CEL P2456 after WP/TB change

[Wasserpest]

Hey all,

My water pump recently started to leak, so I had it replaced by a local mechanic, along with a timing belt change that was almost due anyway.

Picked up the car and after a short drive got a P2456 code. Mechanic said he test drove the car for quite a bit (20 miles) and all seemed good.

Checking the P2456 description mentions that the PCM detects an "implausible signal". I checked the sensors themselves and they don't look melted or anything.

Is it possible that they hooked them up incorrectly? If so, how could I figure out how they need to be hooked up?

Thank you for any guidance...

 

[oilhammer]

Yep, very common. He (or she) broke the pressure sensor on top of the engine. Don't drive the car, open the hood, pop off the engine cover, it is under the space blanket right on top. The nipple is cracked on the left one, may not be able to tell unless you actually remove the assembly.

It happens. Do a search. Dealers (at least here) keep all that on the shelf.

 

[oilhammer]

Here, read all about it:

DPF Pressure Sensors Melted | TDIClub Forums

That's just ONE thread, there are probably a dozen or more.

 

[Wasserpest]

Thank you OH! I checked both sensors (under the heat blanket) and they look fine, as in Not Melted.
I disconnected the plug on both and reconnected them, no obvious issues, loose wires, bent posts or anything. I don't think they can be connected incorrectly.
I reset the CEL, and this morning it has not come on yet.

Is it possible that the mechanic let the car idle for an extended time during the repairs (to test the fans coming on, as he stated), and that this caused the DPF to get a bit sooty and report "implausible" back pressure?

And furthermore, some highway driving might clear up the issue? We're driving about 25-30 miles daily, mostly highway. I know, not very much, but hopefully enough to warm up the fluids sufficiently.

One can hope, right?

 

[oilhammer]

I've found the little plastic nipple will crack right where it goes into the sensor, and the only way you can find it is to actually take it off and look. The pressure will "push" it open worse, and eventually will start blowtorching a bigger hole and start damaging more stuff.

 

[Wasserpest]

I've found the little plastic nipple will crack right where it goes into the sensor, and the only way you can find it is to actually take it off and look. The pressure will "push" it open worse, and eventually will start blowtorching a bigger hole and start damaging more stuff.

I took another look and it seems like they did not connect some of the hoses??

^^ This is the front sensor... there is some partially melted plastic crud, not sure where that comes from, but should that hose be connected to the nipple??

^^ this is the one towards the back, again, one of the nipples seems to be without hose?!

 

[oilhammer]

Yep, broken nipple... like I said...

 

[Wasserpest]

Thank you sir for your time! You are absolutely right, as usual. Appreciate your help! Going to talk to the mechanic, and maybe just order a replacement.

 

[Wasserpest]

Would this be an appropriate replacement, or is it go OEM or go home?

(besides the fact that they may send a MAP sensor instead, as pictured in most images).

 

[oilhammer]

Here:

Differential Pressure Sensor Assembly (CRUA)(CVCA) 04L131552GB 04L131552DL | IDParts.com - Diesel Parts

Or, as I already stated, the dealers typically have these on the shelf, because it happens so often.

 

[Wasserpest]

I know, they are supporting the site and all... but $16 vs $155+shipping. Tough one.

 

[Mozambiquer]

Would this be an appropriate replacement, or is it go OEM or go home?

(besides the fact that they may send a MAP sensor instead, as pictured in most images).

OEM, not cheap Chinese aftermarket. I've seen so many aftermarket parts, especially sensors which are not near the same quality and they are bad from the box.

 

[Wasserpest]

Got it, thank you. Is it possible to drive this way (plugging the hose), or does that risk sooting up the DPF beyond repair?

 

[oilhammer]

I wouldn't drive it like that.

You posted this yesterday... I responded this morning. Have you bothered to try and call your local dealer? You could have possibly had this fixed already.

 

[Wasserpest]

My local dealer is about 50mi away, therefore the question. Towing there will probably not be covered. As I said, the job was done by a local shop. I contacted them and they're a bit hesitant to pay for the part.

 

[oilhammer]

Well I can't help any more than I already have.

I drive nearly 50 miles one way to work every day. Of course, I'm also driving a much older TDI, so I have no worries about all the stuff your cars have that can break. With the newer ones, you simply HAVE to have some form of contingency plan if you want to own one. Pile of money in the bank, extra car, an old F250 with a trailer on hand, whatever. A ~$200 part only 50 miles away and ~10 min worth of work shouldn't be a shocker. I've got CR Volkswagens in the shop EVERY DAY that require over FIVE GRAND worth of repairs.

 

[Wasserpest]

You helped a lot, and I appreciate your time to reply and pinpoint the issue. The mechanic ordered the part from the dealer, I put it in and now all seems to be good.
Am worried about more DPF issues looming and just waiting for the extended emissions warranty to be over to pop up more CELs.
Really love the power and efficiency of these cars, but yeah, lots of stuff that can break.