | Go to Diagnostic Aids | |
| 5 | Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set? | Go to Diagnostic Trouble Code (DTC) List | System OK |
| IMPORTANT |
|---|
| Whenever the ignition is turned ON, ignition positive voltage is supplied to the HO2S heaters. After verifying the enable criteria, turn OFF the ignition for approximately 5 minutes to allow the sensors to cool before continuing with the test. |
Inspection/Maintenance (I/M) Heated Oxygen Sensor (HO2S) Heater System Set Procedure
See also:
• Diagnostic System Check - Engine Controls
• Scan Tool Data List
• Charging System Test (CS/AD/SI Generators)
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Power Distribution Schematics
• Service Programming System (SPS)
• Power and Grounding Component Views
• Engine Controls Schematics
• Temperature vs Resistance
• DTC P0121
• Ignition System Specifications
• Spark Plug Inspection
• Distributor Inspection
• Spark Plug Wire Inspection
• Oil Consumption Diagnosis
• Engine Compression Test
• Camshaft and Bearings Cleaning and Inspection
• Cylinder Head Cleaning and Inspection
• Piston, Connecting Rod, and Bearings Cleaning and Inspection
• Crankshaft and Bearings Cleaning and Inspection
• Restricted Exhaust
• Silicon Contamination of Heated Oxygen Sensors Notice
• Heated Oxygen and Oxygen Sensor Notice
• Exhaust Leakage
• DTC P0300
• Torque Converter Diagnosis Procedure
• Loss of Coolant
• Thermostat Diagnosis
• Fan Clutch Diagnosis
• Symptoms - Instrument Panel, Gages and Console
• Scan Tool Data Definitions
• Brakes Drag
• Engine Controls Connector End Views
• Powertrain Control Module (PCM) Connector End Views
• Diagnostic System Check - Instrument Cluster
• Circuit Testing
• Wiring Repairs
• Powertrain Control Module (PCM) Replacement
• Diagnostic Trouble Code (DTC) List
• Intermittent Conditions
• Battery Inspection/Test (Non-HP2)
• Engine Cranks Slowly
• Diagnostic System Check - Theft Deterrent
• Probing Electrical Connectors
• Fuel Pressure Relief Procedure
• Engine Cover Replacement
• Testing for Continuity
• Fuel Injector Cleaning Procedure
• Lifting and Jacking the Vehicle
• Fuel System Cleaning
• Circuit Protection - Fuses
• Measuring Voltage
• Road Test Caution
• DTC P1133 or P1153
• Hard Start
• Surges/Chuggles
• Lack of Power, Sluggishness, or Sponginess
• Detonation/Spark Knock
• Hesitation, Sag, Stumble
• Cuts Out, Misses
• Poor Fuel Economy
• Poor Fuel Fill Quality
• Rough, Unstable, or Incorrect Idle and Stalling
• Dieseling, Run-On
• Backfire
• Symptoms - Engine Controls
• Intermittent Conditions
• Inspection/Maintenance (I/M) System DTC Table