Buick Regal: DTC P0300-P0304

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

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

Circuit/System Description

The engine control module (ECM) uses information from the crankshaft position sensor and the camshaft position sensor to determine when a engine cylinder misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM can detect individual cylinder misfire events.

Extreme cylinder misfire events can cause catalytic converter damage. The malfunction indicator lamp (MIL) will flash when the conditions for catalytic converter damage are present. DTCs P0301 through P0304 correspond to cylinders 1 through 4. When the ECM detects that one or more specific cylinders are misfiring, the DTC for the respective misfiring cylinder will set and up to 2 of the corresponding fuel injectors are disabled for a minimum of 30 s. The ECM will then re-enable the fuel injector and, after approximately 200 engine revolutions, will determine if the misfire is still present. If the misfire is still present, the ECM will disable the fuel injector again repeating the process. If the misfire is not present, the fuel injector will remain enabled by the ECM. In Spark Ignition Direct Injection (SIDI) system applications, if a fuel injector fault DTC is set during a misfire event, the ECM will not re-enable the injector.

Conditions for Running the DTC

• DTC P0010, P0011, P0013, P0014, P0016, P0017, P0068, P00C8, P00C9, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114, P0117, P0118, P0119, P0122, P0123, P0191, P0192, P0193, P0222, P0223, P0335, P0336, P0340, P0341, P0365, P0366, P0601, P0604, P0606, P0651, P16A0, P16A1, P16A2, P16F3, P2101, P2135, P2227, P2228, P2229, or P2230 is not set.
• The engine speed is less than 1, 000 RPM and DTC P0315 is set.
• The engine speed is greater than 1, 050 RPM.
• The crankshaft position and camshaft position sensors are synchronized.
• The engine coolant temperature (ECT) is between -12 and 127ºC (10 - 261ºF).
• If the ECT is colder than -12ºC (10ºF) at start-up, this diagnostic will not run until the ECT is between 21 - 127ºC (70 - 261ºF).
• The battery voltage is between 9 - 32 V.
• The ECM is not detecting a rough road signal.
• The fuel level is at least 11%.
• The ECM is not in fuel cut-off or deceleration fuel cut-off mode.

The DTCs run continuously when the above conditions are met.

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 or a misfire rate high enough to cause catalyst damage.

P0301, P0302, P0303, or P0304

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

• DTCs P0300 - P0304 are Type B DTCs.
• The ECM will flash the malfunction indicator lamp (MIL) when a catalyst damaging level of misfire is present.
• If a hybrid application, engine idle speed will increase to between 1750-2500 RPM.

Conditions for Clearing the DTC

DTCs P0300 - P0304 are Type B DTCs.

Diagnostic Aids

• A misfire DTC could be caused by an excessive vibration from sources other than the engine.

  Inspect for the conditions listed below:

  • A tire or wheel that is out of round or out of balance
  • Variable thickness brake rotors
  • An unbalanced drive shaft
  • Certain rough road conditions
  • Transmission operation
  • A damaged or defective accessory drive component or belt
• High resistance in the circuits of the injectors or ignition coils may set a misfire DTC without setting an injector or ignition coil DTC. Test the injector and ignition coil circuits of the affected cylinder (s) for a high resistance if you suspect a condition. Also check for poor terminal tension at the injectors and ignition coils of the affected cylinder (s).
• If the condition is intermittent, wiggle the related wiring harnesses and connectors, with the ignition/vehicle on or engine running, while monitoring the scan tool circuit status parameters for the component. The parameters will display if there is a condition with the circuit or a connection.
• A condition in the heated O2 sensor (HO2S) heater control circuits may set a DTC P0300.

Reference Information

Description and Operation

• Electronic Ignition System Description
• Fuel System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL26792 Spark Tester

For equivalent regional tools, refer to Special Tools (diagnostic tools) and Special Tools (Mechanical Tools).

Circuit/System Verification

NOTE: Before starting the engine, review the freeze frame failure records data to determine if the misfire sets during a cold start or at operating temperature. If there is a cold start condition and the engine is started, the engine will need to be cooled down before the next attempt to start the engine within the fail conditions.

If this a hybrid application and the hybrid battery is fully charged, the engine runs at a very low load since the hybrid battery cannot accept any additional charge. At this very low engine load, engine misfire may not be detected. It may be necessary to drive the vehicle in battery only propulsion mode in order to discharge the hybrid battery before diagnosis can be performed.

1. If this is a hybrid application, skip to step 4.

2. Engine Running at normal operating temperature.

3. Verify there is no abnormal engine noise.

• If abnormal engine noise is present

Refer to Symptoms - Engine Mechanical.

