Circuit/System Testing

Fuel Pressure Low

1. Verify none of the conditions listed below exist:
   • Restricted fuel feed pipe
   • Restricted or plugged strainer
   • Poor connections at the fuel pump harness connector and the ground circuits.
   • If a condition exist 

     Repair as necessary.

   • Go to next step: If a condition does not exist 
2. Test or replace the G12 Fuel Pump.

Fuel Pressure Leaks Down

1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief .
2. Install the CH-37287-1A  Fuel Pressure Gauge Adapter between the fuel feed pipe and the fuel rail.
3. Open both of the valves on the CH-37287-1A  Fuel Pressure Gauge Adapter.
4. Ignition ON, command the Fuel Pump Enable ON with a scan tool.
5. Close one of the valves on the CH-37287-1A  Fuel Pressure Gauge Adapter.
6. Verify that the Fuel Pressure Sensor parameter does not decrease greater than 34 kPa (5 psi) in 1 minute.
   • If the fuel pressure drops 

     Test or replace the G12 Fuel Pump.

   • Go to next step: If the fuel pressure does not drop 
7. Locate and replace the leaking Q17 Fuel Injector.

Fuel Pressure Drops OFF

1. Verify none of the conditions listed below exist:
   • Restricted fuel feed pipe
   • Restricted or plugged strainer
   • Poor connections at the Fuel Pump harness connector and the ground circuit.
   • If a condition exist 

     Repair as necessary.

   • Go to next step: If a condition does not exist 
2. Test or replace the G12 Fuel Pump.