# Cleaned MAP sensor, got CEL w/ 3 codes



## BodhiBenz1987 (Jan 13, 2018)

I've seen a few tutorials/stories about Gen 1 MAP sensors being gunked up and needing cleaning so I checked my out today ... at 27k miles it was chock full of sludge. So I took it out, disconnected the harness, and sprayed MAF cleaner on it. Not all of it came off, some was caked to the sensor element and I didn't want to touch it since I know it is sensitive. I let it dry, put it back in, connected everything, and started the car. It started sort of awkwardly and the CEL came on (well it stayed on after the startup test). The three codes were P00EB, P0106, and P0108, all related to high voltage for the air/temp sensor. I tried driving a bit to see if they would clear up but I was really down on power, just wouldn't rev up at all. I pulled aside and cleared the codes, and then things went back to mostly normal ... I took it on a highway spin and the codes didn't come back. Power seemed a little down as did fuel economy, but both seemed like they were slipping before, over the last month, which is why I checked the MAP sensor in the first place. But when the codes were on it was a serious power limit and that symptom didn't come back.
I haven't heard of this happening with other people cleaning the MAP, so I'm worried maybe I damaged it? Or maybe it just didn't like being unplugged, even though the car was never running while it was unplugged.


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## Snipesy (Dec 7, 2015)

Well the MAP sensor has some learning system so that when it does get caked up it is still functional. So it not behaving for some time and then spontaneously working as it readjusts isn't too unordinary.

There is a reset function but ain't nobody got time for that. Just drive.


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## BodhiBenz1987 (Jan 13, 2018)

Snipesy said:


> Well the MAP sensor has some learning system so that when it does get caked up it is still functional. So it not behaving for some time and then spontaneously working as it readjusts isn't too unordinary.
> 
> There is a reset function but ain't nobody got time for that. Just drive.


Thanks, I was kind of surprised it never threw a code before as bad as it looked, but I guess if it was continually relearning that would avoid that. My Jeep would throw codes with even a little gunk in the MAP sensor, but being a 2005 I'm sure it was a more primitive system.


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## Cruz15 (Mar 17, 2016)

Where is that located in the engine bay?


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## BodhiBenz1987 (Jan 13, 2018)

Cruz15 said:


> Where is that located in the engine bay?


It is between the engine and the firewall, about halfway along the intake manifold maybe a bit more to the left (if you are facing the car). It sticks into the intake and is held down by a torx screw. You can kind of see it with the engine shield in place but easier if you take the shield off.

Seeing how gross the intake looks, I wish I could take it off and clean it, but R&Ring the intake looks like a nightmare job.


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## Cruz15 (Mar 17, 2016)

I looked for it when I first got the car I will look again. Thank you.


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## BodhiBenz1987 (Jan 13, 2018)

Cruz15 said:


> I looked for it when I first got the car I will look again. Thank you.


Here is a photo showing the location.


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## Cruz15 (Mar 17, 2016)

Ok thank you.


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## Cruz15 (Mar 17, 2016)

How in the world does thats sensor come off? From the connector.


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## BodhiBenz1987 (Jan 13, 2018)

Cruz15 said:


> How in the world does thats sensor come off? From the connector.


When you slide the little white tab all the way up, you can then squeeze the white tab, like pinch it like a clothespin, and it will lift a black tab inside the clip. I had to use a small screwdriver to prop the black tab up and gently push the clip apart but was _very_ careful having broken a connector before (on the MAF, which fortunately I could replace the clip housing for $2).
For what it's worth I think my codes were a result of having it unplugged or like Snipesy said trying to recalibrate itself. Today I drove it 80 miles and did not see a repeat of any codes. The car seems back to pretty much the same now as it has been the last couple months.


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## Cruz15 (Mar 17, 2016)

My sensor was a little lose I think everyone should check it to be honest. It is tight now, I cannot believe how dirty it was. Way more dirty than my Gen1 ever was it was plugged solid.


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## BodhiBenz1987 (Jan 13, 2018)

Cruz15 said:


> My sensor was a little lose I think everyone should check it to be honest. It is tight now, I cannot believe how dirty it was. Way more dirty than my Gen1 ever was it was plugged solid.


Were you having any issues prior to cleaning it? Just curious. I wasn't having any specific problems, other than my longstanding frequent regen issue and a slight dip in highway mpg over the last couple months or so. No change after cleaning so far but it seemed like a good maintenance item. I was surprised too, and at how dirty my intake is. I know this is inevitable with an EGR system, but I don't remember my Jeep or Mercedes (both diesel with EGR) ever looking that bad. The Jeep would throw codes for much less on the MAP though; I assume the modern sensor is designed to be less sensitive to being covered in glop. My pressure and temp readings seem to be the same as when it was filthy.


