What it means
Voltage on the second auxiliary transmission fluid pump control line is above the expected window. 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
How it works
The TCM uses the pump B control circuit to switch the second auxiliary transmission fluid pump and monitors its voltage. This code sets when the circuit voltage is higher than expected, often because the control wire is shorted to battery power or the pump winding is open.
Common causes
Most likely first.
- Control wire shorted to B+
- Open motor winding
- 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 check live pump B command and circuit readings to determine when the high voltage is present.
- Inspect pump B's connector and harness for chafing against a B+ wire, moisture, loose terminals, or pushed-back pins.
- With pump B uncommanded, measure the control circuit for unwanted battery voltage and compare it with the manufacturer's specification.
- Disconnect pump B and test its winding for an open circuit, which can leave the control line reading high.
- If the winding is sound, check the control wire for a short to B+ and verify connector contact resistance.
Common fixes
- Repair the pump B control wire where it is shorted to battery power.
- Restore secure, clean contact at corroded or loose pump B connector pins.
- Replace pump B if its motor winding is open.
- Repair an open or damaged section of the pump B harness.
Can I keep driving?
Avoid driving if the transmission is slipping, shuddering, or shifting harshly or late; these symptoms can indicate impaired hydraulic control and further damage. If shifts are normal, keep driving to a minimum and arrange diagnosis 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.