Engine Controls and Fuel - 8.1l - Troubleshooting & Diagnosis — Engine Performance — Testing & Diagnostics — Chevrolet Cab & Chassis Silverado 3500 (2003-2012)

Important Preliminary Inspections Before Starting

Perform Diagnostic System Check - Vehicle before using the symptom tables, and verify that all of the following are true

The powertrain control module (PCM) and malfunction indicator lamp (MIL) are operating correctly.
There are no DTCs stored.
Verify that the engine is not in a torque reduction mode. The PCM turns certain injectors OFF or reduces the engine timing when the PCM detects an over torque condition or an abusive maneuver.
Verify that the engine coolant temperature (ECT) is not above 130°C (266°F). This condition causes the PCM to operate in Engine Coolant Over Temperature-Fuel Disabled Mode. While in Engine Coolant Over Temperature-Fuel Disabled Mode, the PCM turns the fuel OFF to four cylinders at a time in order to keep engine temperatures from reaching damaging levels. The system perceives Engine Coolant Over Temperature as a lack of power, miss, or rough idle. If the vehicle is operating in Engine Coolant Over Temperature-Fuel Disabled Mode, refer to «Engine Overheating»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/cooling-system-mechanical/#engine-cooling-system__engine-overheating) for diagnosis.
The scan tool data is within the normal operating range, refer to «Scan Tool Data List»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-introduction-1-of-2__scan-tool-data-list) .
Verify the customer concern and locate the correct symptom in the table of contents. Inspect the items indicated under that symptom.

Visual/Physical Inspection

Several of the symptom procedures ask for a careful visual and physical inspection. This step is extremely important. The visual and physical inspection can lead to correcting a condition without further inspections, and can save valuable time. Ensure that

The PCM grounds are clean, tight, and in the proper location.
The vacuum hoses are not split or kinked, and properly connected, as shown on the Vehicle Emission Control Information label. Inspect thoroughly for any type of leak or restriction.
The mass air flow (MAF) sensor is properly installed. The arrows on the plastic portion of the sensor must point toward the engine.
The air intake ducts are not collapsed or damaged.
There are no leaks at the throttle body mounting area, the MAF sensor, or the intake manifold sealing surfaces.
The ignition wires are not cracked, brittle, or carbon tracked.
The engine harness wiring and terminals are properly connected and are not pinched or cut.

Intermittent

IMPORTANT

Inspect for improper installation of electrical components if an intermittent condition exists. Inspect for aftermarket theft deterrent devices, lights, and cellular phones. Verify that no aftermarket equipment is connected to the class 2 circuit. If you can not locate an intermittent condition, a cellular phone communication signal may cause the condition.

IMPORTANT

The condition may or may not turn ON the MIL or store a DTC.

Faulty electrical connections or wiring cause most intermittent conditions. Perform a careful visual and physical inspection of the suspect connectors for the following conditions

Improperly mated connector halves
Terminals that are not seated
Terminals that are damaged or improperly formed

Reform or replace connector terminals in the affected circuit to ensure proper contact tension. Refer to Connector Repairs . Remove the terminal from the connector body in order to inspect for poor terminal wire connection. Refer to Testing for Intermittent Conditions and Poor Connections .

Road test the vehicle with the DMM connected to the suspected circuit. An abnormal reading that is observed when the symptom occurs is a good indication that there is a malfunction in the circuit being monitored.

Use a scan tool to help detect intermittent conditions. Useful features of the GM Techline scan tool include the following

Trigger the Snapshot feature in order to capture and store engine parameters when the malfunction occurs. Review this stored information in order to see the specific running conditions that caused the malfunction.
Freeze Frame/Failure Records can also aid in locating an intermittent condition. Review and capture the information in the Freeze Frame/Failure Record associated with the intermittent DTC being diagnosed. Drive the vehicle within the conditions that were present when the DTC originally set.
Use the Plot Function on the scan tool to plot selected data parameters. Review this stored information to aid in locating an intermittent condition. Refer to the scan tool Users Guide for more information.

IMPORTANT

If the intermittent condition exists as a start and then stall, test for DTCs relating to the vehicle theft deterrent system. Test for improper installation of electrical options such as lights, cellular phones, etc.

Any of the following may cause an intermittent MIL with no stored DTC

The ignition coils are shorted to a ground or arcing at the ignition wires or the spark plugs.
The PCM grounds are loose or dirty. Refer to «Engine Controls Schematics»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-introduction-2-of-2) .
The ignition control (IC) wires are routed too close to the secondary ignition wires, coils, or the generator. Ensure that all of the circuits from the PCM to the ignition coils have good connections.
There is an open diode across the A/C compressor clutch or any other open diodes.

Use the following tables when diagnosing a symptom complaint

«Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
«Hard Start»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__hard-start)
«Surges/Chuggles»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__surgeschuggles)
«Lack of Power, Sluggishness, or Sponginess»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__lack-of-power-sluggishness-or-sponginess)
«Detonation/Spark Knock»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__detonationspark-knock)
«Hesitation, Sag, Stumble»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__hesitation-sag-stumble)
«Cuts Out, Misses»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__cuts-out-misses)
«Poor Fuel Economy»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__poor-fuel-economy)
«Poor Fuel Fill Quality»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__poor-fuel-fill-quality)
«Rough, Unstable, or Incorrect Idle and Stalling»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__rough-unstable-or-incorrect-idle-and)
«Dieseling, Run-On»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__dieseling-run-on)
«Backfire»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__backfire)

Hard Start

Inspection/Test	Action
DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies.
Preliminary	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views and Engine Controls Schematics . Search for bulletins.
Sensor/System	Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Connect a scan tool. Compare the engine coolant temperature to the intake air temperature (IAT) on a cold engine. The ECT and IAT sensor values should be within ± 3°C (5°F) of each other. If the ECT sensor is out of range with the IAT sensor, measure the resistance of the ECT sensor. Refer to Temperature Versus Resistance for resistance specifications. IMPORTANT: The embossed arrows on the MAF sensor indicate the direction of the intake air flow. The arrows must point toward the engine. Inspect the mass air flow (MAF) sensor installation. A MAF sensor that is incorrectly installed may cause a hard start. Install the MAF in the proper direction. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Inspect the camshaft position (CMP) sensor for proper mounting and/or a bad connection. An extended crank occurs if the PCM does not receive a CMP signal.
Fuel System	Inspect the fuel pump relay operation. The fuel pump should turn ON for 2 seconds when you turn ON the ignition. Refer to Fuel Pump Electrical Circuit Diagnosis . A faulty in-tank fuel pump check valve allows the fuel in the lines to drain back to the tank after the engine stops. Refer to Fuel System Diagnosis . Verify that both fuel injector fuses are not open. An open fuel injector fuse causes four injectors and four ignition coils not to operate. Inspect the injector circuits and the ignition coil circuits for an intermittent short to ground. Replace the fuse. Refer to Circuit Testing . Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) .
Ignition System	Verify that both fuel injector fuses are not open. An open fuel injector fuse causes four ignition coils and four fuel injectors not to operate. Inspect the ignition coil circuits and the fuel injector circuits for an intermittent short to ground. Refer to Circuit Testing . Replace the fuse. 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 bare or shorted ignition wires. Refer to Spark Plug Wire Inspection . Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .
Engine Mechanical	Inspect for the following conditions: Excessive oil in combustion chamber or leaking valve seals. Low cylinder compression. Combustion chambers for excessive carbon buildup-Clean the chambers using top engine cleaner. Follow the instructions on the can. Incorrect basic or worn engine parts-Inspect the following: Cylinder heads Camshaft Pistons, etc.

IMPORTANT
The embossed arrows on the MAF sensor indicate the direction of the intake air flow. The arrows must point toward the engine.

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 powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Verify the driver understands the operation of the transmission torque converter clutch (TCC) and A/C compressor operation as explained in the owners manual. Inform the customer how the TCC and the A/C clutch operates.
Sensor/System	NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice . 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 connections. Repair or replace damaged terminals. Refer to Connector Repairs .
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 (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary. Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . 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 . An inaccurate mass air flow (MAF) sensor Blockage on the inlet screen of the MAF sensor-Refer to Manifold Absolute Pressure Sensor Replacement . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted-Refer Intake Air Resonator Replacement . An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage . Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel System Diagnosis . An inaccurate MAF sensor Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without 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 gauge gap tool. Refer to 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. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .
Engine Mechanical	Verify that the engine coolant temperature (ECT) is not above 130°C (266°F). This condition causes the PCM to operate in Engine Coolant Over Temperature - Fuel Disabled Mode. While in Engine Coolant Over Temperature - Fuel Disabled Mode, the PCM turns fuel OFF to four cylinders at a time to keep engine temperatures from reaching damaging levels. The system perceives Engine Coolant Over Temperature - Fuel Disabled Mode as a lack of power, miss, or rough idle. If the vehicle operates in Engine Coolant Over Temperature - Fuel Disabled Mode, refer to Engine Overheating for diagnosis.
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. A TCC applying too soon can cause the engine to spark knock. Refer to Diagnostic Starting Point - Automatic Transmission .

NOTE
Refer to Silicon Contamination of Heated Oxygen Sensors Notice .

