Diagnostic Aids
WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.
- The IAT Sensor scan tool temperature parameter is reduced when the vehicle enters CNG Mode.
- MY14 vehicles - The K130 Fuel Pump Disable Control Module is located inside the driver side frame rail of the vehicle. It is bolted to the CNG fuel pressure regulator bracket.
- MY15 vehicles - The K130 Fuel Pump Disable Control Module is located on the driver side of the engine compartment. It is bolted to the CNG module bracket.
- The FICM is also known as the CNG control module.
- A fault on the IAT low reference circuit may prevent the vehicle from entering CNG mode.
- The ECM supplies the engine coolant temperature (ECT) signal to the FICM. When the ECT signal is at least 65°C (149°F) and the vehicle has been running for at least 2 minutes, the FICM enables both CNG cut-off solenoid valves, allowing the CNG system to pressurize.
When the system is pressurized, the FICM commences the change from gasoline to CNG fuel. Beginning with cylinder #1, the FICM sequentially disables each gasoline injector and enables the matching CNG injector. All injector pulse and ignition timing calculations are performed by the ECM.
The ignition timing calculations are adjusted by the ECM based in part on the IAT temperature. In CNG mode, the IAT signal modification module lowers the IAT temperature to the ECM. In CNG mode the ECM may advance timing up to 12 additional degrees.
If any FICM DTC is set, the FICM switches the vehicle back to gasoline mode.