Engine Controls - 2.6l & 3.2l - Troubleshooting

Important Preliminary Inspections Before Starting

Before using this section, perform the Diagnostic System Check - Engine Controls and verify all of the following conditions

The engine control module (ECM) and the malfunction indicator lamp (MIL) are operating correctly.
Diagnostic trouble codes (DTCs) are not stored.
The scan tool data is within the normal operating range. Refer to «Scan Tool Data List»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-diagnostic-information-procedures__scan-tool-data-list) .
Verify the customer concern and locate the correct symptom. Inspect the items indicated under that symptom.
Several of the symptom procedures ask for a careful visual/physical inspection. This step is extremely important, and can lead to correcting a condition without further inspections and can save valuable time.
If the intermittent condition exists as a start and then stall, inspect for any DTCs related to the theft deterrent system. Refer to «Diagnostic System Check - Engine Controls»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-diagnostic-information-procedures)
Verify the proper installation of any of the following non-original equipment accessories: Lights Cellular phone Remote starter system Non-factory installed alarm

Use the following tables when diagnosing a symptom concern: «Poor Fuel Fill Quality»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__poor-fuel-fill-quality) «Hard Start»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__hard-start) «Surges/Chuggles»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__surgeschuggles) «Lack of Power, Sluggishness, or Sponginess»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__lack-of-power-sluggishness-or-sponginess) «Detonation/Spark Knock»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__detonationspark-knock) «Hesitation, Sag, Stumble»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__hesitation-sag-stumble) «Cuts Out, Misses»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__cuts-out-misses) «Poor Fuel Economy»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__poor-fuel-economy) «Rough, Unstable, or Incorrect Idle and Stalling»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__rough-unstable-or-incorrect-idle-and) «Dieseling, Run-On»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__dieseling-run-on) «Backfire»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__backfire)
If the condition can not be isolated using the appropriate table, refer to «Intermittent Conditions»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__intermittent-conditions) for further diagnosis.

Intermittent Conditions

Inspections	Action
DEFINITION: The condition is not currently present but is indicated in DTC history. OR There is a customer concern, but the symptom cannot currently be duplicated, if the condition is not DTC related.
Preliminary	Refer to Important Preliminary Inspection Before Starting in Symptoms - Engine Controls . The fault must be present to locate a problem using the DTC table. If a fault is intermittent, the use of DTC tables may result in the replacement of good parts.
Visual/Physical	This step is an important aid for locating a condition without extensive testing. Perform a thorough visual and physical inspection of the following components: Wiring harness for damage or cuts A misrouted harness that is too close to high voltage or high current devices such as the following: Secondary ignition components Motors Generators Vacuum hoses for the following conditions: Proper routing Proper connections Splits in the hose or the connections Kinks Air leaks at the throttle body mounting area-Refer to Throttle Body Service . Air leaks at the mass air flow (MAF) sensor and at the intake manifold The MAF sensor installation-Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement Engine control module (ECM) and body grounds are clean and tight Battery connections are clean and tight Charging system for proper operation-Refer to Diagnostic System Check - Engine Electrical in Engine Electrical.
Harness/Connector Test	Many intermittent open or shorted circuits come and go with harness and connector movement caused by vibration, engine torque, bumps and rough pavement, etc. Test for this type of condition by performing the applicable procedure from the following list: Move the related connectors and wiring while monitoring the appropriate scan tool data. Move the related connectors and wiring with the component commanded ON and OFF, with the scan tool. Observe the components operation. With the engine running, move the related connectors and wiring while monitoring engine operation. If harness or connector movement affects the data displayed, the component and system operation, or the engine operation, inspect and repair the harness or connections as necessary. Refer to Electrical Connections or Wiring in this table.
Electrical Connections or Wiring	Poor electrical connections and terminal tension or wiring faults cause most intermittents. Perform a careful inspection of the suspected circuit for the following: Inspect for incorrect mating of the connector halves, or terminals not fully seated in the connector body, backed-out. Inspect for improperly formed or damaged terminals. Test for incorrect terminal tension. Inspect for poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body. Inspect for corrosion or water intrusion. Pierced or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation with little visible evidence. Look for swollen and stiff sections of wire in the suspect circuits. Inspect for wires that are broken inside the insulation. Inspect the harness for pinched, cut, or rubbed through wiring. Make sure the wiring does not come in contact with hot exhaust components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
ECM Power and Grounds	Poor power or ground connections can cause widely varying symptoms. Test all engine control module (ECM) power circuits. Many vehicles have multiple circuits supplying power to the ECM. Inspect connections at the ECM connectors, fuses, and any intermediate connections between the power source and the ECM or component. A test lamp or a DMM may indicate that voltage is present, but neither tests a circuits ability to carry sufficient current. Ensure that the circuit can carry the current necessary to operate the component. Refer to Power Distribution Schematics in Wiring Systems. Test all ECM ground and system ground circuits. The ECM may have multiple ground circuits. Other components in the system may have separate grounds that may also need to be tested. Make sure the ground connections are clean and tight at the grounding point. Inspect the connections at the component and in splice packs, where applicable. Ensure that the circuit can carry the current necessary to operate the component.
Temperature Sensitivity	An intermittent condition may occur only when the component is cold, or only when the component is hot. The heat that affects the circuit can be engine generated or due to a poor connection in the circuit or a high electrical load. Information from the customer may help to determine if the trouble follows a pattern that is temperature related. The Freeze Frame/Failure Records or Snapshot data may help with this type of intermittent condition, where applicable. If the intermittent is related to heat, review the data for a relationship with the following: High ambient temperatures Underhood/engine generated heat Circuit generated heat due to a poor connection, or high electrical load Higher than normal load conditions (towing, etc.) If the intermittent is related to cold, review the data for the following: Low ambient temperatures-In extremely low temperatures, ice may form in a connection or component. Inspect for water intrusion. The condition only occurs on a cold start. The condition goes away when the vehicle warms up.
Electromagnetic Interference (EMI) and Electrical Noise.	Some electrical components and circuits are sensitive to electromagnetic interference (EMI) or other types of electrical noise. Inspect for the following conditions: A misrouted harness that is too close to high voltage and high current devices such as secondary ignition components, motors, generator, etc. These components may induce electrical noise on a circuit that could interfere with normal circuit operation. Electrical system interference caused by a malfunctioning relay, ECM driven solenoid, or switch. They can cause a sharp electrical surge. Normally, the problem will occur when the malfunctioning component is operating. Incorrect installation of non-factory, aftermarket, add-on accessories such as lights, 2-way radios, amplifiers, electric motors, remote starters, alarm systems, cell phones, etc. Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode or resistor. Test the generator for a faulty rectifier bridge that may be allowing AC noise into the electrical system. Refer to Diagnostic System Check - Engine Electrical in Engine Electrical.
Incorrect ECM Programming	There are only a few situations where reprogramming an ECM is appropriate: An ECM from another vehicle is installed. Revised software/calibration files have been released for this vehicle. IMPORTANT: DO NOT reprogram the ECM with the SAME software/calibration files that are already present in the ECM. This is not an effective repair for any type of driveability problem. Verify that the ECM contains the correct software/calibration. If incorrect programming is found, reprogram the ECM with the most current software/calibration. Refer to Engine Control Module (ECM) Replacement .
Duplicating Failure Conditions	If the previous tests were not successful, attempt to duplicate and/or capture the failure conditions. Freeze Frame/Failure Records data, where applicable, contains the conditions that were present when the DTC set. Review and record the Freeze Frame/Failure Records data. Clear any DTCs with a scan tool. Turn OFF the key and wait 15 seconds. Operate the vehicle under the same conditions that were noted in Freeze Frame/Failure Records. The vehicle must also be operating within the Conditions For Running the DTC. Refer to Conditions for Running the DTC in the supporting text of the DTC being diagnosed. Monitor DTC status for the DTC being tested. The scan tool will indicate Ran when the enabling conditions have been satisfied long enough for the DTC to run. The scan tool will also indicate whether the DTC passed or failed. An alternate method is to drive the vehicle with a DMM connected to a suspected circuit. An abnormal reading on the DMM when the problem occurs may help you locate the problem.
Scan Tool Snapshot	The scan tool can be set up to take a snapshot of the parameters available via serial data. The Snapshot function records live data over a period of time. The recorded data can be played back and analyzed. The scan tool can also graph parameters singly or in combinations of parameters for comparison. The snapshot can be triggered manually at the time the symptom is noticed or set up in advance to trigger when a DTC sets. An abnormal value captured in the recorded data may point to a system or component that needs to be investigated further. Refer to the scan tool user instructions for more information on the Snapshot function.

IMPORTANT
DO NOT reprogram the ECM with the SAME software/calibration files that are already present in the ECM. This is not an effective repair for any type of driveability problem.

Intermittent Conditions

Hard Start

Inspections	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 . Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Search for service bulletins that may address this condition.
Sensor/System	Confirm the correct operation of the theft deterrent system. Refer to Diagnostic System Check - Theft Deterrent in Theft Deterrent. IMPORTANT: Allow the engine to cool before performing this test. Inspect the engine coolant temperature (ECT) sensor for being skewed in value. Connect a scan tool. Compare the ECT against 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, test the resistance of the ECT sensor. Refer to Temperature vs Resistance - Engine Coolant Temperature (ECT) Sensor for resistance specifications. Replace the ECT sensor if the resistance is not within the specification. Refer to Engine Coolant Temperature (ECT) Sensor Replacement . If the sensor is within the specification, repair the high resistance in the ECT signal circuit. Inspect the MAF sensor installation. A MAF sensor that is incorrectly installed may cause a hard start. Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement . Verify proper operation of the throttle actuator control (TAC) system by performing the following procedure: Observe the TP sensor angle with a scan tool Turn the key ON, with the engine OFF. Slowly depress the accelerator pedal to wide open throttle (WOT), then slowly return the pedal to the rest position. Repeat several times. TP sensor angle should increase to near 100 percent as the pedal is depressed, and decrease as the pedal is released. A verification of the entire TAC system will be performed.
Fuel System	Test the fuel pump relay operation. Refer to Fuel Pump Electrical Circuit Diagnosis . Test for any of the following fuel pressure related conditions. Refer to Fuel System Diagnosis . An inoperative check valve in the fuel pump allowing the fuel in the lines to drain back to the tank after the engine stops Incorrect fuel pressure Restricted fuel filter Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Test for plugged or restricted injectors. Refer to Fuel Injector Balance Test with Special Tool .
Ignition System	Test for proper ignition system operation. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions. Refer to Spark Plug Replacement . Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant or oil fouled. Refer to Spark Plug Inspection . Once you determine the cause of the fouling, refer to one of the following procedures: For diagnosis of a rich condition, refer to DTC P0172 or P0175 . For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant (M 35) or Loss of Coolant (M 82) in Engine Cooling. For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis in Engine Mechanical.
Engine Mechanical	Low cylinder compression-Refer to Engine Compression Test in Engine Mechanical. Combustion chambers for excessive carbon buildup-Clean the chambers using top engine cleaner. Follow the instructions on the can. Inspect for incorrect camshaft timing-Refer to Timing Belt Timing Procedure in Engine Mechanical. Excessive oil in combustion chamber due to leaking valve seals-Refer to Oil Consumption Diagnosis in Engine Mechanical. Inspect the following components for incorrect basic engine parts: The cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The camshafts-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. The pistons, connecting rod, and/or bearings-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical.

