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 the crankshaft sensor and inspect the reluctor wheel through the sensor mount hole. Check for porosity and condition of the wheel. Refer to Engine Mechanical section of the service manual.
Verify the electronic Ignition Control Module (ICM) 11 pin harness connector terminal K, ground circuit for less than 0.5 ohms resistance.
Important: A Crankshaft Position System Variation Learning Procedure must be performed at any time that 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 if this procedure is not performed. Refer to Powertrain Control Module (PCM) for the Crankshaft Position System Variation Procedure.
If DTC is intermittent, refer to Symptoms.
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check 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 fault occurred. The scan tool stores this data for later reference.
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If a DTC P0200 is present, this indicates that the condition that is causing the misfire is in the injector circuitry. The DTC P0200 table will diagnose the injectors and the circuitry.
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Visually/physically inspect the following items:
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This step determines if DTC P0301 is the result of a hard failure or an intermittent condition.
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If a plug boot is burned, the other plug on that ignition coil may still fire at idle. This step tests the system's ability to produce at least 25,000 volts at each spark plug.
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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 indicates that a misfire is present. A history misfire counter will store the number of misfires that have occurred until the DTC clears. The current counter must count a total of at least 195 misfires before writing to the history counter.
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A spark is available at the misfiring cylinder. At this point, the misfire is being caused by a spark plug or from a basic engine problem.
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A basic engine problem or a basic injector problem that affects only cylinder #2 is possible at this point (i.e. the valve train, the compression, etc.). Refer to Engine Mechanical section of the service manual.
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Replace any spark plugs that are worn, cracked or fouled. Refer to Engine mechanical of the service manual if any plugs are fouled or damaged due to an engine mechanical failure.
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An open secondary circuit can cause no spark on one coil. This indicates that you should check the coil's secondary resistance. Resistance readings above 20,000 ohms, but not infinite, will probably not cause a no start but can cause an engine miss under certain conditions.
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If the no spark condition is caused by coil connections, a coil or a secondary boot assembly, the test light will blink.
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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 ground signal to the ignition coils at the ignition coil electrical connector.
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Refer to Ignition Coils for on vehicle service of the ignition system.
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Refer to Ignition Coils for on vehicle service of the ignition system.
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Refer to Ignition Control Module Replacement for on vehicle service of the ignition system.
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Thoroughly check any suspected circuitry for the following conditions:
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Reprogram the replacement PCM and perform the crankshaft position system variation learning procedure. Refer to the latest Techline information for PCM programming and Powertrain Control Module (PCM) for the crankshaft position system variation learning procedure.
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Conditions for setting the DTC P0420 need to be run in order to determine if the catalyst was damaged from the misfire.
| • | The wiring for proper connections, pinches and cuts |
| • | The PCM grounds for being clean and tight |
| • | The 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. |
| • | Any air leaks at the intake manifold sealing surface |
| • | Backed out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Poor terminal to wiring connections |
| • | Physical damage to the wiring harness |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Install a scan tool. Was a DTC P0200 set? | -- | |||
Were any repairs necessary? | -- | |||
Idle the engine. Is the Misfire Current #2 counter incrementing? | -- | |||
Does the spark tester spark? | -- | |||
Is the Misfire Current #1 counter incrementing? | -- | |||
Is the Misfire Current #2 counter incrementing? | -- | |||
Is the action complete? | -- | -- | ||
Replace the spark plug. Is the action complete? | -- | -- | ||
Is the resistance less than the specified value? | 10Kohms | |||
Does the test light blink? | -- | |||
12 | Remove the ignition coil from the ignition coil housing and recheck the resistance between the secondary terminals of the ignition coil. Is the resistance less than the specified value? | 10Kohms | ||
Repair the open or the shorted ignition coil harness, the poor ignition coil connection, or replace the ignition coil, the ignition coil housing or the boot assembly. Is the action complete? | -- | -- | ||
14 |
Were any repairs necessary? | -- | ||
Replace the ignition coil springs for cylinders #2 and #3 coil. Is the action complete? | -- | -- | ||
Replace cylinders #2 and #3 ignition coil. Is the action complete? | -- | -- | ||
17 |
Are the resistance readings within the specified value? | 0.6K-2.6Kohms | ||
18 | Check the ignition control circuit for an open or a short and repair the circuit as necessary. Was a repair necessary? | -- | ||
Replace the ICM. Is the action complete? | -- | -- | ||
Inspect the PCM connector and the connections. Repair the PCM connector and the connections as necessary. Was a repair necessary? | -- | |||
Replace the PCM. Is the action complete? | -- | -- | ||
Does the scan tool indicate that these diagnostics have ran and passed? | -- | |||
23 | Check if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
