For 1990-2009 cars
Engine Controls Components
Ignition Controls
OBD II Symbol Description Notice
Engine Controls Connector End Views
Handling ESD Sensitive Parts Notice

### System Description

The Powertrain Control Module (PCM) monitors both the crankshaft and the camshaft position in order to detect an engine misfire. A rapid decrease in the crankshaft speed indicates misfire. The PCM may require that several consecutive misfire conditions are detected before storing this DTC and before illuminating the MIL. Under light misfire conditions, the PCM may require more than one trip to set this DTC. Under a severe misfire, the PCM flashes the MIL. A flashing MIL indicates that there is a misfire that is capable of damaging the catalytic converter. The torque converter clutch (TCC) disables momentarily in order to determine if the misfire was due to a rough road condition, automatic transmission only.

### Conditions for Setting the DTC

• | The misfire total is greater than 12 counts.

• | The engine speed is between 469 RPM and 6400 RPM.

• | The battery voltage is between 9 volts and 17 volts.

• | The Engine Coolant Temperature (ECT) is between -7°C (20°F) and 123°C (254°F).

• | The engine has been running for a period that is longer than 5 seconds.

• | The Throttle Position (TP) has not changed more than 8 percent in 1 second.

• | DTC(s) P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0171, P0172, P0325, P0335, P0341, P0342, P0404, P0405, P0503, P0506, P0507, P0601, P0740, P0742, P1133, P1336, P1404 and 1621 are not set.

### Action Taken When the DTC Sets

• | The malfunction indicator lamp (MIL) illuminates if the fault is active within the same conditions for two out of eighty ignition cycles and a misfire is present.

| OR

| The MIL illuminates after two consecutive ignition cycles during in which the diagnostic runs with the fault active

| OR

| The MIL illuminates immediately and flashes if a misfire is severe enough to cause any catalyst damage.

• | In vehicles with automatic transmission only, the torque converter clutch (TCC) is disablesd when a misfire is present.

• | The PCM records the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.

• | A history DTC is stored.

• | The coolant fan turns ON.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after three consecutive ignition cycles during which the diagnostic runs without a fault present under the Freeze Frame conditions that existed when the DTC failed.

• | A history DTC clears after 40 consecutive warm up cycles without a fault.

• | Clear the MIL/DTCs with a scan tool.

### Diagnostic Aids

An intermittent can also be the result of a defective reluctor wheel. Remove crankshaft sensor and inspect reluctor wheel through sensor mount hole. Check for porosity and condition of wheel. Refer to DTC P0300 Engine Misfire Detected .

Verify the electronic Ignition Control Module (ICM) 11 pin harness connector terminal K, ground circuit should have less than 0.5 ohms of resistance.

If DTC is intermittent, refer to Symptoms .

When checking the electrical terminal connections with a test light or DMM, a malfunctioning electrical terminal connection maybe cleaned and not detected as a problem. You may also clean a corroded or dirty electrical terminal connection when disconnecting and reconnecting any electrical connector.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.

2. If a DTC P0200 is present, the condition causing the misfire is in the fuel injector circuitry. The DTC P0200 table will diagnose the fuel injectors and circuitry.

3. A visual/physical inspection should include checking the following items:

• | Wiring for proper electrical connections, pinches and cuts.

• | PCM grounds for being clean and tight.

• | Vacuum hoses for splits, kinks and proper connections as shown on the Vehicle Emission Information label. Check thoroughly for any type of leak or restriction.

• | Check the throttle body mounting area and intake manifold sealing surfaces for air leaks.

4. This step determines if the DTC P0300 is the result of a hard malfunction or an intermittent condition.

5. If the misfire is not present, it may be necessary to duplicate the conditions in the Freeze Frame Data in order to detect the misfire. Depending on the engine load, the conditions may have to be maintained for up to 20 seconds. If the misfire accumulators start to increment, then the misfire is present. A sudden change in the throttle, rough road, or other crankshaft rotation disturbances may cause the counter to increment a few counts and them stop. This can be considered normal and should not be diagnosed as a misfire. The history counter begins counting after the DTC is set and will indicate only true misfires. A history misfire counter will store the number of misfires that have occurred until the DTC is cleared.

