2009 Audi A5 Looking for more info
I was called to look at this 2009 Audi A5 today brought in to a shop for the check engine light on. The shop has replaced the MAP sensor with an OE part already and it sets the same code after 30 seconds of running or so. Of note, the freeze frame (3rd capture) says the code set KOEO even though I didn't see it set then. I thought it pertinent to look at the MAP sensor to see what it was doing KOEO. I compared it to the Ambient Pressure reading on the scantool and noticed a difference right away(see first capture). Pressure where I live was right around 100kPa today so I'd say the MAP is reading correctly, but the BARO looks off. Running, the MAP goes down to 29kPa. My question is in regards to the BARO and if anyone has any further information on this.
The only piece of info I could find in SI was the second capture posted (highlighted) where it says to “check the altitude sensor co-located in the ECM” which makes me believe that the BARO is actually measured internally in the ECM, not derived from the MAP.
I'd appreciate anyone who has any more data to share.
Most likely ECM, it is comparing actual map pressure with internal barometric pressure sensor. Usually internal(ECM) pressure sensor reads incorrectly thus throwing map sensor fault. At idle and at sea level your MAP should be reading 425mbar.
If code set while KOEO, that means have short circuit or open circuit on harness between sensor and pcm or pcm circuit related to map sensor inside damaged, or maybe the phenomenon that sensor measure has problem like not enough air, check first the air leakage.
Jamie - the Baro sensor is internal to the ECM. It is a separate senor on the board. VW's often have a data pid called “heights correlation factor” which can be used for comparison as well. If your into a little electronics repair you can actually replace just the Baro sensor on the board. I had a Beetle earlier this year that I did successfully. I will include some pics for reference.
Thanks Bill, Great info, thank you! I feel confident now that the problem is in the ECM. May I ask where you sourced a replacement sensor for that?
Jamie - if you search “DS-U3 pressure sensor” you can find several different vendors. here is a link for you also --- aliexpress.com/wholesale?catI… another option is to take it from a used ECM.
Hi Bill. Do you have a simple definition of the “Hights Corr. Factor”? Tried to websearch but wasn't very helpful. Thanks!
Not to derail this but I've seen ECM-mounted baro sensors on old Chrysler and Toyota. They are rare but it has been done just from my memory back to the 80's. I'm surprised to see it in use in 2009 but I don't have any euro experience.
AUDI still uses an ECM mounted Baro on most models. I've got a 2019 currently that sets a boost/baro correlation fault intermittently.
Well the customer opted to put a used ECM in their vehicle. I went back to program it, but first took some pressure readings. It’s definitely better than the original although still off by a couple of kPa. Programmed the ECM and test drove with no more codes…for now. I think Ill keep the old ECM around and fix it for the next time it needs replacement 🤣.