Circuit Description
The 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. This diagnostic will only run once per ignition cycle.
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 malfunction indicator lamp (MIL) will not illuminate. |
| • | The PCM will record the operating conditions at the time the diagnostic fails. This information will be stored in Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn off the MIL after three consecutive trips with out a fault condition |
| • | A History DTC will clear after forty consecutive warm-up cycles, if this or any other emmision related diagnostic does not report any failures. |
| • | A History DTC will clear after 40 consecutive engine warm up cycles if no failures are reported by this or any other emissions related diagnostic. |
| • | Use of a scan tool. |
Diagnostic Aids
The most likely cause for this DTC is the following:
| • | A mechanical failure causing low cylinder compression. |
| • | A fuel leak at the high pressure fuel injection lines or injection nozzles. |
| • | A fuel injection nozzle stuck closed. |
If an injection nozzle is suspected, it can be transferred to another cylinder to determine if the DTC follows the nozzle.
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 most likely cause of failure.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 |
Important: Before clearing any DTCs, use the scan tool Capture Info to save the Freeze Frame and Failure records for reference. The control module's data is deleted once the Clear Info function is used. Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||
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. Does the scan tool display any additional undiagnosed codes? | -- | Go to the applicable DTC table | Go to Diagnostic Aids | ||||
Check for basic engine mechanical or fuel delivery problems in that cylinder.
Did you perform a repair? | -- | |||||||
5 | Replace the fuel injection pump. Refer to Fuel Injection Pump Replacement . Is the 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 |
