X115 - Continuous Code 556/557: Check EEC-IV Harness

A Continuous Memory Diagnostic Trouble Code (DTC) 556/557 indicates a fuel pump primary circuit failure has occurred during vehicle operation. DTC 556 refers to the High Speed Fuel Pump primary circuit and DTC 557 refers to the Low Speed Fuel Pump primary circuit.

Possible causes are:
- Open VPWR in the Constant Control Relay Module (CCRM).
- Open coil in fuel pump relay.
- Open in fuel pump circuit (Powertrain Control Module (PCM) Pin 22 or 41)
- Open VPWR to Low Speed Fuel Pump (LFP) relay.

- Start engine.

- Check for engine stall/stumble while performing the following (also, if possible, listen for fuel pump turning off):

- Shake, wiggle, bend the EEC-IV vehicle harness fuel pump circuit (Pin 22) between the PCM and the CCRM.
- Lightly tap the CCRM to simulate road shock.

- With DTC 557, shake, wiggle, bend the VPWR circuit between the CCRM and LFP relay. Also lightly tap on the LFP relay to simulate road shock.

- Key "OFF".

- Inspect the PCM connector and the fuel pump relay connectors for corrosion, damaged pins, etc.

- Is fault indicated/found?

Yes -- Isolate fault and service as necessary. Clear continuous memory. Clearing Diagnostic Trouble Codes

Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)

No -- For dual Heated Oxygen Sensor (HO2S) applications with a DTC 524/543 only: Go to X116. X116 - Check Left Front HO2S Circuit For Short to Power

ALL others: For further diagnosis using the EEC-IV monitor box or Scan Tool, go to Normal Scan Data Values. If an EEC-IV monitor box or Scan Tool is not available, go to X120. X120 - Road Test