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## Cruz15 (Mar 17, 2016)

My Gen1 intake stayed pretty clean my Gen 2 is disgusting. Not sure how I am going to clean it. Is it something GM can do?
To the Diesel Techs around. Clean the whole intake, is it something GM offers? 
After cleaning the Map sensor it seems my snappy acceleration is diminished with cleaning the map. How would that even work?


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## BodhiBenz1987 (Jan 13, 2018)

Cruz15 said:


> My Gen1 intake stayed pretty clean my Gen 2 is disgusting. Not sure how I am going to clean it. Is it something GM can do?
> To the Diesel Techs around. Clean the whole intake, is it something GM offers?
> After cleaning the Map sensor it seems my snappy acceleration is diminished with cleaning the map. How would that even work?


Looking at the AllDataDIY instructions for removing the intake, it's not something I would even think about doing under warranty myself ... a lot has to come out and be disturbed. That said I don't know if it can be cleaned in place. I would worry about large chunks going into the valves or combustion chambers and maybe causing issues. It's something I plan to ask the dealer whenever the car goes back since the regen problem wasn't solved by the last repairs ... I will probably wait until things have eased restriction-wise.
Mine seems about the same acceleration-wise as pre-cleaning though I haven't pushed it much in the last day, today I took a more leisurely cruise. Based on what Snipesy said in his post responding to mine, I would say maybe yours is just relearning values after learning over time in its previous state. I would give it some driving time and see if it comes back.


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## Cruz15 (Mar 17, 2016)

Since cleaning the map I have definitely lost power with no codes. Not sure how long the training lasts.


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## Snipesy (Dec 7, 2015)

Cruz15 said:


> Since cleaning the map I have definitely lost power with no codes. Not sure how long the training lasts.


Assuming the learning model is perfect. They are generally biased toward a certain point and if the MAP sensor really does get caked with soot more than likely that bias point also assumes the sensor is a forbidden chocolate cake.

The sensor would then give a higher reading which will lead to less boost. On modern diesels less boost means less NOx, more soot, more fuel economy, and last but not least more ‘pedal lag’.

On all modern diesels pedal lag beyond obviously being from the turbo is 100% dictated by the O2 sensor reading (or internal model in closed loop). O2 sensor sees lack of oxygen and demands MOAR oxygen... Which means the turbo needs to work harder which takes time annnnnnnd yeah engines are just marvelous creatures aren’t they.


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## Cruz15 (Mar 17, 2016)

Thank you Snipsey. I have all my power back and a little more, feels that way anyway. I didnt floor it and broke traction until I got off the throttle was not even 1/2 throttle. That never happened before. I think my car really needs a clean map. I think I am going to clean it once or twice a month.
TC could not reel it in.


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## chadtn (Feb 27, 2018)

Cruz15 said:


> Thank you Snipsey. I have all my power back and a little more, feels that way anyway. I didnt floor it and broke traction until I got off the throttle was not even 1/2 throttle. That never happened before. I think my car really needs a clean map. I think I am going to clean it once or twice a month.
> TC could not reel it in.


Did you have to do anything after cleaning it, or did it just need some drive time before you noticed a difference?

Thanks!

Chad


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## Cruz15 (Mar 17, 2016)

It just needed some time. I put a couple hours driving each day and on the third, after start it felt better. Power was restored.


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## BodhiBenz1987 (Jan 13, 2018)

Cruz15 said:


> Thank you Snipsey. I have all my power back and a little more, feels that way anyway. I didnt floor it and broke traction until I got off the throttle was not even 1/2 throttle. That never happened before. I think my car really needs a clean map. I think I am going to clean it once or twice a month.
> TC could not reel it in.


Glad yours ended up being a positive result. I don't think mine has really changed since I cleaned it one way or the other, after 200 miles. Though as shown in my picture I couldn't get mine completely clean. At least it didn't seem to hurt like I initially feared. It wasn't bad to begin with before the cleaning, like I wouldn't describe it as slow, but I feel like over recent time it's gotten sort of "boggier" when I try to rev high, plus I find I have to shift a little later than I used to (less low-end power). And my highway mpg has been down ... the numbers are still good, but overall it's not a trend I want to see in combo with the car still sometimes doing a regen every 100 miles. I never know whether to drive it hard or not, it makes me cringe thinking of something potentially being clogged, stuck, broken etc. But I know driving it too lightly can make stuff clog worse ... so it's a catch 22.


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