What it means
The motor supply voltage of the second auxiliary transmission fluid pump is above the operating range.
At a glance
- Usually lights the check-engine light
How it works
Electric or auxiliary transmission fluid pump B uses its motor supply circuit to power a pump that supports transmission hydraulic pressure when required. P276C sets when the module detects supply voltage above the expected operating range, which can indicate an overvoltage or unintended feed.
Common causes
Most likely first.
- Alternator regulator failed to limit output
- Wiring shorted to a higher-voltage circuit
- Connector pins corroded - high contact resistance
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Save freeze-frame data and monitor pump B supply voltage to establish when it rises above range.
- Check battery and charging-system voltage for evidence of an overcharging condition.
- Inspect pump B’s supply wiring for contact with a higher-voltage circuit or damaged insulation.
- Check the pump connector for corrosion, loose pins, or signs of heat damage.
- Test the circuit voltage and charging system against the manufacturer's specification to identify the source of the high reading.
Common fixes
- Repair an alternator regulator or charging fault confirmed by testing.
- Repair wiring shorted to a higher-voltage circuit.
- Clean or replace damaged pump B connector terminals.
- Repair a pump B supply circuit fault found during voltage testing.
Can I keep driving?
Have the high-voltage fault diagnosed promptly, and avoid driving if other charging-system warnings appear or shifting becomes unreliable. Excess voltage can damage pump B or its control circuit and may disrupt transmission pressure support.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.