Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSFORD1994F 150 2WD PICKUP L6-300 4.9LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONPINPOINT TESTSX - CONSTANT CONTROL RELAY MODULE (CCRM)X115 - CONTINUOUS CODE 556/557: CHECK EEC-IV HARNESS
1994 Ford F 150 2WD Pickup L6-300 4.9L
X115 - Continuous Code 556/557: Check EEC-IV Harness
1994 Ford F 150 2WD Pickup L6-300 4.9LSECTION 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.
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)
- 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.
- 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
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.