IMPORTANT
Allow the engine to cool before performing this test.

Hard Start

Surges/Chuggles

Inspections	Action
DEFINITION: Engine power variation under steady throttle or cruise. Feels like the vehicle speeds up and slows down without a change in the accelerator pedal position.
Preliminary	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Ensure that the driver understands the operation of the transmission torque converter clutch (TCC) and A/C compressor operation as explained in the owner's manual. Inform the customer how the TCC and the A/C clutch operates.
Sensor/System	NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Inspect the heated oxygen sensor (HO2S) wiring for damage and/or poor connections. NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. Inspect the HO2S for silicon or other contaminants. Inspect the crankshaft position (CKP) sensor and wiring for an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Inspect the intake air ducts for proper installation and for leaks. Inspect the mass air flow (MAF) sensor connections. Repair or replace the terminals. Refer to Connector Repairs in Wiring Systems.
Fuel System	Test the Fuel System. Refer to Fuel System Diagnosis . Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Verify that each injector harness is connected to the correct injector/cylinder. Relocate injector harnesses as necessary. Test the fuel injectors. Refer to Fuel Injector Coil Test . Test the items which can cause an engine to run rich (long term fuel trim near -13 percent). For a rich condition, refer to DTC P0172 or P0175 . Test the items that can cause an engine to run lean (long term fuel trim near 23 percent). For a lean condition, refer to DTC P0171 or P0174 .
Ignition System	Inspect for proper installation of the ignition coil seal. Improper installation may allow water to enter spark plug area. Inspect for moisture and corrosion. Test for proper ignition system operation. 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 Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant or oil fouled. Refer to Spark Plug Inspection . Once you determine the cause of the fouling, refer to one of the following procedures: For diagnosis of a rich condition, refer to DTC P0172 or P0175 . For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant (M 35) or Loss of Coolant (M 82) in Engine Cooling. For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis in Engine Mechanical.
Additional	Visually/physically inspect vacuum hoses for splits, kinks, and proper connections and routing as shown on the vehicle emission control information label. Refer to Emission Hose Routing Diagram . Inspect the exhaust system for the following conditions: Damaged or collapsed pipes Heat distress such as cracking or for an internal failure of the muffler Restricted exhaust-Refer to Restricted Exhaust in Engine Exhaust. Test the transmission TCC operation. A TCC applying too soon can cause the engine to spark knock. Refer to Symptoms - Automatic Transmission in Automatic Transmission. Test the A/C clutch for proper operation. Refer to Symptoms - HVAC Systems - Automatic in HVAC Systems-Automatic.

NOTE
Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices.

NOTE
Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices.

Surges/Chuggles

Lack of Power, Sluggishness, or Sponginess

Inspections	Action
DEFINITION: The engine delivers less than expected power. Little increase in speed, or a total lack of acceleration when the accelerator pedal is pushed down part way.
Preliminary	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Remove the air filter element and inspect for dirt or for being restricted. Inspect the intake air ducts for the following conditions: Restrictions Improperly installed hoses Leaks Collapsed hoses
Fuel System	Inspect the fuel system. Refer to Fuel System Diagnosis . Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Coil Test . Inspect the items which can cause an engine to run rich, long term fuel trim near -13 percent. For a rich condition, refer to DTC P0172 or P0175 . Inspect the items that can cause an engine to run lean, long term fuel trim near 23 percent. For a lean condition, refer to DTC P0171 or P0174 .
Sensor/System	Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Detonation/Spark Knock . Verify the proper operation of the throttle actuator control (TAC) system by performing the following procedures: Observe the throttle position (TP) sensor angle and the accelerator pedal position (APP) sensor angle with a scan tool. Turn the key ON, with the engine OFF. Slowly depress the accelerator pedal to wide open throttle (WOT), then slowly return the pedal to the rest position. The TP sensor angle and the APP sensor angle should increase to nearly 100 percent as the pedal is depressed and decrease as the pedal is released. A verification of the entire TAC system will be performed. If the TP sensor angle and the APP sensor angle values do not increase as the pedal is depressed, verify the APP sensor connections. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Ignition System	Test for proper ignition system operation. Refer to Electronic Ignition (EI) System Diagnosis . Test for secondary ignition leakage. 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 Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant or oil fouled. Refer to Spark Plug Inspection . Once you determine the cause of the fouling, refer to one of the following procedures: For diagnosis of a rich condition, refer to DTC P0172 or P0175 . For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant (M 35) or Loss of Coolant (M 82) in Engine Cooling. For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis in Engine Mechanical.
Engine Mechanical	Excess oil in combustion chamber due to leaking valve seals-Refer to Oil Consumption Diagnosis in Engine Mechanical. Inspect for incorrect camshaft timing. Refer to Timing Belt Timing Procedure in Engine Mechanical. Inspect the following components for incorrect basic engine parts: Camshafts-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. Cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. Pistons, connecting rods or bearings-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical.
Additional	Inspect the following components of the exhaust system for possible restrictions: The exhaust system for physical damage The mufflers for heat distress or possible internal failure The catalytic converters for possible plugged pipes by comparing the exhaust system back pressure on each side of engine-Refer to Restricted Exhaust in Engine Exhaust. Test for proper operation of the intake manifold tuning valve and the intake manifold runner control valve. Refer to Intake Manifold Runner Control System Diagnosis . Test the transmission torque converter clutch (TCC) for proper operation. Refer to Torque Converter Diagnosis Procedure in Automatic Transmission. Test for other transmission related faults that might cause the transmission to operate in a default mode. Refer to Diagnostic System Check - Automatic Transmission in Automatic Transmission.

Lack of Power, Sluggishness, or Sponginess

Detonation/Spark Knock

Inspection	Action
DEFINITION: A mild to severe ping which usually occurs worse while under acceleration. The engine makes sharp metallic knocks that change with throttle opening.
Preliminary	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in their proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . If the scan tool readings are normal and there are not any engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicle's minimum octane requirements. Test the vehicle and re-evaluate the vehicle's performance.
Fuel System	Inspect the fuel system. Refer to Fuel System Diagnosis . Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Inspect the MAF sensor for proper operation. This can be done by disconnecting the sensor and looking for an improvement in the operation or the loss of the symptom. Another test is to monitor the MAF sensor reading on the scan tool at idle on a warm engine with all of the accessories turned OFF. The reading should be between 5-15 g/s. Refer to Scan Tool Data List . Inspect the engine coolant temperature (ECT) sensor for proper operation or intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Test for a restricted or plugged fuel injector. Refer to Fuel Injector Balance Test with Special Tool . Test the items that can cause an engine to run lean, long term fuel trim near 23 percent. For a lean condition, refer to DTC P0171 or P0174 .
Ignition System	Ensure that the spark plugs are the correct heat range. Refer to Ignition System Specifications .
Engine Cooling System	Test for an overheating condition. Refer to Engine Overheating (LY7) , Engine Overheating (LA3, LY9) or Engine Overheating (LS6) in Engine Cooling.
Engine Mechanical	Inspect for the following engine mechanical problems: Excessive oil in combustion chamber/leaking valve seals-Refer to Oil Consumption Diagnosis in Engine Mechanical. Combustion chambers for excessive carbon buildup-Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can. Incorrect camshaft timing-Refer to Timing Belt Timing Procedure in Engine Mechanical. Inspect the following components for incorrect basic engine parts: Camshafts-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. Cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. Pistons, connecting rods or bearings-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical.
Additional	Test the transmission torque converter clutch (TCC) for proper operation. Applying the TCC too soon can cause the engine to spark knock. Refer to Torque Converter Diagnosis Procedure in Automatic Transmission.

Detonation/Spark Knock

Hesitation, Sag, Stumble

Inspections	Action
DEFINITION: Momentary lack of response as the accelerator is pushed down. This condition can occur at any vehicle speed. This condition is usually more pronounced when first trying to make the vehicle move, as from a stop sign. This condition may cause the engine to stall if severe enough.
Preliminary	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics .
Sensor/System	Test the heated oxygen sensors (HO2S). The HO2S should respond quickly to the 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. This type of contamination may result in a rich exhaust indication. The ECM will then reduce the amount of fuel delivered to the engine, causing a severe driveability condition. Inspect the mass air flow (MAF) sensor connections. Repair or replace the terminals as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Inspect the CMP sensor for proper operation or intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Inspect the CKP sensor for proper operation or intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Verify the proper operation of the TAC system by performing the following procedure: Observe the TP sensor angle with a scan tool. Slowly depress the accelerator pedal to wide open throttle (WOT) with the key ON and the engine OFF, then slowly return the pedal to the rest position. The TP sensor angle should increase to near 100 percent as the pedal is depressed and decrease as the pedal is released. A verification of the entire TAC system is being performed by performing this test.
Fuel System	Inspect the fuel system. Refer to Fuel System Diagnosis . Test for incorrect fuel pressure. Test for a restricted fuel filter. Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Test the fuel injectors. Refer to Fuel Injector Coil Test . Inspect the items which can cause an engine to run rich (long term fuel trim near -13 percent). For a rich condition, refer to DTC P0172 or P0175 . Inspect the items that can cause an engine to run lean (long term fuel trim near 23 percent). For a lean condition, refer to DTC P0171 or P0174 .
Ignition System	Test for proper ignition system operation. Refer to Electronic Ignition (EI) System Diagnosis . Test for secondary ignition system leakage. 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 Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant or oil fouled. Refer to Spark Plug Inspection . Once you determine the cause of the fouling, refer to one of the following procedures: For diagnosis of a rich condition, refer to DTC P0172 or P0175 . For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant (M 35) or Loss of Coolant (M 82) in Engine Cooling. For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis in Engine Mechanical.
Engine Cooling System	Test the engine thermostat for proper operation and correct heat range. Refer to Thermostat Diagnosis (LA3, LY9) , Thermostat Diagnosis (LY7) or Thermostat Diagnosis (LS6) in Engine Cooling.
Additional	Test the generator output voltage. Refer to Diagnostic System Check - Engine Electrical in Engine Electrical. Repair the charging system if the generator output voltage is less than 9 volts or more than 16 volts.