• Go to next step: If abnormal engine noise is not present

4. Perform the scan tool Crankshaft Position Variation Learn procedure.

5. Verify no DTCs are set.

• If any DTCs other than P0300 - P0304 are set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

• If DTC P0300 - P0304 is set

Refer to Circuit/System Testing.

• Go to next step: If no DTCs are set

6. Verify the scan tool Cylinder 1 - 4 Current Misfire Counter parameters do not increment.

• If increments

Refer to Circuit/System Testing.

• Go to next step: If does not increment

7. Engine Running, perform the Cylinder Power Balance Test with a scan tool.

8. Verify the engine speed changes when each injector is disabled and then enabled.

• If engine speed does not change

Refer to Circuit/System Testing.

• Go to next step: If engine speed does change

9. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

10. Verify the DTC does not set.

• If the DTC sets

Refer to Circuit/System Testing.

• Go to next step: If the DTC does not set

11. All OK.

Circuit/System Testing

1. Verify none of the following conditions listed below exist:

• Damage, carbon tracking, or fluid intrusion of the spark plug boots and/or spark plugs
• Vacuum hose splits, kinks, and incorrect connections
• Engine vacuum leaks
• Crankcase ventilation system for vacuum leaks
• Fuel pressure that is too low or too high. Refer to Fuel System Diagnosis.
• Contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
• Exhaust system restrictions
  • If a condition exists

    Repair or replace as necessary.

  • Go to next step: If no conditions exist

NOTE: An erratic or weak spark is considered a no spark condition.

2. Ignition OFF, remove the appropriate T 8 Ignition Coil from the spark plug and connect the EL 26792 HEI Spark Tester to the spark plug boot, engine Cranking.

3. Verify the spark output.

• If no output or the output is weak

Refer to Electronic Ignition System Diagnosis.

• Go to next step: If the output is good

4. Ignition OFF.

5. Verify the conditions listed below. Refer to Ignition System Specifications.

• The correct spark plug type
• The correct spark plug gap
• The correct spark plug torque
• If a condition exists

Repair or replace as necessary.

• Go to next step: If no conditions exist

6. Exchange the suspect spark plug with another cylinder that is operating correctly.

7. Engine Running.

8. Verify the scan tool Cylinder 1 - 4 Current Misfire Counter does not increment for the cylinder where the suspect spark plug was installed.

• If increments

Replace the spark plug.

• Go to next step: If does not increment

9. Test or inspect for the conditions listed below:

• A lean or rich Q17 Fuel Injector - Refer to Fuel Injector Diagnosis.
• An engine mechanical condition - Refer to Symptoms - Engine Mechanical.

Repair Instructions

• Ignition Coil Replacement
• Spark Plug Replacement

Repair Verification

1. Install any components or connectors that have been removed or replaced during diagnosis.

2. Perform any adjustment, programming or setup procedures that are required when a component or module is removed or replaced.

3. Clear the DTCs.

4. Turn OFF the ignition for 60 s.

5. 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 the Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure.

6. Engine Running, verify the scan tool Cylinder 1 - 4 Current Misfire Counter parameters do not increment.

• If the misfire counter parameters increment, a misfire condition still exists.

7. 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. Refer to DTC P0420.

DTC P0315

Diagnostic Instructions

• Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle
• Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis
• An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions

DTC Descriptor

DTC P0315

Crankshaft Position System Variation Not Learned

Circuit/System Description

The crankshaft position sensor variation or reluctor ring learn is used to calculate reference period errors caused by slight tolerance variations in the crankshaft and the crankshaft position sensor. The calculated error allows the ECM to accurately compensate for reference period variations. This enhances the ability of the ECM to detect misfire events over a wider range of engine speed and load. The compensation values are stored in ECM memory after a learn procedure has been performed.

Conditions for Running the DTC

Engine=Running

Frequency the DTC runs=Continuously - After the running conditions are met

Conditions for Setting the DTC

Crankshaft Position Variation Learn=Not Learned

Actions Taken When the DTC Sets

DTCs listed in the DTC Descriptor Category=Type A DTC

Conditions for Clearing the DTC

DTCs listed in the DTC Descriptor Category=Type A DTC

Diagnostic Aids

This test procedure requires that the vehicle battery has passed a load test and is completely charged.

Refer to: Battery Inspection/Test

Reference Information

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References

Circuit/System Verification

1. Ignition - On / Vehicle - In Service Mode.

2. Perform the scan tool learn/reset function: Crankshaft Position Variation Learn.

3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Verify the DTC does not set.

• If the DTC sets

Replace the component: K20 Engine Control Module

• Go to next step: If the DTC is not set

4. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification

For control module replacement, programming, and setup refer to: Control Module References

READ NEXT: