Code 22

FUEL PUMP CONTROL CIRCUIT - DTC 22

The ECM looks for an incorrect internal circuit voltage that indicates the state of the fuel pump relay coil switching circuit (oxygen sensor heater relay: 1993 MY ON XJ6). This internal voltage cannot be measured.

The ECM switches ON the fuel pump by grounding the fuel pump relay coil circuit (85 pin) (all XJS and 1990 - 92 MY XJ6). On 1993 MY ON XJ6, the ECM switches on the fuel pump by grounding the oxygen sensor heater relay, which in turn switches the fuel pump relay. The fuel pump is switched on for approximately 1 second after the ignition is switched ON, and when an engine speed signal is present.

The ECM will flag DTC 22 if the fuel pump control circuit is open or short circuit while the fuel pump is operating.

Condition Required For DTC 22 Flagging
Ignition - Ignition ON.
Fuel pump - Fuel pump operating.
ECM internal circuit - Indicates that the fuel pump control circuit is open or short circuit.
Response time - 600 milliseconds.

Limp Home Default
None

Possible Faults
- Low battery voltage
- Poor ECM power feed or ground connections
- Short circuit or open circuit wiring from the ECM to the fuel pump relay (all XJS and 1990 - 92 MY XJ6).
- Short circuit or open circuit wiring from the ECM to the oxygen sensor heater relay (1993 MY ON XJ6).
- Short circuit or open circuit wiring in ignition switched power to above relays pin 86.
- Loose connector pins (LI18) - 6-way PM4 yellow connector under air cleaner (1991 - 92 MY XJ6).
- Faulty relay.
- air pump relay circuit fault.

Diagnostics Notes
1. If DTC 66 is also flagged, first investigate the cause of the air injection relay control circuit.
2. If the fuel pump is inoperative but DTC is not (flagged, investigate the fuel pump switched power supply (relay), fuel pump ground and the fuel pump mechanical condition.

Circuit Diagram

Circuit Diagram:

Flow Chart - DTC 22

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Flow Chart: DTC 22: