P276D: Electric/Auxiliary Transmission Fluid Pump B Motor Current
What to do
The car will drive normally — the most likely sign is that stop-start no longer switches the engine off. That is the system protecting itself rather than a battery problem, which is what usually gets blamed. You may also notice a slight delay before the car moves after the engine restarts. Worth diagnosing, not urgent.
What this code means
The electric auxiliary transmission fluid pump B motor current is outside its expected range.
An automatic gearbox loses all its hydraulic pressure the moment the engine stops turning, and stop-start made that a problem worth solving.
The main pump is driven by the engine. Engine off, no pressure, no clutch applied — which is fine when the engine only stops at the end of a journey. On a car that shuts the engine off at every red light, the transmission would have to rebuild pressure before the car could move, and the delay is exactly the hesitation that makes people dislike stop-start.
So an electric auxiliary pump keeps pressure up while the engine is stopped, and lets the car pull away the instant the engine restarts. Hybrids need it for the same reason and more often. A fault here does not usually stop the car — it stops the stop-start, and many vehicles simply disable engine shutdown, which is the system failing safe.
Current is how the module tells whether the pump is really pumping. There is often no pressure sensor on this circuit, so the current draw is the only evidence the motor did any work — which makes this code a performance check rather than a wiring check.
What the driver notices is usually nothing, or that stop-start has stopped working. That is worth stating plainly, because an unexplained loss of stop-start is often blamed on the battery — and on a car with this code the transmission is the reason.
Pump B implies a pump A, so this is a vehicle with more than one auxiliary pump or one that numbers them for a second circuit. Read every stored code before assuming which unit is meant.
Transmission fluid is the first thing to check and the thing most often skipped.
It is not a lubricant that also happens to move things — it is the working fluid of a hydraulic machine. It carries the pressure that applies every clutch, it carries the heat away, it lubricates, and it is the friction surface itself: the additive package is tuned so clutches grip smoothly rather than snatching.
So fluid that is low, old, burnt or of the wrong specification changes how the transmission behaves, and it does so before any part has failed. Burnt fluid smells burnt and looks dark; healthy fluid is translucent. Checking it costs nothing and rules out a great deal.
"Filled for life" is a claim about the warranty, not the transmission. Many sealed units have no dipstick and a manufacturer schedule that never changes the fluid, and they still wear out faster on original fluid than on serviced fluid.
Likely causes
Start here
- Corroded or loose connector · specialist
- Faulty auxiliary transmission fluid pump · specialist
- Damaged wiring harness · specialist
- Poor module ground connection · specialist
Less common
- Low or degraded transmission fluid · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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