What does it mean?
OBD II fault code B1202 is a manufacturer-specific code that is defined by carmaker Jaguar as, “Fuel Sender Circuit Open”, and is set when the PCM detects an open circuit in the fuel sender unit’s signal circuit. NOTE: Although code B1202 – “Fuel sender: circuit open” affects a large number of Jaguar models from many different production years, the most commonly affected models are 2010 to 2012 X150 and X250 models that are fitted with 5.0L and C/S 5.0L V8 gasoline engines.
As on all other modern vehicles, affected Jaguar models use a simple potentiometer that is linked to a floating device to indicate the fuel level in the fuel tank. In terms of operating principles, a potentiometer is fitted with a resistive element that carries the full voltage of the reference voltage that is supplied by the PCM, across its entire length.
In the case of a fuel level sender unit, the floating device is connected to a sliding element that contacts the resistive element, and as the fuel level changes, the sliding element slides across the resistive element, which changes the voltage between the point where the sliding contact touches the resistive element and the reference voltage’s input point.
Put differently, this means that the voltage that is passed back to the PCM, and from there to the fuel gauge, changes as the fuel level changes because the sliding contact follows the changes in the fuel level. Therefore, the voltage that is passed back to the PCM at any point depends on the actual fuel level in the tank, and it is this voltage that a driver sees displayed on a fuel gauge as the fuel level in the tank.
In most cases, potentiometers that are used to indicate fuel levels are robust and very reliable, albeit not always very accurate. Nonetheless, when an open circuit is present in the fuel sender’s signal circuit, the PCM cannot display the fuel level in the tank, and when this happens, the PCM will set code B1202 and may also illuminate a warning light.
Symptoms
- Fuel gauge reads empty and stays there, or sits at full and never moves
- Low fuel warning lamp permanently on regardless of the real level
- Distance to empty display missing, frozen or clearly unrealistic
- Gauge does not respond at all after refuelling
- Warning lamp on the dash with the code stored
- Risk of running out of fuel because the driver has no usable indication
Likely causes
- Worn or burnt track on the sender potentiometer inside the tank, leaving the wiper with no contact
- Broken, corroded or backed-out terminal at the fuel pump module connector on top of the tank
- Float arm detached, bent or the float itself saturated and sunk, so the wiper sits off the track
- Harness between the tank and the module chafed through or broken where it passes a body edge or heat shield
- Open reference voltage supply or a blown fuse feeding the sender circuit
- Poor or open ground for the sender unit
- Deposits from contaminated fuel or additives insulating the resistive track
- Failed input circuit inside the module
How to fix it
- Watch the fuel level sender voltage or percentage in live data while fuel is added and see whether it moves at all
- Access the fuel pump module connector on top of the tank and inspect it for corrosion, melted housings and backed-out terminals
- With the ignition on, confirm the reference voltage is present at the tank connector
- Following the manufacturer's procedure, bridge the signal to ground at the connector and see whether the gauge sweeps; if it does, the fault is inside the tank unit
- Check continuity from the tank connector back to the module and confirm the sender ground
- Repair the harness fault, or remove the pump module and replace the sender/float assembly
- Observe fuel handling safety precautions, then refit, clear the code and verify the gauge tracks correctly over a full tank