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For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 2002 🢒 Alero 🢒 Engine 🢒 Engine Controls - 2.2L (L61) 🢒 DTC P0300

Circuit Description

The powertrain control module (PCM) uses information from the ignition control module (ICM) and the crankshaft position (CKP) sensor in order to determine when an engine misfire is occurring. By monitoring the variations in the crankshaft rotation speed for each cylinder the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the three-way catalytic (TWC) converter to overheat under certain conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC converter overheating are present.

Conditions for Running the DTC
    • DTCs P0105, P0107, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0171, P0172, P0325, P0336, P0340, P0341, P0342, P0502, P0503, P0506, P0507, P0601, P0740, P0742, P1133, or P1621 are not set.
    • The engine speed is between 469-6,400 RPM.
    • The battery voltage is between 9-17 volts.
    • The engine coolant temperature (ECT) is between -7 to +123°C (20-254°F).
    • The engine has been running for more than 5 seconds.
    • The throttle position (TP) has not increased more than 8 percent in 1 second.
    • The TP has not decreased more than 1.5 percent in 1 second.

Conditions for Setting the DTC

The misfire total is more than 8 counts on more than one cylinder.

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

An intermittent can also be the result of a defective reluctor wheel. Remove the crankshaft sensor and inspect the reluctor wheel through the sensor mount hole. Inspect for porosity and the general condition of the wheel.

Verify that the ICM ground circuit has less than 0.5 ohms resistance.

Important: The CKP system variation learning procedure must be performed any time a change is made to the crankshaft sensor to crankshaft relationship. Changing the crank sensor to crankshaft relationship will not allow the PCM to detect a misfire at all speeds and loads accurately, resulting in a possible false misfire DTC being set. Removing a part for inspection and then reinstalling the same part is considered a disturbance. A false DTC P0300 could be set by not performing the CKP system variation learn procedure.

Test Description

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

  1. This step determines if the DTC is the result of a hard malfunction or an intermittent condition.

    2.

  2. If a spark plug boot is burned, the other spark plug on that ignition coil may still fire at idle. This step tests the systems ability to produce at least 25,000 volts at each spark plug.

DTC P0300-Engine Misfire Detected

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

Are any other DTCs set?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Perform a visual and physical inspection. Refer to Symptoms - Engine Controls .
  3. If a problem is found, repair as necessary.

Did you find and correct any conditions?

Go to Step 11

Go to Step 4

4

  1. Start the engine and idle the engine.
  2. Use the scan tool in order to observe the Misfire Current Counts.
  3. Operate the vehicle within the Freeze Frame data and the Conditions for Running the DTC as specified in the supporting text.

Are any Misfire Current counts incrementing?

Go to Step 5

Go to Diagnostic Aids

5

Is misfire present in all cylinders?

Go to Step 6

Go to Step 9

6
  1. Start and idle the engine.
  2. Compare the manifold absolute pressure (MAP) voltage indicated by the scan tool with the typical scan data. Refer to Scan Tool Data List .

Is the indicated value more than the typical value?

Go to DTC P0108

Go to Step 7

7

Perform the Fuel System Diagnosis .

Did you find and correct the condition?

Go to Step 11

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Perform the Alcohol/Contaminants-in-Fuel Diagnosis .

Did you find and correct the condition?

Go to Step 11

Go to Symptoms - Engine Mechanical in Engine Mechanical

9

  1. Turn OFF the ignition.
  2. Remove the fuel pump relay.
  3. Remove the ignition coil housing assembly keeping the ICM assembly connected to the harness connector. Refer to Ignition Control Module Replacement .

    4. Important:: Not grounding the ignition coil housing may cause an erratic spark.

  4. Install a jumper wire with clips on both ends from the top of the ICM to ground.
  5. Install the J 36012-A Spark Plug Jumper Wire Kit.
  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. Make sure the companion wire is grounded.

Does the spark tester spark on all cylinders?

Go to Step 10

Go to Electronic Ignition (EI) System Diagnosis

10
  1. Turn OFF the ignition.
  2. Inspect for malfunctioning spark plugs in the cylinders that indicated a misfire. Refer to Spark Plug Inspection .
  3. If a problem is found, repair as necessary.

Did you find and correct the condition?

Go to Step 10

Go to Symptoms - Engine Mechanical in Engine Mechanical

11
  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 as specified in the supporting text.

Does the DTC run and pass?

Go to Step 12

Go to Step 2

12

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK