Hi all (first post here)

I have a 2015MY DB9 and just had the ‘emission system service required’ warning. The faults on the car from the OBD reader are:

• P0128 (thermostat range/performance)
• P2800 (shift by wire transmission range sensor circuit fault.

I’m wondering if the combination helps somebody clever to suggest likely issues/places to check. I’m reasonably handy mechanically but I’m not about to start stripping down an AM so anything too complex and it will be off to the garage with it!

Interestingly there’s an old post on this forum where someone had the P2800 error and also had a ‘low coolant level’ message. Might suggest the codes are linked. P0128 suggests it’s not warming up quickly enough and could be a faulty thermostat. I’ve not looked at the coolant itself as the car is currently warm but it’s fully serviced and the last service was only 500 miles ago.

if it is a garage job would you be ok with a good independent or might it be one for the AM dealership?

As an aside I have sometimes had failure to select D, with a gearbox error message, but always selects second time. I wonder if the P2800 might be a red herring on the emissions fault issue, and indicative of this occasional gear selection issue.

Thanks for reading, hopefully someone can help.

 

Doesn't seem like those codes would cause an emission systems warning. Are you using an Aston specific OBD reader or a generic one? Could try clearing the codes and see what comes back.

 

Hi, thanks. It’s Aston specific on a Foxwell but it was my first time using it and so maybe there were other codes. I have cleared it now so will take it for a gentle drive on the weekend and see what happens.

I have seen mention it could be the thermostat and that could throw up an emissions warning, but I’m not equipped to remove undertray so will be going to my local specialist I expect if it does come back.

 

P0128 is in deed a sticky thermostat. Recommend replacing the thermostat it's fairly straightforward and it's unique to the V12 engine. The P2800 code is due to button fault or not pressing them in the middle. The P2800 will not produce a CEL but will store a code which shouldn't have an issue. Replace the thermostat first.

 

There are some pretty good threads on replacing the thermostat on the DB9. Pretty straightforward if you are handy. Based on your comment above, the hardest part would be draining the coolant. You could do the job in the driveway and just remove the hoses from the Tstat housing... That will drain the fluid

 

I did my thermostat a while back when I did the plugs and coils. It's not a big deal other than the cost of the parts. The shop manual recommends replacing the pressed in seal in the front housing. Getting the seal ring installed was probably the most challenging part. I had to bake the housing in the oven and freeze the seal in order to tap it back in with a wood block and a mallet. It probably would've gone easier with a proper press, but I worked with what I had.