Hesitation, Sag, Stumble

Cuts Out, Misses

Inspections	Action
DEFINITION: A steady pulsation or jerking that follows engine speed, which is usually more pronounced as the 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 at low speed.
Preliminary	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Inspect the intake air ducts for leaks and proper location. Remove the air filter element and inspect for dirt or for being restricted. Refer to Air Cleaner Element Replacement .
Fuel System	Test the fuel injectors. Refer to Fuel Injector Coil Test . Inspect the fuel system. Refer to Fuel System Diagnosis . Test for incorrect fuel pressure. Test for a restricted fuel filter. Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Inspect the items which can cause an engine to run rich (long term fuel trim near -13 percent). For a rich condition, refer to DTC P0172 or P0175 . Inspect items that can cause an engine to run lean, long term fuel trim near 23 percent. For a lean condition, refer to DTC P0171 or P0174 .
Sensor/System	Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Scan Tool Data List . Inspect the CKP sensor for proper operation or intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Ignition System	Test for proper ignition system operation. Refer to Electronic Ignition (EI) System Diagnosis . Test for secondary ignition system leakage. 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 Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant, or oil fouled. Refer to Spark Plug Inspection . Once you determine the cause of the fouling, refer to one of the following procedures: For diagnosis of the rich condition, refer to DTC P0172 or P0175 . For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant (M 35) or Loss of Coolant (M 82) in Engine Cooling. For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis in Engine Mechanical.
Engine Mechanical	Inspect the following conditions: Low compression-Refer to Engine Compression Test in Engine Mechanical. Sticking or leaking valves Worn camshaft lobes-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. Camshaft timing-Refer to Timing Belt Timing Procedure in Engine Mechanical. Broken valve springs Excessive oil in combustion chamber-Leaking valve seals-Refer to Oil Consumption Diagnosis in Engine Mechanical. Inspect the following components for incorrect basic engine parts: Camshafts-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. Cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. Pistons, connecting rods, or bearings-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical.
Additional	Inspect the following exhaust system components for possible restrictions: The exhaust system for physical damage The mufflers for heat distress or possible internal failure The catalytic converters for possible plugged pipes by comparing the exhaust system back pressure on each side of the engine-Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the CKP reference circuit can cause an engine miss condition. A sudden increase in RPM with little change in actual engine RPM indicates that EMI may be present. Inspect for high voltage components near the ignition control circuits if a condition exists. Inspect the intake manifold and the exhaust manifold passages for casting flash. Refer to: Intake Manifold Replacement in Engine Mechanical Exhaust Manifold Replacement - Left (LY7) , Exhaust Manifold Replacement - Left (LA3, LY9) or Exhaust Manifold Replacement - Left (LS6) in Engine Exhaust Exhaust Manifold Replacement - Right (LA3, LY9) , Exhaust Manifold Replacement - Right (LY7) or Exhaust Manifold Replacement - Right (LS6) in Engine Exhaust

Cuts Out, Misses

Poor Fuel Economy

Inspections	Action
DEFINITION: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, the fuel economy is noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test.
Preliminary	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Verify the owner's driving habits, by asking the following questions: Is the A/C or the Defroster mode ON full time? Are the tires at the correct pressure? Is there excessively heavy loads being carried? Is the acceleration rate too much, too often? Is the vehicle used for towing? Remove the air filter element and inspect for dirt or for being restricted. Refer to Air Cleaner Element Replacement .
Fuel System	Determine 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 (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Test the fuel injectors. Refer to Fuel Injector Coil Test . Inspect the fuel system. Refer to Fuel System Diagnosis . Test for incorrect fuel pressure. Test for a restricted fuel filter. Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Confirm that each injector harness is connected to the correct injector/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. Refer to Throttle Body Service . Also inspect for throttle body tampering. Inspect for items which can cause an engine to run rich, long term fuel trim near -13 percent. For a rich condition, refer to DTC P0172 or P0175 .
Sensor/System	Inspect the air intake system and the crankcase for air leaks. Test the crankcase ventilation system for proper operation. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. Test for proper calibration of the speedometer. Incorrect tire size or axle ratios can affect speedometer calibration and vehicle mileage. Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Scan Tool Data List .
Ignition System	Test for proper ignition system operation. Refer to Electronic Ignition (EI) System Diagnosis . Test for secondary ignition system leakage. 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 Determine the cause of the fouling before replacing the spark plugs if spark plugs are gas, coolant or oil fouled. Refer to Spark Plug Inspection . Once you determine the cause of the fouling, refer to one of the following procedures: For diagnosis of a rich condition, refer to DTC P0172 or P0175 . For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant (M 35) or Loss of Coolant (M 82) in Engine Cooling. For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis in Engine Mechanical.
Engine Cooling System	Inspect the engine coolant level for being low. Refer to Draining and Filling Cooling System (LA3, LY9) , Draining and Filling Cooling System (LY7) or Draining and Filling Cooling System (LS6) in Engine Cooling. Test the engine thermostat for proper operation and correct heat range. Refer to Thermostat Diagnosis (LA3, LY9) , Thermostat Diagnosis (LY7) or Thermostat Diagnosis (LS6) in Engine Cooling.
Engine Mechanical	Inspect the following: Low compression-Refer to Engine Compression Test in Engine Mechanical. Sticking or leaking valves Worn camshaft lobes-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical Camshaft timing-Refer to Timing Belt Timing Procedure in Engine Mechanical Broken valve springs Excessive oil in combustion chamber-Leaking valve seals-Refer to Oil Consumption Diagnosis in Engine Mechanical Inspect the following components for incorrect basic engine parts: Camshafts-Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. Cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. Pistons, connecting rods or bearings-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical.
Additional	Visually/physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on vehicle emission control information label. Refer to Emission Hose Routing Diagram . Inspect for air leaks in the following areas: The throttle body mounting area-Refer to Throttle Body Assembly Replacement . The mass air flow (MAF) sensor-Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement . The duct between the MAF and the throttle body-Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement . Test the transmission torque converter clutch (TCC) for proper operation. The scan tool should indicate an RPM drop, when the system commands the TCC ON. Refer to Torque Converter Diagnosis Procedure in Automatic Transmission. Inspect the exhaust system components for the following possible restrictions: The exhaust system for physical damage-Refer to Restricted Exhaust in Engine Exhaust. The catalytic converters for possible plugged pipes by comparing the exhaust system back pressure on each side of engine-Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the CKP reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine speed. A sudden increase in engine speed with little change in actual engine speed, indicates that EMI is present. Inspect for high voltage components near ignition control circuits. Inspect the intake manifold and the exhaust manifold passages for casting flash. Refer to Intake Manifold Cleaning and Inspection and Exhaust Manifold Cleaning and Inspection in Engine Mechanical. Inspect the brake system, including the parking brake, for dragging or improper operation. Refer to Symptoms - Hydraulic Brakes in Hydraulic Brakes. Ensure that the vehicle operator does not drive with a foot on the brake pedal. Refer to Symptoms - Park Brake in Park Brake.

Poor Fuel Economy

Poor Fuel Fill Quality

Condition	Causes
DEFINITION: Difficulty when refueling the vehicle.
Difficult to fill	Restricted vent lines The evaporative emission (EVAP) vent valve is stuck closed High fuel temperature Condition with the internal components of the fuel tank assembly
Over fill	Condition with the internal components of the fuel tank assembly
Pre-mature shut-off of the fuel dispensing nozzle	The EVAP vent valve is stuck closed Restricted vent lines High reid vapor pressure or high fuel temperature Condition with the internal components of the fuel tank assembly
Fuel Spitback	High reid vapor pressure or high fuel temperature Condition with the internal components of the fuel tank assembly
Fuel Odor	Saturated EVAP canister Condition with the internal components of the fuel tank assembly

Poor Fuel Fill Quality

Rough, Unstable, or Incorrect Idle and Stalling

Inspections	Action
DEFINITION: The engine runs unevenly at idle. If severe, the engine or the vehicle may shake. Engine idle speed may vary in RPM. Either condition may be severe enough to stall the engine.
Preliminary	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Remove and inspect the air filter element for dirt or for being restricted. Refer to Air Cleaner Element Replacement .
Fuel System	Test the fuel injectors. Refer to Fuel Injector Coil Test . Inspect the fuel system. Refer to Fuel System Diagnosis . Test for incorrect fuel pressure. Test for a restricted fuel filter. Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Confirm that each injector harness is connected to the correct injector/cylinder. Relocate the injector harnesses as necessary. Inspect for items which can cause an engine to run rich, long term fuel trim near -13 percent. For a rich condition, refer to DTC P0172 or P0175 . Inspect for items that can cause an engine to run lean, long term fuel trim near 23 percent. For a lean condition, refer to DTC P0171 or P0174 .
Sensor/System	Test the crankcase ventilation system. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. Test 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 Vent Housing Replacement in Engine Mechanical. Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Scan Tool Data List .
Ignition System	Test for proper ignition system operation. 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 Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant or oil fouled. Refer to Spark Plug Inspection . Once you determine the cause of the fouling, refer to one of the following procedures: For diagnosis of a rich condition, refer to DTC P0172 or P0175 . For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant (M 35) or Loss of Coolant (M 82) in Engine Cooling. For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis in Engine Mechanical.
Engine Mechanical	Inspect engine mechanical for the following conditions: Low compression-Refer to Engine Compression Test in Engine Mechanical. Sticking or leaking valves Worn camshaft lobes-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. Camshaft timing-Refer to Timing Belt Timing Procedure in Engine Mechanical. Broken valve springs Excessive oil in combustion chamber-Leaking valve seals-Refer to Oil Consumption Diagnosis in Engine Mechanical. Inspect the following components for incorrect basic engine parts: Camshaft-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. Cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. Pistons, connecting rods, or bearings-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical.
Additional	Inspect the exhaust system for the following possible restrictions: The exhaust system components for physical damage The catalytic converters for possible plugged pipes by comparing the exhaust system back pressure on each side of engine-Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the CKP 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 indicates that EMI is present. If a condition exists, inspect for high voltage components near ignition control circuits. Inspect for faulty engine mounts. Refer to Engine Mount Replacement - Left or Engine Mount Replacement - Right in Engine Mechanical. Inspect the intake manifold and the exhaust manifold passages for casting flash. Refer to: Intake Manifold Replacement in Engine Mechanical Exhaust Manifold Replacement - Left (LY7) , Exhaust Manifold Replacement - Left (LA3, LY9) or Exhaust Manifold Replacement - Left (LS6) in Engine Exhaust Exhaust Manifold Replacement - Right (LA3, LY9) , Exhaust Manifold Replacement - Right (LY7) or Exhaust Manifold Replacement - Right (LS6) in Engine Exhaust

Rough, Unstable, or Incorrect Idle and Stalling

Dieseling, Run-On

Inspections	Action
DEFINITION: The engine continues to run after the key is turned OFF, but runs very rough. If the engine runs smooth, inspect the ignition switch and the ignition switch adjustment.
Preliminary	Refer to Important Preliminary Checks Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics .
Fuel System	Inspect the fuel pressure regulators atmospheric vent hose for the presence of fuel. Replace the fuel pressure regulator if fuel is found in the hose. Refer to Fuel Pressure Regulator Replacement . Test the 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	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics .
Fuel System	Inspect the fuel system. Refer to Fuel System Diagnosis . Test for incorrect fuel pressure. Test for a restricted fuel filter. Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Test the fuel injectors. Refer to Fuel Injector Coil Test . Inspect that each injector harness is connected to the correct injector/cylinder. Relocate injector harnesses as necessary. Inspect the items that can cause an engine to run lean, long term fuel trim near 23 percent. For a lean condition, refer to DTC P0171 or P0174 .
Sensor/System	Inspect the air intake system and the crankcase for air leaks. Test the crankcase ventilation system for proper operation. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Scan Tool Data List .
Ignition System	Test for proper ignition system operation. Inspect for an intermittent ignition system malfunction in the ignition control circuit. Use the Snapshot feature on the scan tool in order to help locate an intermittent ignition failure. Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant or oil fouled. Refer to Spark Plug Inspection . Once you determine the cause of the fouling, refer to one of the following procedures: For diagnosis of a rich condition, refer to DTC P0172 or P0175 . For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant (M 35) or Loss of Coolant (M 82) in Engine Cooling. For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis in Engine Mechanical.
Engine Cooling System	Inspect the engine coolant level for being low. Refer to Draining and Filling Cooling System (LA3, LY9) , Draining and Filling Cooling System (LY7) or Draining and Filling Cooling System (LS6) in Engine Cooling. Inspect the engine thermostat for proper operation and correct heat range. Refer to Thermostat Diagnosis (LA3, LY9) , Thermostat Diagnosis (LY7) or Thermostat Diagnosis (LS6) in Engine Cooling.
Engine Mechanical	Excessive oil in combustion chamber due to leaking valve seals-Refer to Oil Consumption Diagnosis in Engine Mechanical. Inspect for incorrect camshaft timing-Refer to Timing Belt Timing Procedure in Engine Mechanical. Inspect the following components for incorrect basic engine parts: Camshafts-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. Cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. Pistons, connecting rods or bearings-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical.
Additional	Visually/physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on Vehicle Emission Control Information label or in Emission Hose Routing Diagram . Inspect the intake manifold and the exhaust manifold passages for casting flash. Test the transmission torque converter clutch (TCC) for proper operation. The scan tool should indicate an RPM drop when the TCC is commanded ON. Refer to Torque Converter Diagnosis Procedure in Automatic Transmission. Inspect the exhaust system for the following possible restrictions: The exhaust system components for physical damage-Refer to Restricted Exhaust in Engine Exhaust. The catalytic converters for possible plugged pipes by comparing the exhaust system back pressure on each side of engine-Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM with little change in actual engine RPM, may indicate that EMI is present. If a problem exists, inspect for high voltage components near ignition control circuits. Test the park neutral position (PNP) switch circuit. Refer to DTC P0850 .

Backfire

Description

The Engine Cranks but Does Not Run diagnostic table is an organized approach to identifying a condition that prevents an engine from starting. The Engine Cranks but Does Not Run diagnostic table directs the service technician to the appropriate system diagnosis.

The Engine Cranks but Does Not Run diagnostic table assumes the following

The battery is completely charged. Refer to «Battery Inspection/Test»(/cadillac/cts/i-2002-2007/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
The engine speed is acceptable. Refer to «Engine Cranks Slowly»(/cadillac/cts/i-2002-2007/remont/charging-system/#battery-charging-system-and-starting-system__engine-cranks-slowly) in Engine Electrical.
There is adequate fuel in the fuel tank.

Test Description

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

3: The engine control module (ECM) ground is located on the mounting bracket the ECM attaches to. All ground connections should be tight and free of any corrosion. This step determines if the ECM is being grounded properly.
4: This step determines if the battery is being grounded properly. All ground connections should be tight and free of any corrosion.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check-Engine Controls?		Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Turn ON the ignition, with the engine OFF. Observe the DTC information with a scan tool. Is DTC P0201-P0206, P0261, P0264, P0267, P0270, P0273, P0276, P0335, P1629, P1630, P1631 or P2105 set?		Go to Diagnostic Trouble Code (DTC) List	Go to Step 3
3	Test the ground circuits of the engine control module (ECM) for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 10	Go to Step 4
4	Test the ground circuit between the battery and the body for high resistance or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 10	Go to Step 5
5	Observe the ECM in VTD fail enable status parameter with a scan tool. Does the scan tool display an ECM in VTD fail enable status of NO?		Go to Step 6	Go to Diagnostic System Check - Theft Deterrent in Theft Deterrent
6	IMPORTANT: Inspect the fuel system for damage or external leaks before proceeding with this diagnostic. Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON with a scan tool. Does the fuel pump operate?		Go to Step 7	Go to Fuel Pump Electrical Circuit Diagnosis
7	Turn OFF the ignition. Remove the coil pack from the engine. Refer to Ignition Coil(s) Replacement - Bank 1 or Ignition Coil(s) Replacement - Bank 2 . Leave the electrical connector connected. Disconnect the fuel injector harness multi-connector. Install a J 26792 Spark Tester into one coil and connect it to a good ground. Turn ON the ignition, with the engine OFF. Operate the ignition coil with a scan tool. Repeat the above steps for the remaining coils. Does the spark tester show spark on all cylinders?		Go to Step 8	Go to Electronic Ignition (EI) System Diagnosis
8	Turn OFF the ignition. Install a fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. IMPORTANT: It may be necessary to command the fuel pump ON a few times in order to obtain the highest possible fuel pressure. Command the fuel pump ON with a scan tool. Observe the fuel pressure gage, with the fuel pump commanded ON. Is the fuel pressure within the specified range?	337-379 kPa (49-55 psi)	Go to Step 9	Go to Fuel System Diagnosis
9	Inspect for the following conditions: Fouled spark plugs-Refer to Spark Plug Inspection . If the spark plugs are fouled, determine the cause of the fouling before replacing them. Water or alcohol contaminated fuel-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . A restricted exhaust-Refer to Restricted Exhaust . An engine mechanical condition that would cause the engine not to start, such as low compression, broken timing belt, bent or burned intake or exhaust valves-Refer to Engine Compression Test in Engine Mechanical. A Collapsed or leaking air intake duct A skewed engine coolant temperature (ECT) Did you find and correct the condition?		Go to Step 10	Go to Intermittent Conditions
10	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Attempt to start the engine. Does the engine start and continue to run?		Go to Step 11	Go to Step 2
11	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	System OK

IMPORTANT
Inspect the fuel system for damage or external leaks 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.

Engine Cranks but Does Not Run

Circuit Description

When the ignition switch is turned ON, the engine control module (ECM) energizes the fuel pump relay which applies power to the in-tank fuel pump. The fuel pump relay will remain on as long as the engine is running or cranking and the ECM is receiving crankshaft position (CKP) sensor reference pulses. If no CKP sensor reference pulses are present, the ECM de-energizes the fuel pump relay within 2 seconds after the ignition is turned ON or the engine is stopped. The ECM applies a low current signal of approximately 7 volts to the fuel pump relay control circuit with the key ON and the engine OFF. The ECM uses this signal to detect the integrity of the fuel pump relay control circuit.

Diagnostic Aids

Fuel Relay Right Rear Bussed Electrical Center Terminal Identification
Front of vehicle
Left side of vehicle	Control	Fuel pump supply	Right side of vehicle
	Ignition 1 voltage	Ground

Fuel Pump Electrical Circuit Diagnosis

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. This can be determined by listening for an audible hiss from the fuel pump when the fuel pump relay is commanded ON or a vibration in the fuel feed line.
3: This step determines if the condition is located on the coil side or the switch side of the relay.
5: This step determines if the fuel pump relay is stuck closed.
7: This step tests for a grounded voltage supply circuit. The fuel pump fuse supplies power to fuel pump. Disconnecting the fuel pump in-line harness connector isolates the fuel pump voltage supply circuit.
9: This step verifies that the ECM is providing voltage to the fuel pump relay.
10: This step verifies that the fuel pump fuse is providing voltage to the fuel pump relay.
11: This step tests for an open circuit or a short to ground causing an open MaxiFuse.
12: This step bypasses the fuel pump relay in order to activate the fuel pump.
13: This step tests for an open in the fuel pump feed circuit between the in-line connector and the fuel pump relay.
16: This step tests for an open or high resistance in the fuel pump ground circuit.
18: This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.

Step	Action	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check-Engine Controls?	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON and OFF with a scan tool. Does the fuel pump turn ON and OFF?	Go to Intermittent Conditions	Go to Step 3
3	Remove the rear seat. Refer to Seat Cushion Replacement - Rear in Seats. IMPORTANT: An audible click should be heard. Command the fuel pump relay ON and OFF with a scan tool. Do you hear a click when you command the fuel pump relay ON and OFF?	Go to Step 4	Go to Step 9
4	Turn ON the ignition, with the engine OFF. Does the fuel pump operate continuously?	Go to Step 5	Go to Step 6
5	Turn OFF the ignition. Disconnect the fuel pump relay. Turn ON the ignition, with the engine OFF. Does the fuel pump operate continuously?	Go to Step 20	Go to Step 24
6	Is the fuel pump fuse open?	Go to Step 7	Go to Step 10
7	Disconnect the fuel pump harness in-line connector located near the fuel tank. Refer to Power and Grounding Component Views in Wiring Systems. Test the supply voltage circuit of the fuel pump for a grounded circuit. Refer to Wiring Repairs and Connector Repairs in Wiring Systems. Replace the fuel pump fuse if necessary. Did you find and correct the condition?	Go to Step 26	Go to Step 8
8	Lower the fuel tank if necessary. Refer to Fuel Tank Replacement . Test or inspect the fuel tank electrical harness for the following conditions: Damage to the harness A grounded fuel pump voltage supply circuit-Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Replace the fuel pump fuse if necessary. Did you find and correct the condition?	Go to Step 26	Go to Step 17
9	Turn OFF the ignition. Disconnect the fuel pump relay. Turn ON the ignition, with the engine OFF. Probe the fuel pump relay control circuit with a test lamp connected to a ground. Command the fuel pump ON and OFF with a scan tool. Did the test lamp illuminate?	Go to Step 18	Go to Step 19
10	Turn OFF the ignition. Disconnect the fuel pump relay. Turn ON the ignition, with the engine OFF. Probe the battery positive voltage circuit of the fuel pump relay with a test lamp connected to a good ground. Does the test lamp illuminate?	Go to Step 12	Go to Step 11
11	Turn OFF the ignition. Disconnect the fuel pump fuse. Turn ON the ignition, with the engine OFF. Probe the battery positive side of the fuel pump fuse, with a test lamp connected to a good ground. Does the test lamp illuminate?	Go to Step 21	Go to Step 22
12	Connect a 15-amp fused jumper wire between the battery positive voltage circuit and the fuel pump supply circuit in the fuel pump relay cavity. Does the fuel pump operate?	Go to Step 18	Go to Step 13
13	Disconnect the fuel pump harness in-line connector located near the fuel tank. Refer to Power and Grounding Component Views in Wiring Systems. Test the supply voltage circuit of the fuel pump for an open or for high resistance between the fuel pump relay and the in-line connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 26	Go to Step 14
14	IMPORTANT: Inspect the fuel pump ground circuit for being tight, corrosion on the terminals, or damage to the wiring harness. Test the ground circuit of the fuel pump for an open or for high resistance between the body pass through connector and the ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?	Go to Step 26	Go to Step 15
15	Test for an intermittent and for a poor connection at the fuel pump in-line connector to the body pass through connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 26	Go to Step 16
16	Lower the fuel tank. Refer to Fuel Tank Replacement . Test or inspect the fuel tank electrical harness for the following conditions: Damage to the harness A short to ground An open circuit-Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 26	Go to Step 23
17	Connect all disconnected components. Install a new fuel pump fuse. Command the fuel pump ON with a scan tool. Is the fuel pump fuse open?	Go to Step 23	Go to Intermittent Conditions
18	Test for an intermittent and for a poor connection at the fuel pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 26	Go to Step 24
19	Test for an intermittent and for a poor connection at the harness of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 26	Go to Step 25
20	Repair the supply voltage circuit of the fuel pump for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 26
21	Repair the battery positive voltage circuit of the fuel pump relay for an open. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 26
22	Repair the battery positive voltage circuit of the fuel pump fuse for an open or a short to ground. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 26
23	IMPORTANT: Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump. Replace the right fuel tank module. Refer to Fuel Tank Module Replacement - Primary . Replace the fuel pump fuse if necessary. Did you complete the replacement?	Go to Step 26
24	Replace the fuel pump relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Did you complete the replacement?	Go to Step 26
25	Replace the ECM. Refer to Engine Control Module (ECM) Replacement . Did you complete the replacement?	Go to Step 26
26	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 2

IMPORTANT
An audible click should be heard.

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

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

Fuel Pump Electrical Circuit Diagnosis

System Description

When you turn the ignition switch to the ON position, the engine control module (ECM) enables the fuel pump relay, which in turn powers the fuel pump. The fuel pump remains ON as long as the engine is cranking or running and the ECM receives ignition reference pulses. If there are no ignition reference pulses, the ECM shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position, or if the engine stops.

The fuel tank stores the fuel supply. The fuel pump is an electric pump that is attached to the right fuel tank module assembly. The fuel pump also supplies fuel to the siphon jet pump, also attached to the right fuel tank module. The siphon jet pump draws fuel from the left side of the fuel tank to the right side of the fuel tank. The fuel pump is designed to provide fuel at a pressure above the pressure that is needed by the fuel injectors. A fuel pressure regulator, which is also located in the fuel tank, is attached to the right fuel tank module. The fuel pressure regulator keeps the fuel available to the fuel injectors at a regulated pressure. The port on the fuel pressure regulator is an atmospheric vent. The fuel pressure regulator does not compensate for changes in intake manifold vacuum. Unused fuel is returned from the fuel filter to the fuel tank by a separate fuel return pipe.

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

2: This step verifies that the fuel pump is operating.
4: This step verifies that the vehicle is not out of fuel. If the right fuel sender is below 0.8 V, and the left fuel sender is above 0.8 V, a fuel transfer condition exists.
7: This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated.
10: This step isolates the condition. Replace the primary fuel tank module assembly, if the fuel pressure remains constant, after closing the valve on the fuel pipe shut-off adapter. Locate and replace the leaking fuel injector if the pressure continues to decrease after closing the valve on the adapter.
13: This step isolates the condition. Replace the primary fuel tank module assembly for a stuck open or leaking fuel pressure regulator, if the fuel pressure increases above the specified value.
16: This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.

Step	Action	Value(s)	Yes	No
Schematic Reference: Fuel Hose/Pipes Routing Diagram
1	Did you perform the Diagnostic System Check-Engine Controls?		Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	IMPORTANT: Inspect the fuel system for the following conditions before proceeding with this diagnostic procedure: Damage to the fuel system External fuel leaks Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Does the fuel pump operate?		Go to Step 3	Go to Fuel Pump Electrical Circuit Diagnosis
3	Observe the fuel level sensor left voltage with a scan tool. Is the fuel level sensor left voltage less than the specified value?	0.8 V	Go to Step 4	Go to Step 6
4	Observe the fuel level sensor right voltage with a scan tool. Is the fuel level sensor right voltage less than the specified value?	0.8 V	Go to Step 5	Go to Step 14
5	Add the specified amount of fuel. Operate the vehicle within the conditions of the customer's concern. Monitor the fuel trim related parameters with a scan tool. Refer to Scan Tool Data List . Do any of the scan tool parameters indicate a lean condition?	19 liters (5 gallons)	Go to Step 15	Go to Symptoms - Engine Controls
6	Turn OFF the ignition. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. IMPORTANT: The fuel pump may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. Command the fuel pump ON with a scan tool. Observe the fuel pressure gage, while the fuel pump is operating. Is the fuel pressure within the specified range?	380-410 kPa (55-60 psi)	Go to Step 7	Go to Step 11
7	IMPORTANT: The fuel pressure will drop when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Allow the fuel pressure to stabilize. Observe the fuel pressure gage for 1 minute. Does the fuel pressure decrease by more than the specified value?	34 kPa (5 psi)	Go to Step 10	Go to Step 8
8	Relieve the fuel pressure to the first specified value. Observe the fuel pressure gage for 5 minutes. Does the fuel pressure decrease by more than the second specified value?	69 kPa (10 psi) 14 kPa (2 psi)	Go to Step 19	Go to Step 9
9	Operate the vehicle within the conditions of the customer's concern. Observe the fuel related parameters with a scan tool. Do any of the scan tool parameters indicate a lean condition?		Go to Step 15	Go to Symptoms - Engine Controls
10	Turn OFF the ignition. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure . Disconnect the fuel feed pipe from the fuel rail. Refer to Quick Connect Fitting(s) Service (Metal Collar) . Install the appropriate J 37287 Fuel Pipe Shut-off Adapter between the fuel feed pipe and the fuel rail inlet. Open the valve on the fuel feed pipe shut-off adapter. Command the fuel pump ON, with a scan tool. Bleed the air from the fuel system. Command the fuel pump ON, with a scan tool. Close the fuel pipe shut-off valve. Observe the fuel pressure gage for 1 minute. Does the fuel pressure remain constant?		Go to Step 19	Go to Step 18
11	Is the fuel pressure more than the specified value?	410 kPa (60 psi)	Go to Step 12	Go to Step 13
12	Inspect the fuel return hose/pipe at the fuel filter for a restriction. Did you find and correct the condition?		Go to Step 20	Go to Step 19
13	Turn OFF the ignition. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure . Disconnect the fuel return hose from the fuel return outlet of the fuel filter. Refer to Quick Connect Fitting(s) Service (Metal Collar) . Install the appropriate J 37287 between the return outlet of the fuel filter and the fuel return hose. Open the valve in the fuel pipe shut-off adapter. Turn ON the ignition, with the engine OFF. Command the fuel pump ON, with a scan tool. Bleed the air from the fuel system. Observe the fuel pressure gauge. Slowly close the valve in the fuel pipe shut-off adapter. Use a scan tool in order to command the fuel pump ON. Does the fuel pressure increase to more than the specified value?	380-410 kPa (55-60 psi)	Go to Step 19	Go to Step 15
14	Remove both fuel tank modules. Refer to Fuel Tank Module Replacement - Primary and Fuel Tank Module Replacement - Secondary . Inspect the feed fuel pipe of the siphon jet pump for a restriction. Inspect the fuel strainer for contaminants. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Did you find and correct the condition?		Go to Step 20	Go to Step 19
15	Inspect the following components for a restriction: The fuel filter The fuel feed pipe Did you find and correct the condition?		Go to Step 20	Go to Step 16
16	Test for an intermittent and for a poor connection at the primary fuel tank module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 20	Go to Step 17
17	Remove the primary fuel tank module. Refer to Fuel Tank Module Replacement - Primary . Inspect the following items: The fuel pump flex hose for damage The in-tank fuel pump harness connectors for poor connections The fuel strainer for a restriction For contaminates in the fuel tank-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Did you find and correct the condition?		Go to Step 20	Go to Step 19
18	Turn OFF the ignition. Raise the fuel rail, with the fuel lines connected. Refer to Fuel Injectors and Fuel Rail Replacement . Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Locate and replace the leaking fuel injector. Refer to Fuel Injectors and Fuel Rail Replacement . Did you complete the replacement?		Go to Step 20
19	Replace the primary fuel tank module. Refer to Fuel Tank Module Replacement - Primary . Did you complete the replacement?		Go to Step 20
20	Operate the system in order to verify the repair. Did you correct the condition?		System OK	Go to Step 3

IMPORTANT
Inspect the fuel system for the following conditions before proceeding with this diagnostic procedure: Damage to the fuel system External fuel leaks

IMPORTANT
The fuel pump may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine.

IMPORTANT
The fuel pressure will drop when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

Fuel System Diagnosis

The engine control module (ECM) enables the fuel injector on the intake stroke for each cylinder. Ignition voltage is supplied directly to the fuel injectors. The ECM 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.

Injector	1	2	3	4	5	6
Measured resistance of each fuel injector	12 ohms	13 ohms	13.5 ohms	14 ohms	10 ohms	12 ohms
Lowest resistance value subtracted from the highest resistance value	Injector 4 = 14ohms Injector 5 = 10ohms =4ohms
Sum of all fuel injector resistance values divided by the total number of fuel injectors	Injector 1 = 12ohms Injector 2 = 13ohms Injector 3 = 13.5ohms Injector 4 = 14ohms Injector 5 = 10ohms Injector 6 = 12ohms = 74.5ohms Average resistance value: 74.5 /6 = 12.4ohms
Subtract the lowest injector resistance value from the average resistance value	Average resistance value = 12.4ohms Injector 5 = 10ohms Difference = 2.4ohms
Compute the difference between the highest injector resistance value and the average resistance value Subtract the average resistance value from the highest injector resistance value.	Injector 4 = 14ohms Average resistance value = 12.4ohms Difference = 1.6 ohms Replace fuel injector 5.

Fuel Injector Coil Test

Monitoring the misfire current counters, or misfire graph, may help to isolate the fuel injector that is causing the condition.
Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.
Perform the fuel injector coil test within the conditions of the customer's concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.
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»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting) .

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.
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.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check-Engine Controls?		Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Observe the engine coolant temperature (ECT) with a scan tool. Is the ECT parameter above the specified value?	20°C (68°F)	Go to Step 3	Go to Step 4
3	Disconnect the fuel injector multi-way harness connector. Measure the resistance of each fuel injector between the ignition feed circuit and the fuel injector control circuit, at the multi-way connector, with the DMM. Refer to Testing for Continuity in Wiring Systems. Do any of the fuel injectors display a resistance outside the specified range?	13-15.5 ohms	Go to Step 6	Go to Diagnostic Aids
4	Disconnect the fuel injector multi-way harness connector. Measure the resistance of each fuel injector between the ignition feed circuit and the fuel injector control circuit, at the multi-way connector, with the DMM. Refer to Testing for Continuity in Wiring Systems. Record each fuel injector value. Subtract the lowest resistance value from the highest resistance value. Is the difference equal to, or less than, the specified value?	3 ohms	Go to Fuel Injector Balance Test with Special Tool	Go to Step 5
5	Add all of the fuel injector resistance values to obtain a total resistance value. Divide the total resistance value by the number of fuel injectors, to obtain an average resistance value. Subtract the lowest individual fuel injector resistance value from the average resistance value. Subtract the average resistance value from the highest individual fuel injector resistance value. Replace the fuel injector that displays the greatest resistance difference above or below the average. Refer to Fuel Injectors and Fuel Rail Replacement . Did you complete the replacement?		Go to Step 7
6	Replace the fuel injector or fuel injectors that are out of the specified range. Refer to Fuel Injectors and Fuel Rail Replacement . Did you complete the replacement?	13-15.5 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 Coil Test

Scheme 203

Scheme 203: 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 (ECT) 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 Fuel Injector Balance Test Example.

