For 1990-2009 cars

### System Description

The powertrain control module (PCM) uses information from the ignition control (IC) module and the camshaft position (CMP) 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 converter to overheat under certain conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for three-way catalytic converter overheating are present.

### Conditions for Running the DTC

• | DTCs P0105, P0107, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0171, P0172, P0325, P0335, 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 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 PCM is detecting a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed mandated standard.

### 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 crankshaft sensor and inspect reluctor wheel through sensor mount hole. Check for porosity and condition of wheel.

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

When checking the electrical terminal connections with a test lamp 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

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

1. The Diagnostic System Check-Engine Controls prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data on the scan tool for later reference.

2. If a DTC P0201-P0204 is present, the condition causing the misfire is in the fuel injector circuitry. The DTC P0201-P0204 table will diagnose the fuel injectors and circuitry.

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

• | The following in the electrical wiring:

- | Proper electrical connections

- | Pinches in the wires

- | Cuts in the wires

• | The PCM grounds for being clean and tight

• | Check the following components for air leaks:

- | The throttle body mounting

- | The intake manifold sealing surfaces

4. This step determines if DTC P0301 is the result of a hard malfunction or an intermittent condition.

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

6. If the misfire is not present, it may be necessary to duplicate the conditions in the Freeze Frame Data in order to detect a 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, this is an indication that a misfire is present. A history misfire counter will store the number of misfires that have occurred until the DTC is cleared. The current counter must count a total of at least 195 misfires before writing to the history counter.

7. A spark is available at the misfiring cylinder. At this point, the misfire is being caused by the following conditions:

• | Spark plug

• | Basic engine problem

• | Leaky fuel injector

8. A basic engine or fuel injector problem, such as a valve train condition or a compression condition that affects only cylinder #1 is possible.

   If a spark plug saturated with fuel or the cylinder is full of fuel, the fuel injector is probably stuck open.

9. Check for a fuel injector or engine mechanical problem that may have caused the spark plug to malfunction.

10. No spark on one coil may be caused by an open secondary circuit. Check the coil's secondary resistance. Resistance readings that are above 20,000 ohms but are not infinite will probably not cause a no-start, and can cause an engine miss during certain conditions.

11. The test lamp will blink if the no-spark condition is caused by the following items:

• | Ignition coil electrical connections

• | Ignition coil harness

• | Ignition coil

• | Secondary boot assembly

12. You can easily check the ignition coil harness by performing the previous step with the ignition coil harness connected to the ICM. Check for a voltage and a ground signal to the ignition coils at the ignition coil electrical connector.

13. Thoroughly check any suspected circuitry the following conditions:

• | Backed out terminals

• | Improper mating

• | Broken locks

• | Improperly formed or damaged terminals

• | Poor terminal to wiring connections

• | Physical damage to the wiring harness

14. Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Techline information for PCM programming.

15. Conditions for setting the DTC P0420 need to be run in order to determine if the catalyst has been damaged from the misfire.

#### DTC P0301-Cylinder 1 Misfire Detected

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Turn ON the ignition, with the engine OFF.
2. Install a scan tool.

Are any injector DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3 |

1. Turn OFF the ignition.
2. Perform a visual/physical inspection. Refer to Symptoms for the visual/physical inspection procedure.
3. Make any necessary repairs.

Were any repairs necessary?

--

Go to Step 25

Go to Step 4

4 |

1. Start the engine.
2. Idle the engine.
3. Observe the Misfire Current Counters with the scan tool.

Is the Misfire Current #1 counter incrementing?

--

Go to Step 5

Go to Step 6

5 |

1. Turn OFF the ignition.
2. Remove the air cleaner outlet resonator assembly. Refer to the Air Cleaner Outlet Resonator Replacement for the removal procedure.
3. Disconnect all the fuel injector electrical connectors.
4. Disconnect the IC module 11 pin electrical connector.
5. Temporarily remove the ignition coil and the electronic Ignition Control (IC) module assembly.
6. Reconnect the IC module 11 pin electrical connector.
7. Install the J 36012-A Spark Plug Jumper Wires into the spark plug boot assemblies.
8. Install the J 26792 Spark Plug Tester on the spark plug jumper wire for the affected cylinder.
9. Remove the spark plug boot assembly from the companion cylinder of the ignition coil housing.
10. Install a jumper wire from the companion spark plug connector of the ignition coil housing to ground.
11. Connect a jumper wire to the IC module assembly to ground.
12. Crank the engine with the remaining spark plugs wires still connected.

Does the spark tester spark?

--

Go to Step 7

Go to Step 10

6 |

1. Turn OFF the engine, with the ignition ON.
2. Review the Freeze Frame data and record the parameters.
3. Start the engine.
4. Operate the vehicle within the Freeze Frame conditions and Conditions For Running the DTC as specified.
5. Observe the Misfire Current Counters with the scan tool.

Is the Misfire Current counter for the affected cylinder incrementing?

--

Go to Step 5

Go to Step 25

7 |

1. Turn OFF the ignition.
2. Remove the spark plug from the affected cylinder.
3. Exchange the spark plug with a spark plug from a known good cylinder.
4. Reconnect all the fuel injector electrical connectors.
5. Install the spark plug boot assembly to the affected cylinder spark plug connection at the ignition coil housing.
6. Reconnect the spark plug jumper wire to the spark plug boot assembly.
7. Start the engine.
8. Run the vehicle when the misfire was present.

Is the Misfire Current for the affected cylinder counter incrementing?

