Fuel Gauge

Fuel Gauge Description and Operation

The ECM uses the signal circuits of the primary and secondary fuel level senders to calculate the percentage of fuel remaining in the fuel tank. The ECM supplies 5 volts via the 5 volt reference circuit and also provides a low reference to the primary and secondary fuel level senders. When the fuel tank is full, the resistance of both fuel level senders are low and the ECM senses a low signal voltage on both the signal circuits of the primary fuel level sender and the secondary fuel level sender. When the fuel tank is empty, the resistance of both fuel level senders are high and the ECM senses a high signal voltage on both the signal circuits of the primary fuel level sender and the secondary fuel level sender. The engine control module (ECM) sends fuel level information to the instrument panel cluster (IPC) via the serial data circuit. The instrument panel cluster (IPC) displays the fuel level information in the fuel gauge. When the fuel level is less than a predetermined value, the low fuel message displays in the driver information center (DIC). Refer to:

* Evaporative Emission Control System Description Description and Operation for the 3.6L engine
* Fuel System Description Fuel System Description for the 3.6L engine
* Evaporative Emission Control System Description Description and Operation for the 4.8L, 5.3L, 6.0L, 6.2L or 7.0L engine
* Fuel System Description Fuel System Description for the 4.8L, 5.3L, 6.0L, 6.2L or 7.0L engine

The fuel gauge defaults to empty if:

* The ECM detects a malfunction in the fuel level sensor circuit.
* The IPC detects a loss of serial data communications with the ECM.

Note: Partially filling the fuel tank or filling the fuel tank with the ignition ON or engine RUNNING may cause any of the following conditions:

* Inaccurate and erratic fuel gauge
* Fuel gauge slow to update after fuel fill
* A fuel system diagnostic trouble code (DTC) set in the ECM causing the fuel gauge to default to empty.

Note: When any of the above stated conditions exists, it is necessary to perform the following actions before undertaking any repairs.

* An erratic or inaccurate fuel gauge may be as a result of filling the tank with the ignition ON or engine RUNNING. Refueling with the ignition ON or engine RUNNING may also result in the fuel gauge being slow to update after a partial fill. Always refuel with the key OFF. If the ignition is ON when refueling, it is necessary to cycle the ignition after the fuel fill. Powering the ignition OFF for approximately 1-2 minutes gives the ECM the chance to update the current fuel level information to be displayed in the fuel gauge.
* Fuel system DTCs may set because of a refueling activity with the ignition ON or engine RUNNING. If the ECM does not detect a change in fuel level in the primary and secondary fuel tank of at least 3.0 L (0.79 gal) over a distance of 320 km (200 miles) or the ECM detects a difference between the engine consumed fuel and change of the fuel level signal of less than 1 L (0.264 gal) over a range of 30 L (7.92 gal) , DTCs P0461 or P2066 sets in the ECM and the fuel gauge defaults to empty. If any DTC is set, determine that the DTC is current and repeatable before undertaking any repairs. If the DTC is history or not repeatable, it may have set due to a refueling activity with the ignition ON or engine RUNNING and the ECM did not update the fuel level information. Cycling the ignition after a fuel fill with the ignition ON or engine RUNNING is necessary. Powering the ignition OFF for approximately 1-2 minutes gives the ECM the chance to update the current fuel level information to be displayed in the fuel gauge. Always refuel with the key OFF.
* A partial fill of the fuel tank can cause the fuel gauge to not read accurately. This condition would likely occur when the fuel tank level is low and only enough fuel is added to the fuel tank to bring the fuel tank level near the half tank level. The resistor levels between the primary and the secondary fuel tanks creates an unreadable amount of fuel in the fuel tank system.
* Driving your vehicle on a hill or a hard cornering may affect the fuel gauge leading to an inaccurate or erratic fuel gauge. No corrective measures are required in this instance and symptoms should go away momentarily.