What Does B1203 Mean?
This code indicates the Body Control Module (BCM) or instrument cluster has detected that the fuel level sender circuit is shorted to battery voltage (12V+). Instead of receiving a variable resistance signal from the fuel tank sending unit that corresponds to fuel level, the control module is seeing constant battery voltage on the signal wire. This prevents accurate fuel level reading and typically causes the fuel gauge to read full or peg at maximum regardless of actual fuel level.
Common Causes
45%
Damaged or chafed wiring harness between fuel tank and BCM/instrument cluster causing signal wire to contact power wire or chassis where power is present
30%
Failed fuel level sending unit with internal short circuit to power supply terminal
15%
Corroded or damaged connector at fuel tank causing cross-circuit short between battery feed and signal pins
10%
BCM or instrument cluster internal fault causing erroneous short-to-battery detection
Diagnostic Steps
1
Step 1: Perform visual inspection of fuel sender wiring harness from tank to instrument cluster/BCM, checking for pinched, chafed, or damaged wiring especially near exhaust components, suspension mounting points, and body seams
2
Step 2: Disconnect fuel sender connector at fuel tank and measure resistance between signal wire terminal (at harness side) and battery positive - should read infinite resistance (open circuit); if continuity or low resistance exists, trace and repair short in harness
3
Step 3: With sender disconnected, use multimeter to measure resistance of fuel sender unit between signal terminal and ground - should vary between approximately 10-180 ohms depending on float position; if reading shows 0 ohms or direct battery voltage, replace sender unit
4
Step 4: Inspect fuel tank connector terminals for corrosion, bent pins, or moisture intrusion that could cause cross-circuit contamination between power and signal circuits; clean or replace connector as needed
5
Step 5: Reconnect all components, clear codes, and monitor fuel gauge operation and code return; verify proper voltage range on signal wire during operation (typically 0.5-4.5V variable signal, not constant 12V)
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) or instrument cluster has detected that the fuel level sender circuit is shorted to battery voltage (12V+). Instead of receiving a variable resistance signal from the fuel tank sending unit that corresponds to fuel level, the control module is seeing...
The most common cause of B1203 (Fuel Sender Circuit Short To Battery) is: Damaged or chafed wiring harness between fuel tank and BCM/instrument cluster causing signal wire to contact power wire or chassis where power is present
Typical repair costs for B1203 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive, but fuel gauge will not accurately display fuel level, creating risk of running out of fuel unexpectedly. Track mileage manually and refuel conservatively until repaired to avoid being stranded.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1203 to identify the root cause.
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Quick Info
Category
Body
System
Fuel System Monitoring
Difficulty
Type
Manufacturer
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