X90 - Does Engine Start

Diagnostic Trouble Code (DTC) 543/524 indicates a fuel pump secondary circuit failure between the B(+) supply and the Fuel Pump Monitor (FPM) connection to the power-to-pump circuit.

Possible causes:

- No Starts:
- Open circuit between the B(+) supply and the FPM connection to the power-to-pump circuit.
- Fuel pump relay contacts always open.

- Engine Starts:
- Left/Front Heated Oxygen Sensor (HO2S) short to power
- Damaged Powertrain Control Module (PCM).

- Does the engine start?

Yes -- For all dual HO2S applications: Go to X86. X86 - Check Front/Left HO2S For Short to Power

For single HO2S applications: Replace PCM. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)

No -- Go to X91. X91 - Check B+ Supply to Fuel Pump Relay(s)