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 an instrument cluster component that is not related to the fuel indication system, refer to the symptom chart in Conventional Cluster for diagnosis of that component. Diagnosis By Symptom - Conventional Cluster - Instrument Cluster
DO NOT carry out NGV module diagnostics. The components monitored by the NGV module include:
- fuel tank temperature sensors
- fuel tank pressure sensor
- fuel gauge
- 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 tank temperature drops to extremely low temperatures; this may cause the fuel tank temperature sensors to drop below their operating temperature range, causing the NGV module to store a DTC. When fast filling is complete, the fuel tank temperature sensors will return to normal operation after it reaches normal operating temperature range. However, the DTC will still be stored.
- Fast filling with the ignition switch in the RUN position will cause the fuel gauge to move very slowly toward Full; this is eliminated when the vehicle is filled with the ignition switch in the OFF position.

B. Fuel system leaks

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

Fuel leaks can cause inaccurate fuel gauge readings. Depending on the size of the leak, the fuel gauge may not be able to maintain an accurate reading if the fuel leak exceeds the low fuel level warning switch and NGV module's ability to update the fuel gauge. This creates a possibility for the fuel gauge to display a fuel level when the fuel tanks are empty. Before diagnosing this type of concern, make sure the fuel system is not leaking.

- 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.

C. Erratic instrument cluster operation
- The NGV module has an internal on-board diagnostic mode which is not used with diagnostic tool diagnostic procedures. However, if the ignition switch is cycled from OFF to RUN four times and left in the RUN position without the engine being started, the NGV module will cause the instrument cluster to react erratically. Warning indicators will remain illuminated and the voltage and fuel gauge pointers will move sporadically. If this concern exists, start the engine. If the concern is still present, continue with NGV module diagnostics.

INSPECTION AND VERIFICATION

1. Verify the customer concern by operating the system.

Visual Inspection Chart:

2. Visually inspect for obvious signs of mechanical or electrical damage.
3. If the concern remains after the inspection, connect the diagnostic tool to the data link connector (DLC) located beneath the instrument panel 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

4. If the diagnostic tool still does not communicate with the vehicle, refer to the diagnostic tool manual.
5. Carry out the DATA LINK DIAGNOSTIC TEST. If the diagnostic tool responds with:
- CKT914, CKT915 or CKT70 = ALL ECUS NO RESP/NOT EQUIP, refer to Module Communications Network (Information Bus).
- NO RESP/NOT EQUIP for NGV module, go to Pinpoint Test A. Test A

6. SYSTEM PASSED, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs and carry out the self-test diagnostics for the NGV module.
7. If the DTCs retrieved are related to the concern, go to the NGV Module Diagnostic Trouble Code (DTC) Index to continue diagnostics. Trouble Code Diagnostic Charts - Natural Gas - Instrument Cluster
8. If no DTCs related to the concern are retrieved, proceed to the Symptom Chart to continue diagnostics. Diagnosis By Symptom - Natural Gas - Instrument Cluster