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check-Engine Controls?		Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Did you perform the Fuel Injector Coil Test?		Go to Step 3	Go to Fuel Injector Coil Test
3	IMPORTANT: DO NOT perform this test if the engine coolant temperature is above 94°C (201°F). Observe the ECT with a scan tool.Is the ECT less than the specified value?	94°C (201°F)	Go to Step 4
4	IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. IMPORTANT: The fuel pump may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure. DO NOT start the engine. Command the fuel pump ON with a scan tool. Observe the fuel pressure gage, with the fuel pump commanded ON. Is the fuel pressure within the specified range?	337-379 kPa (49-55 psi)	Go to Step 5	Go to Fuel System Diagnosis
5	IMPORTANT: The fuel pressure will drop slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gage for 1 minute.Does the fuel pressure decrease by more than the specified value?	34 kPa (5 psi)	Go to Fuel System Diagnosis	Go to Step 6
6	Connect the J 39021 Fuel Injector Coil/Balance Tester, J 39021-210 Injector Tester Adapter Box, and J 39021-360 Fuel Injector Test Adapter to the fuel injector harness multi-way connector. 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 after the fuel injector stops pulsing. This is the second fuel pressure reading. Repeat steps 1 through 6 for each fuel injector. Subtract the second pressure reading from the first pressure reading for one fuel injector. The result is the pressure drop value. Obtain a pressure drop value for each fuel injector. Add all of the individual pressure drop values. This is the total pressure drop. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop. 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?	10 kPa (1.5 psi)	Go to Step 7	Go to Symptoms - Engine Controls
7	Replace the affected fuel injector. Refer to Fuel Injectors and Fuel Rail Replacement . Did you complete the replacement?		Go to Step 8
8	Operate the system in order to verify the repair. Did you correct the condition?		System OK	Go to Symptoms - Engine Controls

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

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

IMPORTANT
The fuel pump may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure. DO NOT start the engine.

IMPORTANT
The fuel pressure will drop 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 Procedure

The fuel tank leak test is used to locate any fuel or fuel vapor escaping the fuel tank area. Fuel vapors escaping above the fuel level will be detected when the EVAP leak diagnostic completes one test cycle. The MIL will illuminate after the EVAP leak diagnostic completes two test cycles only when a condition is detected.

Operate the vehicle under the condition of the customers concern. Under high temperature conditions fuel vapors may increase to the point of EVAP canister vapor saturation. Fuel vapors would then be released into the atmosphere. Once the engine is running and EVAP purge is enabled, all fuel vapor release would be eliminated.
Movement of the EVAP pipes or fuel pipes may help find an intermittent condition.

1: This step determines that no EVAP diagnostic DTC is present.
3: This step tests for location of fuel leakage in the fuel lines.
4: This step tests for fuel leaks below the fuel level in the fuel tank.
5: This step tests for a location of fuel vapors escaping above the fuel level in the fuel tank.

Step	Action	Yes	No
1	Did you perform the Diagnostic System Check-Engine Controls?	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	CAUTION: Refer to Gasoline/Gasoline Vapors Caution in Cautions and Notices. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information. Inspect the fuel tanks and the fuel pipes for damage or external leaks. Did you find fuel leaking from the fuel tank?	Go to Step 7	Go to Step 3
3	Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Inspect for fuel leaking from the fuel pipe. Did you locate a fuel leak from the fuel pipes?	Go to Step 8	Go to Step 4
4	Install the J 41415-40 Fuel Tank Cap Adapter. Connect the J 41413-200 Evaporative Emissions System Tester (EEST) to the J 41415-40 . Command the EVAP vent valve ON with a scan tool. Pressurize the fuel tank with the J 41413-200 . Inspect for a fuel leak from the fuel tank. Did you locate a fuel leak from the fuel tank?	Go to Step 7	Go to Step 5
5	Maintain pressure in the fuel tank with the J 41413-200 . IMPORTANT: It may be necessary to partially lower the fuel tank. Refer to Fuel Tank Replacement . Test for leaks above the fuel level in the following locations with the J 41416 Ultrasonic Leak Detector. The fuel tank, fill limiter vent valve, pressure relief valve and rollover valves-Refer to Fuel Tank Replacement . The fuel sender housing and fuel sender seal-Refer to Fuel Tank Module Replacement - Primary and Fuel Tank Module Replacement - Secondary . The fuel tank pressure (FTP) sensor seal-Refer to Fuel Tank Pressure Sensor Replacement . The EVAP vapor pipes-Refer to Evaporative Emission (EVAP) Hoses/Pipes Replacement - Chassis/Canister . The fuel fill pipe and hose-Refer to Filler Tube Replacement . Did you locate a fuel leak in any area?	Go to Step 6	Go to Diagnostic Aids
6	Repair the system as necessary. Did you complete the repair?	System OK
7	Replace the fuel tank. Refer to Fuel Tank Replacement . Did you complete the repair?	System OK
8	Replace the leaking fuel pipe. Refer to Fuel Hoses/Pipes Replacement - Filter to Tank and Fuel Hose/Pipes Replacement - Chassis . Did you complete the replacement?	System OK

CAUTION
Refer to Gasoline/Gasoline Vapors Caution in Cautions and Notices.

IMPORTANT
It may be necessary to partially lower the fuel tank. Refer to Fuel Tank Replacement .

Fuel Tank Leak Test

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

Alcohol concentrations more than 10 percent in the fuel can be detrimental to fuel system components. Alcohol contamination may cause fuel system corrosion, deterioration of rubber components, and subsequent fuel filter restriction. Fuel contaminated with alcohol may cause driveability conditions such as hesitation, lack of power, stalling, or no start. Some types of alcohol are more detrimental to fuel system components than others.

Alcohol in Fuel Testing Procedure

The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be detected. The sample should be bright and clear. If alcohol contamination is suspected then use the following procedure to test the fuel quality.

Using a 100 ml (3.38 oz) specified cylinder with 1 ml (0.34 oz) graduation marks, fill the cylinder with fuel to the 90 ml (3.04 oz) mark.
Add 10 ml (0.34 oz) of water in order to bring the total fluid volume to 100 ml (3.38 oz) and install a stopper.
Shake the cylinder vigorously for 10-15 seconds.
Carefully loosen the stopper in order to release the pressure.
Re-install the stopper and shake the cylinder vigorously again for 10-15 seconds.
Put the cylinder on a level surface for approximately 5 minutes in order to allow adequate liquid separation.

If alcohol is present in the fuel, the volume of the lower layer, that now contains both alcohol and water, will be more than 10 ml (0.37 oz). For example, if the volume of the lower layer is increased to 15 ml (0.51 oz), this indicates at least 5 percent alcohol in the fuel. The actual amount of alcohol may be somewhat more because this procedure does not extract all of the alcohol from the fuel.

Particulate Contaminants in Fuel Testing Procedure

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

Using an approved fuel container, draw approximately 0.5 liter (0.53 qt) 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 .

Fuel quality can affect vehicle performance. Gasoline and gasoline blends that are contaminated or contain excessive amounts of alcohol can affect vehicle driveability, fuel economy, fuel system components and emissions. Excessive alcohol in the fuel may cause fuel system corrosion, deterioration of rubber components, and subsequent fuel filter restriction. Some types of alcohol are more detrimental to fuel system components than others. Ethanol is commonly used in gasoline, but in concentrations of no more than 10 percent. Some fuels, such as E85, contain a very high percent of ethanol. Fuel with more than 10 percent ethanol may cause driveability conditions in vehicles such as hesitation, lack of power, stalling, or no start. If excessive alcohol in the fuel is suspected, then use the following procedure to test the fuel quality.

Test Procedure

Turn ON the J 44175 Fuel Composition Tester.
Verify the fuel J 44175 is operational by measuring the AC frequency output with a DMM. Refer to Measuring Frequency in Wiring Systems. A frequency without a fuel sample in the test cell indicates that the tester is working correctly.
Close the bleed valve on the fuel pressure gage.
Place the bleed hose (1) of the fuel pressure gage into the 100 ml (3.380 oz) beaker (2).
Command the fuel pump ON with a scan tool.
Slowly open the bleed valve on the fuel pressure gage, until an adequate fuel sample is obtained.
If water appears in the fuel sample, clean the fuel system and replace the fuel in the vehicle. Refer to Fuel System Cleaning.
Pour the fuel sample from the beaker (1) into the J 44175 , until the level of the fuel is at the top of each fuel test port (2).
Observe the diagnostic LEDs on the fuel composition tester. If the red fuel diagnostic LED is illuminated, a fuel contamination condition exists. Refer to Fuel System Cleaning.
Measure the output frequency of the fuel composition tester.
Subtract 50 from the reading on the DMM to obtain the percentage of alcohol in the fuel sample. Refer to the examples in the following table.
If the fuel sample contains more than 10 percent ethanol, replace the fuel in the vehicle.

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

Fuel Composition Test Examples

The multi-ram system uses variable air induction tuning in order to achieve maximum performance and efficiency over the entire operating range of the engine. The system consists of two main parts: the intake manifold runner control valve and the intake manifold tuning valve. The engine control module (ECM) controls two solenoids that apply vacuum to each of the valve actuators. When the ECM commands the solenoid ON, vacuum is supplied to that actuator, causing the valve to open or close. Vacuum is supplied to each of the solenoids from a vacuum reservoir located near the intake air duct. The reservoir is required to maintain the vacuum supply during extended acceleration conditions. The intake manifold contains the intake manifold runner control valve. This vacuum operated valve is a moveable divider that changes the airflow characteristics of the intake manifold. The second part of the multi-ram system is the intake manifold tuning valve. This vacuum operated valve is located in the air intake duct assembly. This is a moveable divider that changes the tuning of the air intake system. By opening and closing these valves independently, in different combinations, four different air flow configurations can be created, each optimizing a set of engine operating conditions.

Both solenoid valves are supplied switched battery power from the engine controls power relay. Both solenoid valves have a control circuit to the ECM. The ECM controls a valve by grounding the control circuit. If a fault is detected with either of the solenoid valve control circuits, a diagnostic trouble code (DTC) will set.

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

5: This step is to confirm that the valve inside the housing is moving correctly and is not loose or damaged in any way.

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check-Engine Controls?		Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Are any other DTCs set?		Go to Diagnostic Trouble Code (DTC) List	Go to Step 3
3	Visually inspect the system for the following conditions and repair as necessary: Inspect for any disconnected or damaged vacuum hoses and components. Refer to Emission Hose Routing Diagram . Inspect the linkage between the vacuum actuators and the valves. Move the linkage by hand. Check for binding, or interference with the hoses, the wiring, or any other components. Did you find and correct the condition?		Go to Step 13	Go to Step 4
4	Start the engine. Observe the vacuum actuator linkages for the intake manifold runner control (IMRC) valve and the intake manifold tuning (IMT) valve. Command each solenoid ON and OFF with a scan tool. Do both valves operate?		Go to Step 5	Go to Step 6
5	Turn OFF the ignition. Remove the duct between the IMT valve and the throttle body. Move the actuator linkage at the rear of the intake plenum by hand and listen for confirmation that the divider is moving freely in the plenum. If a problem is suspected with the valve, refer to Intake Plenum Switchover Valve Replacement for further inspection. Look down the passages in the IMT valve in order to view the moveable divider between the two sides of the intake air duct. Move the actuator linkage by hand. Then ensure that the divider moves with the linkage. Do both valves operate properly?		System OK	Go to Step 12
6	Turn OFF the ignition. Disconnect the vacuum supply hose at each of the actuators. Start and idle the engine. Test for vacuum at each of the actuators. Is vacuum present at either actuator?		Go to Step 11	Go to Step 7
7	Command the IMRC valve solenoid and the IMT valve solenoid ON with a scan tool. Measure the vacuum at each of the actuators while the respective solenoid is commanded ON. Is the vacuum above the specified value?	33 kPa (10 in Hg)	Go to Step 12	Go to Step 8
8	Turn OFF the ignition. Disconnect the vacuum supply hose from the solenoid that did not have vacuum at the actuator. Start and idle the engine. Measure the vacuum at the supply hose. Is the vacuum above the specified value?	33 kPa (10 in Hg)	Go to Step 9	Go to Step 10
9	Turn OFF the ignition. Inspect the vacuum hose from the solenoid to the actuator for a leak or a restriction. Repair or replace the hose as necessary. Did you find and correct the condition?		Go to Step 13	Go to Step 11
10	Repair the leak or restriction in one of the following components of the vacuum supply system: Vacuum hose from the reservoir to the solenoids Reservoir Vacuum hose from the intake manifold to the reservoir Did you complete the repair?		Go to Step 13
11	Replace the affected solenoid. Refer to Intake Plenum Switchover Solenoid Replacement or Intake Resonance Switchover Solenoid Replacement . Did you complete the replacement?		Go to Step 13
12	Replace the affected valve actuator assembly. Refer to Intake Plenum Switchover Valve Replacement or Intake Resonance Switchover Valve Replacement . Did you complete the replacement?		Go to Step 13
13	Start the engine. Observe the vacuum actuator linkages for the IMRC valve and the IMT valve. Command each valve ON and OFF with a scan tool. Do both valves operate?		System OK	Go to Step 2

