Important Preliminary Inspections Before Starting
Before using this section, perform the Diagnostic System Check - Vehicle in Vehicle DTC Information and verify all of the following conditions
- The engine control module (ECM) and the malfunction indicator lamp (MIL) are operating correctly.
- Diagnostic trouble codes (DTCs) are not stored.
- The scan tool data is within the normal operating range. Refer to «Scan Tool Data List»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-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/physical inspection. This step is extremely important, and can lead to correcting a condition without further inspections and can save valuable time.
- If the intermittent condition exists as a start and then stall, inspect for any DTCs related to the theft deterrent system. Refer to «Diagnostic System Check - Vehicle»(/cadillac/sts/i-2004-2007/remont/oem-general-information/#vehicle-dtc-information) in Vehicle DTC Information.
- Verify the proper installation of any of the following non-original equipment accessories: Lights Cellular phone Remote starter system Non-factory installed alarm
- Use the following tables when diagnosing a symptom concern: «Poor Fuel Fill Quality»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__poor-fuel-fill-quality) «Hard Start»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__hard-start) «Surges/Chuggles»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__surgeschuggles) «Lack of Power, Sluggishness, or Sponginess»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__lack-of-power-sluggishness-or-sponginess) «Detonation/Spark Knock»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__detonationspark-knock) «Hesitation, Sag, Stumble»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__hesitation-sag-stumble) «Cuts Out, Misses»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__cuts-out-misses) «Poor Fuel Economy»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__poor-fuel-economy) «Rough, Unstable, or Incorrect Idle and Stalling»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__rough-unstable-or-incorrect-idle-and) «Dieseling, Run-On»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__dieseling-run-on) «Backfire»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__backfire)
- If the condition can not be isolated using the appropriate table, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-troubleshooting__intermittent-conditions) for further diagnosis.
Intermittent Conditions
| Inspections | Action |
|---|---|
| DEFINITION: The condition is not currently present but is indicated in 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 Starting 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 Air leaks at the throttle body mounting area - Refer to Throttle Body Service . Air leaks at the mass air flow (MAF) sensor and at the intake manifold Engine control module (ECM) and body grounds are clean and tight Battery connections are clean and tight Charging system for proper operation - Refer to Charging System Test 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. Refer to Electrical Connections or Wiring in this table. |
| 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. |
| ECM Power and Grounds | Poor power or ground connections can cause widely varying symptoms. Test all engine control module (ECM) power circuits. Many vehicles have multiple circuits supplying power to the ECM. Inspect connections at the ECM connectors, fuses, and any intermediate connections between the power source and the ECM 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 ECM ground and system ground circuits. The ECM 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, ECM 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 ECM Programming | There are only a few situations where reprogramming an ECM is appropriate: An ECM from another vehicle is installed. Revised software/calibration files have been released for this vehicle. IMPORTANT: DO NOT reprogram the ECM with the SAME software/calibration files that are already present in the ECM. This is not an effective repair for any type of driveability problem. Verify that the ECM contains the correct software/calibration. If incorrect programming is found, reprogram the ECM with the most current software/calibration. Refer to Service Programming System (SPS) in Programming. |
| 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 ECM with the SAME software/calibration files that are already present in the ECM. 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 Symptoms - Engine Controls . Inspect the engine control module (ECM) 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 | Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature vs Resistance for resistance specifications. Verify proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . |
| Fuel System | Verify there is adequate fuel. A faulty in-tank sender 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 and Fuel Injector Coil Test . Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . |
| Ignition System | Inspect for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . Determine the cause of the conditions before replacing the spark plugs. Inspect for loose ignition coil grounds. Inspect the ignition coils for cracks or carbon tracking. Soak the secondary ignition with water may help locate an intermittent problem. Ignition voltage will arc to ground when a secondary component is faulty. |
| Engine Mechanical | Inspect for the following conditions: Excessive oil in combustion chamber or leaking valve seals - Refer Oil Consumption Diagnosis in Engine Mechanical. Cylinder compression - Refer to Engine Compression Test in Engine Mechanical. 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 or damaged basic engine parts-Inspect the following components: The camshaft - Refer to Camshaft 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 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, especially between the MAF sensor and the throttle body. |
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 Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) 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. Inform the customer how the TCC and the A/C clutch operates. |
| Sensor/System | NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. Inspect the heated oxygen sensors (HO2S). The HO2S should respond quickly to different throttle positions. If they do not, inspect the HO2S for silicon or other contaminates from fuel or the use of improper RTV sealant. The sensors may have a white, powdery coating and result in a high but false signal voltage rich exhaust indication. The PCM will then reduce the amount of fuel delivered to the engine causing a severe driveability problem. Inspect the mass air flow (MAF) sensor for any contamination on the sensing element. Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking especially between the MAF sensor and the throttle body. Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature vs Resistance . |
| 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 or Fuel Injector Coil Test . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary. 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 HO2S connector Engine oil contaminated by fuel - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . An EVAP canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . For proper operation of the manifold absolute pressure (MAP) sensor - Refer to Scan Tool Data Definitions . For proper operation of the mass air flow (MAF) sensor Blockage on the inlet screen of the MAF sensor 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 . For proper operation of the manifold absolute pressure (MAP) sensor - Refer to Scan Tool Data Definitions . For proper operation of the mass air flow (MAF) sensor Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Ignition System | 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. Test for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Monitor the Misfire Current Counters while driving the vehicle within the conditions that the misfire occurred. Inspect for loose ignition coil grounds. Inspect the ignition coils for cracks or carbon tracking. |
| 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) operation. Test the A/C clutch for proper operation. Refer to Symptoms - HVAC Systems - Automatic in HVAC Systems Automatic. 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 Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) 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 contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . 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 Engine oil contaminated by fuel An evaporative emission (EVAP) canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Blockage on the inlet screen of the MAF sensor 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 . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Sensor/System | Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Scan Tool Data Definitions . Inspect for a dirty or damaged air cleaner element. Inspect for a collapsed or damaged intake air duct. |
| Ignition System | 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 water is applied. Monitor the Misfire Current Counters while driving the vehicle within the conditions that the misfire occurred. Inspect for proper ignition voltage output with the J 26792 Spark Tester. Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Inspect the spark plug boots for signs of arcing, cracks, carbon tracking, or damage. Inspect for loose ignition coil ground. |
| Engine Mechanical | Inspect for incorrect camshaft timing. Refer to Setting Camshaft Timing in Engine Mechanical. Inspect for excessive oil in the combustion chambers and leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical. Test cylinder compression. Refer to Engine Compression Test in Engine Mechanical. Inspect for incorrect basic engine parts, including the following components: The camshaft - Refer to Camshaft 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. |
| 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, Sluggish or Spongy
Detonation/Spark Knock
| Inspection/Tests | Action |
|---|---|
| DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that changes with throttle opening. | |
| Preliminary Inspections | Refer to Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) 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 vehicles performance. |
| 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 or Fuel Injector Coil Test . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O 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 HO2S connector An exhaust leak between the HO2S and the engine - Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Restricted fuel injectors - Refer to Fuel Injector Balance Test with Special Tool . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O 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 | 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 water is applied. Inspect for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . Verify that the spark plugs are of the type. Refer to Ignition System Specifications . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Inspect the spark plug boots for signs of arcing, cracks, carbon tracking, or damage. Inspect for loose ignition coil ground. |
| Engine Cooling System | Inspect for obvious overheating conditions: Low engine coolant - Refer to Loss of Coolant in Engine Cooling. A faulty thermostat - Refer to Thermostat Diagnosis in Engine Cooling. Restricted air flow to the radiator or restricted coolant flow through the radiator An inoperative electric cooling fan - Refer to Cooling Fan Inoperative in Engine Cooling. Proper tension on the drive belts - Refer to Drive Belt Tensioner Diagnosis in Engine Mechanical. The 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 conditions: 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 - Refer to Setting Camshaft Timing in Engine Mechanical. Inspect for incorrect basic engine parts. Inspect the following components: The camshaft - Refer to Camshaft 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. |
| Additional Inspections | Inspect the park/neutral position (PNP) switch operation. Inspect the transmission torque converter clutch (TCC) operation. The TCC applying too soon can cause the engine to spark knock. |
| 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, as from a stop. May cause the engine to stall if severe enough. | |
| Preliminary | Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) 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 the heated oxygen sensors (HO2S). The HO2S should respond quickly to different throttle positions. If they do not, inspect the HO2S for silicon or other contaminates from fuel or the use of improper RTV sealant. The sensors may have a white, powdery coating and result in a high but false signal voltage rich exhaust indication. The PCM will then reduce the amount of fuel delivered to the engine causing a severe driveability problem. Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking especially between the MAF sensor and the throttle body. Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature vs Resistance for resistance specifications. Inspect the mass air flow (MAF) sensor and intake air system for proper operation. Refer to Scan Tool Data Definitions . |
| 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 (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Test the fuel injector Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . 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 HO2S connector Engine oil contaminated by fuel An EVAP canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . 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 . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Ignition System | 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 water. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. Test for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and check for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gauge gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Inspect the spark plug boots for signs of arcing, cracks, carbon tracking, or damage. Inspect for loose ignition coil ground. Refer to Power and Grounding Component Views in Wiring Systems. |
| Engine Cooling System | Inspect the engine thermostat for proper operation and for correct heat range. Refer to Thermostat Diagnosis in Engine Cooling. |
| Engine Mechanical | Inspect for excessive crankshaft endplay that will cause the 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 generator output voltage. Refer to Charging System Test in Engine Electrical. |