6. If all the accumulators are relatively equal, then the misfire is being caused by something that affects the entire engine. If they are not equal, the misfire is being caused by something that is specific to two or more cylinders.

7. A basic engine problem or fuel injector problem that affects all the cylinders is possible at this point (e.g. valve train, compression, etc.). Refer to the Engine Mechanical portion of the service manual. Also refer to the DTC P0200 Injector Control Circuit .

8. After repairs, verify no misfire by duplicating the conditions within Freeze Frame Data while watching the misfire counters.

9. 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.

10. Replace any spark plugs that are worn, cracked or fouled. Refer to the Engine mechanical portion of the service manual if any plugs are fouled or damaged due to an engine mechanical malfunction.

11. No spark, on one coil, may be caused by an open secondary circuit. Therefore, the coils secondary resistance should be checked. Resistance readings above 20,000 ohms, but not infinite, will probably not cause a no start but may cause an engine miss under certain conditions.

12. If the no spark condition is caused by coil connections, a coil or a secondary boot assembly, the test light will blink.

13. Refer to the Ignition Coils for on vehicle service of the ignition system.

14. Refer to the Ignition Coils for on vehicle service of the ignition system.

15. Refer to the Ignition Control Module Replacement for on vehicle service of the ignition system.

16. Any circuitry, that is suspected as causing the complaint, should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness.

17. The replacement PCM must be programmed and the crankshaft position system variation learn procedure must be preformed. Refer to the latest Techline procedure for PCM reprogramming and also refer to the Powertrain Control Module (PCM) for the Crankshaft Position System Variation Procedure .

18. Conditions for setting the DTC P0420 need to be run to determine the catalyst has been damaged from the misfire.

#### DTC P0300-Engine Misfire Detected

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Install a scan tool. Was a DTC P0200 set? | -- | Go to DTC P0200 Injector Control Circuit | Go to Step 3
3 |

1. Perform a visual/physical inspection.
2. Make any repairs that are necessary.

Were any repairs necessary?

--

Go to Step 26

Go to Step 4

4 | Start the engine and allow the engine to idle. Are any Misfire Current counters incrementing? | -- | Go to Step 6 | Go to Step 5
5 |

1. Turn the ignition switch ON, with the engine OFF.
2. Review the Freeze Frame data and note the parameters.
3. Operate the vehicle within the conditions and Conditions For Setting The DTC as noted.

Are any Misfire Current counters incrementing?

--

Go to Step 6

Go to Step 26

6 | Are all the counters equal (within a small percentage of each other)? | -- | Go to Step 7 | Go to Step 11
7 |

1. Turn the ignition switch OFF.
2. Install a fuel pressure gauge.
3. Note the fuel pressure with the engine running.

Is the fuel pressure within the specified range?

211-304 kPa (31-44 psi)

Go to Step 8

Go to Fuel System Diagnosis

8 | Check the fuel for water, alcohol or other contamination. Is the fuel OK (uncontaminated)? | -- | Go to Step 9 | Go to Step 10
9 |

1. Check for an fuel injector problem. Refer to DTC P0200 Injector Control Circuit starting at step 5.
2. Check for a basic engine problem. Refer to the Engine Mechanical portion of the service manual.

Is the action complete?

--

Go to Step 26

--

10 | Replace the contaminated fuel. Is the action complete? | -- | Go to Step 26 | --
11 |

1. Disconnect the fuel injector harness electrical connector.
2. Temporarily remove the ignition coil and electronic Ignition Control Module (ICM) assembly.
3. Install the spark plug jumper wires J 36012.
4. Install the spark plug tester J 26792 on the spark plug jumper wire for each of the cylinders one at a time.
5. Remove the spark plug boot from the companion cylinder of the ignition coil housing and install a jumper wire from the spark plug connector of the ignition coil housing to ground (1-4, or 2-3).
6. Crank the engine with the remaining spark plug wires still connected.

