What Does B1204 Mean?
This code indicates the Body Control Module (BCM) or instrument cluster has detected a short circuit to ground in the fuel level sender circuit. The fuel sending unit, which measures the fuel level in the tank via a variable resistor on a float mechanism, is showing an abnormally low or zero resistance reading that indicates the signal wire is grounded. This prevents accurate fuel gauge readings and typically causes the gauge to read full or empty depending on the manufacturer's design.
Common Causes
40%
Damaged or chafed wiring harness between fuel tank sender and BCM/instrument cluster creating ground short
30%
Failed fuel level sending unit with internal short to ground or damaged float arm contact
20%
Corroded or moisture-damaged fuel sender connector at tank allowing short to ground
10%
Failed BCM or instrument cluster with internal circuit fault misreading sender resistance
Diagnostic Steps
1
Step 1: Perform visual inspection of fuel sender wiring from tank to instrument cluster/BCM, checking for pinched, chafed, or damaged wires especially along frame rails and near exhaust components
2
Step 2: Disconnect fuel sender connector at tank and measure resistance from sender signal terminal to ground with multimeter - should read open circuit (OL/infinite resistance) if sender is good; zero ohms confirms internal sender short
3
Step 3: If sender tests good, measure resistance on vehicle harness side from sender signal wire to ground with sender disconnected - zero ohms indicates wiring harness short to ground between tank and module
4
Step 4: Inspect fuel sender connector terminals for corrosion, pushed-back pins, or moisture intrusion that could cause intermittent grounding; clean and seal connector if corrosion found
5
Step 5: If wiring and sender test good, check fuel sender signal voltage at BCM/cluster connector (sender connected) - voltage should vary with fuel level typically 0.5-4.5V range; stuck at 0V confirms module-side issue
6
Step 6: Clear codes, repair identified fault, cycle ignition and monitor fuel gauge operation through full tank range to verify accurate readings and confirm no code return
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) or instrument cluster has detected a short circuit to ground in the fuel level sender circuit. The fuel sending unit, which measures the fuel level in the tank via a variable resistor on a float mechanism, is showing an abnormally low or zero resista...
The most common cause of B1204 (Fuel Sender Circuit Short To Ground) is: Damaged or chafed wiring harness between fuel tank sender and BCM/instrument cluster creating ground short
Typical repair costs for B1204 range from $150 to $650, 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 be inaccurate or non-functional, requiring manual tracking of fuel consumption to avoid running out of fuel. Repair at earliest convenience to prevent being stranded with empty tank.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1204 to identify the root cause.
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Quick Info
Category
Body
System
Fuel Gauge/Instrument Cluster System
Difficulty
Type
Manufacturer
Recommended Tools
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