Circuit Description
The PCM has the ability to increase and decrease the amount of fuel to each cylinder order to provide for a smooth idle operation. If the fuel correction amount exceeds the defined limits, DTC P0284 will set.
Conditions for Running the DTC
| • | The engine is at idle. |
| • | The engine coolant is at the normal temperatures. |
| • | The cylinder fault must be constant. |
Conditions for Setting the DTC
| • | The fuel correction amount exceeds the limits (internal to PCM). |
| • | All diagnostic set conditions met for 2 seconds. |
Action Taken When the DTC Sets
| • | The PCM will not illuminate the Malfunction Indicator Lamp (MIL). |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Failure Record. |
Conditions for Clearing the MIL/DTC
| • | A History DTC will clear after forty consecutive warm-up cycles during which the diagnostic does not fail (the coolant temperature has risen 5°C (40°F) from the start up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle). |
| • | Use of a scan tool will clear the DTC codes. |
Diagnostic Aids
The injector balance test on the scan tool should be used in order to confirm the cylinder problems. The scan tool will cutout the specific cylinder requested. If the original complaint was multiple cylinder balance DTCs and the vehicle has a manual transmission, a dual mass flywheel could be at fault. If a cylinder balance fault has been detected and the engine has been running for a long time, the PCM might try to increase or decrease the fuel in the other cylinders in order to compensate for a rough idle which may cause multiple cylinder balance DTCs to set. The scan tool snap shot mode can be used in order to properly identify the suspected cylinder. The most likely cause of cylinder balance DTCs are malfunctioning nozzles or engine mechanical (low compression) problems.
If multiple cylinder balance DTCs are set and no problem is found, check for the following:
| • | Pinched or restricted fuel feed lines between the fuel tank and the fuel injection pump |
| • | Restricted fuel filter |
| • | Fuel waxing |
A fuel system restriction could cause the fuel correction to exceed the limits.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool Capture Information function to record the Freeze Frame and the Failure records for reference. The control module's data is deleted once the Clear DTC Information 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 additional DTCs were stored refer to the applicable DTC table(s) first. Are any additional DTCs stored? | -- | Go to the Applicable DTC Table | Go to Diagnostic Aids |
4 | Check for the following basic engine mechanical or fuel delivery problems in that cylinder:
If a problem is found, repair the problem as necessary. Did you perform a repair? | -- | ||
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 . 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 |