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

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. Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views 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	Inspect both injector fuses for being open. An open injector fuse causes four ignition coils and four injectors not to operate. Replace the fuse. Inspect the ignition coil circuits and the injector circuits for an intermittent short to ground. Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Inspect the fuel injectors. Refer to Fuel Injector Solenoid Coil Test . Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . 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 . An inaccurate mass air flow (MAF) sensor Blockage on the inlet screen of the MAF sensor-Refer to Manifold Absolute Pressure Sensor Replacement . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted-Refer Intake Air Resonator Replacement . An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage . Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel System Diagnosis . An inaccurate MAF sensor Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without 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 Knock Sensor (KS) System Description .
Ignition System	Verify that both fuel injector fuses are not open. An open fuel injector fuse causes four ignition coils and four fuel injectors not to operate. Inspect the ignition coil circuit and the injector circuits for an intermittent short to ground. Refer to Circuit Testing . Replace the fuse. 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. 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 gauge gap tool. Refer to 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. If a misfiring cylinder can be located with a misfire, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .
Engine Mechanical	Verify that the engine coolant temperature (ECT) is not above 130°C (266°F). This condition causes the PCM to operate in Engine Coolant Over Temperature - Fuel Disabled Mode. While in Engine Coolant Over Temperature - Fuel Disabled Mode, the PCM will disable the fuel injectors to four cylinders at a time to keep engine temperatures from reaching damaging levels. The system perceives the Engine Coolant Over Temperature - Fuel Disabled Mode as a lack of power, miss, or rough idle. If the vehicle operates in Engine Coolant Over Temperature - Fuel Disabled Mode, refer to Engine Overheating for diagnosis. Inspect for excessive oil in the combustion chambers and leaking valve seals. Test for low cylinder compression. Inspect for incorrect basic engine parts, including the following: The camshaft The cylinder head The pistons, etc.
Additional Inspections	Inspect the exhaust system for possible restrictions. Perform the following: Inspect the exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or internal failure. Inspect for plugged three-way catalytic converters by comparing the exhaust system back pressure on each side of the engine. Test back pressure by removing the secondary air injection (AIR) check valves near the exhaust manifolds. Refer to Restricted Exhaust . Inspect the transmission torque converter clutch (TCC) for proper operation. Refer to Diagnostic Starting Point - Automatic Transmission .

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

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 change with throttle opening.
Preliminary Inspections	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views 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	Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . Water intrusion in the heated oxygen sensor (HO2S) connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage . Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel System Diagnosis . An inaccurate mass air flow (MAF) sensor-Refer to Scan Tool Data List . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Vacuum hoses that are split, kinked, or improperly connected
Ignition System	Verify that the spark plugs are of the proper heat range. Refer to Spark Plug Inspection .
Engine Cooling System	Inspect for obvious overheating conditions: Low engine coolant-Refer to Loss of Coolant for the type and amount of engine coolant to be used. Restricted air flow to the radiator or restricted coolant flow through the radiator Inoperative cooling fan-Refer to Cooling Fan Inoperative (Diesel) .
Engine Mechanical	Inspect for the following engine mechanical conditions: Excessive oil in combustion chamber-Leaking valve seals. Low cylinder compression. Combustion chambers for excessive carbon buildup-Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can. Inspect for incorrect basic engine parts. Inspect the following: The camshaft. The cylinder heads. The pistons, etc.
Additional Inspections	Inspect the park/neutral position (PNP) switch operation. Refer to Range Selector Displays Incorrect Range for the 4L60-E/4L65-E transmission or Range Selector Displays Incorrect Range . 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 .

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. Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Ground Distribution Schematics .
Sensor/System	Inspect the manifold absolute pressure (MAP) sensor operation.
Fuel System	Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Verify that both fuel injector fuses are not open. An open fuel injector fuse causes 4 ignition coils and 4 fuel injectors not to operate. Inspect the ignition coil circuits and the fuel injector circuits for an intermittent short to ground. Refer to Circuit Testing and Wiring Repairs . Replace the fuse. Inspect the fuel injectors. Refer to Fuel Injector Solenoid Coil Test . Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . 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 . An inaccurate mass air flow (MAF) sensor-Refer to Scan Tool Data List . Blockage on the inlet screen of the MAF sensor-Refer to Manifold Absolute Pressure Sensor Replacement . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted-Refer Intake Air Resonator Replacement . An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage . Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel System Diagnosis . An inaccurate MAF sensor-Refer to Scan Tool Data List . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without 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. Test for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis for the procedure. 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 condition. Gap the spark plugs using a wire gage gap tool. Refer to Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .
Engine Cooling System	Inspect the engine thermostat for proper operation and for proper heat range. Refer to Thermostat Diagnosis .
Additional Inspections	Inspect the generator output voltage. Repair the charging system if the generator output voltage is less than 9 volts or more than 16 volts.

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

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 powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views 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 Solenoid 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 (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . 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 . An inaccurate mass air flow (MAF) sensor-Refer to Scan Tool Data List . 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-Refer Intake Air Resonator Replacement . An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage . Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel System Diagnosis . An inaccurate MAF sensor-Refer to Scan Tool Data List . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without 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.
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. Test 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 may cause a driveability problem. Refer to Spark Plug Inspection . Gap the spark plugs using a wire gauge gap tool. Refer to Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Visually and physically inspect the secondary ignition for the following conditions: The ignition wires arcing to ground The ignition wires for proper engagement to spark plug The ignition coils for cracks or carbon tracking Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 .
Engine Mechanical	Inspect engine mechanical for the following conditions: Inspect compression. Sticking or leaking valves Worn camshaft lobes Valve timing Bent push rods Worn rocker arms Broken valve springs Excessive oil in combustion chamber. For incorrect basic engine parts inspect the following: The camshaft The cylinder heads. The pistons, etc.
Additional Inspections	Inspect the exhaust system for possible restrictions. Inspect for the following: Inspect the exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or possible internal failure. Inspect for possible plugged catalytic converters by comparing the exhaust system back pressure on each side of engine. Refer to Restricted 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.

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

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. Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views and Engine Controls Schematics . Inspect the owners driving habits for the following conditions: The A/C ON or the Defroster mode ON full time The tires at the correct pressure Excessively heavy loads being carried The acceleration rate is 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	Inspect the type, quality, and alcohol content of the fuel. Oxygenated fuels have lower energy and may deliver reduced fuel economy. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Test the fuel injectors. Refer to Fuel Injector Solenoid 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 (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Inspect that each fuel injector harness is connected to the correct injector and cylinder. Relocate the injector harnesses as necessary. Inspect for foreign material accumulation in the throttle bore, coking on the throttle valve, or on the throttle shaft. Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . 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 . An inaccurate mass air flow (MAF) sensor-Refer to Scan Tool Data List . Blockage on the inlet screen of the MAF sensor-Refer to Manifold Absolute Pressure Sensor Replacement . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted-Refer Intake Air Resonator Replacement . 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. Inspect the crankcase ventilation system. Refer to Crankcase Ventilation System Inspection/Diagnosis . Inspect for an inaccurate speedometer. Refer to Instrument Cluster Gages Inoperative . Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Knock Sensor (KS) System Description .
Ignition System	Inspect for proper ignition voltage output with the J 26792 Spark Tester. 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 condition. Refer to Spark Plug Inspection . Gap the spark plugs using a wire gage gap tool Refer to Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Refer to Spark Plug Inspection . Visually and physically inspect the secondary ignition for the following conditions: Ignition wires arcing to ground Ignition wires for proper routing 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 Electronic Ignition (EI) System Diagnosis .
Engine Cooling System	Inspect the engine coolant level for being low. Refer to Loss of Coolant . Inspect the engine thermostat for proper operation and for the correct heat range. Refer to Thermostat Diagnosis .
Engine Mechanical	Inspect engine mechanical for the following conditions: Compression. Sticking or leaking valves Worn camshaft lobes Valve timing Bent push rods Worn rocker arms Broken valve springs Excessive oil in combustion chamber-Leaking valve seals. For incorrect basic engine parts inspect for the following: The camshaft. The cylinder heads. The pistons, etc.
Additional Inspections	Visually and physically inspect 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. Refer to Torque Converter Diagnosis . Inspect the exhaust system for a possible restriction. Inspect for the following: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure For possible plugged three-way catalytic converters by comparing the exhaust system back pressure on each side of the engine-Inspect the back pressure by removing the secondary air injection (AIR) check valves near the exhaust manifolds. Refer to Restricted 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 park neutral position (PNP) switch circuit. Refer to Range Selector Displays Incorrect Range for the 4L60-E/4L65-E transmission or Range Selector Displays Incorrect Range for the 4L80-E/4L85-E transmission. Inspect the brake system for dragging or improper operation. Refer to Brake Caliper Inspection . Verify that the vehicle operator does not drive with a foot on the brake pedal.