| 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 Starting in Symptoms - Engine Controls . Search for bulletins. Verify that the engine control module (ECM) 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 or Fuel Injector Coil Test . Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for proper operation of the evaporative emission (EVAP) control system. Refer to Evaporative Emission (EVAP) Control System Description . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O 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 Engine oil contaminated by fuel An EVAP canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Blockage on the inlet screen of the MAF sensor. 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 . Inspect for proper operation of the MAP sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the MAF sensor. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O 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. Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking especially between the MAF sensor and the throttle body. Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature vs Resistance . Inspect for a vacuum leak. Inspect the crankcase ventilation operation. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. |
| Ignition System | 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 water. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. Performing a Cylinder Balance Test with a scan tool may also help isolate which cylinder may be misfiring. Test for proper ignition voltage output. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications . Determine the cause of the fouling before replacing the spark plugs. Visually and physically inspect for the following conditions: The spark plug boots for signs of arcing, cracks, carbon tracking, or damage The spark plug boots for proper engagement to spark plug The ignition coils for cracks or carbon tracking |
| Engine Mechanical | Inspect engine mechanical for the following conditions: Test compression - Refer to Engine Compression Test in Engine Mechanical. Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms - Refer to Valve Rocker Arms Cleaning and Inspection in Engine Mechanical. Broken valve springs - Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. Excessive oil in combustion chamber-Leaking valve seals For more information refer to one of the following procedures: Engine Compression Test Symptoms - Engine Mechanical Oil Consumption Diagnosis For incorrect basic engine parts inspect the following components: The camshaft - Refer to Camshaft 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 Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnostic procedures. |
| Additional Inspections | Inspect the exhaust system for possible restrictions. Inspect for the following conditions: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure For 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 sudden increase in indicated RPM 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. Refer to Intake Manifold Cleaning and Inspection or Exhaust Manifold Cleaning and Inspection - Left and Exhaust Manifold Cleaning and Inspection - Right in Engine Mechanical |
| 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 Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) 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 driving habits with the owner. 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. Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Inspect that each fuel injector harness is connected to the correct injector and cylinder. Relocate the injector harnesses as necessary. 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 Engine oil contaminated by fuel An evaporative emission (EVAP) canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . For proper operation of the manifold absolute pressure (MAP) sensor - Refer to Scan Tool Data Definitions . For proper operation of the mass air flow (MAF) sensor Blockage on the inlet screen of the MAF sensor 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 . |
| Sensor/System | Inspect the air intake system and crankcase for air leaks. Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature vs Resistance for resistance specifications. Inspect for an inaccurate speedometer. Refer to Symptoms - Instrument Panel, Gages and Console in Instrument Panel, Gages, and Console. Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Scan Tool Data Definitions . |
| Ignition System | Inspect for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions: Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Spark Plug Replacement and Ignition System Specifications . Determine the cause of the fouling before replacing the spark plugs. Soaking the secondary ignition system with water from a spray bottle may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water. Inspect for loose ignition coil grounds. Refer to Power and Grounding Component Views in Wiring Systems. |
| 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 conditions: Compression Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms Broken valve springs Excessive oil in combustion chamber-Leaking valve seals. For more information refer to one of the following procedures: Engine Compression Test Symptoms - Engine Mechanical Oil Consumption Diagnosis For incorrect basic engine parts inspect for the following components: The camshaft - Refer to Camshaft 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 diagnostic procedures. |
| Additional Inspections | Visually and physically check the vacuum hoses for splits, kinks, and proper connections and routing as shown on Vehicle Emission Control Information label. Inspect the transmission torque converter clutch (TCC) operation. The scan tool should indicate a RPM drop, when the system commands the TCC ON. Inspect the exhaust system for a possible restriction. Inspect for the following conditions: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure For possible plugged catalytic converters - Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM 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 brake system for dragging or improper operation. Refer to Symptoms - Hydraulic Brakes 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 |
| 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 |
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 Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) 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 | Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O 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 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 Engine oil contaminated by fuel An evaporative emission (EVAP) canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Blockage on the inlet screen of the MAF sensor 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 . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the MAF sensor. Refer to Scan Tool Data Definitions . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Sensor/System | Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the MAF sensor and the throttle body. Inspect the Transaxle Range Switch input with the vehicle in drive and the gear selector in drive or overdrive. Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Scan Tool Data Definitions . |
| Ignition System | Inspect for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis for the procedure. Remove spark plugs and check for the following conditions: Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits 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 An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Determine the cause of the fouling before replacing the spark plugs. Inspect the spark plug boots for signs of arcing, cracks, carbon tracking, or damage. 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 water. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. Inspect for loose ignition coil grounds. Refer to Power and Grounding Component Views in Engine Electrical. |
| Engine Mechanical | Inspect engine mechanical for the following conditions: 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 basic engine parts. Inspect the following components: The camshaft - Refer to Camshaft 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 Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnosis procedures. |
| Additional Inspections | Inspect the exhaust system for the following possible restrictions: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure For possible plugged catalytic converters - Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM with little change in actual engine RPM change indicates that EMI is present. If a problem exists, inspect routing of 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. Refer to Intake Manifold Cleaning and Inspection , or Exhaust Manifold Cleaning and Inspection - Left and Exhaust Manifold Cleaning and Inspection - Right in Engine Mechanical. |
| 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 Starting in Symptoms - Engine Controls . Search for bulletins. Verify that the engine control module (ECM) 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 and Fuel Injector Coil Test . |
| Additional Inspections | Remove the spark plugs and inspect for the following conditions: Correct heat range Heavy deposits Refer to Spark Plug Inspection . |
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 Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views and Engine Controls Schematics in Wiring Systems. |
| Fuel System | Test for correct fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary. |
| Sensor/System | Inspect the air intake system and crankcase for air leaks. Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. |
| Ignition System | Inspect for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Inspect the coils for cracks, carbon tracking/arcing. Inspect spark plug boots for signs of arcing, cracks, carbon tracking, or damage. Remove spark plugs and inspect for the following conditions: Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. 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. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. Inspect for loose ignition coil ground. Refer to Power and Grounding Component Views in Engine Electrical. |
| 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 conditions: Compression - Refer to Engine Compression Test in Engine Mechanical. Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms Broken valve springs Excessive oil in combustion chamber or leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical. For incorrect basic engine parts. Inspect the following components: The camshaft - Refer to Camshaft 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 intake manifold and the exhaust manifold passages for casting flash. Refer to Intake Manifold Cleaning and Inspection or Exhaust Manifold Cleaning and Inspection - Left and Exhaust Manifold Cleaning and Inspection - Right in Engine Mechanical. Inspect the transmission torque converter clutch (TCC) operation. The scan tool should indicate an RPM drop when the TCC is commanded ON. Inspect the exhaust system for possible restrictions. Inspect the following conditions: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure For possible plugged catalytic converters - Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM 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
Voltage is supplied to the malfunction indicator lamp (MIL) internally by the instrument panel cluster (IPC). The engine control module (ECM) 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 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 ECM.
MIL Illumination
- The MIL will illuminate with the 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 as 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.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 2 | Turn ON the ignition, with the engine OFF. Is the instrument cluster completely inoperative? | Go to Symptoms - Instrument Panel, Gages and Console in Instrument Panel, Gages, and Console | Go to Step 3 | |
| 3 | Turn ON the ignition, with the engine OFF. Command the MIL ON and OFF with a scan tool. Does the malfunction indicator lamp (MIL) turn ON and OFF when commanded with a scan tool? | Go to Intermittent Conditions | Go to Step 4 | |
| 4 | Inspect the fuse that supplies voltage to the cluster. Is the fuse open? | Go to Step 11 | Go to Step 5 | |
| 5 | Turn OFF the ignition. Remove the fuse that supplies voltage to the cluster. Disconnect the engine control module (ECM). Turn ON the ignition with the engine OFF. Measure the voltage from the MIL control circuit in the ECM harness connector to a good ground. Is the voltage less than the specified value? | 1 V | Go to Step 6 | Go to Step 12 |
| 6 | Turn OFF the ignition. Install the fuse that supplies voltage to the cluster. Turn ON the ignition with the engine OFF. Connect a 3-amp fused jumper wire between the MIL control circuit in the ECM harness connector and a good ground. Is the MIL illuminated? | Go to Step 10 | Go to Step 7 | |
| 7 | Turn OFF the ignition. Remove the instrument panel cluster (IPC). Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Turn ON the ignition. Probe the voltage supply 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 8 | Go to Step 13 | |
| 8 | 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 16 | Go to Step 9 | |
| 9 | 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 16 | Go to Step 14 | |
| 10 | Test for an intermittent and for a poor connection at the ECM. 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 16 | Go to Step 15 | |
| 11 | Test all circuits and components that use this voltage supply for excessive current draw. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 16 | ||
| 12 | 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 16 | ||
| 13 | Repair the open in the voltage supply circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 16 | ||
| 14 | Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Did you complete the replacement? | Go to Step 16 | ||
| 15 | Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 16 | ||
| 16 | Turn the ignition OFF for 30 seconds. Start the engine. Does the MIL operate correctly? | Go to Step 17 | Go to Step 2 | |
| 17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | |
Malfunction Indicator Lamp (MIL) Inoperative
Voltage is supplied to the malfunction indicator lamp (MIL) internally by the instrument panel cluster (IPC). The engine control module (ECM) turns the MIL ON by grounding the MIL control circuit.
The MIL is located on the 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 the 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 as 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.
- 2: This step determines if the condition is with the MIL control circuit or the ECM.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Turn OFF the ignition. Disconnect the engine control module (ECM). Turn ON the ignition, with the engine OFF. Observe the malfunction indicator lamp (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 ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | |
| 6 | Turn the ignition OFF for 30 seconds. Start the engine. Does the MIL operate correctly? | Go to Step 7 | Go to Step 2 |
| 7 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
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 causes an engine to not start. The diagnostic table directs the service technician to the appropriate system diagnosis. The diagnostic table assumes the following conditions are met
- The battery is completely charged. Refer to «Battery Inspection/Test»(/cadillac/sts/i-2004-2007/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
- The engine cranking speed is acceptable. Refer to «Engine Cranks Slowly»(/cadillac/sts/i-2004-2007/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 | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 2 | Turn ON the ignition, with the engine OFF. Observe the DTC information with a scan tool. Does the scan tool display DTCs P0102, P0113, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0261, P0264, P0267, P0270, P0273, P0276, P0279, P0282, P0335, P0336, P0601, P0602, P0604, P0606, P0628, P0629, P0686, P0687, P0689, P0690, P1626, P1631, or P1636? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 3 | |
| 3 | Does the scan tool display any body control module (BCM) vehicle theft deterrent (VTD) DTCs? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 4 | |
| 4 | Turn ON the ignition, with the engine OFF. Probe both test points of the V8 ECM fuse located in the underhood electrical center using a test lamp connected to a good ground. Does the test lamp illuminate on at least one test point of the fuse? | Go to Step 5 | Go to Powertrain Relay Diagnosis | |
| 5 | Observe the engine speed parameter on the scan tool, while cranking the engine. Does the scan tool display 0 RPM? | Go to Step 9 | Go to Step 6 | |
| 6 | Turn OFF the ignition. Remove the ignition coil assembly from either bank. DO NOT disconnect any electrical connectors from the ignition coil assembly. Refer to Ignition Coil(s) Replacement - Bank 1 or Ignition Coil(s) Replacement - Bank 2 . Install the J 36012-A Ignition Diagnostic Harness. See Special Tools . Install the J 26792 Spark Tester on one of the spark plug jumper wires. Attach the clamp end of the spark tester to a good ground. Crank the engine with the remaining spark plug jumper wires connected. Repeat steps 5-7 for each remaining cylinder on this bank. Repeat the procedure for the opposite bank. Reassemble the vehicle after performing the procedure. Did the spark tester spark on all cylinders? | Go to Step 7 | Go to Electronic Ignition (EI) System Diagnosis | |
| 7 | IMPORTANT: 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. Install a J 34730-1A Fuel Pressure Gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. IMPORTANT: The fuel pump may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. Command the fuel pump ON with a scan tool. Observe the fuel pressure while the fuel pump is operating. Is the fuel pressure within the specified range? | 380-410 kPa (55-60 psi) | Go to Step 8 | Go to Fuel System Diagnosis |
| 8 | Inspect for the following conditions: A collapsed air intake duct A restricted air filter element - Refer to Air Cleaner Element Replacement . Fouled spark plugs - Refer to Spark Plug Replacement and Spark Plug Inspection . If the spark plugs are fouled, determine what caused the condition. Contaminated fuel - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . An engine mechanical condition, for example, broken timing chain, low compression - Refer to Setting Camshaft Timing and Engine Compression Test in Engine Mechanical. A restricted exhaust system - Refer to Restricted Exhaust in Engine Exhaust. An ECT sensor that has shifted in value - Refer to Temperature vs Resistance . Proper operation of the MAP sensor - Refer to DTC P0106 . Did you complete the action? | Go to Step 15 | ||
| 9 | Turn ON the ignition with the engine OFF. Test for a short between the mass air flow (MAF) sensor 12-volt reference circuit and the following circuits: The intake air temperature (IAT) 5-volt reference circuit The IAT low reference circuit Refer to Circuit Testing in Wiring Systems. Did you find and correct the condition. | Go to Step 15 | Go to Step 10 | |
| 10 | Disconnect a camshaft position sensor. Install a DMM between the camshaft position sensor 12-volt reference circuit and a good ground. Monitor the DMM while disconnecting the MAF/IAT sensor. If the voltage changes while disconnecting the MAF/IAT sensor, replace the MAF/IAT sensor. Did you replace the sensor? | Go to Step 15 | Go to Step 11 | |
| 11 | Disconnect the MAF sensor. Install a DMM between the MAF sensor 12-volt reference circuit and a good ground. Monitor the DMM while disconnecting all other sensors connected to the 12-volt reference circuit, one at a time. If the voltage changes when one of the sensors are disconnected, replace the sensor. Did you replace a sensor? | Go to Step 15 | Go to Step 12 | |
| 12 | Test the 12-volt reference circuits of the following components for a short to ground. Refer to Circuit Testing in Wiring Systems. MAF/IAT airflow sensor Crankshaft position (CKP) Sensor CMP sensor bank 1 (right) exhaust CMP sensor bank 2 (left) exhaust CMP sensor bank 1 (right) Intake CMP sensor bank 2 (left) Intake Did you find and correct the condition? | Go to Step 15 | Go to Step 13 | |
| 13 | Test for shorted terminals and poor connections at the engine control module (ECM). 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 | |
| 14 | Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 15 | ||
| 15 | With a scan tool, clear the DTCs. Attempt to start the engine. Does the engine start and continue to operate? | Go to Step 16 | Go to Step 2 | |
| 16 | Idle the engine. Allow the engine to reach operating temperature. Observe the DTC information with a scan tool. Are any DTCs displayed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK | |
| IMPORTANT |
|---|
| 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. |
| IMPORTANT |
|---|
| The fuel pump may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. |
Engine Cranks but Does Not Run
The main relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the powertrain relay coil and the armature contact at all times. The engine control module (ECM) supplies the ground path to the relay coil control circuit, via an internal integrated circuit, called an output driver module. When the ECM commands the relay ON, the relay coil creates an electromagnetic field. This electromagnetic field overcomes the spring tension and pulls the armature contact into the stationary contact of the relay load circuit. The closing of the relay contacts allows current to flow from the battery to the following fuses and relays.
- V8 ECM fuse
- Post O2
- ODD coils fuse
- EVEN coils fuse
- Pre O2/CAM fuse
- S/P fan relay
- Low speed fan relay
- High speed fan relay
When the ignition switch is turned to the OFF position, power is interrupted to the output driver module in the ECM, and the powertrain relay electromagnetic field collapses. This action allows the spring tension pulling on the armature to separate from the relay load circuit contact, which interrupts current flow to the fuses and relays.
If the powertrain relay fails to close, the engine will crank, but will not run. The GMLAN and class II data communications will be available, with the use of a CANdi module and scan tool.
Diagnostic Aids
- The main relay will remain powered up for 15 seconds after the ignition switch is turned OFF.
- The powertrain relay system diagnosis table assumes that the vehicle battery is fully charged. Refer to «Battery Inspection/Test»(/cadillac/sts/i-2004-2007/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Are DTCs P0686, P0687, P0689 or P0690 set? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 3 |
| 3 | Turn ON the ignition, with the engine OFF. Remove the underhood fuse block cover. Probe the following fuses with a test lamp that is connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems. V8 ECM fuse Post O2 fuse ODD coils fuse EVEN coils fuse Pre O2/CAM Fuse Does the test lamp illuminate on at least one test point of each fuse? | Go to Step 6 | Go to Step 4 |
| 4 | Turn OFF the ignition. Remove the powertrain relay from the underhood junction block with the J 43244 Relay Puller Pliers. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Connect a 20-amp fused jumper wire from the battery positive voltage terminal for the powertrain relay armature at the underhood fuse block to the relay load circuit terminal at the underhood fuse block. Refer to Using Fused Jumper Wires in Wiring Systems. Probe the following fuses with a test lamp that is connected to a good ground: V8 ECM fuse Post O2 fuse ODD coils fuse EVEN coils fuse Pre O2/CAM Fuse Does the test lamp illuminate on at least one test point of each fuse? | Go to Intermittent Conditions | Go to Step 5 |
| 5 | Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems. Did you complete the replacement? | Go to Step 6 | |
| 6 | Replace any open fuses. Turn OFF the ignition for 30 seconds. Attempt to start the engine. Does the engine start and run? | Go to Step 7 | Go to Intermittent Conditions |
| 7 | Clear the DTCs with a scan tool. Operate the vehicle for 5 minutes. Does a DTC set during this ignition cycle? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | |
Powertrain Relay Diagnosis
When you turn the ignition switch ON, the control module energizes the fuel pump relay which applies power to the in-tank fuel pump. The fuel pump relay will remain ON as long as the engine is running or cranking and the control module is receiving reference pulses. If no reference pulses are present, the control module de-energizes the fuel pump relay within 2 seconds after the ignition is turned ON or the engine is stopped.
Listen for an audible hiss from the fuel pump when the fuel pump relay is commanded ON. A vibration in the fuel feed line when the fuel pump relay is commanded ON indicates that the fuel pump is operating.
For an intermittent condition, refer to Intermittent Conditions .
The numbers below refer to the step numbers on the diagnostic table
- 2: Command both the ON and OFF states. Repeat the commands as necessary.
