Initial Inspection - Natural Gas - Instrument Cluster

DIAGNOSTIC INSTRUCTIONS

The NGV module monitors the components and circuitry required for fuel indication during normal operation. If an error or concern is detected, the NGV module will store a diagnostic trouble code (DTC) in memory. DTCs are retrieved from the NGV module using the diagnostic tool. If a concern exists with the instrument cluster that is not related to the fuel indication system. DO NOT carry out NGV module diagnostics. The components monitored by the NGV module include the:
- fuel tank temperature sensor
- fuel tank pressure sensor
- circuitry

Fuel gauge accuracy can be affected by certain conditions. These conditions will cause abnormal fuel gauge movement, possibly causing unnecessary diagnostics. Make sure the following conditions do not exist before continuing with fuel indication system diagnostics:

A. Fast filling
- After fast filling a vehicle, the fuel gauge reading can drop as much as 1/16 of a tank. This is caused by the rapid expansion and compression of the fuel during fast fills. This is considered normal gauge movement.
- Fast filling with the ignition switch in the RUN position can cause the NGV module to store DTCs in error. With the ignition switch in the RUN position, the NGV module is monitoring the sensors. During fast fill situations, the fuel tank temperature drops to extremely low temperatures; this may cause the fuel tank temperature sensor to drop below its operating temperature range, causing the NGV module to store a DTC. When fast filling is complete, the fuel tank temperature sensor will return to normal operation after it reaches normal operating temperature range. However, the DTC will still be stored.

B. Fuel system leaks

- NOTE: Refer to Fuel Delivery and Air Induction for the Fuel System Leak Test.

After repair of a fuel system that has been drained, the fuel gauge will display Empty during the initial key-on of the ignition switch since there is no pressure in the fuel lines. After 4-5 key-ons, the fuel gauge will display the appropriate reading.

INSPECTION AND VERIFICATION

1. Verify the customer concern.
2. Observe the indicators, warning displays, and gauges to determine if they are operating correctly with the ignition switch:
- in RUN with the engine off.
- in START before the ignition switch is released.
- in RUN with the engine running.

Visual Inspection Chart:

3. Visually inspect for obvious signs of mechanical and electrical damage.
4. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
5. If the cause of the concern is not visually evident, connect the diagnostic tool to the data link connector and select the vehicle to be tested from the diagnostic tool menu. If the diagnostic tool does not communicate with the vehicle:
- check that the program card is correctly installed.
- check the connections to the vehicle.
- check the ignition switch position.

6. If the diagnostic tool still does not communicate with the vehicle, refer to the diagnostic tool operating manual.
7. Carry out the diagnostic tool data link test. If the diagnostic tool responds with:
- SCP, ISO or UBP circuit fault; all electronic control units no response/not equipped, refer to Information Bus (Module Communications Network).
- No response/not equipped for the NGV module, refer to Computers and Control Systems.
- No response/not equipped for the instrument cluster.
- System passed, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs for the NGV module and carry out self-test diagnostics for the instrument cluster.

8. If the DTCs retrieved are related to the concern, go to the Natural Gas Vehicle (NGV) Module Diagnostic Trouble Code (DTC) Index to continue diagnostics. Trouble Code Diagnostic Charts - Natural Gas - Instrument Cluster
9. If no DTCs related to the concern are retrieved, GO to Symptom Chart to continue diagnostics. Diagnosis By Symptom - Natural Gas - Instrument Cluster