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

Poor Fuel Economy

Poor Fuel Fill Quality

Problem	Causes
DEFINITION: Difficulty when refueling the vehicle.
Difficult to fill	If the vehicle is equipped with dual fuel tanks and a single filler neck the flow of the fuel into the tanks may exceed the ability of the system to compensate, the fill nozzle will automatically shut off. The system will require 10-20 seconds to equalize pressure before filling can resume. Refer to Fuel System Description . The check valve is stuck closed. The fill limiter vent valve is stuck closed. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) . The evaporative emission (EVAP) canister is restricted. Refer to Evaporative Emission Canister Replacement (Pickup) or Evaporative Emission Canister Replacement (Cab/Chassis) . The EVAP canister vent solenoid is stuck closed. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement (Pickup) Evaporative Emission Canister Vent Solenoid Valve Replacement (Cab/Chassis) . Restricted EVAP pipes-Refer to Evaporative Emission Hoses/Pipes Replacement - Canister/Fuel Tank . High reid vapor pressure High fuel temperature The fuel filler hose/pipe is pinched, kinked or blocked. Refer to Filler Tube Replacement (Pickup) or Filler Tube Replacement (Cab/Chassis - Front) or Filler Tube Replacement (Cab/Chassis - Rear) . The fuel feed hose, or crossover hose, is pinched, kinked or blocked. Refer to Fuel Injection Fuel Rail Assembly Replacement . The ignition switch is ON.
Over fill	The pressure relief valve in the fill limiter vent valve is stuck open. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) . The pressure relief valve in the fill limiter vent is valve leaking. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) . The fill limiter vent valve is stuck open. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) . The fill limiter vent valve is leaking. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) .
Premature shut-off of the fuel dispensing nozzle	The fill limiter vent valve is stuck closed. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) . The EVAP canister is restricted. Refer to Evaporative Emission Canister Replacement (Pickup) or Evaporative Emission Canister Replacement (Cab/Chassis) . The EVAP canister vent solenoid is stuck closed. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement (Pickup) Evaporative Emission Canister Vent Solenoid Valve Replacement (Cab/Chassis) . Restricted EVAP pipes-Refer to Evaporative Emission Hoses/Pipes Replacement - Canister/Fuel Tank . High Reid vapor pressure High fuel temperature The fuel filler hose/pipe is pinched, kinked or blocked. Refer to Filler Tube Replacement (Pickup) or Filler Tube Replacement (Cab/Chassis - Front) or Filler Tube Replacement (Cab/Chassis - Rear) . The fuel feed hose, or crossover hose, is pinched, kinked or blocked. Refer to Fuel Injection Fuel Rail Assembly Replacement . The ignition switch is ON.
Fuel spit back	The check valve is stuck open. The check valve is stuck closed. The check valve is leaking. High Reid vapor pressure High fuel temperature
Liquid fuel in the EVAP canister	The fill limiter vent valve is stuck open. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) . The fill limiter vent valve is leaking. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) .
Liquid fuel leak	The pressure relief valve in the fill limiter vent valve is stuck open. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) . The pressure relief valve in the fill limiter vent valve is leaking. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) . The fuel filler hose is loose or torn. Refer to Filler Tube Replacement (Pickup) or Filler Tube Replacement (Cab/Chassis - Front) or Filler Tube Replacement (Cab/Chassis - Rear) . The fuel feed hose, or crossover hose, is loose or torn. Refer to Fuel Injection Fuel Rail Assembly Replacement . The fill limiter vent valve is stuck open. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) .
Fuel odor	The pressure relief valve in the fill limiter vent valve is stuck open. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) . The pressure relief valve in the fill limiter vent valve is leaking. Refer to Fuel Tank Replacement (Pickup) or Fuel Tank Replacement (Cab/Chassis - Front) or Fuel Tank Replacement (Cab/Chassis - Rear) . The EVAP canister is saturated. Refer to Evaporative Emission Canister Replacement (Pickup) or Evaporative Emission Canister Replacement (Cab/Chassis) .

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. Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views and Engine Controls Schematics . Remove and inspect the air filter element for dirt or for restrictions. Refer to Air Cleaner Element Replacement . Replace as necessary.
Fuel System	Inspect the fuel injectors. Refer to Fuel Injector Solenoid 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 (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Inspect that each fuel injector harness is connected to the correct injector/cylinder. Relocate fuel injector harnesses as necessary. Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . 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 . An inaccurate mass air flow (MAF) sensor Blockage on the inlet screen of the MAF sensor-Refer to Manifold Absolute Pressure Sensor Replacement . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted-Refer Intake Air Resonator Replacement . An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage . Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel System Diagnosis . An inaccurate MAF sensor Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Vacuum hoses that are split, kinked, or improperly connected
Sensor/System	Inspect the crankcase ventilation valve for proper operation. Place a finger over the inlet hole of the valve end several times. The valve should snap back. If not, replace the valve. Refer to Crankcase Ventilation System Description . 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 for procedure. Remove spark plugs and check 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. Refer to Spark Plug Inspection . Gap the spark plugs using a wire gage gap tool. Refer to Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Visually and physically inspect secondary ignition for the following conditions: Ignition wires arcing to ground Ignition wires for proper routing 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. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .
Engine Mechanical	Inspect engine mechanical for the following conditions: Compression. Sticking or leaking valves Worn camshaft lobes Valve timing Bent push rods Worn rocker arms Broken valve springs Excessive oil in combustion chamber or leaking valve seals. For incorrect basic engine parts. Inspect the following: The camshaft. The cylinder heads. The pistons, etc.
Additional Inspections	Inspect the exhaust system for possible restrictions. Inspect for the following: Inspect the exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or possible internal failure. Inspect for possible plugged three-way catalytic converters by comparing exhaust system back pressure on each side of engine. Inspect the back pressure by removing secondary air injection (AIR) check valves near exhaust manifolds. Refer to Restricted 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 secondary ignition wires or high voltage components near the ignition control circuits. Inspect the park neutral position (PNP) switch circuit. Refer to Park/Neutral Position Switch Adjustment . Inspect for faulty motor mounts. Refer to Engine Mount Inspection . Inspect the intake manifold and the exhaust manifold passages for casting flash. Inspect for an exhaust gas recirculation (EGR) valve stuck open or EGR pintle not seating properly. Inspect EGR valve gasket for leaks.

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice .

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 powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views and Engine Controls Schematics .
Fuel System	Inspect the fuel injectors for a leaking condition. Refer to Fuel System Diagnosis for the proper procedure.

Dieseling, Run-On

Backfire

Inspections	Actions
DEFINITION: Fuel ignites in the intake manifold or in the exhaust system, making a loud popping noise.
Preliminary Inspections	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views and Engine Controls Schematics .
Fuel System	Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Inspect the fuel injectors. Refer to Fuel Injector Solenoid Coil Test . Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary.
Sensor/System	Inspect the secondary air injection (AIR) system. Inspect the air intake system and crankcase for air leaks. Inspect the crankcase ventilation valve for proper operation. Place a finger over the inlet hole in the valve end several times. The valve should snap back. If not, replace the valve. Refer to Crankcase Ventilation System Description . Inspect for an inaccurate speedometer. Refer to Instrument Cluster Gages Inoperative . Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Knock Sensor (KS) System Description .
Ignition System	Inspect for proper ignition voltage output with the J 26792 Spark Tester. 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 condition. Refer to Spark Plug Inspection . Gap the spark plugs using a wire gage gap tool. Refer to Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Refer to Spark Plug Inspection for diagnosis. Visually and physically inspect secondary ignition for the following conditions: Ignition wires arcing to ground Ignition coils arcing to ground 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. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 . Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .
Engine Cooling System	Inspect the engine coolant level for being low. Refer to Loss of Coolant . Inspect the engine thermostat for proper operation and for the correct heat range. Refer to Thermostat Diagnosis .
Engine Mechanical	Inspect engine mechanical for the following conditions: Compression. Sticking or leaking valves Worn camshaft lobes Valve timing Bent push rods Worn rocker arms Broken valve springs Excessive oil in combustion chamber or leaking valve seals. For incorrect basic engine parts. Inspect the following: The camshaft The cylinder heads The pistons, etc.
Additional Inspections	Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on the Vehicle Emission Control Information label. Inspect the intake manifold and the exhaust manifold passages for casting flash. Inspect the transmission torque converter clutch (TCC) operation. The scan tool should indicate an RPM drop when the TCC is commanded ON. Refer to Torque Converter Diagnosis for the 4L60-E/4L65-E transmission or Torque Converter Diagnosis . Inspect the exhaust system for possible restrictions. Inspect the following: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure Possible plugged 3-way catalytic converters by comparing exhaust system back pressure on each side of engine-Inspect back pressure by removing AIR check valves near exhaust manifolds. Refer to Restricted 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 condition exists, inspect for high voltage components near the ignition control circuits. Inspect the park/neutral position (PNP) switch operation. Refer to Park/Neutral Position Switch Adjustment . Inspect for faulty motor mounts. Refer to Engine Mount Inspection . Inspect the intake manifold and the exhaust manifold passages for casting flash.

Backfire

Diagnostic Instructions

Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
«Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Circuit/System Description

Ignition voltage is supplied to the malfunction indicator lamp (MIL). The engine control module (ECM) turns the MIL ON by grounding the MIL control circuit.

Reference Information

Schematic Reference

«Instrument Cluster Schematics»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-and-gauges)
«Engine Controls Schematics»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-introduction-2-of-2)

Connector End View Reference

«Displays and Gages Connector End Views»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-and-gauges)
«Powertrain Control Module Connector End Views»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-introduction-2-of-2)

Electrical Information Reference

«Circuit Testing»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__circuit-testing)
«Connector Repairs»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__connector-repairs)
«Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
«Wiring Repairs»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

«Scan Tool Data List»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-introduction-1-of-2__scan-tool-data-list)
«Scan Tool Output Controls»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-introduction-1-of-2__scan-tool-output-controls)
«Scan Tool Data Definitions»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-introduction-1-of-2__scan-tool-data-definitions)

Circuit/System Verification

Ignition ON, the MIL should turn ON and OFF when commanded with a scan tool.

Circuit/System Testing

Ignition OFF, disconnect the harness connector at the instrument panel cluster (IPC).
Ignition ON, verify that a test lamp illuminates between the ignition circuit and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, replace the IPC.
Connect a test lamp between the control circuit and the ignition circuit.
Command the MIL ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
If all circuits test normal, replace the IPC.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

«Control Module References»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)
«Instrument Cluster Replacement»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-and-gauges)

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 (Non-HP2)»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Inspection/Test (HP2)»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/charging-system/#battery-charging-system-and-starting-system) .
The engine cranking speed is acceptable. Refer to «Engine Cranks Slowly»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/charging-system/#battery-charging-system-and-starting-system__engine-cranks-slowly) .
There is adequate fuel in the fuel tank.

