Fuel Pump "B" Control Circuit High
The fuel pump B control circuit is detecting a high voltage condition, meaning the ECU is receiving a signal higher than expected when commanding the fuel pump. This prevents proper fuel pump operation and can leave the vehicle unable to start or run properly.
What You Might Notice
- Check engine light is illuminated
- Engine won't start or cranks but fails to start
- Engine misfires, stalls, or dies during operation
- Engine dies when reaching operating temperature
- Reduced fuel economy
Most Common Causes
- 1
Fuel pump relay failure
A faulty relay can send excessive voltage to the fuel pump control circuit, triggering the high voltage code.
- 2
Wiring harness short to power
Damaged or pinched fuel pump wiring that contacts a live power source will cause high voltage on the circuit.
- 3
ECU control circuit fault
A defective engine control module may incorrectly read or fail to properly regulate fuel pump voltage, causing high voltage detection.
- 4
Fuel pump driver module failure
Some vehicles use a separate fuel pump driver module that can fail and output excessive voltage to the fuel pump circuit.
How to Diagnose It
- 1
Check Fuel pump relay failure — A faulty relay can send excessive voltage to the fuel pump control circuit, triggering the high voltage code.
- 2
Check Wiring harness short to power — Damaged or pinched fuel pump wiring that contacts a live power source will cause high voltage on the circuit.
- 3
Check ECU control circuit fault — A defective engine control module may incorrectly read or fail to properly regulate fuel pump voltage, causing high voltage detection.
- 4
Check Fuel pump driver module failure — Some vehicles use a separate fuel pump driver module that can fail and output excessive voltage to the fuel pump circuit.
How to Fix It
- 1
Test and replace fuel pump relay
Locate the fuel pump relay in the vehicle's relay box, test it with a multimeter, and replace if defective. This is the most common cause of high voltage codes.
- 2
Inspect fuel pump wiring harness
Carefully inspect the fuel pump wiring from the relay to the pump for damage, pinches, or exposed wires. Repair or replace any damaged sections and ensure proper routing away from heat sources.
- 3
Check fuel pump driver module
If equipped, test the fuel pump driver module with a scan tool and replace if it is not properly regulating voltage to the fuel pump circuit.
- 4
Test ECU and connectors
Use a scan tool to verify ECU fuel pump control signals and inspect ECU connectors for corrosion or loose pins. Clean contacts or replace connectors as needed.
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