GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Spark 🢒 DTC 🢒 DTC P0300

Description

The engine control module (ECM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order 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 3-way catalytic converter damage. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for catalytic converter damage are present. If the misfire rate is sufficient to cause emission levels to exceed a predetermined value, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0300 Engine Misfire Detected

Conditions for Running the DTC
    • DTCs P0107, P0108, P0122, P0123, P0341, P0342, P0335, P0336, P0337, P0400, P0404, P0405, P0406, P1320, P1321, and P0501 are not set.
    • Engine speed is between 800-4,500 RPM.
    • The ignition 1 voltage is more than 11 volts.
    • Engine coolant temperature (ECT) is more than -7°C (20°F).
    • The A/C compressor clutch is not changing states.
    • The torque management is not active.
    • The fuel tank level is more than 20 percent.
    • The ECM is not in fuel cut-off or decel cut-off mode.
    • The ECM is not receiving a rough road signal.
    • The throttle angle is steady.
    • DTC P0300 runs continuously when the above conditions are met.

Conditions for Setting the DTC

The ECM detects a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed a predetermined value.

Action Taken When the DTC Sets
    • The MIL will illuminate after 3 consecutive trips with a failure or the MIL will flash.
    • The ECM will record operating conditions at the time the diagnostic fails. The information will be stored in the Freeze Frame and Failure Records.
    • A history DTC is stored.

Conditions for Clearing the MIL/DTC
    • The MIL will turn OFF after 4 consecutive ignition cycles in which the diagnostic runs without a fault.
    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • DTCs can be cleared by using the scan tool.
    • Disconnect the ECM battery feed for 10 seconds.

Diagnostic Aids
    • A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect for the following possible sources:
       - 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
       - A damaged accessory drive component or belt
    • For an intermittent condition, refer to Intermittent Conditions .

Step

Action

Values

Yes

No

1

Did you perform the Perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: The engine may only misfire when the engine is under a load. An engine load may be necessary to verify the condition.

  1. Turn ON the ignition, with the engine OFF.
  2. Clear the DTCs with a scan tool.
  3. Start the engine.
  4. Allow the engine to reach the normal operating temperature.

Does DTC P0300 set?

--

Go to Step 4

Go to Step 3

3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4

Important: Excessive vibration from other sources than the engine, or mechanical engine condition can cause a misfire DTC to set. For example, an accessory drive belt could cause this condition.

Is the engine misfiring?

--

Go to Step 5

Go to Symptoms - Engine Mechanical in Engine Mechanical - 0.8L (LBF)

5

Are DTCs P0261, P0262, P0264, P0265, P0267, P0268, P0335, P0336, P0337, P0351, P0352, P0353, P1320, or P1321 set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 6

6

Is there an abnormal engine noise?

--

Go to Symptoms - Engine Mechanical in Engine Mechanical - 0.8L (LBF)

Go to Step 7

7
  1. Inspect or test for the following conditions:
    2. • Inspect the vacuum hoses for splits, kinks, and proper connections.
    • Inspect the throttle body and the intake manifold for vacuum leaks.
    • Inspect the crankcase ventilation valve and/or system for any vacuum leaks.
    • Test for the correct fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect the fuel system for any restrictions, leaks or fuel contamination. Refer to Fuel System Diagnosis .
    • Inspect for fouled or damaged spark plugs. Determine what caused the spark plugs to foul. Refer to Spark Plug Inspection .
    • Inspect the exhaust system for restrictions.
    • Inspect the engine control grounds for being clean, tight, and in the correct location.
  2. Repair as necessary.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 8

8
  1. Start the engine.
  2. Isolate the misfiring cylinder by disconnecting the harness connector of the fuel injectors one at a time. The engine speed should change with an injector disconnected.
  3. Turn OFF the ignition.
  4. Disconnect the spark plug wire from the spark plug that corresponds with the misfiring cylinder.
  5. Install the J 26792 Spark Tester to the boot of the spark plug and a good ground.
  6. Attempt to start the engine and observe the J 26792 . An erratic or inconsistent spark is considered a no spark condition.
  7. Repeat steps 3-6 for the remaining cylinders, if necessary.

Does the spark jump the tester gap for each cylinder?

--

Go to Step 10

Go to Step 9

9
  1. Remove the spark plug wire from the misfiring cylinder. Refer to Spark Plug Wire Replacement .
  2. Inspect the spark plug wire. Refer to Spark Plug Wire Inspection .
  3. Measure the resistance of the spark plug wire with a DMM.

Is the spark plug wire resistance less than the specified value?

1000 ohms per cm (per ft)

Go to Electronic Ignition (EI) System Diagnosis

Go to Step 19

10
  1. Remove the spark plugs from the cylinders 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 11

Go to Step 12

11
  1. Exchange the suspected spark plug with another cylinder that is operating correctly. 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 18

Go to Step 15

12

Is the spark plug coolant or oil fouled?

--

Go to Symptoms - Engine Mechanical in Engine Mechanical - 0.8L (LBF)

Go to Step 13

13

Is the spark plug gas fouled?

--

Go to Step 16

Go to Step 14

14

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

--

Go to Step 17

Go to Step 15

15

Perform the fuel injector coil test. Refer to Fuel Injector Solenoid Coil Test .

Did you find and correct the condition?

--

Go to Step 20

Go to Symptoms - Engine Mechanical in Engine Mechanical - 0.8L (LBF)

16

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

Did you find and correct the condition?

--

Go to Step 20

Go to Symptoms - Engine Mechanical in Engine Mechanical - 0.8L (LBF)

17

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

Did you complete the action?

--

Go to Step 20

--

18

Replace the spark plug. Refer to Spark Plug Replacement .

Did you complete the replacement?

--

Go to Step 20

--

19

Replace the spark plug wires. Refer to Spark Plug Wire Replacement .

Did you complete the replacement?

--

Go to Step 20

--

20

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

--

Go to Step 21

Go to Step 22

21

Operate the vehicle within the Conditions for Running the DTC P0420 as specified in the supporting text. Refer to DTC P0420 .

Did the DTC run and pass?

--

Go to Step 22

Go to DTC P0420

22
  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.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 23

23

Are any DTCs displayed that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK