Circuit Description
The powertrain control module (PCM) has the ability to increase and decrease the amount of fuel to each cylinder to provide smooth idle operation. If the PCM decides that the fuel reduction amount to a specific cylinder exceeds defined limits, this DTC will set. This DTC only monitors fuel reduction.
Conditions for Running the DTC
| • | The engine has idled for more than 90 seconds. |
| • | All engine misfire DTCs ran and passed. |
| • | The engine coolant has reached normal temperatures. |
| • | Any cylinder fault must be constant. |
Conditions for Setting the DTC
| • | The amount of fuel reduction for a specific cylinder exceeds limits (internal to PCM). |
| • | The conditions are met for 2 seconds. |
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | 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 non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
The injector balance test on the scan tool should be used to confirm fault cylinder problems. The scan tool will cut out the specific cylinder requested. The PCM will increase or decrease fuel to other cylinders to compensate for a rough idle if a cylinder balance fault is detected over a long period of time. This can cause multiple cylinder balance DTCs to set. The scan tool snap shot mode can be used to properly identify the suspected cylinder. The most likely cause of cylinder balance DTCs are malfunctioning nozzles.
If multiple cylinder balance DTCs are set and no problem is found, check for the following conditions:
| • | Pinched or restricted fuel feed lines between fuel tank and fuel injection pump |
| • | Restricted fuel filter |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No | ||||
|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |||||
Does the RPM drop in the suspected cylinder? | Go to Step 3 | Go to Step 4 | |||||
3 | The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored refer to the applicable DTC tables first. Are any additional DTCs stored? | Go to Diagnostic Aids | |||||
4 |
Did you find and correct the condition? | Go to Step 6 | Go to Step 5 | ||||
5 |
Important: The new injection pump must be timed. Refer to Fuel Injection Pump Timing Adjustment . Replace the fuel injection pump. Refer to Fuel Injection Pump Replacement . Did you complete the replacement? | Go to Step 6 | -- | ||||
6 |
Does the DTC run and pass? | Go to Step 7 | Go to Step 2 | ||||
7 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK | |||||
