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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2006 🢒 Pursuit 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 DTC P0300

System Description

The engine control module (ECM) uses information from the crankshaft position (CKP) sensor and the ignition control (IC) module to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. A misfire rate that is high enough can cause the 3-way catalytic converter (TWC) to overheat under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC overheating are present. If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0300 Engine Misfire Detected

Conditions for Running the DTC
    • DTC P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0125, P0128, P0131, P0132, P0171, P0172, P0217, P0315, P0336, P0506, P0601, P0602, P0606, P0641 are not set.
    • The engine speed is between 400-6,500 RPM.
    • The ignition voltage is between 8-18 volts.
    • The engine coolant temperature (ECT) is between -7°C and +122°C (+19°F and +252°F).
    • The fuel level is more than 10 percent.
    • DTC P0300 runs continuously when the above conditions are met.

Conditions for Setting the DTC

The ECM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

You must perform the CKP system variation learn procedure before proceeding with this diagnostic table. Refer to Crankshaft Position System Variation Learn .

Test Description

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

  1. If the actual CKP variation values are not within the learned values, the misfire counters may increment.

    2.

  2. P0300, P0340, and P0341 may all be set by similar conditions.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Start the engine.
  2. Allow the engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records.
  3. Monitor all of the Misfire counters with the scan tool.

Are any of the Misfire Current counters incrementing?

--

Go to Step 3

Go to Intermittent Conditions

3

Are any DTCs other than P0340 or P0341 set?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 4

4

Can any abnormal engine noise be heard?

--

Go to Symptoms - Engine Mechanical

Go to Step 5

5

Observe the Misfire History Cyl# parameter with a scan tool.

Does more than one cylinder indicate a large count value for the Misfire History Cyl# parameter?

--

Go to Step 6

Go to Step 8

6

Are the Misfire History Cyl# counts indicated for companion cylinders 1/4 or 2/3?

--

Go to Step 8

Go to Step 7

7

Inspect the following components:

    • The vacuum hoses and seals for splits, restrictions, and improper connections--Refer to Emission Hose Routing Diagram .
    • The crankcase ventilation system for vacuum leaks--Refer to Crankcase Ventilation System Inspection/Diagnosis.
    • The engine control module (ECM) grounds for corrosion and loose connections--Refer to Ground Distribution Schematics.
    • The exhaust system for restrictions--Refer to Restricted Exhaust.
    • The fuel for contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Did you find and correct the condition?

--

Go to Step 17

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Remove the fuel pump relay. Refer to Relay Replacement in Wiring Systems.
  3. Remove the ignition coil housing assembly, keeping the ignition control (IC) module assembly connected to the harness connector. Refer to Ignition Coil Housing Replacement .

    4. Important: Not grounding the IC module housing may cause an erratic spark.

  4. Connect a jumper wire between the top of the IC module and a good ground.
  5. Install the J 36012-A Ignition System Diagnosis Harness.
  6. Install a J 26792 Spark Tester on the #1 spark plug jumper wire.
  7. Ground the #4 spark plug jumper wire. The #4 wire is the companion to #1.
  8. Crank the engine with the remaining spark plug wires connected.
  9. Repeat the above steps by installing the spark tester on #4 and grounding #1. Do the same for the #2 and the #3 spark plugs. Ensure the companion wire is grounded.

Does the spark tester spark on all cylinders?

--

Go to Step 9

Go to Electronic Ignition (EI) System Diagnosis

9
  1. Remove the spark plug from the cylinder that indicated a misfire. Refer to Spark Plug Replacement .
  2. Inspect the spark plug. Refer to Spark Plug Inspection .

Does the spark plug appear to be OK?

--

Go to Step 10

Go to Step 11

10
  1. Exchange the suspected spark plug with another cylinder that is operating properly. Refer to Spark Plug Replacement .
  2. Operate the vehicle under the same conditions that the misfire occurred.

Did the misfire move with the spark plug?

--

Go to Step 17

Go to Step 14

11

Is the spark plug oil or coolant fouled?

--

Go to Symptoms - Engine Mechanical

Go to Step 12

12

Is the spark plug gas fouled?

--

Go to Step 15

Go to Step 13

13

Did the spark plug show any signs of being cracked, worn, or improperly gapped?

--

Go to Step 16

Go to Step 14

14

Perform the fuel injector coil test. Refer to Fuel Injector Diagnosis .

Did you find and correct the condition?

--

Go to Step 18

Go to Symptoms - Engine Mechanical

15

Perform the fuel system diagnosis. Refer to Fuel System Diagnosis .

Did you find and correct the condition?

--

Go to Step 18

Go to Symptoms - Engine Mechanical

16

Replace or gap the spark plug. Refer to Spark Plug Replacement .

Did you complete the action?

--

Go to Step 18

--

17

Replace the faulty spark plug. Refer to Spark Plug Replacement .

Did you complete the replacement?

--

Go to Step 18

--

18

Was the customer concern the malfunction indicator lamp (MIL) flashing?

--

Go to Step 19

Go to Step 20

19
  1. Operate the vehicle at the specified value for 4 minutes.
  2. Operate the vehicle within the Conditions for Running the DTC P0420, as specified in the supporting text. Refer to DTC P0420 .

Does the DTC run and pass?

2,500 RPM

Go to Step 20

Go to DTC P0420

20
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 21

21

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK