P2AD6: Reductant Pump Motor Position Sensor Circuit
What to do
Do not leave this. AdBlue faults run on a legally mandated countdown to a no-restart, and the dashboard will state the remaining miles. There is a second reason to be prompt: the pump also purges the lines when you stop, and a fault here can leave AdBlue in them to crystallise.
What this code means
The circuit for the reductant pump motor's position sensor is faulty.
A position sensor on a reductant pump motor tells you this is a piston pump rather than a spinning one, and that changes what its faults mean.
AdBlue has to be metered precisely — too little and NOx is not converted, too much and unreacted ammonia leaves the tailpipe, which is its own regulated emission. So the dosing system meters by displacement: a piston of known volume, moved a known distance, delivers a known quantity.
Which makes the position sensor the metering instrument, not a monitor. Without it the pump cannot know how much it has delivered, so the module cannot dose at all — it does not fall back to an estimate, because an estimate on AdBlue risks ammonia slip.
There is a second reason a piston pump is used here, and it explains a fault pattern. The system must be able to purge itself back into the tank when the engine stops, because AdBlue left in the lines freezes and crystallises. A reversible piston pump does that naturally. A position fault therefore also stops the purge, and crystalline deposits in the injector and lines are the expensive consequence that follows weeks later.
As with every reductant fault, the countdown applies: reduced power and eventually no restart, on a legally mandated schedule.
The base circuit fault: no plausible signal.
Likely causes
Start here
- Faulty reductant pump · specialist
- Corroded or loose connector · specialist
- Open circuit in sensor wiring · specialist
Less common
- Crystallised reductant deposits · specialist
- Damaged wiring harness · specialist
Symptoms
Components involved
Information, not instruction
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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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