- 3: This step determines if the condition is located on the coil side or the switch side of the circuit.
- 7: This step tests for a grounded voltage supply circuit. The fuel pump fuse supplies power to fuel pump. Disconnecting the fuel pump in-line harness connector isolates the fuel pump voltage supply circuit.
- 9: This step verifies that the fuel pump fuse is providing voltage to the fuel pump relay.
- 10: This step jumps the fuel pump relay in order to activate the fuel pump.
- 15: This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Controls Schematics | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON and OFF with a scan tool. Does the fuel pump turn ON and OFF? | Go to Diagnostic Aids | Go to Step 3 |
| 3 | Command the fuel pump relay ON and OFF with a scan tool. Do you hear a click when you command the fuel pump relay ON and OFF? | Go to Step 4 | Go to Step 16 |
| 4 | Turn ON the ignition, with the engine OFF. Does the fuel pump operate continuously? | Go to Step 5 | Go to Step 6 |
| 5 | Turn OFF the ignition. Remove the rear seat. Refer to 7288 3 in Seats. Disconnect the fuel pump relay. Turn ON the ignition, with the engine OFF. Does the fuel pump operate continuously? | Go to Step 17 | Go to Step 20 |
| 6 | Is the fuel pump fuse open? | Go to Step 7 | Go to Step 9 |
| 7 | Disconnect the fuel pump harness in-line connector located near the fuel tank. Refer to Power and Grounding Connector End Views in Wiring Systems. Test the supply voltage circuit of the fuel pump for a grounded circuit. Refer to Wiring Repairs and Connector Repairs in Wiring Systems. Replace the fuel pump fuse, if necessary. Did you find and correct the condition? | Go to Step 21 | Go to Step 8 |
| 8 | Lower the fuel tank, if necessary. Refer to Fuel Tank Replacement . Test or inspect the fuel tank electrical harness for the following conditions: Damage to the harness A grounded circuit - 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 21 | Go to Step 15 |
| 9 | Turn OFF the ignition. Disconnect the fuel pump relay. Turn ON the ignition, with the engine OFF. Probe the battery positive voltage circuit of the fuel pump relay with a test lamp connected to a good ground. Does the test lamp illuminate? | Go to Step 10 | Go to Step 18 |
| 10 | Connect a 15-amp fused jumper wire between the battery positive voltage circuit and the fuel pump supply circuit of the fuel pump relay. Does the fuel pump operate? | Go to Step 16 | Go to Step 11 |
| 11 | Disconnect the fuel pump harness in-line connector located near the fuel tank. Refer to Power and Grounding Connector End Views in Wiring Systems. Test the supply voltage circuit of the fuel pump for an open or for high resistance between the fuel pump relay and the in-line connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 21 | Go to Step 12 |
| 12 | IMPORTANT: Inspect the ground circuit for being tight, for corrosion on the terminals, or for damage to the wiring harness. Test the ground circuit of the fuel pump for an open or for high resistance between the body pass through connector and the ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition? | Go to Step 21 | Go to Step 13 |
| 13 | Inspect for poor connections at the fuel pump in-line connector to the body pass through connector. 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 21 | Go to Step 14 |
| 14 | Lower the fuel tank. Refer to Fuel Tank Replacement . Test or inspect the fuel tank electrical harness for the following conditions: Damage to the harness An open circuit - Refer to Circuit Testing and Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 21 | Go to Step 19 |
| 15 | Connect all disconnected components. Install a new fuel pump fuse. Command the fuel pump ON with a scan tool. Is the fuel pump fuse open? | Go to Step 19 | Go to Diagnostic Aids |
| 16 | Inspect for poor connections 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 21 | Go to Step 20 |
| 17 | Repair the supply voltage circuit of the fuel pump for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 21 | |
| 18 | Repair the battery positive voltage circuit of the fuel pump relay for an open. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 21 | |
| 19 | IMPORTANT: Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump. Replace the fuel tank module. Refer to Fuel Tank Module Replacement - Primary . Replace the fuel pump fuse, if necessary. Did you complete the replacement? | Go to Step 21 | |
| 20 | Replace the fuel pump relay. Did you complete the replacement? | Go to Step 21 | |
| 21 | 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 being tight, for corrosion on the terminals, or for 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 Diagnostic
System Description
When you turn the ignition switch to the ON position, the control module enables the fuel pump relay, which in turn powers the fuel pump. The fuel pump remains ON as long as the engine is cranking or running and the control module receives ignition reference pulses. If there are no ignition reference pulses, the control module shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position, or if the engine stops.
The fuel tank stores the fuel supply. The fuel pump is an electric pump that is attached to the primary fuel tank module assembly. The fuel pump also supplies fuel to the siphon jet pump, also attached to the primary fuel tank module. The siphon jet pump draws fuel from the secondary side of the fuel tank to the primary side of the fuel tank. The fuel pump is designed to provide fuel at a pressure above the pressure that is needed by the fuel injectors. A fuel pressure regulator, which is also located in the fuel tank, is attached to the primary fuel tank module. The fuel pressure regulator keeps the fuel available to the fuel injectors at a regulated pressure. The port on the fuel pressure regulator is an atmospheric vent. The fuel pressure regulator does not compensate for changes in intake manifold vacuum. Unused fuel is returned from the fuel filter to the fuel tank by a separate fuel return pipe.
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step verifies that the fuel pump is operating.
- 4: This step verifies that the vehicle is not out of fuel. If the right fuel sender is below 0.8 volts, and the left fuel sender is above 0.8 volts, a fuel transfer condition exists.
- 7: This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated.
- 10: This step isolates the condition. Replace the primary fuel tank module assembly, if the fuel pressure remains constant, after closing the valve on the fuel pipe shut-off adapter. Locate and replace the leaking fuel injector if the pressure continues to decrease after closing the valve on the adapter.
- 13: This step isolates the condition. Replace the primary fuel tank module assembly for a stuck open or leaking fuel pressure regulator, if the fuel pressure increases above the specified value.
- 16: This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Fuel Hose/Pipes Routing Diagram | ||||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 2 | IMPORTANT: Inspect the fuel system for the following conditions before proceeding with this diagnostic procedure: Damage to the fuel system External fuel leaks Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Does the fuel pump operate? | Go to Step 3 | Go to Fuel Pump Electrical Circuit Diagnosis | |
| 3 | Observe the fuel level sensor left voltage with a scan tool. Is the fuel level sensor left voltage less than the specified value? | 0.8 V | Go to Step 4 | Go to Step 6 |
| 4 | Observe the fuel level sensor right voltage with a scan tool. Is the fuel level sensor right voltage less than the specified value? | 0.8 V | Go to Step 5 | Go to Step 14 |
| 5 | Add the specified amount of fuel. Operate the vehicle within the conditions of the customer's concern. Monitor the fuel trim related parameters with a scan tool. Refer to Scan Tool Data List . Do any of the scan tool parameters indicate a lean condition? | 19 L (5 gal) | Go to Step 15 | Go to Symptoms - Engine Controls |
| 6 | Turn OFF the ignition. 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 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 ON with a scan tool. Observe the fuel pressure gage while the fuel pump is operating. Is the fuel pressure within the specified range? | 380-410 kPa (55-60 psi) | Go to Step 7 | Go to Step 11 |
| 7 | IMPORTANT: The fuel pressure will drop when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Allow the fuel pressure to stabilize. 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 10 | Go to Step 8 |
| 8 | 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 19 | Go to Step 9 |
| 9 | 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 | |
| 10 | Turn OFF the ignition. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure . Disconnect the fuel feed pipe from the fuel rail. Refer to Quick Connect Fitting(s) Service (Metal Collar) . Install the appropriate J 37287 Fuel Line Shut-Off Adapters between the fuel feed pipe and the fuel rail inlet. Open the valve on the fuel feed pipe shut-off adapter. Command the fuel pump ON with a scan tool. Bleed the air from the fuel system. Close the fuel pipe shut-off valve. Monitor the fuel pressure gage for 1 minute. Does the fuel pressure remain constant? | Go to Step 19 | Go to Step 18 | |
| 11 | Is the fuel pressure more than the specified value? | 410 kPa (60 psi) | Go to Step 12 | Go to Step 13 |
| 12 | Inspect the fuel return hose/pipe for a restriction. Did you find and correct the condition? | Go to Step 20 | Go to Step 19 | |
| 13 | Turn OFF the ignition. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure . Disconnect the fuel return hose from the fuel return outlet of the fuel filter. Refer to Quick Connect Fitting(s) Service (Plastic Collar) . Install the appropriate J 37287 between the return outlet of the fuel filter and the fuel return hose. Open the valve in the fuel pipe shut-off adapter. Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Bleed the air from the fuel system. Monitor the fuel pressure gauge. Slowly close the valve in the fuel pipe shut-off adapter. Command the fuel pump ON with a scan tool. Does the fuel pressure increase to more than the specified value? | 380-410 kPa (55-60 psi) | Go to Step 19 | Go to Step 15 |
| 14 | Remove both fuel tank modules. Refer to Fuel Tank Module Replacement - Primary and Fuel Tank Module Replacement - Secondary . Inspect the feed fuel pipe of the siphon jet pump for a restriction. Inspect the fuel strainer for contaminants. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Did you find and correct the condition? | Go to Step 20 | Go to Step 19 | |
| 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 20 | Go to Step 16 | |
| 16 | Inspect the harness connectors and 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 20 | Go to Step 17 | |
| 17 | Remove the primary fuel tank module. Refer to Fuel Tank Module Replacement - Primary . 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 For contaminates in the fuel tank Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Did you find and correct the condition? | Go to Step 20 | Go to Step 19 | |
| 18 | Turn OFF the ignition. Raise the fuel rail, with the fuel lines connected. Refer to Fuel Injectors and Fuel Rail Replacement . Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Locate and replace the leaking fuel injector. Refer to Fuel Injectors and Fuel Rail Replacement . Did you complete the replacement? | Go to Step 20 | ||
| 19 | Replace the primary fuel tank module. Refer to Fuel Tank Module Replacement - Primary . Did you complete the replacement? | Go to Step 20 | ||
| 20 | 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 the following conditions before proceeding with this diagnostic procedure: Damage to the fuel system External fuel leaks |
| IMPORTANT |
|---|
| The fuel pump 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 will drop when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. |
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.