Step	Action	Values	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
2	IMPORTANT: DO NOT allow the ignition switch to be interrupted during this step. Crank the engine for the specified amount of time.Does the scan tool display any DTCs that failed this ignition?	15 seconds	Go to Diagnostic Trouble Code (DTC) List - Vehicle	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	Go to Step 4
4	Turn ON the ignition, with the engine OFF. Probe both test points of the PCM 1 fuse located in the underhood fuse block, with 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 Ignition Relay Diagnosis
5	Turn OFF the ignition. Disconnect the spark plug wire from the spark plug. Install the J 26792 Spark Tester to the spark plug wire. Attach the clamp end of the spark tester to a good engine ground. Observe the spark tester. Crank the engine. Repeat the test for the remaining cylinders. Does the spark tester produce a spark on all cylinders?		Go to Step 6	Go to Electronic Ignition (EI) System Diagnosis
6	Monitor the ignition 1 signal parameter with a scan tool. Is the ignition 1 signal parameter at the specified value?	B+	Go to Step 7	Go to Step 10
7	Command the fuel pump ON with a scan tool. Does the fuel pump operate?		Go to Step 8	Go to Fuel Pump Electrical Circuit Diagnosis
8	Turn OFF the ignition. Install a fuel pressure gage. Refer to Fuel System Diagnosis . IMPORTANT: The fuel pump operates for about 2 seconds when the ignition is turned ON. The fuel pressure must be observed when the fuel pump is operating. Turn ON the ignition, with the engine OFF. Observe the fuel pressure while the fuel pump is operating. Is the fuel pressure within the specified range?	385-425 kPa (55-62 psi)	Go to Step 9	Go to Fuel System Diagnosis
9	Inspect for the following conditions: The engine coolant temperature (ECT) sensor is not close to the actual engine temperature. The duct work between the mass air flow (MAF) sensor and the throttle body for air leaks A restricted exhaust system-Refer to Restricted Exhaust . A malfunctioning MAF sensor may cause a no start or a stall after a start. If you suspect this, disconnect the MAF sensor. The powertrain control module (PCM) will default to the speed density in order to calculate the engine load and the intake air flow. If disconnecting the MAF sensor corrects the condition and the connections are OK. Refer to DTC P0102 . The spark plugs for being gas fouled-Refer to Spark Plug Inspection . An engine mechanical failure that causes an engine not to start such as timing chain, low compression-Refer to Symptoms - Engine Mechanical . Compare the MAP/BARO parameters to another vehicle. The parameter values should be close to each other. Did you complete the action?		Go to Step 13
10	Test the ignition 1 voltage circuit for an open or for a short to ground. Refer to Circuit Testing and Wiring Repairs . Replace the fuse if necessary. Did you find and correct the condition?		Go to Step 13	Go to Step 11
11	Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?		Go to Step 13	Go to Step 12
12	Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?		Go to Step 13
13	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Attempt to start the engine. Does the engine start the continue to run?		Go to Step 14	Go to Step 2
14	Allow the engine to reach operating temperature. Observe the DTC information with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle	System OK

IMPORTANT
DO NOT allow the ignition switch to be interrupted during this step.

IMPORTANT
The fuel pump operates for about 2 seconds when the ignition is turned ON. The fuel pressure must be observed when the fuel pump is operating.

Engine Cranks but Does Not Run

Circuit Description

The ignition relay is a normally open relay. The relay armature is held in the open position by spring tension. When the ignition switch is turned to the run or start position, current will flow through the relay coil. A wire connected to the other end of the relay coil completes the path to ground. The electomagnetic field created by the relay coil, overcomes the spring tension and moves the armature allowing the relay contacts to close. The closed relay contacts allow current to flow from the battery to the following fuses

The PCM 1 fuse
The ETC/ECM fuse
The INJ 1 fuse
The INJ 2 fuse
The SBA fuse, if equipped

When the ignition switch is turned to the OFF position, the electromagnetic field collapses. This action allows the spring tension to move the armature away from the relay contacts, which interrupts current flow to the fuses.

If the ignition relay fails to close, the engine will crank, but will not run. The class 2 communications will be available with the use of a scan tool.

The ignition relay table assumes that the vehicle battery is fully charged. Refer to Battery Inspection/Test (Non-HP2) or Battery Inspection/Test (HP2) .

Step	Action	Yes	No
Schematic Reference: Power Distribution Schematics and Ground Distribution Schematics and Engine Controls Schematics Connector End View Reference: Powertrain Control Module 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
2	Turn ON the ignition, with the engine OFF. Remove the underhood junction block cover. Probe the following fuses with a test lamp that is connected to a good ground: The PCM 1 fuse The ETC/ECM fuse The INJ 1 fuse The INJ 2 fuse The SBA fuse, if equipped-Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate on at least one test point of each fuse?	Go to Step 3	Go to Step 10
3	Turn OFF the ignition. Probe both test points of the PCM 1 fuse with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate on either test point of the fuse?	Go to Step 4	Go to Step 30
4	Turn OFF the ignition. Remove the ignition relay from the underhood junction block with the J 43244 Relay Puller Pliers. Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) . NOTE: Refer to Test Probe Notice . Probe the ignition 1 voltage circuit of the ignition relay at the underhood junction block with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate?	Go to Step 7	Go to Step 5
5	Test the relay load bus bar of the underhood junction block between the ignition relay and the fuses to the circuit components for a short to battery positive voltage. Refer to Circuit Testing . Did you find a condition?	Go to Step 29	Go to Step 6
6	Turn OFF the ignition. Remove the following fuses from the underhood junction block: The PCM 1 fuse The ETC/ECM fuse The INJ 1 fuse The INJ 2 fuse The SBA fuse, if equipped Probe the above fuse terminals in the underhood junction block with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate at any of the fuse terminals?	Go to Diagnostic System Check - Vehicle	Go to Step 27
7	Turn OFF the ignition. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection (Auxiliary Battery) or Battery Negative Cable Disconnection and Connection (Single Battery) . Disconnect the underhood junction block electrical connector that contains the ignition 1 voltage circuit for the ignition relay. Disconnect the ignition switch electrical connector that contains the ignition 1 voltage circuit for the ignition relay. Connect the negative battery cable to the battery. Test the ignition 1 voltage circuit for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 30	Go to Step 8
8	Turn OFF the ignition. Probe the ignition 1 voltage terminal on the ignition switch side of the ignition switch electrical connector with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate?	Go to Step 28	Go to Step 9
9	Test the ignition 1 voltage bus bar circuit in the underhood junction block for a short to battery positive voltage. Refer to Circuit Testing . Did you find a condition?	Go to Step 29	Go to Step 27
10	Turn OFF the ignition. Inspect the 40-amp IGN B fuse in the underhood junction block. Refer to Circuit Protection - Fuses . Is the fuse open?	Go to Step 11	Go to Step 18
11	Remove the 40-amp IGN B fuse from the underhood junction block. NOTE: Refer to Test Probe Notice . Probe both fuse terminals in the underhood junction block with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate on at least one fuse terminal?	Go to Step 12	Go to Step 17
12	Test the ignition 1 voltage circuit between the ignition switch and the underhood junction block for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 30	Go to Step 13
13	Test the ignition switch assembly for a short to ground. Refer to Circuit Testing . Did you find a condition?	Go to Step 28	Go to Step 14
14	Test the battery positive voltage circuit between the underhood junction block and the ignition switch for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 30	Go to Step 15
15	Test the battery positive voltage bus bar circuit of the underhood junction block between the 40-amp IGN B fuse and the ignition switch for a short to ground. Did you find a condition?	Go to Step 29	Go to Step 16
16	Test the ignition 1 voltage bus bar circuit of the underhood junction block that contains the ignition relay for a short to ground. Did you find a condition?	Go to Step 29	Go to Step 27
17	Turn OFF the ignition. Probe the mounting stud for the battery positive cable at the underhood junction block with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate?	Go to Step 29	Go to Diagnostic System Check - Vehicle .
18	Turn OFF the ignition. Remove the ignition relay with the J 43244 from the underhood junction block. Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) . NOTE: Refer to Test Probe Notice . Probe the battery positive voltage circuit of the ignition relay at the underhood junction block with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate?	Go to Step 19	Go to Step 29
19	Turn ON the ignition, with the engine OFF. Probe the ignition 1 voltage circuit of the ignition relay at the underhood junction block with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate?	Go to Step 23	Go to Step 20
20	Turn OFF the ignition. Test the ignition 1 voltage circuit between the ignition switch and the underhood junction block for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 30	Go to Step 21
21	Test the ignition switch assembly for a high resistance or for an open. Refer to Circuit Testing . Did you find a condition?	Go to Step 28	Go to Step 22
22	Test the battery positive voltage circuit between the ignition switch and the underhood junction block for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 30	Go to Step 29
23	Turn ON the ignition, with the engine OFF. Probe the coil ground circuit of the ignition relay at the underhood junction block with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate?	Go to Step 25	Go to Step 24
24	Turn OFF the ignition. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection (Auxiliary Battery) or Battery Negative Cable Disconnection and Connection (Single Battery) . Disconnect the underhood junction block electrical connectors. Test the coil ground circuit of the ignition relay at the underhood junction block electrical connector for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 30	Go to Step 29
25	Turn OFF the ignition. Jumper the ignition relay battery positive voltage circuit and the ignition relay load circuit together at the underhood junction block with a 20-amp fused jumper wire. Refer to Using Fused Jumper Wires . Probe the following fuses with a test lamp that is connected to a good ground: PCM 1 ETC/ECM INJ 1 INJ 2 SBA, if equipped Refer to Probing Electrical Connectors and Troubleshooting with a Test Lamp . Does the test lamp illuminate on at least one test point of each fuse?	Go to Step 26	Go to Step 29
26	Test for an intermittent and for a poor connection at the underhood junction block, ignition relay connector location. Refer to Testing for Intermittent Conditions and Poor Connections . Did you find a condition?	Go to Step 29	Go to Step 27
27	Replace the ignition relay. Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) . Did you complete the replacement?	Go to Step 30
28	Replace the ignition switch. Refer to Ignition and Start Switch Replacement . Did you complete the replacement?	Go to Step 30
29	Replace the underhood electrical center. Refer to Underhood Electrical Center or Junction Block Replacement . Did you complete the replacement?	Go to Step 30
30	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 31	Go to Engine Cranks but Does Not Run
31	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 .	System OK

NOTE
Refer to Test Probe Notice .

