XB110 - KOEO Code 556: Does Engine Start

Key On Engine Off Diagnostic Trouble Code (DTC) 556 indicates a fuel pump primary circuit failure.

Possible causes:

No Start:
- Open or short to power in Fuel Pump (FP) circuit.
- Damaged Variable Control Relay Module (VCRM).
- Damaged Powertrain Control Module (PCM).

Engine Starts:

- Short to ground in FP circuit.

- Damaged VCRM.

- Damaged PCM.

- Does the engine start?

Yes -- Go to XB115 (to check for short to ground). XB115 - Check PCM For Short to Ground

No -- Go to XB111 (to check for opens and short to power). XB111 - Check Fuel Pump (FP) Circuit Continuity