- Excessive resistance in the fuel injector ignition 1 voltage circuit or the fuel injector control circuit may cause the following symptoms: Lean condition Misfire Rough idle
- Monitoring the misfire current counters, or misfire graph, may help 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 Control Module (ECM) Connector End Views or Engine Controls Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 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 fuel injector sight shield. Refer to Fuel Injector Sight Shield Replacement in Engine Mechanical - 4.6L (LH2). Measure the resistance of each fuel injector with a DMM. Refer to Testing for Continuity in Wiring Systems. Do any of the fuel injectors display a resistance outside the specified range? | 11-14 ohms | Go to Step 6 | Go to Diagnostic Aids |
| 4 | Remove the fuel injector sight shield. Refer to Fuel Injector Sight Shield Replacement in Engine Mechanical - 4.6L (LH2). Measure the resistance of each fuel injector with a DMM. Refer to Testing for Continuity in Wiring Systems. Record each fuel injector value. Subtract the lowest resistance value from the highest resistance value. Is the difference equal to, or less than, the specified value? | 3 ohms | Go to Fuel Injector Balance Test with Special Tool | 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 Injectors and Fuel Rail Replacement . Did you complete the replacement? | Go to Step 8 | ||
| 6 | Test for an intermittent and for a poor connection at the fuel injectors. 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 8 | Go to Step 7 | |
| 7 | Replace the fuel injector or fuel injectors that are out of the specified range. Refer to Fuel Injectors and Fuel Rail Replacement . Did you complete the replacement? | 11-14 ohms | Go to Step 8 | |
| 8 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Diagnostic Aids | |
Fuel Injector Coil Test
The scan tool is first used to energize the fuel pump. 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 | 380 kPa (55 psi) | 380 kPa (55 psi) | 380 kPa (55 psi) | 380 kPa (55 psi) |
| 2nd Reading | 215 kPa (31 psi) | 201 kPa (29 psi) | 208 kPa (30 psi) | 229 kPa (33 psi) |
| Amount of Drop | 165 kPa (24 psi) | 179 kPa (26 psi) | 172 kPa (25 psi) | 151 kPa (22 psi) |
| Average Range: 156-176 kPa (22.5-25.5 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)
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check- Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 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). IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. 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 may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure. Command the fuel pump ON with a scan tool. Observe the fuel pressure gage, with the fuel pump operating. Is the fuel pressure within the specified range? | 380-427 kPa (55-62 psi) | Go to Step 4 | Go to Fuel System Diagnosis |
| 4 | IMPORTANT: The fuel pressure will decrease 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 5 minutes.Does the fuel pressure decrease to less than the specified value? | 350 kPa (51 psi) | Go to Fuel System Diagnosis | Go to Step 5 |
| 5 | NOTE: Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding. Connect the J 39021 Fuel Injector Tester to a fuel injector using the J 44602 Injector Test Adapter. 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 ON and 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: 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 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 fuel pressure reading. Repeat steps 1 through 6 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 6 | Go to Symptoms - Engine Controls |
| 6 | Replace the affected fuel injector. Refer to Fuel Injectors and Fuel Rail Replacement . Did you complete the replacement? | Go to Step 7 | ||
| 7 | 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 may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure. |
| IMPORTANT |
|---|
| The fuel pressure will decrease 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 |
|---|
| 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 Special Tool
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 when the evaporative emissions (EVAP) leak diagnostic completes one test cycle. The malfunction indicator lamp (MIL) will illuminate after the EVAP leak diagnostic completes two test cycles only when a condition is detected.
- Operate the vehicle under the condition of the customers 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 fuel pipes may help find an intermittent condition.
- 3: This step tests for location of fuel leakage in the fuel lines.
- 4: This step tests for fuel leaks below the fuel level in the fuel tank.
- 5: This step tests for a location of fuel vapors escaping above the fuel level in the fuel tank.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | CAUTION: Refer to Gasoline/Gasoline Vapors Caution in Cautions and Notices. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information. Inspect the fuel tanks and the fuel pipes for damage or external leaks. Did you find fuel leaking from the fuel tank? | Go to Step 7 | Go to Step 3 |
| 3 | Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Inspect for fuel leaking from the fuel pipe. Did you locate a fuel leak from the fuel pipes? | Go to Step 8 | Go to Step 4 |
| 4 | Install the J 41415-40 or GE-41415-50 Fuel Tank Cap Adapter. See Special Tools . Connect the J 41413-200 Evaporative Emissions System Tester (EEST) to the J 41415-40 or GE-41415-50 . See Special Tools . Command the evaporative emissions (EVAP) vent valve ON with a scan tool. Pressurize the fuel tank with the J 41413-200 . Inspect for a fuel leak from the fuel tank. Did you locate a fuel leak from the fuel tank? | Go to Step 7 | Go to Step 5 |
| 5 | Turn the Nitrogen/Smoke valve on the J 41413-200 control panel to SMOKE. Use the remote switch to introduce smoke into the sealed system. Inspect the entire system with the with the J 41413-SPT High Intensity White Light for exiting smoke. Did you locate a leak source? | Go to Step 6 | Go to Diagnostic Aids |
| 6 | Repair the system as necessary. Did you complete the repair? | System OK | |
| 7 | Replace the fuel tank. Refer to Fuel Tank Replacement . Did you complete the repair? | System OK | |
| 8 | Replace the leaking fuel pipe. Refer to Fuel Hoses/Pipes Replacement - Filter to Tank and Fuel Hose/Pipes Replacement - Chassis . Did you complete the replacement? | System OK |
| CAUTION |
|---|
| Refer to Gasoline/Gasoline Vapors Caution in Cautions and Notices. |
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.
Test Procedure
- Test the fuel composition using J 44175 Fuel Composition Tester and J 44175-3 Instruction Manual.
- If water appears in the fuel sample, perform the following steps: Clean the fuel system. Refer to «Fuel System Cleaning»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-introduction__fuel-system-cleaning) . Replace the fuel filter. Refer to «Fuel Filter Replacement»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-46l-lh2-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 Tank Draining Procedure»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction__fuel-tank-draining-procedure) .
| 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
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 rail and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the fuel system components for rust or deterioration.
Alcohol concentrations more than 10 percent in the fuel can be detrimental to fuel system components. Alcohol contamination may cause fuel system corrosion, deterioration of rubber components, and subsequent fuel filter restriction. Fuel contaminated with alcohol may cause driveability conditions such as hesitation, lack of power, stalling, or no start. Some types of alcohol are more detrimental to fuel system components than others.
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, use the following procedure to test the fuel quality
- Fill the cylinder with fuel to the 90 ml (3.04 oz) mark with a 100 ml (3.38 oz) specified cylinder with 1 ml (0.34 oz) graduation marks.
- 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 that now contains both alcohol and water will be more than 10 ml (0.37 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 contaminants 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.
- Draw approximately 0.5 liter (0.53 qt) of fuel with an approved fuel container.
- Place the cylinder 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. If particles are found, clean the entire fuel system thoroughly. Refer to Fuel System Cleaning .
The ignition system utilizes an individual module/coil for each spark plug. The following 4 circuits support each ignition module/coil assembly.
- The ignition 1 voltage circuit
- The ground circuit
- Ignition control (IC) circuit
- Low reference circuit
Each ignition module/coil connects directly to its spark plug through a wire spring conductor internal to the spark plug boot. The IC circuits transmits timing pulses from the engine control module (ECM) to each ignition module/coil assembles in the proper sequence for the spark plug firing event. The ECM monitors each IC circuit for improper voltage levels. If an improper voltage level is detected on an IC circuit a DTC will set.
- This Electronic Ignition (EI) System Diagnostic table assumes that the battery is fully charged. Refer to «Battery Inspection/Test»(/cadillac/sts/i-2004-2007/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
- Other electrical, fuel, or mechanical conditions can cause an engine to crank but does not run, or set a DTC P0300 misfire code.
- An ignition coil, boots, or spark plugs may misfire only when moisture is present. Although difficult to test on this engine, selectively wetting down parts of the ignition system and monitoring for a misfire may help in isolating an intermittent condition. Replace any worn or torn spark plug boots or seals.
