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12.22 - Fuel Fail 22 fuel pump control circuit ( Brett Gadzinsky,  )

ECU flags FF22 if the signal to the fuel pump relay indicates open or shorted.

Conditions for flagging FF22:

- Ignition on,
- Fuel pump operating,
- indications of open or shorted fuel pump relay coil circuit.
- Response time 600 milliseconds

Possible faults:

- Low battery voltage,
- Poor ecu power feed or ground connections,
- Short or open circuit between ecu and fuel pump relay,
- Short or open circuit to oxy sensor heater relay (1993 and up),
- Loose connector pins (li18) 6 way PM4 yellow connector under air cleaner (1991-1992)
- Bad relay,
- Air pump relay circuit fault.

If the fuel pump does not work, but FF22 is NOT flagged, its the relay (contacts), the connections at the fuel pump, or a bad fuel pump.


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