What it means
The auxiliary transmission fluid pump phase U-V-W output reports a circuit low condition. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The auxiliary transmission fluid pump is driven by a three-phase motor with U, V, and W phase outputs. This code sets when the controller detects a low condition on those phase outputs, which can point to a phase circuit shorted to ground, a poor connection, or a pump or driver fault.
Common causes
Most likely first.
- Short to ground in the pump phase circuit
- Faulty pump motor or driver
- Poor connector connection
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 check live transmission data for pump commands and whether the fault appears during a particular operating condition.
- Inspect the U, V, and W phase wiring and pump connector for chafing, water intrusion, pushed-back pins, or a short to the vehicle body.
- If the fault is active, carefully move the accessible harness while monitoring the relevant scan-tool data to see whether the low condition changes.
- With the vehicle wiring information, test each phase circuit for a short to ground and check connector terminal fit.
- If the wiring is sound, test the pump motor and controller driver using the manufacturer's procedure.
Common fixes
- Clean, dry, and reseat a poor pump connector connection.
- Repair chafed phase wiring or a wire shorted to ground.
- Replace the auxiliary pump if its motor is faulty.
- Repair or replace the pump driver or control module if its output is faulty.
Can I keep driving?
Do not drive if shifts are slipping, harsh, delayed, or missing, or if limp mode is active; continued operation can worsen transmission problems. If shifting feels normal, limit driving and have the phase circuit checked soon.
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.