What it means
The controller detects a fault in the auxiliary transmission fluid pump control circuit.
At a glance
- Usually lights the check-engine light
How it works
Some transmissions use an auxiliary fluid pump to circulate transmission fluid when the main pump cannot provide the needed flow. P2796 sets when the controller detects a fault in the pump's control circuit, such as an open motor winding or broken control wire, which may affect shift operation.
Common causes
Most likely first.
- Open pump motor winding
- Broken control wire
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
- Record freeze-frame data and transmission codes, then check whether the fault appears during conditions when the auxiliary pump is commanded on.
- Inspect the auxiliary pump connector and harness for a loose connection, damaged insulation, corrosion, or a broken control wire.
- Use a scan tool to command or monitor the auxiliary pump if the vehicle supports it, and check whether the controller reports the expected pump response.
- Test pump motor winding continuity and the control wire using the manufacturer's circuit procedure.
- If the pump and wiring pass, check the controller output and connector for a fault in the pump control circuit.
Common fixes
- Reconnect and secure the auxiliary pump connector.
- Repair a broken or corroded pump control wire.
- Replace the auxiliary pump if its motor winding is open.
- Repair the controller output connection if testing identifies a control-circuit fault.
Can I keep driving?
Avoid towing, heavy loads, and prolonged driving if shifts are harsh, delayed, or slipping, since inadequate fluid circulation can worsen transmission damage. Stop if the transmission enters limited operation or loses reliable drive.
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.