What Does B2451 Mean?
This code indicates the Body Control Module (BCM) or heating system control module has detected a short circuit to ground in the auxiliary heater fuel pump circuit. The auxiliary heater system, commonly found in diesel vehicles or cold climate packages, uses a separate fuel-fired heater to warm the engine coolant or cabin. The control module detected abnormally low resistance or voltage in the fuel pump control circuit, indicating current is flowing directly to ground instead of through the pump.
Common Causes
45%
Damaged or chafed wiring harness between control module and auxiliary heater fuel pump creating ground short
30%
Failed auxiliary heater fuel pump with internal short to ground
15%
Corroded or damaged connector at auxiliary heater fuel pump causing ground short
10%
Failed auxiliary heater control module or relay with internal short
Diagnostic Steps
1
Step 1: Perform visual inspection of auxiliary heater fuel pump and wiring harness for obvious damage, chafing, melted insulation, or corrosion. Check routing near sharp edges, hot components, or moving parts.
2
Step 2: Disconnect auxiliary heater fuel pump connector and use multimeter to measure resistance between pump power/control terminal and ground. Reading should be infinite (open circuit); low resistance confirms pump internal short.
3
Step 3: With pump disconnected, measure resistance from control module side of harness connector to ground. Should read infinite resistance; low resistance confirms wiring harness short to ground.
4
Step 4: If harness shows short, trace wiring using schematic and physically inspect entire length, paying attention to grommet pass-throughs, mounting brackets, and areas where harness contacts metal. Use continuity test to isolate short location.
5
Step 5: Repair or replace shorted component (pump, wiring, or connector). Clear code and operate auxiliary heater through scan tool active test or allow normal operation cycle to verify pump functions and code does not return.
6
Step 6: Monitor freeze frame data and live data for fuel pump command vs actual status to confirm proper circuit operation under load conditions.
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) or heating system control module has detected a short circuit to ground in the auxiliary heater fuel pump circuit. The auxiliary heater system, commonly found in diesel vehicles or cold climate packages, uses a separate fuel-fired heater to warm the ...
The most common cause of B2451 (Aux Heater Fuel Pump Circuit Short to Ground) is: Damaged or chafed wiring harness between control module and auxiliary heater fuel pump creating ground short
Typical repair costs for B2451 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 as the auxiliary heater is a supplemental comfort and cold-start aid system, not required for basic vehicle operation. However, cold weather starting may be more difficult and cabin heating may be reduced in extreme cold conditions, so repair should be completed before winter or in cold climates.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2451 to identify the root cause.
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Quick Info
Category
Body
System
Auxiliary Heating System
Difficulty
Type
Generic (SAE)
Recommended Tools
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