Intake Manifold Runner Control System Diagnosis

The Ignition System uses a ignition coil assembly for each bank. Each ignition coil assembly consist of 3 ignition coils. The ignition coil assemblies consist of the following circuits

An ignition voltage circuit
A ground circuit
An ignition control (IC) circuit for each ignition coil

The ignition coil assemblies are mounted in the center of each camshaft cover with short boots connecting the coils to the spark plugs. The engine control module (ECM) primarily uses engine speed and position information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor to control the sequence, dwell, and timing of the spark. The ECM can command each ignition coil ON/OFF by grounding the IC circuit of the ignition coil. The IC circuits are pulse width modulated (PWM) in order to precisely control the spark events.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check-Engine Controls?		Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Attempt to start the engine. Does the engine start and idle?		Go to Step 3	Go to Step 6
3	Turn OFF the ignition. Remove the fuel pump relay. Test for spark at each cylinder with a J 26792 Spark Tester. Did you have spark on all cylinders?		Go to Step 4	Go to Step 10
4	Does the spark tester indicate a bright blue spark on all cylinders?		Go to Step 5	Go to Step 15
5	Remove the spark plugs. Examine the spark plugs for any abnormal conditions or damage. Refer to Spark Plug Inspection . Are the spark plugs in good condition?		System OK	Go to Step 21
6	Turn OFF the ignition. Disconnect the harness connector of the inoperative ignition coil assembly. Turn ON the ignition, with the engine OFF. Connect a test lamp from the ignition voltage circuit of the ignition coil assembly to a good ground. Does the test lamp illuminate?		Go to Step 7	Go to Step 17
7	Connect a test lamp from the ignition voltage circuit to the ground circuit of the ignition coil assembly. Does the test lamp illuminate?		Go to Step 8	Go to Step 18
8	Turn OFF the ignition. Remove the IGN MOD fuse in the underhood fuse block. Measure the resistance of ignition voltage circuit of the ignition coil assembly from the IGN MOD fuse in the underhood fuse block to the harness connector of the ignition coil assembly with a DMM. Is the resistance less than the specified value?	3 ohms	Go to Step 9	Go to Step 19
9	Measure the resistance of ground circuit of the ignition coil assembly from the harness connector of the ignition coil assembly to a good ground with a DMM. Is the resistance less than the specified value?	3 ohms	Go to Step 15	Go to Step 20
10	Turn OFF the ignition. Disconnect the harness connector of the ignition coil assembly. IMPORTANT: If using a different test lamp, the bulb resistance needs to be 4 ohms or less. Using jumper wires, connect the J 34730-405 TBI Harness Test Lamp from the ignition voltage circuit of the ignition coil assembly to the IC circuit of the inoperative ignition coil in the harness connector of the ignition coil assembly Turn ON the ignition, with the engine OFF. Command the inoperative ignition coil ON with a scan tool. Does the test lamp flash?		Go to Step 12	Go to Step 11
11	Does the test lamp remain ON?		Go to Step 13	Go to Step 14
12	Using jumper wires, connect the J 34730-405 from the ignition voltage circuit of the ignition coil assembly to the IC circuit of a known good ignition coil in the harness connector of the ignition coil assembly. Command the ignition coil ON with a scan tool. Compare the illumination of the good coil to that of the inoperative coil. Does the test lamp illuminate with same brightness for both circuits?		Go to Step 15	Go to Step 14
13	Test the IC circuit of the inoperative ignition coil for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 24	Go to Step 16
14	Test the IC circuit of the inoperative ignition coil for one of the following conditions: An open A short to voltage High resistance of more than 3 ohms Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 24	Go to Step 16
15	Test for shorted terminals or a poor connection at the ignition coil assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 24	Go to Step 22
16	Test for shorted terminals or a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 24	Go to Step 23
17	Repair an open or a short to ground in the ignition voltage circuit of the ignition coil assembly. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 24
18	Repair an open in the ground circuit of the ignition coil assembly. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 24
19	Repair the high resistance in the ignition voltage circuit of the ignition coil assembly. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 24
20	Repair the high resistance in the ground circuit of the ignition coil assembly. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 24
21	Replace the spark plugs. Refer to Spark Plug Replacement . Did you complete the replacement?		Go to Step 24
22	Replace the ignition coil assembly. Refer to Ignition Coil(s) Replacement - Bank 1 or Ignition Coil(s) Replacement - Bank 2 . Did you complete the replacement?		Go to Step 24
23	Replace the ECM. Refer to Engine Control Module (ECM) Replacement . Did you complete the replacement?		Go to Step 24
24	Turn the ignition OFF for 30 seconds. Start the engine and operate the vehicle. Observe the vehicle performance and driveability. Does the vehicle operate normally?		System OK	Go to Step 2

IMPORTANT
If using a different test lamp, the bulb resistance needs to be 4 ohms or less.

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 (A/C) System
The catalytic converter efficiency
Comprehensive component monitoring-Emission related inputs and outputs
The Evaporative Emissions (EVAP) System
The EGR System
The Fuel Delivery System
Heated catalyst monitoring
Misfire monitoring
The Oxygen Sensor System (O2S or HO2S)
The Oxygen Sensor Heater System (HO2S heater)
The AIR System

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

Step	Action	Yes	No
1	Perform Diagnostic System Check - Engine Controls . IMPORTANT: Many DTC related repairs will instruct the technician to clear the DTC information. This procedure will reset ALL of the I/M System Status indicators to NO, and require performing the I/M Complete System Set Procedure. Repair any DTCs or driveability concerns that would prevent the I/M System Status tests from completing. Did you find and repair a DTC or driveability concern?	Go to Step 3	Go to Step 2
2	Review any service bulletins for software updates that may prevent I/M readiness. Perform any reprogramming or repairs indicated by the service bulletins. Was a reprogramming or repair service required?	Go to Inspection/Maintenance (I/M) Complete System Set Procedure	Go to Step 3
3	Observe the I/M System Status display with a scan tool. Is more than one test indicating a NO status?	Go to Inspection/Maintenance (I/M) Complete System Set Procedure	Go to the I/M System Set Procedure for the indicated system that was not updated

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

Inspection/Maintenance (I/M) System Check

The purpose of the inspection/maintenance (I/M) complete system set procedure is to satisfy the enable criteria necessary to execute all of the I/M readiness diagnostics, and complete the trips for those particular diagnostics. When all diagnostic tests are completed, the I/M System Status indicators are set to YES. Perform this test when more than one of the I/M System Status indicators are set to NO.

Conditions for Running

Cold Start

The barometric pressure is more than 68 kPa.
The engine coolant temperature (ECT) is between 4-35°C (39-95°F).
The intake air temperature (IAT) is between 4-35°C (39-95°F).
The difference between the IAT and the ECT is 10°C (18°F) or less.
The battery voltage is between 10.5-17 volts.
The fuel level is between 15-85 percent.
The ambient air temperature is between 2-32°C (36-90°F).
The difference between the startup ECT and ambient air temperature is less than 10°C (18°F).
The engine is in Closed Loop fuel control.
The fuel tank pressure is between -3.8 and +1.0 kPa (-0.6 and +0.1 psi).
The vehicle has traveled more than 5 miles this trip.

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

2: This step is to run the HO2S Heater Tests and initiate the EVAP System Test.
3: This step is to run the EVAP, AIR and the Oxygen Sensor Tests. The EVAP Test begins once the engine coolant reaches a calibrated temperature. The AIR Test, if equipped, begins shortly after Closed Loop and the indicated speed is achieved. The Oxygen Sensor Tests begin once the engine is at operating temperature, in Closed Loop Fuel Control, and a calibrated amount of time has elapsed.
4: This step is to run the EGR Tests. The EGR Tests are run during a gradual deceleration with a closed throttle. The vehicle speed is required in order to maintain a high, steady MAP signal.
5: This step is to run the Catalyst Tests. This test runs during the idle period immediately following a cruise period that meets a minimum calibrated RPM and time period.
7: The I/M System Status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

Step	Action	Value(s)	Yes	No
1	Did you perform the Inspection/Maintenance (I/M) System Check?		Go to Step 2	Go to Inspection/Maintenance (I/M) System Check
2	Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Set the vehicle parking brake. Verify the transmission is in Park for automatic transmissions and Neutral for manual transmissions. Start the engine and allow the engine to idle for the specified time. Is the action complete?	2 minutes	Go to Step 3
3	CAUTION: Refer to Road Test Caution in Cautions and Notices. In order for the next group of tests to run, the vehicle must operate in the following conditions: Acceleration at part throttle to 72 km/h (45 mph) with this speed maintained until the engine reaches operating temperature-This may be up to 16 minutes depending on the start up coolant temperature. Continued operation under these conditions for an additional 7 minutes Is the action complete?		Go to Step 4
4	CAUTION: Refer to Road Test Caution in Cautions and Notices. In order for the next group of tests to run, the vehicle must operate in the following conditions: Accelerate to 89 km/h (55 mph) with this speed maintained for one additional minute. Decelerate to 48 km/h (30 mph) while the following criteria is maintained: The throttle is closed There is NO brake application on either manual or automatic transmission There is NO clutch actuation on a manual transmission There is NO manual downshift Is the action complete?		Go to Step 5
5	CAUTION: Refer to Road Test Caution in Cautions and Notices. In order for the next group of tests to run, the vehicle must operate in the following conditions: Acceleration at part throttle to 72 km/h (45 mph) with this speed maintained for 10 minutes. Deceleration to 0 km/h (0 mph). Engine idling for 2 minute while the following criteria is maintained: Service brake depressed Automatic transmission in drive Manual transmission in neutral with the clutch pedal depressed Turn OFF the ignition for 1 hour. After 1 hour, turn ON the ignition. Is the action complete?		Go to Step 6
6	Observe the I/M System Status display with a scan tool. Did all of the I/M System Status indicators update to YES?		Go to Step 7	Go to the I/M System Set Procedure for the indicated systems that have not updated
7	Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set?		Go to Diagnostic Trouble Code (DTC) List	System OK

CAUTION
Refer to Road Test Caution in Cautions and Notices.

CAUTION
Refer to Road Test Caution in Cautions and Notices.

CAUTION
Refer to Road Test Caution in Cautions and Notices.

