P0627: feed-fuel-pump relay driver detects an open load

P0627 checks the feed-fuel-pump relay's high-side output driver for an open circuit while the output is powered on. The cited controller compares its voltage response with controller-specific limits.

The monitored circuit is the relay control path

The table characterizes the open-load specification as impedance of at least 200 kilohms between the signal and controller ground. It does not directly measure fuel pressure, pump flow or the motor's mechanical condition. A pump replacement cannot be justified solely from this driver diagnosis.

The source lists eight failed samples among ten at 250 ms per sample, with Type A reporting. Its run/crank enable column gives an 11 V supply condition without a clear comparator, so this article does not invent a universal voltage inequality.

Code combinations need careful interpretation

The row notes that P0629 may also set in certain controllers. Therefore, concurrent open-circuit and high-circuit codes are not automatically evidence of two unrelated failures; the output-stage design can influence the reported combination.

Verification should establish the normal driver response during an eligible on command and use the applicable service procedure to isolate the relay-control path. The impedance value is not an instruction to place an ohmmeter on a powered circuit. The summary cannot distinguish an open connection, relay-load problem or controller-output problem without further electrical evidence.

Source and applicability

2025 GM 25OBDG04B diagnostic parameter tables; the cited monitor only. Vehicle, engine and calibration applicability must be confirmed separately. These tables describe detection logic, not a complete repair procedure or a component replacement verdict. gm-2025-04b, PDF page 623.