Does the spark tester spark on all the cylinders?

--

Go to Step 12

Go to Step 13

12 | Check for any malfunctioning spark plugs in the cylinders that indicated misfire and replace if necessary. Were any spark plugs malfunctioning? | -- | Go to Step 26 | Go to Step 9
13 |

1. Turn the ignition switch OFF.
2. Disconnect the PCM electrical connectors.
3. Reconnect the J 26792 spark tester on a plug wire that did not show spark.
4. Turn the ignition switch ON.
5. Connect a fused jumper wire to B+.

Notice: Do not leave the jumper wire connected to the PCM IC circuit connector for longer than 5 seconds at a time. Failure to do so may damage the ignition coil and/or the Ignition Control Module.

6. Momentarily touch the affected IC circuit at the PCM electrical connector. A spark should be present when the fused jumper is removed from the IC circuit.

Is spark present when the fused jumper wire is removed from the IC circuit?

--

Go to Step 23

Go to Step 14

14 |

1. Turn the ignition switch OFF.
2. Remove the boot assemblies for the affected coil.
3. Connect a DVM between the secondary ignition coil terminals.

Is the resistance between the specified values?

4-8 K ohms

Go to Step 15

Go to Step 16

15 |

1. Remove the coil housing and disconnect the coil harness at the ICM.
2. Connect a test light between B+ and the coil control terminal on the ICM for the cylinders that did not have spark.

Notice: Do not leave the jumper wire connected to the PCM IC circuit connector for longer than 5 seconds at a time. Failure to do so may damage the ignition coil and/or the Ignition Control Module.

3. Again momentarily touch the affected IC curcuit with the fused jumper wire while watching the test light.

Does the test light blink?

--

Go to Step 17

Go to Step 18

16 |

1. Remove the ignition coil from the ignition coil housing.
2. Recheck the resistance between the secondary terminals of the ignition coils.

Is the resistance between the specified values?

4-8 K ohms

Go to Step 20

Go to Step 21

17 | Repair the open or short in the ignition coil harness, poor ignition coil connection or replace the ignition coil, ignition coil housing or boot assembly. Is the action complete? | -- | Go to Step 26 | --
18 |

1. Turn the ignition switch OFF.
2. Disconnect the ICM 11 pin electrical connector.
3. Check the affected IC circuit for an open or short and repair as necessary.

Was a repair necessary?

--

Go to Step 26

Go to Step 19

19 | Visually inspect the ICM 11 pin harness electrical connector to see if the connections are clean and tight and repair as necessary. Were any repairs necessary? | -- | Go to Step 26 | Go to Step 22
20 | Inspect the following items for corrosion and/or damage for the affected cylinder(s):

1. Ignition coil springs and contacts.
2. Ignition coil housing.

Repair as necessary.

Is the action complete?

--

Go to Step 26

--

21 | Replace the affected ignition coil. Is the action complete? | -- | Go to Step 26 | --
22 | Replace the ICM. Is the action complete? | -- | Go to Step 26 | --
23 | Inspect the PCM electrical connector and connections. Are the connections OK? | -- | Go to Step 25 | Go to Step 24
24 | Repair the connector or connections. Is the action complete? | -- | Go to Step 26 | --
25 | Replace the PCM. Is the action complete? | -- | Go to Step 26 | --
26 |

1. Use the scan tool in order to clear the DTCs.
2. Start the engine and idle at normal operating temperature.
3. Operate the vehicle within the conditions for setting this DTC and DTC P0420.

Does the scan tool indicate that these diagnostics have ran and passed?

--

Go to Step 27

Go to Step 2

27 | Check if any additional DTCs are set. Are any DTCs set that have not been diagnosed? | -- | Go to applicable DTC table | System OK