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.
Conditions for Setting 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). |
| • | 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 40 consecutive warm up if no failures are reported by this or any other emissions related diagnostic. |
| • | PCM battery voltage is interrupted. |
| • | Use of a scan tool. |
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.
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This step will identify an area with the mostly likely cause of failure.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 |
Important:: Before clearing DTCs, use the Scan Tool Capture Info to record Freeze Frame and Failure Records for reference, as data will be lost when 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 addtional DTCs stored? | -- | Go to the Applicable DTC Table | Go to Diagnostic Aids | ||||
Check for basic engine mechanical or fuel delivery problems in that cylinder.
Was a repair performed? | -- | |||||||
5 | Replace the fuel injection pump. Refer to Fuel Injection Pump Replacement . Important: The new injection pump must be timed. Refer to Fuel Injection Pump Timing Adjustment . Is the action complete? | -- | -- | |||||
6 |
Does the scan tool indicate that this diagnostic passed? | -- | ||||||
7 | Using the Scan Tool, select Capture Info, Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to the Applicable DTC Table | System OK |
