PRE-RELEASE
DTC P0300-P0306 (LAU)
| DTC P0300-P0306 (LAU) |
| Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
provides an overview of each diagnostic category.
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| DTC Descriptors |
DTC P0300
Engine Misfire Detected
DTC P0301
Cylinder 1 Misfire Detected
DTC P0302
Cylinder 2 Misfire Detected
DTC P0303
Cylinder 3 Misfire Detected
DTC P0304
Cylinder 4 Misfire Detected
DTC P0305
Cylinder 5 Misfire Detected
DTC P0306
Cylinder 6 Misfire Detected
| Circuit/System Description |
The engine control module (ECM) uses information from the crankshaft position sensor and the camshaft position sensors in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM detects individual misfire events. A misfire rate that is high enough can cause 3-way catalytic converter damage. The malfunction indicator lamp (MIL) flashes ON and OFF when the conditions for catalytic converter damage are present.
DTCs P0301 through P0306 correspond to cylinders 1 through 6. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder is set, and the corresponding fuel injector is disabled. To retest for a misfire, the ECM re-enables the fuel injector(s) after 4 crankshaft revolutions or after 8 crankshaft revolutions for manual transmission equipped vehicles. For catalyst damaging misfires the ECM re-enables the fuel injector(s) after a 30 second delay to retest for a misfire. This 30 second periodic re-enabling occurrs until the end of the drive cycle or until no further catalyst damaging misfire events are present.
| Conditions for Running the DTC |
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DTC P0016, P0017, P0018, P0019, P0335, P0336, or P0338 is not set.
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The engine speed is between 450 and 6,500 RPM and steady.
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The engine coolant temperature (ECT) is warmer than -30°C (-22°F).
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The intake air temperature (IAT) is warmer than -30°C (-22°F).
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The delivered torque signal is greater than 6 % at idle, transmission not in drive.
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The delivered torque signal is between 6-21 % with the transmission in drive.
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DTCs P0300 through P0306 run continuously when the above conditions exist for at least 1,000 engine revolutions for the first failure occurance; 4,000 engine revolutions after the fist failure occurance.
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DTCs P0300 through P0306 run continuously when the above conditions exist for at least 200 engine revolutions when the ECT is warmer than 0°C (32°F), for catalyst damaging misfire(s).
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DTCs P0300 through P0306 run continuously when the above conditions exist for 1,000 engine revolutions while the ECT is colder than 0°C (32°F), for catalyst damaging misfire(s).
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| Conditions for Setting the DTC |
P0300
The ECM detects a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed a predetermined value.P0301, P0302, P0303, P0304, P0305, P0306
The ECM detects a crankshaft rotation speed variation indicating a single cylinder misfire rate sufficient to cause emissions levels to exceed mandated standards.| Action Taken When the DTC Sets |
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DTCs P0300-P0306 are Type B DTCs.
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When the MIL is flashing, the injector may be disabled for the misfiring cylinder to protect the catalytic converter.
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Depending on the conditions that set the code, the engine may go into Open Loop.
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| Conditions for Clearing the DTC |
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DTCs P0300-P0306 are Type B DTCs.
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The DTC must pass under the same conditions that were present when the DTC failed.
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| Diagnostic Aids |
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A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect for the following possible sources:
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A tire or wheel that is out of round or out of balance
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Variable thickness brake rotors
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An unbalanced drive shaft
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Certain rough road conditions
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Transmission operation
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A damaged accessory drive component or belt; remove the belt and safely operate the engine to evaluate
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High resistance in the circuits of the injectors may set a misfire DTC without setting an injector DTC. Test the injector circuits of the affected cylinder(s) for a high resistance if you suspect a condition.
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| Reference Information |
Schematic Reference
Engine Controls Schematics (3.0L (LF1)) Engine Controls Schematics (2.8L (LAU))
Connector End View Reference
Component Connector End Views
Electrical Information Reference
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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Powertrain Component Views
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DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
J 26792 HEI Spark Tester
| Circuit/System Verification |
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Engine idling at the normal operating temperature, there should be no abnormal engine noise.
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| 2. |
If there is an abnormal engine noise, refer to
Symptoms - Engine Mechanical
.
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| 3. |
Verify that no other DTCs are set.
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| 4. |
If a DTC is set, refer to
Diagnostic Trouble Code (DTC) List - Vehicle
.
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Observe the scan tool Misfire Current Cyl. 1-6 parameters. The Misfire Current Counters should not be incriminating.
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Observe the scan tool Circuit Test Status parameters for the various components that may cause a misfire. Verify the Circuit Test Status parameters for the components that may cause a misfire display OK or Not Run.
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Engine idling, perform the cylinder power balance test with a scan tool to isolate the misfiring cylinder. The engine speed should change when each injector is disabled.
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Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
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| Circuit/System Testing |
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Verify that the following conditions do not exist:
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Vacuum hose splits, kinks, and incorrect connections
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Engine vacuum leaks
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Crankcase ventilation system for vacuum leaks
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Fuel pressure that is too low or too high-Refer to
Fuel System Diagnosis (LF1 China)
Fuel System Diagnosis (LF1 Except China)
Fuel System Diagnosis (LAU China)
Fuel System Diagnosis (LAU Except China)
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Contaminated Fuel-Refer to
Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool)
Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool)
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Exhaust system restrictions
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If you find any of the above conditions, repair as necessary.
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Ignition OFF, remove the appropriate T8 ignition coil of the misfiring cylinder, but leave the electrical connector connected.
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Inspect the ignition coil boot for the following conditions:
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Holes
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Tears
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Carbon tracking
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Oil contamination
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water intrusion
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If you find any of the above conditions, repair as necessary.
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Remove the fuel pump fuse from the fuse block.
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Install the J 26792 to the boot of the appropriate T8 ignition coil and ground.
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Attempt to start the engine and observe the J 26792 . The spark tester should spark. |
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If there is no spark, refer to
Electronic Ignition System Diagnosis
for diagnosis of the T8 ignition coil.
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Ignition OFF, remove the spark plug from the misfiring cylinder. Verify that the spark plug does not exhibit the following conditions:
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Gas, coolant, or oil fouled-Refer to
Spark Plug Inspection
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Cracked, worn, incorrectly gapped-Refer to
Ignition System Specifications (LAU)
Ignition System Specifications (LF1)
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If there is a condition with the spark plug, replace the spark plug.
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Exchange the suspected spark plug with another cylinder that is operating correctly.
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Install the fuel pump fuse in the fuse block.
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Engine idling, observe the scan tool Misfire Current Counter parameters. The misfire should not follow the spark plug exchange.
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If the misfire follows the spark plug, replace the spark plug.
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If all conditions test normal, test or inspect for the following:
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A lean or rich Q17 fuel injector-Refer to
Fuel Injector Solenoid Coil Test (LAU)
Fuel Injector Solenoid Coil Test (LF1, LFW)
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An engine mechanical condition-Refer to
Symptoms - Engine Mechanical
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| Repair Instructions |
Spark Plug Replacement
| Repair Verification |
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Install any components or connectors that have been removed or replaced during diagnosis.
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Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
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Clear the DTCs.
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Turn OFF the ignition for 60 s.
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If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to
Diagnostic Trouble Code (DTC) List - Vehicle
and perform the appropriate diagnostic procedure.
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To verify that the performance of the catalytic converter has not been affected by the condition that set this DTC, perform the Repair Verification for DTC P0420 or P0430. Refer to
DTC P0420 or P0430 (LF1, LFW)
DTC P0420 or P0430 (LAU)
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