HB16 - HB20

HB16 - FUEL LEAK CHECK

Note: After the vehicle has soaked for several hours (has not run), a slight natural gas smell may emanate from within the intake manifold and intake air system. This is normal, as the fuel injectors leak down from the fuel rail to the intake manifold over several hours.

Possible causes:

- Loose fitting connectors.
- Damaged or worn seals or fittings.
- Damaged fuel lines or fuel system components.

Key off.

Install fuel rail pressure gauge.

Key on, engine off (verify pressure is greater than 586 kPa (85 psi)). If the fuel system does have a fuel leak, it will be necessary to repeat this step to maintain pressure

Check for leaks with the natural gas sniffer provided in Rotunda tool kit 134-00114 or a soapy water solution such as Snoop. Cover the complete joint with this solution. Examine the components or joints for 60 seconds for signs of bubbles.

Are any leaks indicated?

YES VERIFY proper torque on suspect fuel system components. RECHECK for leaks. If leaks still exist, REPAIR or REPLACE as necessary. RESTORE vehicle.

NO No leaks detected. No further diagnostics are required. RESTORE vehicle.

HB17 - DTC P1180 AND P1181 CHECK FUEL PRESSURE

Diagnostic Trouble Code (DTC) P1180 and P1181 indicates the available fuel pressure during normal vehicle operation is too low when DTC P1180 is present and too high when DTC P1181 is present. The PCM uses the fuel tank pressure input received from the Natural Gas Module (NG) and other data to infer the fuel rail pressure. The inferred value is compared to the existing FRP value and must be ±22 psi or a DTC is set. P1180 and P1181 can only be retrieved during Continuous Memory and does not illuminate the check engine light.

Possible causes for P1180:

- Restriction in fuel lines
- Plugged fuel filter

Possible causes for P1181:

- Fuel pressure regulator

Inspect the fuel lines, regulator and fuel filter for restrictions or leaks.

Are there any concerns?

YES REPAIR as necessary. COMPLETE PCM Reset to clear DTC.

NO GO to HB18.

HB18 - CHECK FUEL TANK PRESSURE

Key on, engine running and vehicle in park.

Scan tool connected.

Access and monitor the TANKPR PID from the NGVM menu and record the value.

Access and monitor the FRP PID from the PCM menu and record the value.

Fuel Tank/PCM Inferred Pressure Chart:

Locate the approximate TANKPR value on the chart, from this value determine the PCM inferred pressure.

Is the PCM inferred pressure ±22 psi of the fuel rail pressure (FRP) recorded?

YES ADDRESS other Continuous Memory DTCs if present. If no other DTCs are present COMPLETE PCM Reset to clear DTC.

NO FOR DTC P1180. GO to HB19.
FOR DTC P1181. REPLACE fuel pressure regulator. COMPLETE PCM Reset to clear DTC.

HB19 - CHECK FUEL FILTER FOR WATER OR OTHER CONTAMINATION

Disassemble fuel filter and check for water and other contamination.

Is there any contamination present?

YES CLEAN contaminants from filter housing. REPLACE filter element.

NO GO to HB2O.

HB2O - CHECK FUEL LINE FOR RESTRICTION

Visually inspect all fuel lines for damage which may cause the fuel to be restricted or leaking.

Are there any restrictions?

YES REPAIR fuel line(s) as required. COMPLETE PCM Reset to clear DTC.

NO REPLACE fuel pressure regulator. COMPLETE PCM Reset to clear DTC.