Boost pressure sensor, electrical: Short circuit to ground
Code: 121002

This ^^^ is your problem.

 

According to the PDF link that I posted, this one can mean:

The fault is recognized when the boost-pressure sensor's voltage is less than 4.9 V.
Potential problem source(s):
- Defect in wiring harness between DME and boost- pressure sensor
- Boost-pressure sensor defective
- Defective DME

Obviously the Dinan harness is involved in all of this Doesn't look like this is going to be a fun problem to diagnose...

 

According to the PDF link that I posted, this one can mean:

Obviously the Dinan harness is involved in all of this Doesn't look like this is going to be a fun problem to diagnose...

If there is a Dinan hardware between the sensor and the DME, then it's most likely the Dinan's fault. I don't expect the DME to go wrong.

 

Understood. The Dinan hardness does have a connection between the factory harness and the charge pipe pressure sensor. But also that's where my boost tap is installed. To start with I've removed the boost tap to test. Of course now I can't read boost to make sure it's normal... But I should be able to tell if there's power or not as it was only making 1-2 PSI boost in limp mode.

 

Removed the boost tap, cleared codes, drove again without issue.

Dinan got back to me said they suspect it's a harness issue (I have an early edition harness), which could of course be intermittent. Anyway they offered to swap the harness out, just have to figure out where to take it, I'm not really close to any dealers. Thanks for your feedback.

 

What is the definition of "early edition" in this case? I have a Stage 1 on my 340 and it was installed in March 2017. Obviously a different piece of equipment due to engine difference, but I assume some of the fundamental parts are the same. Thanks.

 

This is for a B48, so a brand new engine. I guess you have the B58? It appears that I have a hand-built harness, I imagine now they're more automated.

 

Yes, B58. I'm just worried now that I'll have the same problem with my Dinan harness, although it's been installed for 7 months and regularly driven for ~2 months (since late August when I bought the car). I imagine the harness itself is the same, but the software is different and perhaps some of the low-level electronics are different - just speculation on my part though.

 

I agree with you the harness *is* the same. The install instructions are actually for a B58 and the harness doesn't fit the B48 perfectly as the sensors are not in the exact same places. It's entirely possible this is why I'm having issues, there's one wire in particular that's a bit short on the B48. I tried to alleviate the pressure as best I could, but this could be related.

 

I wonder if a software update might fix your issues, but that may require a trip to your Dinan dealer. Otherwise swapping out of the harness under the 4yr/50k warranty, and you would have to brig the car to a Dinan dealer.

 

Subbed, thanks for documenting the issue Bigtuna!

 

Hey Bigtuna00, has your problem been fixed? I'm considering getting the Dinan tune, curious to see what came of your issue. Cheers.

 

Car's going to the shop on Friday to get the harness swapped. The original codes I posted in this thread have not come back but I have had 2 others:

Crankcase vent, vent hose: not connected / defective
Code: 20E120

This one occurred on October 3 (which I cleared) and again about a month later. I have not cleared it again since I'm planning to take the car in. Dinan described this one as "oddball". I'm actually wondering if it's related to the intake?

Boost pressure - atmospheric pressure, comparison, boost pressure is too low
Code: 121533

This one put the car in limp mode on November 10. However I parked at Starbucks and when I came back the car was working fine.

So, no conclusions yet but I'm sure the fact that I have an intake may muddy the waters here.

-Josh

 

Sorry to hear that the tune isn't functioning 100% properly. How confident are you that the faults can be corrected permanently? Overall, would you still recommend this tune?

 

It's the only one that's CARB certified, so I don't really have much choice out here in CA

So far, I expect Dinan to stand behind their 5 year warranty, which you won't get from anyone else as well.

I'm sticking with it for now, for sure.

 

Not to be a pest but curious if Dinan/bmw figured this out. Still thinking on this tune but have seen a few folks w same experience. Hopefully new harness addressed. Tks.


Sent from my iPhone using Bimmerfest

 

It's worth reiterating that I only received the original error code I reported once (Boost pressure sensor, electrical: Short circuit to ground Code: 121002)

The new harness is in. I almost immediately got a "Crankcase vent, vent hose: not connected / defective Code: 20E120" with the new harness but, as I said, I don't think this has anything to do with the Dinan tune (the intake seems more likely or there's literally just a defect). I cleared it and it hasn't come back since.

The car goes into the dealer for 10K service in a couple weeks so if it comes back I will have them diagnose.

I contacted AFe Power and they said they're not aware of any codes with the intake...

The journey continues...

 

The saga continues...

With the aFe intake installed I continued to get the "Crankcase vent, vent hose: not connected / defective Code: 20E120" fault code on a regular basis. In total I put 5,089 miles on the intake and got the code ~6 times.

The car went to the dealer to diagnose the code. They "smoke tested" the intake and found no issues. They of course blamed the modifications.

I installed the stock intake and drove for 4,500 miles with no further problems.

Today installed the aFe intake again, this time with the Dinantronics module set to bypass mode, i.e. stock tune.

aFe wants to blame my modifications (Dinantronics, M Performance exhaust). Dinan for their part has been supportive of my process-of-elimination troubleshooting. My hunch is that the car is too lean with both the aFe intake and Dinantronics Stage 1. I'm considering switching to a tunable piggyback but that's obviously more risky. Anyway will see how it goes with the aFe intake back in.