NOTE
Refer to Test Probe Notice .

NOTE
Refer to Test Probe Notice .

Ignition Relay Diagnosis

When the ignition is turned ON, the powertrain control module (PCM) will turn ON the in-tank fuel pump. The in-tank fuel pump will remain ON as long as the engine is cranking or running and the PCM is receiving reference pulses. If there are no reference pulses, the PCM will turn the in-tank fuel pump OFF 2 seconds after the ignition is turned ON or 2 seconds after the engine stops running.

Diagnostic Aids

A fuel pump prime terminal is available at the underhood bussed electrical center (UBEC). Refer to the UBEC cover for terminal location.

The following conditions may have caused the fuel pump fuse to open

The fuse is faulty.
There is an intermittent short in the fuel pump power feed circuit.
The fuel pump has an intermittent internal problem.

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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.
4: This step verifies that the PCM is providing voltage to the fuel pump relay.
5: This step tests for an open in the ground circuit to the fuel pump relay.
6: This step determines if a voltage is constantly being applied to the fuel pump relay.
12: To gain access to the fuel pump connector, the fuel tank may need to be removed.
13: 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.
15: Use the same amperage fuse in the jumper as is used to protect the fuel pump circuit.
16: To gain access to the fuel pump connector, the fuel tank may need to be removed.
17: Inspect the ground connection for the fuel pump. Be certain all ground connections are clean and tight.

Step	Action	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module 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
2	Install a scan tool. 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 9	Go to Step 4
4	Turn OFF the ignition. Disconnect the fuel pump relay. Turn ON the ignition, with the engine OFF. Probe the control circuit of the fuel pump relay with a test lamp that is connected to a good ground. Command the fuel pump relay ON and OFF with a scan tool. Does the test lamp turn ON and OFF?	Go to Step 5	Go to Step 6
5	Connect a test lamp between the control circuit of the fuel pump relay and the ground circuit of the fuel pump relay. Command the fuel pump relay ON and OFF with a scan tool. Does the test lamp turn ON and OFF?	Go to Step 19	Go to Step 22
6	Does the test lamp remain illuminated with each command?	Go to Step 7	Go to Step 8
7	Test the control circuit of the fuel pump relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 27	Go to Step 26
8	Test the control circuit of the fuel pump relay for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 27	Go to Step 20
9	Turn ON the ignition, with the engine OFF. Does the fuel pump operate continuously?	Go to Step 10	Go to Step 11
10	Turn OFF the ignition. Disconnect the fuel pump relay. Turn ON the ignition, with the engine OFF. Does the fuel pump operate continuously?	Go to Step 21	Go to Step 25
11	Is the fuel pump fuse open?	Go to Step 12	Go to Step 14
12	Test the supply voltage circuit of the fuel pump for a grounded circuit between the fuel pump fuse and the fuel pump. Refer to Circuit Testing and Wiring Repairs . Replace the fuel pump fuse if necessary. Did you find and correct the condition?	Go to Step 27	Go to Step 13
13	Install all disconnected electrical components. Install a new fuel pump fuse. Turn ON the fuel pump with a scan tool. Is the fuel pump fuse open?	Go to Step 24	Go to Testing for Intermittent Conditions and Poor Connections
14	Turn OFF the ignition. Disconnect the fuel pump relay. Turn ON the ignition, with the engine OFF. Probe the battery voltage circuit of the fuel pump relay switch with a test lamp that is connected to a good ground. Does the test lamp illuminate?	Go to Step 15	Go to Step 23
15	Connect a 20-amp fused jumper wire between the battery voltage circuit of the fuel pump relay switch and the supply voltage circuit of the fuel pump. Does the fuel pump operate?	Go to Step 19	Go to Step 16
16	Test the supply voltage circuit of the fuel pump for an open or high resistance between the fuel pump relay and the fuel pump. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 27	Go to Step 17
17	IMPORTANT: Inspect the ground circuit for being tight, corrosion on terminals, or damage to the wiring harness. Test the ground circuit of the fuel pump for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?	Go to Step 27	Go to Step 18
18	Inspect for poor connections at the fuel pump. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 27	Go to Step 24
19	Inspect for poor connections at fuel pump relay. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 27	Go to Step 25
20	Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 27	Go to Step 26
21	Repair the supply voltage circuit of the fuel pump for a short to voltage. Refer to Wiring Repairs . Did you complete the repair?	Go to Step 27
22	Repair the open fuel pump relay ground circuit. Refer to Wiring Repairs . Did you complete the repair?	Go to Step 27
23	Repair the battery voltage circuit of the fuel pump relay switch. Refer to Wiring Repairs . Did you complete the repair?	Go to Step 27
24	IMPORTANT: Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump. Replace the fuel pump. Refer to Fuel Sender Assembly Replacement . Replace the fuel pump fuse if necessary. Did you complete the replacement?	Go to Step 27
25	Replace the fuel pump relay. Did you complete the replacement?	Go to Step 27
26	Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?	Go to Step 27
27	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 2

IMPORTANT
Inspect the ground circuit for being tight, corrosion on terminals, or damage to the wiring harness.

IMPORTANT
Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump.

Fuel Pump Electrical Circuit Diagnosis

System Description

The powertrain control module (PCM) enables the fuel pump relay when the ignition switch is turned ON. The PCM will disable the fuel pump relay within 2 seconds unless the PCM detects ignition reference pulses. The PCM continues to enable the fuel pump relay as long as ignition reference pulses are detected. The PCM disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.

The Fuel System is a returnless on-demand design. The fuel pressure regulator is a part of the fuel sender assembly, eliminating the need for a return pipe from the engine. A returnless fuel system reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank. Reducing the internal temperature of the fuel tank results in lower evaporative emissions.

The fuel tank stores the fuel supply. An electric turbine style fuel pump attaches to the fuel sender assembly inside the fuel tank. The fuel pump supplies high pressure fuel through the fuel filter and the fuel feed pipe to the fuel injection system. The fuel pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pump also supplies fuel to a venturi pump located on the bottom of the fuel sender assembly. The function of the venturi pump is to fill the fuel sender assembly reservoir. The fuel pressure regulator, a part of the fuel sender assembly, maintains the correct fuel pressure to the fuel injection system. The fuel pump and sender assembly contains a reverse flow check valve. The check valve and the fuel pressure regulator maintain fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cranking times.

The numbers below refer to the numbers on the diagnostic table.

2: This step verifies that the fuel pump is operating.
4: This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated.
7: This step tests for a loss of fuel pressure between the fuel feed pipe shut-off adapter and the fuel pump.
10: This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.
11: This step tests for a leaking fuel injector, or fuel pressure regulator. If the fuel pressure remains constant during this test, the fuel injectors are not leaking fuel.

Step	Action	Value(s)	Yes	No
Schematic Reference: Fuel System Description
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle
2	IMPORTANT: Inspect the fuel system for damage, or external leaks, before proceeding with this diagnostic. Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Does the fuel pump operate?		Go to Step 3	Go to Fuel Pump Electrical Circuit Diagnosis
3	IMPORTANT: Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. CAUTION: Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete. Install the J 34730-1A Fuel Pressure Gage. Place the bleed hose of the fuel pressure gage into an approved gasoline container. Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Bleed the air out of the fuel pressure gage. IMPORTANT: It may be necessary to command the fuel pump ON several 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, with the fuel pump commanded ON. Is the fuel pressure within the specified value?	384-425 kPa (56-62 psi)	Go to Step 4	Go to Step 8
4	IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Observe the fuel pressure gage for 1 minute.Does the fuel pressure drop more than the specified value?	34 kPa (5 psi)	Go to Step 7	Go to Step 5
5	Relieve the fuel pressure to the first specified value. Observe the fuel pressure gage for 5 minutes. Does the fuel drop more than the second specified value?	69 kPa (10 psi) 14 kPa (2 psi)	Go to Step 12	Go to Step 6
6	Operate the vehicle within the conditions of the customer concern. Observe the fuel related parameters with a scan tool. Do any of the scan tool parameters indicate a lean condition?		Go to Step 9	Go to Symptoms - Engine Controls
7	Turn OFF the ignition. Relieve the fuel pressure. Refer to Fuel Pressure Relief (With CH 48027) or Fuel Pressure Relief (Without CH 48027) . Disconnect the fuel feed hose from the fuel rail pipe. Refer to Metal Collar Quick Connect Fitting Service . Install the J 37287 Fuel Line Shut-Off Adaptor between the fuel hoses and the fuel rail pipe. Open the valve on 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 pressure gage. Command the fuel pump ON and then OFF with a scan tool. Close the fuel feed pipe shut-off valve. Observe the fuel pressure gage for 1 minute. Does the fuel pressure remain constant?		Go to Step 12	Go to Step 11
8	Is the fuel pressure more than the specified value?	427 kPa (62 psi)	Go to Step 12	Go to Step 9
9	Inspect the fuel feed pipe for a restriction. Did you find and correct the condition?		Go to Step 13	Go to Step 10
10	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 . Did you find and correct the condition?		Go to Step 13	Go to Step 12
11	Turn OFF the ignition. Raise the fuel rail, with the fuel lines connected. Refer to Fuel Injection Fuel Rail Assembly 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 Injector Replacement . Did you complete the replacement?		Go to Step 13
12	Replace the fuel pump. Refer to Fuel Sender Assembly Replacement . Did you complete the replacement?		Go to Step 13
13	Operate the system in order to verify the repair. Did you correct the condition?		System OK	Go to Step 3

IMPORTANT
Inspect the fuel system for damage, or external leaks, before proceeding with this diagnostic.