- If the ODD coils or EVEN coils fuse opens, this will also result in the loss of ignition 1 voltage to the odd or even fuel injectors.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 2 | Attempt to start the engine. Does the engine start and run? | Go to Step 37 | Go to Step 3 | |
| 3 | Turn OFF the ignition. Remove the underhood fuse block cover. Probe both test points of the EVEN coils fuse with a test lamp that is connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems. Does the test lamp illuminate on either test point of the fuse? | Go to Step 9 | Go to Step 4 | |
| 4 | Turn OFF the ignition. Probe both test points of the ODD coils fuse with a test lamp that is connected to a good ground. Does the test lamp illuminate on either test point of the fuse? | Go to Step 10 | Go to Step 5 | |
| 5 | Turn ON the ignition, with the engine OFF. Probe both test points of the EVEN coils fuse with a test lamp that is connected to a good ground. Does the test lamp illuminate on both test points of the fuse? | Go to Step 7 | Go to Step 6 | |
| 6 | Does the test lamp illuminate on one test point of the fuse? | Go to Step 11 | Go to Powertrain Relay Diagnosis | |
| 7 | Turn ON the ignition. Probe both test points of the ODD coils fuse with a test lamp that is connected to a good ground. Does the test lamp illuminate on both test points of the fuse? | Go to Step 19 | Go to Step 8 | |
| 8 | Does the test lamp illuminate on one test point of the fuse? | Go to Step 15 | Go to Powertrain Relay Diagnosis | |
| 9 | Turn OFF the ignition. Disconnect the 7-way electrical connector at the bank 2 ignition coil bracket. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical. Disconnect the underhood fuse block electrical connector that contains the ignition 1 voltage circuit for the bank 2 coils. Connect the negative battery cable at the battery. Probe the ignition 1 voltage circuit for the bank 2 ignition coils at the underhood fuse block electrical connector 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 55 | Go to Step 64 | |
| 10 | Turn OFF the ignition. Disconnect the 7-way electrical connector at the bank 1 ignition coil bracket. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical. Disconnect the underhood fuse block electrical connector that contains the ignition 1 voltage circuit for the bank 1 coils. Connect the negative battery cable at the battery. Probe the ignition 1 voltage circuit for the bank 1 ignition coils at the underhood fuse block electrical connector 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 55 | Go to Step 64 | |
| 11 | Turn OFF the ignition. Replace the EVEN coils fuse. Disconnect the 7-way electrical connector at the bank 2 ignition module/coil bracket. Monitor the EVEN coils fuse. Turn ON the ignition, with the engine OFF. Does the EVEN coils fuse open? | Go to Step 12 | Go to Step 13 | |
| 12 | Turn OFF the ignition. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical. Disconnect the underhood fuse block electrical connector that contains the ignition 1 voltage circuit to the bank 2 ignition coils. Connect the negative cable at the battery. Replace the EVEN coils fuse. Monitor the EVEN coils fuse. Turn ON the ignition, with the engine OFF. Does the EVEN coils fuse open? | Go to Step 64 | Go to Step 56 | |
| 13 | Turn OFF the ignition. Connect the 7-way bank 2 ignition module/coil electrical connector. Disconnect the electrical connectors at the bank 2 ignition module/coil assemblies. Monitor the EVEN coils fuse. Turn ON the ignition, with the engine OFF. Does the EVEN coils fuse open? | Go to Step 57 | Go to Step 14 | |
| 14 | Turn ON the ignition, with the engine OFF. Monitor the EVEN coils fuse. Connect one bank 2 ignition module/coil electrical connector at a time. Does the EVEN coils fuse open while connecting a ignition module/coil connector? | Go to Step 65 | Go to Intermittent Conditions | |
| 15 | Turn OFF the ignition. Replace the ODD coils fuse. Disconnect the 7-way electrical connector at the bank 1 ignition module/coil bracket. Monitor the ODD coils fuse. Turn ON the ignition, with the engine OFF. Does the ODD coils fuse open? | Go to Step 16 | Go to Step 17 | |
| 16 | Turn OFF the ignition. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical. Disconnect the underhood fuse block electrical connector that contains the ignition 1 voltage circuit to the bank 1 ignition coils. Connect the negative cable at the battery. Replace the ODD coils fuse. Monitor the ODD coils fuse. Turn ON the ignition, with the engine OFF. Does the ODD coils fuse open? | Go to Step 64 | Go to Step 56 | |
| 17 | Turn OFF the ignition. Connect the 7-way bank 1 ignition module/coil electrical connector. Disconnect the electrical connectors at the bank 1 ignition module/coil assemblies. Monitor the ODD coils fuse. Turn ON the ignition, with the engine OFF. Does the ODD coils fuse open? | Go to Step 57 | Go to Step 18 | |
| 18 | Turn ON the ignition, with the engine OFF. Monitor the ODD coils fuse. Connect one bank 1 ignition module/coil electrical connector at a time. Does the ODD coils fuse open while connecting a ignition module/coil connector? | Go to Step 65 | Go to Intermittent Conditions | |
| 19 | Turn ON the ignition, with the engine OFF. Disconnect the bank 2 electrical connectors at the ignition module/coils. Probe the ignition 1 voltage circuit for each ignition module/coil with a test lamp that is connected to a good ground. Refer to Troubleshooting with a Test Lamp or Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate at each ignition module/coil connector? | Go to Step 20 | Go to Step 21 | |
| 20 | Turn OFF the ignition. Remove the EVEN coils fuse from the underhood fuse block. Measure the resistance of the ignition 1 voltage circuit from the underhood fuse block to each ignition module/coil on bank 2 with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems. Does the resistance measure greater than the specified value to each ignition module/coil? | 2 ohms | Go to Step 23 | Go to Step 25 |
| 21 | Turn ON the ignition with the engine OFF. Disconnect the 7-way electrical connector for the ignition module/coils on bank 2. Probe the ignition 1 voltage circuit that leads from the underhood fuse block, to the 7-way electrical connector with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 58 | Go to Step 22 | |
| 22 | Turn OFF the ignition. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnect/Connect Procedure . Disconnect the underhood fuse block electrical connector that contains the ignition 1 voltage circuit for the bank 2 ignition module/coils. Connect the negative battery cable at the battery. Connect a 20-amp fused jumper wire from the battery positive voltage to the ignition 1 voltage circuit terminal at the underhood fuse block electrical connector. Refer to Using Fused Jumper Wires in Wiring Systems. Probe the ignition 1 voltage circuit at the 7-way bank 2 electrical connector that leads from the underhood fuse block, with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 24 | Go to Step 59 | |
| 23 | Turn OFF the ignition. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical. Disconnect the underhood fuse block electrical connector that contains the ignition 1 voltage circuit for the bank 2 ignition module/coils. Measure the resistance of the ignition 1 voltage circuit from the underhood fuse block electrical connector to each ignition module/ coil on bank 2 with a DMM. Does the resistance measure greater than the specified value to each ignition module/coil? | 2 ohms | Go to Step 60 | Go to Step 24 |
| 24 | Measure the resistance of the underhood fuse block ignition 1 voltage circuit for the bank 2 ignition module/coil with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems. Does the resistance measure more than the specified value? | 2 ohms | Go to Step 64 | Go to Intermittent Conditions |
| 25 | Turn ON the ignition, with the engine OFF. Disconnect the bank 1 electrical connectors at the ignition module/coils. Probe the ignition 1 voltage circuit for each ignition module/coil with a test lamp that is connected to a good ground. Does the test lamp illuminate at each ignition module/coil connector? | Go to Step 26 | Go to Step 27 | |
| 26 | Turn OFF the ignition. Remove the ODD coils fuse from the underhood fuse block. Measure the resistance of the ignition 1 voltage circuit from the underhood fuse block to each ignition module/coil on bank 1 with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems. Does the resistance measure greater than the specified value to each ignition module/coil? | 2 ohms | Go to Step 29 | Go to Step 31 |
| 27 | Turn ON the ignition, with the engine OFF. Disconnect the 7-way bank 1 ignition module/coil electrical connector. Probe the ignition 1 voltage circuit that leads from the underhood fuse block to the 7-way connector with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 58 | Go to Step 28 | |
| 28 | Turn OFF the ignition. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnect/Connect Procedure . Disconnect the underhood fuse block electrical connector that contains the ignition 1 voltage circuit for the bank 1 ignition module/coils. Connect the negative battery cable at the battery. Connect a 20-amp fused jumper wire from battery positive voltage to the ignition 1 voltage circuit at the underhood fuse block. Refer to Using Fused Jumper Wires in Wiring Systems. Probe the ignition 1 voltage circuit at the 7-way bank 1 electrical connector that leads from the underhood fuse block, with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 30 | Go to Step 59 | |
| 29 | Turn OFF the ignition. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical. Disconnect the underhood fuse block electrical connector that contains the ignition 1 voltage circuit for the bank 1 ignition module/coils. Measure the resistance of the ignition 1 voltage circuit from the underhood fuse block electrical connector to each ignition module/ coil on bank 1 with a DMM. Does the resistance measure greater than the specified value to each ignition module/coil? | 2 ohms | Go to Step 60 | Go to Step 30 |
| 30 | Measure the resistance of the underhood fuse block ignition 1 voltage circuit for the bank 1 ignition module/coil with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems. Does the resistance measure greater than the specified value? | 2 ohms | Go to Step 64 | Go to Intermittent Conditions |
| 31 | Turn OFF the ignition. Disconnect the electrical connectors at the bank 2 ignition module/coils assembly. Probe the ground circuit for each bank 2 ignition module/coil with a test lamp that is connected to battery positive voltage. Does the test lamp illuminate? | Go to Step 32 | Go to Step 61 | |
| 32 | Measure the resistance of the ground circuit from each ignition module/coil electrical connector on bank 2 to a good engine ground with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems. Does the resistance measure greater than the specified value from each ignition module/coil electrical connector? | 2 ohms | Go to Step 61 | Go to Step 33 |