Inspection/Maintenance (I/M) Complete System Set Procedure

Inspection/Maintenance (I/M) System DTC Table

System	DTCs Required to Set System Status to YES
Catalyst	DTC P0420 or P0430
EVAP	DTC P0442 DTC P0446 DTC P0455 DTC P0496
Oxygen Sensor	DTC P0132 or P0152 DTC P0133 or P0153 DTC P0134 or P0154 DTC P0138 or P0158 DTC P0140 or P0160 DTC P2096 or P2098 DTC P2097 or P2099
Oxygen Sensor Heater	DTC P0135, P0141, P0155, or P0161

Inspection/Maintenance (I/M) System DTC Table

The purpose of this test is to satisfy the enable criteria necessary to execute inspection/maintenance (I/M) readiness diagnostics for the catalyst system. The test may be used to set the I/M System Status indicators to YES. The I/M System Status display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made even if all of the other tests for that system have not run.

DTCs P0421 and P0431 are not set.
The engine load is between 20-45 percent.
The manifold absolute pressure (MAP) sensor variation is less than 6 kPa.
The catalytic temperature is more than 350°C (662°F).
The engine is in Closed Loop fuel control.
The engine speed is between 1,000-2,120 RPM.

The control module runs a calibrated number of catalyst tests per trip until the Catalyst System Status updates to YES. If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.

If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load such as a cooling fan or A/C compressor clutch turning ON may cause the test to abort.

Step	Action	Yes	No
1	Did you perform the Inspection/Maintenance (I/M) System Check?	Go to Step 2	Go to Inspection/Maintenance (I/M) System Check
2	Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Start the engine and allow the engine to idle for 2 minutes. CAUTION: Refer to Road Test Caution in Cautions and Notices. IMPORTANT: In order for this test to run, the vehicle must operate in the following conditions: Acceleration at part throttle to 72 km/h (45 mph) with this speed maintained for up to 10 minutes Deceleration to 0 km/h (0 mph) Engine idling for 1 minutes while the following criteria is maintained: Service brake depressed Automatic transmission in Drive Observe the I/M System Status display with a scan tool. Did the catalyst System Status update to YES?	Go to Step 5	Go to Step 3
3	Observe the DTC Information with a scan tool. Does the scan tool indicate any failed DTCs?	Go to Diagnostic Trouble Code (DTC) List	Go to Step 4
4	Refer to the Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test. Observe the Not Ran Since Code Cleared display with a scan tool. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the specific DTC menu of the scan tool. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. This may take up to 2 hours. Repeat steps 4-6 for any additional required DTCs that have not run. Observe the I/M System Status display with a scan tool. Did the catalyst System Status update to YES?	Go to Step 5	Go to Diagnostic Aids
5	Observe the emission related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any emission related DTCs set?	Go to Diagnostic Trouble Code (DTC) List	System OK

CAUTION
Refer to Road Test Caution in Cautions and Notices.

IMPORTANT
In order for this test to run, the vehicle must operate in the following conditions: Acceleration at part throttle to 72 km/h (45 mph) with this speed maintained for up to 10 minutes Deceleration to 0 km/h (0 mph) Engine idling for 1 minutes while the following criteria is maintained: Service brake depressed Automatic transmission in Drive

Inspection/Maintenance (I/M) Catalyst System Set Procedure

The purpose of this test is to satisfy the enable criteria necessary in order to execute the I/M readiness diagnostics for the evaporative emission (EVAP) system. The test may be used in order to set the I/M System Status indicators to YES. The I/M System Status Display on the scan tool provides an indication of when the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed and I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run. Performing a visual inspection prior to running the EVAP test may prevent having to repeat the test. A failed or aborted test will require the vehicle to cool down in order to meet the enable criteria to run another test.

DTCs P0442, P0446, P0455, P0496 are not set.
The barometric pressure (BARO) is more than 68 kPa.
The fuel level is between 15-85 percent.
The battery voltage is between 10.5-17 volts.
The engine coolant temperature (ECT) is between 4-35°C (39-95°F).
The intake air temperature (IAT) is between 4-35°C (39-95°F).
The difference between the ECT and the IAT is less than 10°C (18°F).
The ambient air temperature is between 2-32°C (36-90°F).
The difference between the startup ECT and ambient air temperature is less than 10°C (18°F).
The engine is in Closed Loop fuel control.
The fuel tank pressure is between -3.8 and +1.0 kPa (-0.6 and +0.1 psi).
The vehicle has traveled more than 5 miles this trip.

If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load such as a cooling fan or an A/C compressor clutch turning ON may cause the test to abort.

Step	Action	Yes	No
1	Did you perform the Inspection/Maintenance (I/M) System Check?	Go to Step 2	Go to Inspection/Maintenance (I/M) System Check
2	Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, including the A/C and the blower fan. IMPORTANT: Once the engine is started, DO NOT turn the engine OFF for the remainder of the procedure. Start the engine and allow the engine to idle for 2 minutes. CAUTION: Refer to Road Test Caution in Cautions and Notices. IMPORTANT: In order for this test to run, the vehicle must operate in the following conditions: Acceleration at part throttle to 72 km/h (45 mph) with this speed maintained until the engine reaches operating temperature. This may be up to 10 minutes, depending on the startup coolant temperature. Continue the operating conditions for an additional 3 minutes after the engine reaches the operating temperature. Decelerate to 0 km/h (0 mph). Idle the engine for 2 minutes. Turn OFF the ignition for 1 hour. After 1 hour, turn ON the ignition. Observe the EVAP System Status with a scan tool. Did the EVAP System Status update to YES?	Go to Step 5	Go to Step 3
3	Observe the DTC Information with a scan tool. Does the scan tool indicate any failed DTCs?	Go to Diagnostic Trouble Code (DTC) List	Go to Step 4
4	Refer to Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test. Observe the Not Ran Since Code Cleared display with a scan tool. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the Specific DTC menu of the scan tool. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat steps 4-6 for any additional required DTCs that have not run. Observe the I/M System Status display with a scan tool. Did the EVAP System Status update to YES?	Go to Step 5	Go to Diagnostic Aids
5	Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set?	Go to Diagnostic Trouble Code (DTC) List	System OK

IMPORTANT
Once the engine is started, DO NOT turn the engine OFF for the remainder of the procedure.

CAUTION
Refer to Road Test Caution in Cautions and Notices.

IMPORTANT
In order for this test to run, the vehicle must operate in the following conditions

Inspection/Maintenance (I/M) Evaporative Emission (EVAP) System Set Procedure

The purpose of this test is to satisfy the enable criteria necessary to execute inspection/maintenance (I/M) readiness diagnostics for the oxygen sensor (O2S, HO2S) system. The test may be used to set the I/M System Status to YES. The I/M System Status display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run.

The engine is running in Closed Loop fuel control.
The engine has been running for more than 4 minutes.
The battery voltage is more than 10.5 volts.
The engine speed is between 1,400-2,520 RPM.

Step	Action	Yes	No
1	Did you perform the Inspection/Maintenance (I/M) System Check?	Go to Step 2	Go to Inspection/Maintenance (I/M) System Check
2	Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Start the engine and allow the engine to idle for 1 minute. CAUTION: Refer to Road Test Caution in Cautions and Notices. IMPORTANT: In order for this test to run, the vehicle must operate in the following conditions: Acceleration at part throttle to 75-90 km/h (45-55 mph) with this speed maintained for 7 minutes or until the I/M System Status updates to YES. Manual transmissions, either 5 or 6 speed, may require operation in 4th or 5th gear respectively, in order for this test to run. Review the I/M System Status display with a scan tool. Did the HO2S/O2S System Status update to YES?	Go to Step 5	Go to Step 3
3	Observe the DTC Information with a scan tool. Does the scan tool indicate any failed DTCs?	Go to Diagnostic Trouble Code (DTC) List	Go to Step 4
4	Refer to Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test. Observe the Not Ran Since Code Cleared display with a scan tool. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the Specific DTC menu of the scan tool. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat steps 4-6 for any additional required DTCs that have not run. Observe the I/M System Status display with a scan tool. Did the HO2S/O2S System Status update to YES?	Go to Step 5	Go to Diagnostic Aids
5	Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set?	Go to Diagnostic Trouble Code (DTC) List	System OK

CAUTION
Refer to Road Test Caution in Cautions and Notices.

IMPORTANT
In order for this test to run, the vehicle must operate in the following conditions

Inspection/Maintenance (I/M) Heated Oxygen Sensor/Oxygen Sensor (HO2S/O2S) System Set Procedure

The purpose of this test is to satisfy the enable criteria necessary to execute inspection/maintenance (I/M) readiness diagnostics for the heated oxygen sensor (HO2S) Heater System. The test may be used to set the I/M System Status to YES. The I/M System Status Display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run.

The engine is running.
The battery voltage is between 10.5-17.3 volts.
The calculated converter temperature is between 400-580°C (752-1,076°F).

The HO2S Heater Tests will normally run within the 9 minutes allotted in the procedure. If there is an indeterminate condition, the test may take up to 20 minutes on some vehicles before a decision of pass or fail is made. If the test does not update within the allotted period of time, continue operation within the enable conditions until the test updates to YES. If the test does not update to YES, it may have failed or aborted due to the loss of enabling conditions.

If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON may cause the test to abort.

Step	Action	Yes	No
1	Did you perform the Inspection/Maintenance (I/M) System Check?	Go to Step 2	Go to Inspection/Maintenance (I/M) System Check
2	Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Start the engine and allow the engine to idle for 2 minutes. CAUTION: Refer to Road Test Caution in Cautions and Notices. IMPORTANT: In order for this test to run, the vehicle must operate in the following conditions: Acceleration at part throttle to 75-90 km/h (45-55 mph) with this speed maintained for 9 minutes or until the I/M System Status updates to YES. Manual transmissions, either 5 or 6 speed, may require operation in 4th or 5th gear respectively, in order for this test to run. Review the I/M System Status display with a scan tool. Did the HO2S/O2S System Status update to YES?	Go to Step 5	Go to Step 3
3	Observe the DTC Information with a scan tool. Does the scan tool indicate any failed DTCs?	Go to Diagnostic Trouble Code (DTC) List	Go to Step 4
4	Refer to Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test. Observe the Not Ran Since Code Cleared display with a scan tool. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the Specific DTC menu of the scan tool. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. This may take up to 2 hours. Repeat steps 4-6 for any additional required DTCs that have not run. Observe the I/M System Status display with a scan tool. Did the HO2S/O2S System Status update to YES?	Go to Step 5	Go to Diagnostic Aids
5	Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set?	Go to Diagnostic Trouble Code (DTC) List	System OK

CAUTION
Refer to Road Test Caution in Cautions and Notices.

IMPORTANT
In order for this test to run, the vehicle must operate in the following conditions

Inspection/Maintenance (I/M) Heated Oxygen Sensor (HO2S) Heater System Set Procedure

Engine Controls - 2.6l & 3.2l - Troubleshooting Cadillac CTS I

Important Preliminary Inspections Before Starting

Intermittent Conditions

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

Description

Test Description

Circuit Description

Diagnostic Aids

System Description

Scheme 203

Alcohol in Fuel Testing Procedure

Particulate Contaminants in Fuel Testing Procedure

Test Procedure

Conditions for Updating the I/M System Status

Monitored Emission Control Systems

Conditions for Running

Inspection/Maintenance (I/M) System DTC Table

More articles — Engine Performance

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