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CAPS Pump Common Trouble Codes

Some of the most common trouble codes that we encounter are listed here. We have included the diagnostic procedures for them from the Cummins shop manual. We have also included some of our own experiences as well.

Codes 276, 277, and 279 are codes for the fuel control valve or injection control valve. These codes can be triggered by air in the inlet or restriction of the inlet even though they are not mentioned in the Cummins diagnostic procedure.

The most common cause however is the transient suppressor. Often the transient suppressor is not replaced by the servicing technician causing a reoccurrence of the problem.

Codes 268 and 456 are probably the next most common codes we encounter. These are codes for the accumulator pressure sensor. The most common reasons these codes are triggered is a fuel inlet air leak or restriction. Our experience is that replacing the accumulator sensor cures the problem in a minority of the cases. The ICV or a worn accumulator can also trigger these codes. A worn gear pump may also be the cause although these are not mentioned in the Cummins diagnostic procedure.

Codes 328 and 329 are pumping element valve codes. These are probably the next most numerous codes we encounter. These are often the original reason the pump was removed. Inlet air leakage or restrictions were the problem and they trigger the codes again on the replacement pumps. Bad grounds are a common reason these codes are triggered.
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