Hi there folks,

Anyone come across this diagnostic code? It tells me that  " Reductant pump B -open circuit"  I have tried to find mention of a reductant pump b in the workshop manual but can't find any mention of it. Can anyone cast light on this, and is it an easy fix?

According to Google the reductant pump is the AdBlue pump.

Thanks for the reply Kenny, I am struggling to find any information on the adBlue pump, all I can find in the manual and by googling is how to add adblue to the  tank. You don't by any chance know where the pump is located?

Cheers,

Ian

 

I'd start by looking at where the tank is.

Could be in the tank.

This may help... 

 

https://www.engine-codes.com/p208a.html

 

https://partsavatar.ca/p208a-obd-ii-trouble-code-reductant-pump-control-circuit-open-solution-egr-valve-exhaust-fluid

Edited 14 March, 20215 yr by Schtum

To add some background info (for interest but not specifically to answer the question asked) - it is called the "reductant" pump because it is pumping a fluid that is used as a reductant in a chemical reaction.

 

The emissions system this works with is called the "selective catalytic reduction" system, or SCR.  In chemistry (in basic terms) "reduction" is the opposite of "oxidation".  What the SCR is doing is reducing the levels of NOx (or nitrogen oxides) in the exhaust gasses.  The NOx has been formed by the oxidation of nitrogen in the air during the combustion process.  The SCR effectively undoes this, by "reducing" the NOx back to nitrogen and oxygen.  It does this through the use of a catalyst (the box in the exhaust) and a "reductant"; a chemical reagent used to perform the reduction of NOx.  Ideally what you need is ammonia (NH3) but this is a hazardous chemical to handle and carry around so a solution of urea dissolved in water is used - this is known colloquially as "AdBlue", although AdBlue is actually a trade name and the generic terms is "diesel exhaust fluid", or DEF.  The urea breaks down to form ammonia in the exhaust which then reduces the NOx to nitrogen and water (plus a bit of CO2).

 

Hence you need a reductant pump and an injector to spray this stuff into the exhaust stream so that the SCR can do its job and we all get to breathe slightly less toxic air.  If the pump is not working then the SCR is not working so your emissions will be higher than they should be.  It doesn't stop the engine from working per se, but in some cases a car's ECU will either limp or even shut down to prevent high emissions, which may be a requirement of the type approval and qualification.

I am repeatedly impressed by the technical/scientific knowledge of some members of this forum