Fuel Gauge Circuit Malfunction
What does B1403 mean?
The B1403 code means the vehicle's onboard diagnostic system has detected: Fuel Gauge Circuit Malfunction. This is a moderate severity code.
Common Symptoms
- Fuel gauge reads empty when tank is full
- Fuel gauge stuck at one position
- Fuel gauge needle bouncing erratically
- Low fuel warning light inaccurate
- Fuel gauge reads full constantly
Probable Causes (Ranked by Likelihood)
- Failed fuel level sending unit in tank Very High
- Corroded fuel pump connector High
- Faulty fuel gauge stepper motor in cluster Moderate
- Damaged wiring from fuel tank to instrument cluster Moderate
- Instrument cluster circuit board fault Low
Step-by-Step Diagnostic Procedure
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Check fuel level sensor reading with scan tool
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Compare scan tool fuel level to actual fuel level
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Test fuel sending unit resistance at fuel pump connector
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Inspect fuel pump module connector for corrosion
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Perform cluster self-test for fuel gauge
Frequently Asked Questions
Can I run out of fuel because of this?
Yes. If the fuel gauge reads incorrectly, you cannot rely on it to know when to refuel. Track your mileage between fill-ups as a backup until the gauge is repaired.
What is a fuel sending unit?
The fuel sending unit is a variable resistor attached to a float arm inside the fuel tank. As the fuel level changes, the float moves and changes the resistance, which the gauge reads.
Is the sending unit part of the fuel pump?
On most modern vehicles, yes. The fuel level sending unit is integrated into the fuel pump module assembly. However, on some vehicles it can be replaced separately.