Circuit Description
The powertrain control module (PCM) times the intervals between each pulse of the crankshaft position sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred. This pulse is generated from a 4X reluctor wheel located on the front of the crankshaft. If the crankshaft speed is less than an expected amount, the PCM will increase the amount of fuel needed to correct the misfire. If the amount of fuel exceeds the calibrated value, the PCM will interpret this as a misfire and set the DTC. The misfire diagnostic is used only to identify a weak cylinder needing additional fuel.
Conditions for Running the DTC
| • | Engine coolant temperature greater than 56°C (132°F). |
| • | Engine idling for a total of 90 seconds. |
| • | Fuel adjustment is greater than the calibrated value (internal to PCM). |
Conditions for Setting the DTC
Multiple engine misfires detected.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive drive trip the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the Failure Records store this information. If the diagnostic reports a failure on the second consecutive drive trip, the Freeze Frame records the operating conditions at the time of failure and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL off after 3 consecutive trips without a fault condition. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures. |
| • | The scan tool Clear Info function was used. |
Diagnostic Aids
The scan tool can be used to control the suspected cylinder (Inj. Balance Test).
The most likely cause for this DTC is the following:
| • | A mechanical failure causing low cylinder compression in more than one cylinder. |
| • | A fuel leak at the high pressure fuel injection lines or injection nozzles. |
| • | A fuel injection nozzles stuck closed. |
After the repair has been performed, it may take approximately 30 seconds for the vehicle to return to a stable idle.
Test Description
The number(s) below refer to the step number(s) on the Diagnostic Table.
-
This step will help identify a suspected cylinder.
-
This step will identify an area with the mostly likely cause of failure.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Before clearing any DTCs, use the scan tool Capture Info function to save the Freeze Frame and the Failure records for reference. The control moduel's data is deleted once the Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||
Is there an RPM drop in the suspected cylinder? | -- | |||||||||
3 | The DTC is intermittent. If no additional DTCs are stored, refer to diagnostic aids. If any additional DTCs were stored, refer to the applicable DTC table(s) first. Are there any DTCs stored? | -- | Go to the applicable DTC Table | Go to Diagnostic Aids | ||||||
Check for basic engine mechanical or fuel delivery problems in that cylinder, such as:
Did you perform a repair? | -- | |||||||||
5 | Replace the fuel injection pump. Refer to Fuel Injection Pump Replacement . Is action complete? | -- | -- | |||||||
6 |
Does the scan tool indicate the diagnostic Passed? | -- | ||||||||
7 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the Applicable DTC Table | System OK |