--

Go to Step 8

Go to Step 9

8 |

1. Check for a leaking fuel injector. Refer to DTC P0201, P0202, P0203, or P0204 starting at step 5.
2. If the fuel injector is OK, check for a basic engine problem. Refer to Symptoms - Engine Mechanical in Engine Mechanical.

Did you complete the repair?

--

Go to Step 25

--

9 |

1. Turn OFF the ignition.
2. Replace the spark plug.

Did you complete the replacement?

--

Go to Step 25

--

10 |

1. Turn OFF the ignition.
2. Remove the spark plug boot assemblies from the affected coil.
3. Disconnect the IC module 11-pin electrical connector.
4. Connect a DMM between the secondary ignition coil terminals at the ignition coil housing.

Is the resistance between the specified value?

4-8 Kohms

Go to Step 11

Go to Step 12

11 |

1. Remove the coil housing. Refer to the Ignition Coil Replacement for the coil housing removal procedure.
2. Disconnect the coil harness electrical connector from the IC module.
3. Reconnect the IC module 11 pin electrical connector.
4. Connect a test lamp to B+.
5. Probe the affected cylinder coil control terminal with the test lamp.
6. Crank the engine while watching the test lamp.

Does the test lamp blink?

--

Go to Step 13

Go to Step 14

12 |

1. Remove the affected cylinder ignition coil from the ignition coil housing. Refer to the Ignition Coil Replacement .
2. Recheck the resistance between the secondary terminals of the affected cylinder ignition coil.

Is the resistance between the specified value?

4-8 Kohms

Go to Step 15

Go to Step 16

13 |

1. Remove the ignition coils from the ignition coil housing.
2. Disconnect the ignition coil electrical connector from the ignition coils.
3. Reconnect the ignition coil electrical connector to the IC module.
4. Connect a test lamp to ground.

Important: Carefully handle the ignition coils electrical connectors to avoid spark arching from the electrical terminals and causing the fuse to open which would leading to misdiagnosis.

5. Turn ON the ignition, with the engine OFF.
6. Probe the ignition feed circuit to the ignition coils at both of the ignition coil electrical connector terminals B with the test lamp.

Does the test lamp illuminate for both circuits?

--

Go to Step 19

Go to Step 20

14 |

1. Turn OFF the ignition.
2. Disconnect the IC module 11-pin electrical connector.
3. Visually inspect the IC module 11-pin electrical connector to see if the electrical connections are clean and tight. Refer to Symptoms for the inspection procedure.
4. Make any necessary repairs. Refer to Wiring Repairs in Wiring Systems.

Were any repairs necessary?

--

Go to Step 25

Go to Step 17

15 | Check and replace the following items as necessary:

• | Ignition coil spring for the affected coils

• | Ignition coil housing

Did you find and correct the condition?

--

Go to Step 25

--

16 | Replace the affected cylinders ignition coil. Refer to the Ignition Coil Replacement . Did you complete the replacement? | -- | Go to Step 25 | --
17 |

1. Reconnect the IC module 11-pin electrical connector.
2. Disconnect the PCM electrical connector C1.
3. Reconnect the affected cylinder spark plug boot assembly to the spark plug connector at the ignition coil housing.
4. Reconnect the spark plug jumper wire to the affected cylinder spark plug boot assembly.
5. Reconnect the J 26792 Spark Tester on the affected cylinder spark plug wire.
6. Connect a jumper wire to the companion cylinder spark plug connector at the ignition coil housing to ground.
7. Turn ON the ignition, with the engine OFF.
8. Connect a test lamp to B+.

Notice: Do not leave the test lamp 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.

9. Momentarily touch the IC timing control circuit for the affected cylinder at the PCM electrical connector. A spark should be present when the test lamp is removed from the IC timing control circuit.

Is there a spark present when you remove the test lamp from the IC timing control circuit?

--

Go to Step 23

Go to Step 18

18 |

1. Turn OFF the ignition.
2. Check for the following conditions in the IC timing control circuit.

• | Open circuit

• | Short to ground

• | Short to B+

• | Poor electrical connection at the ICM

3. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Were any repairs necessary?

--

Go to Step 25

Go to Step 22

19 |

1. Check the affected cylinder coil control circuit for the following conditions:

• | Poor electrical connection to the IC module and ignition coil

• | Open circuit

• | Short to ground

• | Short to voltage

2. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 25

Go to Step 21

20 |

1. Turn OFF the ignition.
2. Repair the open in the ignition positive voltage circuit between the #1-4 and #2-3 ignition coils electrical connectors. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 25

--

21 |

1. Turn OFF the ignition.
2. Check the ignition positive voltage circuit for a poor electrical connection at the ignition affected cylinder ignition coil.
3. If the electrical connection is OK, replace the spark plug boot assembly.

Did you complete the repair?

--

Go to Step 25

--

22 |

1. Turn OFF the ignition.
2. Replace the IC module. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

--

Go to Step 25

--

23 |

1. Turn OFF the ignition.
2. Inspect the PCM electrical connector and connections.
3. Repair the electrical connector and the connections as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 24

24 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 25 | --
25 |

1. Reconnect all previously disconnected components (if not already reconnected).
2. Connect all the fuel injector electrical connectors.
3. Install the air cleaner outlet resonator assembly. Refer to the Air Cleaner Outlet Resonator Replacement for the installation procedure.
4. Use the scan tool in order to clear the DTCs.
5. Start the engine.
6. Idle the engine at the normal operating temperature.
7. Operate the vehicle within the conditions for running this DTC and DTC P0420, as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 26

Go to Step 2

26 | 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