| 33 | Turn OFF the ignition. Disconnect the electrical connectors at the bank 1 ignition module/coils assembly. Probe the ground circuit at each bank 1 ignition module/coil electrical connector with a test lamp that is connected to battery positive voltage. Does the test lamp illuminate? | Go to Step 34 | Go to Step 61 | |
| 34 | Measure the resistance of the ground circuit from each ignition module/coil electrical connector on bank 1 to a good engine ground with a DMM. Does the resistance measure greater than the specified value from each ignition module/coil? | 2 ohms | Go to Step 61 | Go to Step 35 |
| 35 | Turn OFF the ignition. Disconnect the bank 2 electrical connector at each of the ignition module/coils. Disconnect the electrical connector at the engine control module (ECM) that contains the low reference circuit for bank 2. Measure the resistance of the EST low reference circuit from each ignition module/coil to the ECM with a DMM. Refer to Troubleshooting with a Test Lamp in Wiring Systems. Does the resistance measure greater than the specified value? | 2 ohms | Go to Step 62 | Go to Step 36 |
| 36 | Disconnect the bank 1 electrical connector at each ignition module/coil. Measure the resistance of the EST low reference circuit from each ignition module/coil to the ECM with a DMM. Does the resistance measure greater than the specified value? | 2 ohms | Go to Step 62 | Go to Step 67 |
| 37 | Observe the misfire current counters with a scan tool. Does a cylinder indicate an increasing misfire count? | Go to Step 38 | Go to Intermittent Conditions | |
| 38 | Turn ON the ignition, with the engine OFF. Remove the underhood fuse block cover. Probe both test points of the fuse for the bank of cylinders that are identified as misfiring with a test lamp that is connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems. Does the test lamp illuminate on both test points of the fuse? | Go to Step 44 | Go to Step 39 | |
| 39 | Does the test lamp illuminate on one test point of the fuse? | Go to Step 40 | Go to Powertrain Relay Diagnosis | |
| 40 | Turn OFF the ignition. Replace the open fuse for the bank of cylinders identified as misfiring. Disconnect the 7-way electrical connector for the bank of cylinders identified as misfiring at the ignition module/coil bracket. Turn ON the ignition with the engine OFF. Does the fuse open? | Go to Step 41 | Go to Step 42 | |
| 41 | Turn OFF the ignition. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical. Disconnect the underhood fuse block electrical connector that contains the ignition 1 voltage circuit to the bank of cylinders identified as misfiring. Replace the open fuse. Connect the negative battery cable at the battery. Turn ON the ignition, with the engine OFF. Does the fuse open? | Go to Step 64 | Go to Step 56 | |
| 42 | Turn OFF the ignition. Connect the 7-way electrical connector at the ignition module/coil bracket. Disconnect the electrical connectors at the ignition module/coil assemblies on the bank of cylinders identified as misfiring. Turn ON the ignition with the engine OFF. Does the fuse open? | Go to Step 57 | Go to Step 43 | |
| 43 | Turn ON the ignition, with the engine OFF. Monitor the fuse for the bank of cylinders identified as misfiring. Connect each ignition module coil electrical connector one at a time. Does the fuse open while connecting an ignition module/coil connector? | Go to Step 65 | Go to Intermittent Conditions | |
| 44 | Turn OFF the ignition. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical. Disconnect the underhood fuse block electrical connector that contains the ignition 1 voltage circuit for the affected cylinder. Measure the resistance of the ignition 1 voltage circuit from the underhood fuse block electrical connector to the affected ignition module/coil with a DMM. Refer to Circuit Testing in Wiring Systems. Does the resistance measure greater than the specified value? | 2 ohms | Go to Step 60 | Go to Step 45 |
| 45 | Measure the resistance of the ignition 1 voltage bus bar circuit of the underhood fuse block for a high resistance or an open, with a DMM. Does the resistance measure greater than the specified value? | 2 ohms | Go to Step 64 | Go to Step 46 |
| 46 | Measure the resistance of the ground circuit from the ignition module/coil electrical connector of the affected cylinder to a good ground with a DMM. Does the resistance measure greater than the specified value? | 2 ohms | Go to Step 61 | Go to Step 47 |
| 47 | Disconnect the ECM electrical connector that contains the ignition coil control circuit for the affected cylinder. Measure the resistance of the ignition coil control circuit between the ignition module/coil electrical connector of the affected cylinder and the ECM electrical connector. Does the resistance measure more than the specified value? | 2 ohms | Go to Step 63 | Go to Step 48 |
| 48 | Disconnect the ECM electrical connectors. Measure the resistance of the low reference circuit from the ignition module/coil electrical connector to the ECM electrical connector with a DMM. Does the resistance measure greater than the specified value? | 2 ohms | Go to Step 62 | Go to Step 49 |
| 49 | Turn OFF the ignition. Disconnect the ignition module/coil assembly from the spark plugs on the bank of cylinders which indicated a misfire condition. Inspect the ignition module/coil assembly for the following: Any visible cracks, deterioration or other damage. Any carbon tracking or other signs of arcing. Any missing or damage spark plug boot springs. Replace the component if the inspection reveals a condition. Did you find a condition? | Go to Step 67 | Go to Step 50 | |
| 50 | Remove the spark plug for the cylinder that was identified as causing a misfire. Refer to Spark Plug Replacement . Does the spark plug indicate oil contamination? | Go to Base Engine Misfire with Excessive Oil Consumption in Engine Mechanical | Go to Step 51 | |
| 51 | Does the spark plug indicate coolant contamination? | Go to Base Engine Misfire with Coolant Consumption in Engine Mechanical | Go to Step 52 | |
| 52 | Exchange the suspected spark plug with a spark plug from a different cylinder on the same bank. Refer to Spark Plug Replacement . Reinstall the ignition module/coil assembly. Monitor the misfire current counters with a scan tool. Start the engine. Does the misfire move with the spark plug exchange? | Go to Step 66 | Go to Step 53 | |
| 53 | Turn OFF the ignition. Exchange the ignition module/coil on the cylinder identified as misfiring with a ignition module/coil assembly from a different cylinder on the same bank. Monitor the misfire current counters with a scan tool. Start the engine. Does the misfire move with the ignition module/coil exchange? | Go to Step 65 | Go to Step 54 | |
| 54 | Test for an intermittent and for a poor connection at the ignition module/coil electrical connector. 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 67 | Go to Base Engine Misfire without Internal Engine Noises in Engine Mechanical | |
| 55 | Repair the short to battery positive voltage in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 67 | ||
| 56 | Repair the short to ground in the ignition 1 voltage circuit between the underhood junction block and the 7-way electrical connector. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 67 | ||
| 57 | Repair the short to ground in the ignition 1 voltage circuit between the 7-way electrical connector and the ignition module/coils. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 67 | ||
| 58 | Repair the high resistance or an open in the ignition 1 voltage circuit between the 7-way electrical connector and the ignition module/coils. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 67 | ||
| 59 | Repair the high resistance or an open in the ignition 1 voltage circuit between the underhood fuse block electrical connector and the 7-way electrical connector. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 67 | ||
| 60 | Repair the high resistance or an open in the ignition 1 voltage circuit between the underhood fuse block electrical connector and the ignition module/coil electrical connectors. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 67 | ||
| 61 | Repair the high resistance or an open in the ground circuit for the ignition module/coil assembly. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 67 | ||
| 62 | Repair the high resistance or an open in the low reference circuit for the ignition module/coil assembly. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 67 | ||
| 63 | Repair the high resistance in the ignition coil control circuit. Did you complete the repair? | Go to Step 67 | ||
| 64 | Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems. Did you complete the replacement? | Go to Step 67 | ||
| 65 | Replace the ignition module/coil assembly. Refer to Ignition Coil(s) Replacement - Bank 1 or Ignition Coil(s) Replacement - Bank 2 . Did you complete the replacement? | Go to Step 67 | ||
| 66 | Replace the spark plug. Refer to Spark Plug Replacement . Did you complete the replacement? | Go to Step 67 | ||
| 67 | Were you sent to this diagnostic table from the Engine Cranks but Does Not Run diagnostic table? | Go to Step 69 | Go to Step 68 | |
| 68 | Were you sent to this diagnostic table from DTC P0300 diagnostic table? | Go to Step 70 | ||
| 69 | Replace any open fuses. Attempt to start the engine. Does the engine start and run? | Go to Step 71 | Go to Engine Cranks but Does Not Run | |
| 70 | Replace any open fuses. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Operate the vehicle within the conditions for running the DTC P0300. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? | Go to DTC P0300 | Go to Step 71 | |
| 71 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | |
Electronic Ignition (EI) System Diagnosis
Several states require that a vehicle pass on-board diagnostic (OBD) system tests and the inspection/maintenance (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 4 heated oxygen sensors, either all 4 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 as part of a service procedure.
Monitored Emission Control Systems
The OBD II System monitors all emission control systems that are on-board. Not all vehicles have a full complement of emission control systems. For example, a vehicle may not be equipped with secondary air injection (AIR) or exhaust gas recirculation (EGR). The OBD II regulations require monitoring of the following
- 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 | Value(s) | Yes | No |
|---|---|---|---|---|
| 1 | Perform the Diagnostic System Check - Vehicle in Vehicle DTC Information. 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 |
| 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 Inspection/Maintenance (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 or all of the I/M System Status indicators are set to NO.
