Diagnostic Aids

A mechanical venturi jet pump is located in the fuel tank as an assembly to the secondary fuel pump module (left side of fuel tank). This module is on the opposite side of the fuel tank to that of the fuel pump. The jet pump function is to move fuel from one side of the tank over the hump to the other side. If fuel is added to the fuel tank, the primary fuel level sensor will increase resistance, while the secondary fuel level sensor remains the same until enough fuel is added to make it over the hump. As a result, it may be normal to have each sensor read different resistance values when the vehicle is on level ground. It is the sum of the resistances that make the fuel level accurate.

Fuel level reading on scan tool is instantaneous, not averaged.

Use scan tool to monitor FUEL LEVEL SENSOR voltage while raising vehicle from the rear. Voltage should change indicating moving floats. Voltage may not change if fuel level is too high or too low.

Possible cause of static fuel level is primary or secondary fuel level sensor sweep arm stuck or the sweep arm is bent. A perforated primary or secondary fuel level sensor float is not possible.

Each fuel level sensor resistance: 19 ohms with float at top position (full fuel tank), though 125 ohms with float at bottom position (empty fuel tank).

The fuel tank inline harness connector contains a voltage tap wire that is connected between the primary and secondary fuel level sensor. As a result, this wire in conjunction with the 5-volt supply and reference return wire to the sensors may be used to take a resistance measurement of each sensor.