Test Description

The number below refers to step number in diagnostic procedure.

1. 2
   
   This step verifies adequate fuel exists in CNG fuel tank.
2. 3
   
   This step verifies Fuel Rail Pressure (FRP) sensor is displaying correct fuel pressure.
3. 4
   
   This step tests for a leak in fuel system between Low Pressure Lock-Off (LPL) solenoid and fuel injectors. Fuel pressure should remain constant during test.
4. 5
   
   This step tests High Pressure Regulator (HPR) output pressure. If fuel pressure is within specified values, HPR, fuel lines, and filters are okay.
5. 6
   
   This step tests operation of High Pressure Lock-Off (HPL) solenoid. Cycle ignition quickly from Lock to Run position as you listen for HPL operation.
6. 8
   
   This step tests for an electrical condition that is causing an inoperative HPL. If test light does not illuminate, go to DTC P1215 under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article for diagnosis of electrical circuits.
7. 9
   
   This step tests High Pressure Regulator (HPR) output pressure. If fuel pressure is within specified values, HPR, fuel lines, and filters are okay.
8. 12
   
   This step tests for an electrical condition causing an inoperative LPL. If test light does not illuminate, go to DTC P1215 under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article for diagnosis of electrical circuits.
9. 16
   
   This step verifies fuel filter is not the cause of condition. If fuel pressure is within specified range after fuel filter replacement, a plugged filter was cause of condition.