DTC P0278 Cylinder 6 Balance System. GMC Truck GMC K Pickup

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1997 🢒 GMC K Pickup - 4WD 🢒 Engine 🢒 Engine Controls - 6.5L 🢒 DTC P0278 Cylinder 6 Balance System

Circuit Description

The PCM has the ability to increase and decrease the amount of fuel to each cylinder to provide smooth idle operation. If the fuel correction amount exceeds define limits, DTC P0278 will set. This is a type D DTC.

Conditions for Setting the DTC

•	Engine at idle.

•	Engine coolant at normal temperatures.

•	Cylinder fault must be constant.

•	Fuel correction amount exceeds limits (internal to PCM).

•	Conditions met for 2 seconds.

Action Taken When the DTC Sets

Possible rough idleThe PCM will record operating conditions at the time the diagnostic fails. This information will be stored in Failure Records.

Conditions for Clearing the MIL/DTC

•	A History DTC will clear when forty consecutive warm-up cycles that the diagnostic does not fail (coolant temperature has risen 5°C (40°F) from start up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle.

•	Use of a Scan tool

Diagnostic Aids

Injector balance test on scan tool should be used to confirm fault cylinder problems. Scan tool will cutout specific cylinder requested. It is possible that if a cylinder balance fault has been detected and engine has been running for a long time, the PCM will try to increase or decrease fuel in other cylinders to compensate for a rough idle which 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 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 fuel tank and fuel injection pump

•	Restricted fuel filter

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

This step will properly identify a suspected cylinder by looking for a RPM drop (if RPM drops, cylinder is contributing, if not cylinder is not contributing).

Step

Action

Value(s)

Yes

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?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Scan tool connected.
Start and idle engine.
Engine at operating temperature.
Make sure all DTCs are cleared.
Using the scan tool, cutout (Inj. Balance) the suspected cylinder.

Is there an RPM drop in the suspected cylinder?

Go to Step 3

Go to Step 4

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

Check for the following basic engine mechanical or fuel delivery problems in that cylinder.

•	Low compression (refer to Engine Mechanical)

•	Injection nozzle malfunctioning (refer to Fuel Systems)

•	Kinked or bent injection lines

Was a repair performed?

Go to Step 6

Go to Step 5

Replace the fuel injection pump. Refer to Fuel Injection Pump Replacement .

Is the action complete?

Go to Step 6

Using the Scan Tool, select DTC, Clear Info.
Start engine and idle at normal operating temperature.
Select DTC, Specific, then enter the DTC number which was set.
Operate the vehicle until the Scan Tool indicates that the diagnostic Ran.

Does the Scan Tool indicate that this diagnostic Passed?

Go to Step 7

Go to Step 2

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