IMPORTANT
Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic.

CAUTION
Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete.

IMPORTANT
It may be necessary to command the fuel pump ON several times in order to obtain the highest possible fuel pressure. DO NOT start the engine.

IMPORTANT
The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

Fuel System Diagnosis

The powertrain control module (PCM) enables the appropriate fuel injector on the intake stroke for each cylinder. A voltage is supplied directly to the fuel injectors. The PCM 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 low, will affect engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.

Monitoring the misfire current counters, or misfire graph, may help 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 customers concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.
If the fuel injector coil test does not isolate the condition, perform the fuel injector balance test. Refer to «Fuel Injector Balance Test with Special Tool»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis) or «Fuel Injector Balance Test with Tech 2»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis) .

The numbers below refer to the step numbers on the diagnostic table.

3: This step tests each fuel injector resistance within a specific temperature range. If any of the fuel injectors display a resistance outside of the specified value, replace the fuel injector.
4: This step determines if all of the fuel injectors are within 3 ohms of each other. If the highest resistance value is within 3 ohms of the lowest resistance value, then all of the fuel injector coil windings are OK.
5: This step determines which fuel injector is faulty. After subtracting the highest and lowest resistance values from the average value, replace the fuel injector that has the greatest resistance difference from the average.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module 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
2	Observe the engine coolant temperature (ECT) with a scan tool. Is the ECT value within the specified range?	10-32°C (50-90°F)	Go to Step 3	Go to Step 4
3	Measure the resistance of each fuel injector with a DMM. Refer to Testing for Continuity . 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	Measure the resistance of each fuel injector with a DMM. Refer to Testing for Continuity . 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 Diagnostic Aids	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 and the highest individual fuel injector resistance values, from the average resistance value. Replace the fuel injector that displays the greatest resistance difference, above or below the average. Refer to Fuel Injector Replacement . Did you complete the replacement?		Go to Step 7
6	Replace the fuel injector or fuel injectors that are out of the specified range. Refer to Fuel Injector Replacement . Did you complete the replacement?	11-14 ohms	Go to Step 7
7	Operate the system in order to verify the repair. Did you correct the condition?		System OK	Go to Step 2

Fuel Injector Solenoid Coil Test

Scheme 185

Scheme 185: Fuel Injector Balance Test with Special Tool

Callout	Component Name
1	First Fuel Pressure Gage Reading
2	Second Fuel Pressure Gage Reading

Cylinder	1	2	3	4
1st Reading	296 kPa (43 psi)	296 kPa (43 psi)	296 kPa (43 psi)	296 kPa (43 psi)
2nd Reading	131 kPa (19 psi)	117 kPa (17 psi)	124 kPa (18 psi)	145 kPa (21 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)

The numbers below refer to the step numbers on the diagnostic table.

3: The engine coolant temperature must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
6: If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading. Refer to the illustration above.

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Did you perform the Fuel Injector Coil Test?		Go to Step 3	Go to Fuel Injector Solenoid Coil Test
3	IMPORTANT: Do not perform this test if the engine coolant temperature is above 94°C (201°F). Observe the ECT parameter with a scan tool.Does the scan tool indicate that the ECT parameter is less than the specified value?	94°C (201°F)	Go to Step 4
4	IMPORTANT: Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic. 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. Command the fuel pump ON with a scan tool. IMPORTANT: It may be necessary to command the fuel pump ON a few times, in order to obtain the highest possible fuel pressure. Do not start the engine. Observe the fuel pressure gage, with the fuel pump commanded ON. Is the fuel pressure within the specified range?	384-425 kPa (55-62 psi)	Go to Step 5	Go to Fuel System Diagnosis
5	IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gage for one minute.Does the fuel pressure drop more than the specified value?	34 kPa (5 psi)	Go to Fuel System Diagnosis	Go to Step 6
6	Connect the J 39021 Fuel Injector Coil and Balance Tester and the J 39021-380 Fuel Injector Test Harness to a fuel injector. 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 then OFF with a scan tool. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the first pressure reading. IMPORTANT: 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. This is the second fuel pressure reading. Repeat steps 1-6 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. Does any fuel injector have a pressure drop value that is more than the average pressure drop or less than the average pressure drop by the specified value?	20 kPa (3 psi)	Go to Step 7	Go to Symptoms - Engine Controls
7	Perform the Fuel Injector Cleaning . Did you complete the procedure?		Go to Step 8
8	Operate the vehicle in order to verify the repair. Does a driveability condition still exist?		Go to Symptoms - Engine Controls	System OK

IMPORTANT
Do not perform this test if the engine coolant temperature is above 94°C (201°F).

IMPORTANT
Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic.

IMPORTANT
It may be necessary to command the fuel pump ON a few times, in order to obtain the highest possible fuel pressure. Do not start the engine.

IMPORTANT
The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

IMPORTANT
Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. Do not record the higher fuel pressure value.

Fuel Injector Balance Test with Special Tool

The scan tool first energizes the fuel pump and then the injectors 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.

The numbers below refer to the step numbers on the diagnostic table.

3: The engine coolant temperature must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
4: The fuel pressure should be within the specified range.
5: The fuel pressure should reach a steady value.
6: If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading.

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Did you perform the Fuel Injector Coil Test?		Go to Step 3	Go to Fuel Injector Solenoid Coil Test
3	IMPORTANT: Do not perform this test if the engine coolant temperature is above 94°C (201°F). Observe the ECT parameter with a scan tool.Does the scan tool indicate that the ECT parameter is less than the specified value?	94°C (201°F)	Go to Step 4
4	IMPORTANT: Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. IMPORTANT: It may be necessary to command the fuel pump ON a few times in order to obtain the highest possible fuel pressure. Do not start the engine. Observe the fuel pressure gage, with the fuel pump commanded ON. Is the fuel pressure within the specified value?	384-425 kPa (55-62 psi)	Go to Step 5	Go to Fuel System Diagnosis
5	IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gage for 1 minute.Does the fuel pressure drop more than the specified value?	34 kPa (5 psi)	Go to Fuel System Diagnosis	Go to Step 6
6	With a scan tool, select the Fuel Injector Balance Test function, within the Special Functions menu. Select an injector to be tested. Press Enter. This will prime the fuel system. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the 1st pressure reading. IMPORTANT: Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. Do not record the higher fuel pressure value. Energize the fuel injector by depressing the Pulse Injector button on the scan tool. This will energize the injector and decrease the fuel pressure. Record the fuel pressure indicated by the fuel pressure gage after the fuel injector has stopped pulsing. This is the 2nd pressure reading. Press Enter again to bring you back to the Select Injector screen. Repeat for each fuel injector. Subtract the 2nd pressure reading from the 1st pressure reading for one fuel injector. The result is the pressure drop value. Obtain a pressure drop value for each fuel injector. Add all of the individual pressure drop values. This is the total pressure drop. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop. Does any fuel injector have a pressure drop value that is either higher than the average pressure drop or lower than the average pressure drop by the specified value?	20 kPa (3 psi)	Go to Step 7	Go to Symptoms - Engine Controls
7	Perform the Fuel Injector Cleaning . Did you complete the procedure?		Go to Step 8
8	Operate the vehicle in order to verify the repair. Does a driveability condition still exist?		Go to Symptoms - Engine Controls	System OK

IMPORTANT
Do not perform this test if the engine coolant temperature is above 94°C (201°F).

IMPORTANT
Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic.

IMPORTANT
It may be necessary to command the fuel pump ON a few times in order to obtain the highest possible fuel pressure. Do not start the engine.

IMPORTANT
The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

IMPORTANT
Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. Do not record the higher fuel pressure value.

Fuel Injector Balance Test with Tech 2

Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no start, or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel injection system, and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the fuel system components for rust or deterioration.

Ethanol concentrations of greater than 10 percent can cause driveability conditions and fuel system deterioration. Fuel with more than 10 percent ethanol could result in driveability conditions such as hesitation, lack of power, stalling, or no start. Excessive concentrations of ethanol used in vehicles not designed for it may cause fuel system corrosion, deterioration of rubber components, and fuel filter restriction.

Test Procedure

Test the fuel composition using J 44175 Fuel Composition Tester and J44175-3 Instruction Manual.
If water appears in the fuel sample, Clean the fuel system. Refer to «Fuel System Cleaning»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-introduction-2-of-2__fuel-system-cleaning) .
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»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis) table.
If the fuel sample contains more than 15 percent ethanol, add fresh, regular gasoline to the vehicle's fuel tank.
Test the fuel composition.
If testing shows the ethanol percentage is still more than 15 percent, replace the fuel in the vehicle. Refer to «Fuel System Cleaning»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-introduction-2-of-2__fuel-system-cleaning) .