Conditions for Running
- The barometric pressure (BARO) is more than 74 kPa.
- The start-up intake air temperature is between 4-32°C (39-90°F).
- The difference between the start-up engine coolant temperature (ECT) and the start-up intake air temperature (IAT) is less than 4.5°C (8°F).
- The battery voltage is more than 10.5 volts.
- The fuel level is between 15-85 percent.
Rough road conditions may prevent some of the tests from running. Extreme high or low ambient temperatures may prevent tests such as heated oxygen sensor (HO2S) heater and evaporative emission (EVAP) system from initiating. If a step is interrupted before completion, perform the remaining portion of the set procedures. Any portion of the set procedure that requires the engine at operating temperature may be repeated. This allows most of the diagnostics to run and the remaining tests can be performed using the individual System Set Procedures.
The scan tool can be used to monitor each of the I/M System Status indicators during the I/M Complete System Set Procedure. When all of the indicators for a test step have updated to YES, testing can move on to the next step even if the remaining portion of the test is not complete. For example, step 3 is designed to run the EVAP, secondary air injection (AIR), and HO2S tests. The procedure instructs the technician to operate the vehicle in the enable conditions for 6 minutes. If all 3 tests have updated to YES within 4 minutes, it is not necessary to continue with the enable conditions and testing can advance to the next step.
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 (O2S) 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: The I/M System Status only reports on whether or not a diagnostic has run, not the outcome of the test. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.
| 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 heated oxygen sensor (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 that 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 and Neutral for manual transmissions. Start the engine and 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: Acceleration at part throttle to 90 km/h (55 mph). Continued operation under these conditions for an additional 15 minutes. Is the action complete? | Go to Step 3 | ||
| 4 | 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 5 | Go to the I/M System Set Procedure for the indicated systems. | |
| 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 Inspection/Maintenance (I/M) System DTC Table | System OK |
| IMPORTANT |
|---|
| Whenever the ignition is turned ON, ignition positive voltage is supplied to the heated oxygen sensor (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. |
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 P0451 DTC P0455 DTC P0496 |
| Oxygen Sensor | DTC P0131 or P0151 DTC P0132 or P0152 DTC P0139 or P0159 DTC P0140 or P0160 DTC P0133 or P0153 |
| Oxygen Sensor Heater | DTC P0135 or P0155 DTC P0141 or P0161 |
Inspection/Maintenance (I/M) System DTC Table
The purpose of this test is to satisfy the enable criteria necessary to execute inspection/maintenance (I/M) readiness diagnostics for the Catalyst System. The test may be used to set the I/M System Status indicators to YES.
- The barometric pressure (BARO) is more than 74 kPa.
- The engine coolant temperature (ECT) is more than 63°C (145°F).
- The engine is in closed loop fuel control.
The control module runs a maximum of 12 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 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 that 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 and allow the engine to idle for 2 minutes. CAUTION: Refer to Road Test Caution in Cautions and Notices. Accelerate at part throttle to 90 km/h (55 mph) with this speed maintained for 10 minutes. 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 - Vehicle in Vehicle DTC Information | Go to Step 4 |
| 4 | Refer to the 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 numbers 4 and 5 of this step 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 - Vehicle in Vehicle DTC Information | System OK |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
Inspection/Maintenance (I/M) Catalyst System Set Procedure
The purpose of this test is to satisfy the enable criteria necessary to execute the inspection/maintenance (I/M) readiness diagnostics for the Evaporative Emission (EVAP) System. The test may be used in order 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. If a small leak is detected, a minimum of 3 drive cycles may be required before the I/M System Status will update to YES. 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.
- The barometric pressure (BARO) is more than 74 kPa.
- The start-up intake air temperature (IAT) is between 4-32°C (39-90°F).
- The difference between the start-up engine coolant temperature (ECT) and the start-up IAT is less than 4.5°C (8°F).
- The fuel level is between 15-85 percent.
- The battery voltage is more than 10.5 volts.
- The engine is in closed loop fuel control.
If there is an impending failure, the system may require more time to run the diagnostic than 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 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, including the A/C and the blower fan. IMPORTANT: Once the engine is started, DO NOT turn the engine OFF for the remainder of the procedure until the test is complete. Start and idle the engine 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 72 km/h (45 mph) with this speed maintained for 13 minutes. 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. IMPORTANT: If a small leak is detected, a minimum of 3 drive cycles may be required before the I/M System Status will update to YES. Repeat numbers 1-8 of this step as necessary. Observe the EVAP System Status with a 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 - Vehicle in Vehicle DTC Information | 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 numbers 4 and 5 of this step 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 - Vehicle in Vehicle DTC Information | 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 |
| IMPORTANT |
|---|
| If a small leak is detected, a minimum of 3 drive cycles may be required before the I/M System Status will update to YES. Repeat numbers 1-8 of this step as necessary. |
Inspection/Maintenance (I/M) Evaporative Emission (EVAP) System Set Procedure
The purpose of this test is to satisfy the enable criteria necessary to execute inspection/maintenance (I/M) readiness diagnostics for the heated oxygen sensor (HO2S)/oxygen sensor (O2S) System. The test may be used to set the I/M System Status to YES.
- The barometric pressure (BARO) is more than 74 kPa.
- The engine coolant temperature (ECT) reaches more than 63°C (144°F).
- The engine is running in closed loop fuel control.
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 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 that 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 and allow the engine to idle for 2 minutes. CAUTION: Refer to Road Test Caution in Cautions and Notices. In order for this test to run, the vehicle must operate in the following conditions: Accelerate at part throttle from 75-90 km/h (45-55 mph) with this speed maintained for 6 minutes. Deceleration to 0 km/h (0 mph) 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 - Vehicle in Vehicle DTC Information | Go to Step 4 |
| 4 | Refer to the 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 the 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 numbers 4 and 5 of this step 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 - Vehicle in Vehicle DTC Information | System OK |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
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 inspection/maintenance (I/M) readiness diagnostics for the Heated Oxygen Sensor (HO2S) System. The test may be used to set the I/M System Status to YES.
The battery voltage is more than 10 volts.
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 heated oxygen sensor (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 that the vehicle is within the Conditions for Running specified in the supporting text. Set the vehicle parking brake. Verify that 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 and allow the engine to idle for the specified time. CAUTION: Refer to Road Test Caution in Cautions and Notices. Accelerate at part throttle from 75-90 km/h (45-55 mph) with this speed maintained for 4 minutes. 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 - Vehicle in Vehicle DTC Information | 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 numbers 4 and 5 of this step 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 - Vehicle in Vehicle DTC Information | System OK |
| IMPORTANT |
|---|
| Whenever the ignition is turned ON, ignition positive voltage is supplied to the heated oxygen sensor (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. |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
Inspection/Maintenance (I/M) Heated Oxygen Sensor (HO2S) Heater System Set Procedure
See also:
• Diagnostic System Check - Vehicle
• Scan Tool Data List
• Throttle Body Service
• Charging System Test
• 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
• Scan Tool Data Definitions
• Oil Consumption Diagnosis
• Engine Compression Test
• Camshaft Cleaning and Inspection
• Cylinder Head Cleaning and Inspection
• Restricted Exhaust
• Silicon Contamination of Heated Oxygen Sensors Notice
• Heated Oxygen and Oxygen Sensor Notice
• Exhaust Leakage
• Ignition System Specifications
• Symptoms - HVAC Systems - Automatic
• Setting Camshaft Timing
• Loss of Coolant
• Thermostat Diagnosis
• Cooling Fan Inoperative
• Drive Belt Tensioner Diagnosis
• Valve Rocker Arms Cleaning and Inspection
• Intake Manifold Cleaning and Inspection
• Symptoms - Instrument Panel, Gages and Console
• Symptoms - Hydraulic Brakes
• Engine Mount Inspection
• Engine Control Module (ECM) Connector End Views
• Engine Controls Connector End Views
• Instrument Panel Cluster (IPC) Replacement
• Circuit Testing
• Wiring Repairs
• Control Module References
• Diagnostic Trouble Code (DTC) List - Vehicle
• Battery Inspection/Test
• Engine Cranks Slowly
• Special Tools
• DTC P0106
• Power and Grounding Connector End Views
• Quick Connect Fitting(s) Service (Metal Collar)
• Testing for Continuity
• Lifting and Jacking the Vehicle
• Fuel System Cleaning
• Fuel Tank Draining Procedure
• Probing Electrical Connectors
• Troubleshooting with a Digital Multimeter
• Base Engine Misfire with Excessive Oil Consumption
• Base Engine Misfire with Coolant Consumption
• Base Engine Misfire without Internal Engine Noises
• DTC P0300
• DTC P0420 or P0430
• Road Test Caution
• Poor Fuel Fill Quality
• Hard Start
• Surges/Chuggles
• Lack of Power, Sluggishness, or Sponginess
• Detonation/Spark Knock
• Hesitation, Sag, Stumble
• Cuts Out, Misses
• Poor Fuel Economy
• Rough, Unstable, or Incorrect Idle and Stalling
• Dieseling, Run-On
• Backfire
• Intermittent Conditions
• Symptoms - Engine Controls
• Inspection/Maintenance (I/M) System DTC Table