B1203 code definition

A B1203 diagnostic trouble code indicates that the fuel tank sender circuit has shorted.

What the B1203 code means

The fuel sender uses varying levels of voltage to gauge the vehicle's fuel levels. The insulation for the fuel sender may be faulty or wear to the point where electrical currents cross, resulting in a shorted circuit. This damage will make it impossible for the fuel sender to report accurate fuel levels to the dashboard panel.

What causes the B1203 code?

A B1203 code shorted circuit is usually a result from a fault in the wiring insulation. The fuel sender itself may also be defective.

What are the symptoms of the B1203 code?

In the case of a B1203 code, the fuel gauge may read as empty, regardless of the amount of fuel currently in the tank. The fuel gauge may also read as full regardless of fuel intake.

In addition, for the purpose of diagnosing the issue, the vehicle's onboard computer will log a B1203 code and the dashboard trouble light will be illuminated.

How does a mechanic diagnose the B1203 code?

A mechanic can first diagnose the B1203 code by reading the vehicle's computer with an OBD-II code scanner. The actual tank level may be checked with a dipstick. The fuel sender itself should be examined for signs of fault. All wiring and circuitry relating to the fuel sender unit should be thoroughly inspected for signs of damage.

Common mistakes when diagnosing the B1203 code

The tank should be inspected with the battery leads removed first, as fuel vapour is extremely flammable and a live battery may prove a risk.

How serious is the B1203 code?

A malfunctioning fuel sender will likely render the vehicle's fuel gauge inoperable. This code should be taken seriously and repaired as soon as is possible.

What repairs can fix the B1203 code?

Drain the fuel tank before attempting any repairs. Below are fixes that should resolve the B1203 code:

  • Repairing or replacing faulty or damaged wires
  • Refitting or replacing the fuel sender

Additional comments for consideration regarding the B1203 code

Body-related trouble codes are specific to particular models of vehicle. The meaning of a B Class trouble code will depend on the make and manufacturer. Refer to the vehicle manual if you're unclear on whether a given code description pertains to your model.

Need help with a B1203 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

This article originally appeared on YourMechanic.com as B1203 OBD-II Trouble Code: Fuel Sender Circuit Short To Battery and was authored by Conor Fynes.


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