	Frequency (Hz)	Subtract 50	Ethanol Percent
Example A	50 Hz	50	0
Example B	65 Hz	50	15
Example C	129 Hz	50	79

Fuel Composition Test Examples

Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool)

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 of 10 percent or greater in 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 then use the following procedure to test the fuel quality.

Using a 3.4 oz (100 ml) specified cylinder with 0.03 oz (1 ml) graduation marks, fill the cylinder with fuel to the 3.0 oz (90 ml) mark.
Add 0.34 oz (10 ml) of water in order to bring the total fluid volume to 100 ml and install a stopper.
Shake the cylinder vigorously for 10-15 seconds.
Carefully loosen the stopper in order to release the pressure.
Install the stopper and shake the cylinder vigorously again for 10 to 15 seconds.
Put the cylinder on a level surface for approximately 5 minutes in order to allow adequate liquid separation.

If alcohol is present in the fuel, the volume of the lower layer, which would now contain both alcohol and water, will be more than 0.34 oz (10 ml). For example, if the volume of the lower layer is increased to 0.51 oz (15 ml), this indicates at least 5 percent alcohol in the fuel. The actual amount of alcohol may be somewhat more because this procedure does not extract all of the alcohol from the fuel.

Particulate Contaminants in Fuel Testing Procedure

The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be detected. The sample should be bright and clear. If the sample appears cloudy, or contaminated with water, as indicated by a water layer at the bottom of the sample, use the following procedure to diagnose the fuel.

Using an approved fuel container, draw approximately 0.13 gallons (0.5 liter) of fuel.
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 electronic ignition system uses an individual ignition coil for each cylinder. The powertrain control module (PCM) controls the ignition operation through eight individual ignition control (IC) circuits. Each bank of four ignition coils is connected to the PCM, power, or ground by the following circuits

Low reference
Chassis ground
Ignition 1 voltage
The appropriate IC circuit

The PCM triggers an ignition coil by grounding the appropriate IC circuit using information from the crankshaft position (CKP) and camshaft position (CMP) sensors.

IMPORTANT

A missing CMP sensor signal may cause a long crank condition. The CKP signal must be available for the engine to start. The CMP signal is not needed to start and operate the engine. The PCM can determine when a cylinder is on either the firing or exhaust stroke by the 24X signal. Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM. The 12-volt reference circuit for the CKP and the CMP sensors are shared internally in the PCM.

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .

The numbers below refer to the step numbers on the diagnostic table.

5: Monitoring the misfire current counters determines if a fault is present.
12: A good indication that the fuse is open is all off the misfire current counters are incrementing on one side of the engine. Inspect the ignition positive voltage circuit for a grounded circuit. If the fuse is open and the ignition coil circuits are OK, inspect the injector circuits for being grounded.

Step	Action	Value(s)	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module 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
2	Crank the engine. Observe the engine speed parameter with a scan tool. Does the scan tool display engine RPM?		Go to Step 3	Go to Step 16
3	Is DTC P0335, P0336, or P0351-P0358 also set?		Go to Diagnostic Trouble Code (DTC) List - Vehicle	Go to Step 4
4	Attempt to start the engine. Does the engine start and run?		Go to Step 5	Go to Step 9
5	Idle the engine. Observe the misfire current counters on the scan tool. Does the scan tool display any misfire current counters incrementing?		Go to Step 6	Go to Diagnostic Aids
6	Do the misfire current counters increment for most cylinders on one bank of the engine?		Go to Step 12	Go to Step 7
7	Inspect the spark plug wire for open circuits, cracks, or improper seating of terminals at the spark plug or coil before proceeding with test. Refer to Spark Plug Wire Inspection . Inspect for spark at the plug with the J 26792 Spark Tester or equivalent while cranking. A few sparks, then nothing is considered no spark. Is adequate spark present?		Go to Step 33	Go to Step 8
8	Measure the spark plug wire resistance. Refer to Spark Plug Wire Inspection . Is the resistance more than the specified value?	1,000 ohms/ft	Go to Step 32	Go to Step 9
9	Turn OFF the ignition. Disconnect the ignition coil that corresponds to the Misfire Current counter that was incrementing. Turn ON the ignition, with the engine OFF. Probe the ignition 1 voltage circuit of the ignition coil with a test lamp connected to a good ground. Refer to Probing Electrical Connectors . Does the test lamp illuminate?		Go to Step 10	Go to Step 13
10	Probe the ignition 1 voltage circuit at the ignition coil with a test lamp connected to the ground circuit of the ignition coil. Refer to Probing Electrical Connectors . Does the test lamp illuminate?		Go to Step 11	Go to Step 14
11	Probe the ignition 1 voltage circuit at the ignition coil with a test lamp connected to the low reference circuit of the ignition coil. Refer to Probing Electrical Connectors . Does the test lamp illuminate?		Go to Step 20	Go to Step 15
12	Inspect for an open INJ 1 or INJ 2 fuse. Is the fuse open?		Go to Step 29	Go to Step 23
13	Disconnect the main ignition coil 8-way connector. Probe the ignition 1 voltage circuit at the ignition coil main 8-way connector using the test lamp connected to battery ground. Refer to Probing Electrical Connectors . Does the test lamp illuminate?		Go to Step 24	Go to Step 23
14	Disconnect the main ignition coil 8-way connector. Probe the ignition 1 voltage circuit on the harness side with a test lamp connected to the ground circuit of the ignition coil. Refer to Probing Electrical Connectors . Does the test lamp illuminate?		Go to Step 18	Go to Step 26
15	Disconnect the main ignition coil 8-way connector. Probe the ignition 1 voltage circuit on the harness side with a test lamp connected to the low reference circuit of the ignition coil. Refer to Probing Electrical Connectors . Does the test lamp illuminate?		Go to Step 19	Go to Step 28
16	Turn ON the ignition, with the engine OFF. Disconnect the crankshaft position (CKP) sensor. Measure the voltage from the CKP sensor 12-volt reference circuit and a good ground with the DMM. Compare the measured voltage with the system voltage. Is the difference in the voltage more than the specified value?	0.5 V	Go to Step 17	Go to Step 21
17	Test for a short to ground in the CKP 12-volt reference circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?		Go to Step 35	Go to Step 22
18	Test for an intermittent and for a poor connection at the ignition coil 8-way connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?		Go to Step 35	Go to Step 25
19	Test for an intermittent and for a poor connection at the ignition coil 8-way connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?		Go to Step 35	Go to Step 27
20	Test for an intermittent and for a poor connection at the ignition coil. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?		Go to Step 35	Go to Step 31
21	Test for an intermittent and for a poor connection at the CKP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?		Go to Step 35	Go to Step 30
22	Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?		Go to Step 35	Go to Step 34
23	Repair the open or high resistance in the ignition 1 voltage circuit between the fuse block and the splice. Refer to Wiring Repairs . Did you complete the repair?		Go to Step 35
24	Repair the open or high resistance in the ignition 1 voltage circuit between the splice and the ignition coil connector. Refer to Wiring Repairs . Did you complete the repair?		Go to Step 35
25	Repair the open in the ground circuit between the main 8-way connector and the ignition coil. Refer to Wiring Repairs . Did you complete the repair?		Go to Step 35
26	Repair the open in the ground circuit. Refer to Wiring Repairs . Did you complete the repair?		Go to Step 35
27	Repair the open in the low reference circuit between the main 8-way connector and the ignition coil. Refer to Wiring Repairs . Did you complete the repair?		Go to Step 35
28	Repair the open in the low reference circuit between the PCM and the splice. Refer to Wiring Repairs . Did you complete the repair?		Go to Step 35
29	Repair the ignition 1 voltage for a short to ground. Refer to Wiring Repairs . Replace the fuse. Did you complete the repair?		Go to Step 35
30	Replace the CKP sensor. Refer to Crankshaft Position Sensor Replacement . Did you complete the replacement?		Go to Step 35
31	Replace the ignition coil. Refer to Ignition Coil Replacement . Did you complete the replacement?		Go to Step 35
32	Replace the spark plug wire. Refer to Spark Plug Wire Replacement . Did you complete the replacement?		Go to Step 35
33	Replace the spark plug. Refer to Spark Plug Replacement . Did you complete the replacement?		Go to Step 35
34	Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?		Go to Step 35
35	Attempt to start the engine. Does the engine start and continue to run?		Go to Step 36	Go to Step 2
36	Clear the DTCs with a scan tool. Turn OFF the engine for 30 seconds. Start the engine. Allow the engine to reach operating temperature. Are there any DTCs that have not been diagnosed?		System OK	Go to Diagnostic Trouble Code (DTC) List - Vehicle

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 four heated oxygen sensors, either all four heater circuit tests have passed or one of the heater circuit tests has illuminated the MIL. The I/M System Status will indicate NO under the Completed column when any of the required tests for that system have not run. The following is a list of conditions that would set the I/M System Status indicator to NO

The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
The battery has been disconnected or discharged below operating voltage.
The control module power or ground has been interrupted.
The control module has been reprogrammed.
The control module DTCs have been cleared.

Monitored Emission Control Systems

The OBD II System monitors all emission control systems that are on-board. Not all vehicles have a full complement of emission control systems. For example, a vehicle may not be equipped with secondary air injection (AIR) or exhaust gas recirculation (EGR). The OBD II regulations require monitoring of the following

The air conditioning system
The catalytic converter efficiency
Comprehensive component monitoring-Emission related inputs and outputs
The evaporative emissions (EVAP) system
The EGR System
The fuel delivery system
Heated catalyst monitoring
Misfire monitoring
The oxygen sensor system (O2S or HO2S)
The oxygen sensor heater system (HO2S heater)
The AIR system

For the specific DTCs required for each system, refer to Inspection/Maintenance (I/M) System DTC Table . Systems such as fuel delivery, misfire, and comprehensive components may not be listed in a system status list. These tests run continuously and do not require an I/M System Status indicator.

Step	Action	Yes	No
1	Perform the Diagnostic System Check - Vehicle . 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 inspection/maintenance (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 systems that have not updated

IMPORTANT
Many DTC related repairs will instruct the technician to clear the DTC information. This procedure will reset ALL of the I/M System Status indicators to NO, and require performing the I/M Complete System Set Procedure.

Inspection/Maintenance (I/M) System Check

Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
«Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

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 drive cycles for those particular diagnostics. When all I/M monitored diagnostic tests are completed, the I/M System Status indicators are set to YES. Perform the I/M Complete System Set Procedure if any I/M System Status indicators are set to NO.

I/M Data List

To determine if the I/M readiness diagnostic tests can be run this ignition cycle, use a scan tool to observe the I/M monitor enabled parameters in the I/M Data List.

Conditions for Meeting a Cold Start

The ignition voltage between 11-18 volts.
The barometric pressure (BARO) is more than 75 kPa.
The start-up engine coolant temperature (ECT) is between 4-30°C (39-86°F).
The start-up intake air temperature (IAT) is between 4-30°C (39-86°F).
The difference between the IAT and the ECT is 6°C (10.8°F)
The ambient air temperature is between 4-30°C (39-86°F).
Fuel level is between 15 and 85 percent.

Review the I/M System Status indicators with a scan tool. All I/M System Status indicators should report YES.

Inspection/Maintenance (I/M) System Set Procedure

Ensure that the vehicle meets the conditions for a cold start listed above. If the evaporative emission (EVAP) I/M System Status indicator displays NO, perform the EVAP Service bay test if available. If the EVAP Service bay test is NOT available, it may take up to 6 drive cycles, with up to 17 hours between drive cycles, for the EVAP I/M System Status indicator to transition to YES. If the O2S Heater System Status indicator displays NO, ensure that the ignition has been turned OFF for at least 10 hours.
Set the vehicle parking brake and ensure the vehicle is in park for automatic transmission or neutral for manual transmission.
Turn OFF all accessories; HVAC system, other electrical loads, including aftermarket/add-on equipment, etc.
Start and idle the engine for 2 minutes and until 65°C (149°F) is achieved.
Run the engine for 6.5 minutes within the following conditions: MAF parameter between 4-30 g/s Engine speed steady between 1,000-3,000 RPM
Return the engine to idle for 1 minute.
Apply and hold brake pedal, and shift to Drive for automatic, or apply clutch pedal for manual and operate the vehicle within the following conditions for 2 minutes: Depress the accelerator pedal until throttle position (TP) Sensor angle is more than 2 percent. Mass air flow (MAF) signal between 15-30 g/s RPM steady between 1,200-2,000 RPM
Release the accelerator pedal and shift the vehicle to Park for automatic, or Neutral and release clutch pedal for manual, and allow the engine to idle for 2 minutes.
Quickly depress the accelerator pedal until TP Sensor Angle is more than 8 percent and return to idle, repeat 3 times.
Allow engine to idle for at least 2 minutes.
Release the parking brake and drive vehicle at 24 km/h (15 mph) or slower for 2 minutes.
Continue to drive the vehicle for at least 5.5 miles between 45-112 km/h (28-70 mph) with the vehicle reaching at least 80 km/h (50 mph).
Release the accelerator pedal for at least 2 seconds. This will allow the vehicle to enter decel fuel cut-off.
Depress the accelerator pedal until the TP Sensor angle is increased 3-20 percent and maintain a safe speed for 1 minute.
Safely stop the vehicle, with the engine in drive for automatic or in neutral with the clutch pedal depressed and parking brake applied for manual, idle for 2 minutes.
Shift to Park for automatic and apply the parking brake, or neutral and release clutch pedal for manual.
Turn OFF the ignition and exit the vehicle. Do NOT disturb the vehicle for 45 minutes.
Observe the I/M System Status with a scan tool. All of the I/M System Status indicators should display YES. If the EVAP I/M System Status indicator displays NO turn OFF the ignition for 17 hours, ensure that the vehicle meets the conditions for a cold start, and repeat steps 12-18 six more times, or until the EVAP I/M System Status indicator transitions to YES. If the indicator continues to display NO, refer to the «Inspection/Maintenance (I/M) System DTC Table»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__inspectionmaintenance-im-system-dtc-table) to identify the DTCs that did not run. Follow the Conditions for Running the DTC in order to set the EVAP I/M System Status indicator.

If any of the I/M System Status indicators display NO, refer to the «Inspection/Maintenance (I/M) System DTC Table»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/testing-diagnostics/#engine-controls-and-fuel-81l-troubleshooting-diagnosis__inspectionmaintenance-im-system-dtc-table) for the indicator which did not display YES. The I/M System DTC Table identifies the DTCs associated with each I/M System Status Indicator. Follow the Conditions for Running the DTC in order to set the associated status indicator.

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 P0454 DTC P0461 DTC P0464 DTC P0455 DTC P0496
Oxygen Sensor	DTC P0133 or P0153 DTC P0140 or P0160 DTC P1133 or P1153 DTC P1134 or P1154 DTC P2A01 or P2A04
Oxygen Sensor Heater	DTC P0053, P0054, P0059, or P0060 DTC P0135, P0141, P0155, or P0161

Inspection/Maintenance (I/M) System DTC Table

Perform the «Diagnostic System Check - Vehicle»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
Review «Strategy Based Diagnosis»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
«Diagnostic Procedure Instructions»(/chevrolet/cab-chassis-silverado-3500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The purpose of the evaporative emission (EVAP) Service Bay Test is to aid in resetting the EVAP inspection/maintenance (I/M) system status. For this vehicle that is equipped with the engine off natural vacuum (EONV) diagnostic, the Service Bay Test uses the scan tool to initiate the control module's regular sequence of EVAP system DTC tests, but with different enable criteria. By using the Service Bay Test the I/M indicator can be set without the need for multiple cold soaks.

The scan tool displays for the Service Bay Test are based on the events that occur within the following three categories

The engine running portion of the tests-The vehicle must remain at rest, in Park, or in Neutral, during this portion of the test. This test inspects for large leaks, a leaking purge valve and/or vent system restrictions. The scan tool will display test progress or the reason for an abort or failure.
Drive cycle-The scan tool will display time and distance needed to warm the fuel.
Ignition OFF-During this portion of the test, the engine controller will remain active for up to 45 minutes when the ignition is turned OFF to allow control of the EVAP vent valve and run the EONV test. The engine controller inspects for small leaks during this period by monitoring fuel tank pressure or vacuum. If the system is sealed, there will be a pressure or vacuum change. Pressure or vacuum changes that are less than the calibrated values indicate a leak.

When the EVAP diagnostics are initiated by the Service Bay Test, the scan tool will indicate if the enable conditions listed below are not met, or will display a specific reason if the test aborts. When complete, the display will indicate that the tests passed or failed.

Conditions for Running the Test

The following conditions must be met in order to enable the Service Bay Test

The battery voltage is between 11-18 volts.
The engine coolant temperature (ECT) is less than 70°C (158°F) at start-up.
The EVAP I/M system status indicator is set to NO.
The fuel level is 15-85 percent capacity and cannot be refueled during the tests.
There are no DTCs displayed.
The vehicle must be driven for the time and distance specified on the scan tool.
The ambient air temperature is between 0-40°C (32-104°F)
The ignition must remain OFF during the engine OFF portion of the test, and the vehicle must remain at rest.

IMPORTANT

If the Service Bay Test aborts or fails a DTC will NOT be set.

Install a scan tool.
Select the Service Bay Test with the scan tool.
Follow the instructions on the scan tool. If the test aborts, correct the condition for running the test and then retest. If the test fails, repair the vehicle for the condition indicated by the failure message on the scan tool.
Verify that the EVAP I/M system status is set to YES.

Engine Controls and Fuel - 8.1l - Troubleshooting & Diagnosis Chevrolet Cab & Chassis Silverado 3500

Important Preliminary Inspections Before Starting

Visual/Physical Inspection

Intermittent

Hard Start

Surges/Chuggles

Lack of Power, Sluggishness, or Sponginess

Detonation/Spark Knock

Hesitation, Sag, Stumble

Cuts Out, Misses

Poor Fuel Economy

Poor Fuel Fill Quality

Rough, Unstable, or Incorrect Idle and Stalling

Dieseling, Run-On

Backfire

Diagnostic Instructions

Circuit/System Description

Reference Information

Circuit/System Verification

Circuit/System Testing

Repair Procedures

Description

Circuit Description

Diagnostic Aids

Test Description

System Description

Scheme 185

Test Procedure

Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool)

Alcohol in Fuel Testing Procedure

Particulate Contaminants in Fuel Testing Procedure

Conditions for Updating the I/M System Status

Monitored Emission Control Systems

I/M Data List

Conditions for Meeting a Cold Start

Inspection/Maintenance (I/M) System Set Procedure

Inspection/Maintenance (I/M) System DTC Table

Conditions for Running the Test

More articles — Engine Performance

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