# 08 rabbit - P0101 and p0102, CAI and UM tune



## nekkidlad (Oct 4, 2013)

Sorry this post is very long, trying to give the most info I can off the bat for anybody trying to help.

I had my rabbit UM tuned 93 octane stage1 a few months ago, haven’t had a problem at all until my engine light came on about 5/6weeks ago - still had the OE intake/air filter box/engine cover on. Idles ok, runs ok. Pulled the code had a p0068 map sensor something or other. Cleared it, drove it, didn’t come back. About a week later engine light came back on, still idles and drives ok. Checked codes, it says p0101 maf sensor something or other. Again cleared it, drove it, didn’t come back. 

About another week later engine light came back again still drives and idles ok. Check it P0068 again, open hood, look around, nothing looks loose/broken, checked maf and map no sensors disconnected and any other connectors I can clearly see. Ok, cleared code again, checked live data(have a pocket code reader with limited live data monitoring) it SEEMS ok to me, nothing out of the ordinary. Drive it again, still nothing noticeable, aside from the engine light.

Went on like that bouncing back and forth between p0068 and p0101 for a few weeks. Would come on only one drive about every week, but idles and drives ok. Cleared codes, looked around engine for anything no obvious found nothing, and be fine for about another week.

Finally one week I had enough, took the intake off and tried to install my cai - again(had previously tried it but it didn’t quite seem to fit right - pipe was just too long, so put oe stuff back on). While disconnecting the intake piping found the sai tubes were clicked only one side of the 2 little clips, so I assumed that was the issue and didn’t really think of it again. Tried and tried and tried to fit the CAI in, but eventually was forced to cut off 1.5in from the throttle body side to make it fit. 

Why did I have to cut it? I bought it used 2nd hand from another member and he said he had issues installing it in his rabbit. He claims it’s a BSH CAI kit, however only the filter has a BSH logo and based on me looking up info on why I couldn’t install it the intake tube looks not quite right, but I don’t know if there’s some kind of different early vs late model design or something like that. He said eventually he did get it to fit - kinda wonky tho. But I couldn’t for the life of me. I assumed it was because I had recently replaced an engine mount and my engine was kinda shifted over, however I proved that was not the issue by loosening my the engine mounts and shaking it all around trying to fit it to no avail. The mounting tab it had for a bolt at the fender would line up but it’d be too long to reach the throttle body so the tube would only fit if it was physically on top of the throttle body, or the throttle body would KINDA line up but the sai tubes, maf and mounting no tab were about 1.5in from where they needed to be. So after about an hour of trying to move the engine and trying to jam this tube in, out comes the pipe cutter and now it fits perfect - throttle body lines up, SAI tubes line up, maf lines up and wires have slack. Put it al back together and it’s good. Drove for a few days no problem, no codes. Here’s a picture for reference. 

Now about a week later I have a constant p0101 maf range performance and p0102 low voltage, p0068 has not returned. I’ve cleared them but they come back after a day at most, if not on the test drive. I don’t notice any abnormal idling or driving, mpg seems the same as before the codes(based on the dash mpg and fuel tank mileage readings). I’ve checked to see if the SAI tubes are loose or anything else and can’t find any problems. I have to get them to check maf wiring to see if it’s ok tho.

Looked on forum the other day and earlier today, found it’s possible it’s the maf sensor gone bad. Also possible it’s a problem with the tune and the cai. However(even longer story - bad service), I wish not to return to the tune shop to get diag or retune, and I’m trying to see what I can do before contacting UM - if I need a retune, I’ll mail them my ECM.

I don’t have vagcom(been looking on and off since I bought the car to get some coding no done) and so far haven’t been able to locate one near me - thought of buying obd11, but with my code reader I don’t really NEED it or justify the price for just turning off drls and changing lock patterns. If anybody has vagcom that’s willing to help please contact me, I’m in Bastrop Tx(near Austin).

Again I have limited live data I can monitor, let me know if you want some values and I’ll provide the best that I can. Anybody have any further input or things to check?


----------



## nekkidlad (Oct 4, 2013)

Forgot to mention one reason it could be the tune and CAI is because I found another member having issues with a tune and BSH CAI as well, from a few years ago(I’ll have to find it again later tho for reference). Apparently that member was having p0068 and/or p00101 but only if there was rain in the area(that day or a day or 2 after depending how wet it stayed around). But ran fine after it was nice n dry out. They did a bunch of diag and replaced the maf but found nothing worked. Talked to UM anf apparently their tune was FOR a engine with a CAI, so they had UM reflash with a NON-CAI tune and their problem went away. Apparently when that was going UM knew there was a problem specifically with their stage1 tune and a BSH CAI, but the shop the car was at tuning didn’t know. So UM said try that, it should fix it, if not we’ll try adjusting another tune. And their problem was solved with just flashing it to a NON-CAI tune.

Recently in my area it has been raining and sprinkling much more than usual(hurricanes and tropical storms residue), but I can’t remember if it was or not on the days I had my engine light come on. And the last few days it’s been constantly wet out - so it matches kind of with the other member’s info. 

I’ll look it up again and put up the link for reference if anybody needs it.

EDIT: Here’s the thread I was referencing.
https://forums.vwvortex.com/#/topics/6077894?page=1


----------



## Ichabod0525 (Feb 11, 2018)

MAF output voltage will help point you in the right direction. You are looking for a *linear* rise in voltage as RPM increases. *This helps explain it*. You can use a digital VOM instead of a scan tool and graph volts instead of grams per second. When you're done you'll know if its the MAF or not.


----------



## nekkidlad (Oct 4, 2013)

I’ll have to find and dig out my dvom, in the meantime I’ll check to see if I have a data stream for the tps and or maf voltage jic.

I know it had something measured in percentage for the throttle(input I’m assuming) and I know it measures the maf, but I’ll have to see exactly how/what it measures again. I’ll put up any findings/measurements after. 

EDIT: went out and checks w live data and it shows maf reading 0.0lb/m. Always.

Yeah, that’s normal...And I remember seeing a reading there before.

When it’s not dark out I’ll check the maf itself for dirt and/or loose/broken wiring tomorrow.


----------



## nekkidlad (Oct 4, 2013)

Well I haven’t been able to get to storage and find my DVOM...

BUT, I did have to move stuff around my place because it was just in the way. One of which was the oe intake parts. I was looking at it and just out of curiosity was looking where the maf mounts. I noticed 2 things. So I compared it to the new intake, it appears the stand off where it bolts to is about 1/4 taller on the new intake. Also the sensor position appears to be 180 from the OE positioning.

I don’t know how that affects the maf sensor(not reading at all vs just getting an incorrect reading). But I figured it put it out there if it helps.

I did look around at the wiring on the sensor and it all appears ok, no loose terminals or broken wires at least from the sensor to just behind the battery where it connects to another harness.


----------



## GTIVRon (Jul 24, 2009)

Had a bunch of MAP/MAF related codes on both my wifes MK5 2.5 as well as my moms MK6 2.5. The bolts for the intake manifold were loose. Well a bunch of them near the middle. I forgot what size torx it was but needed to reach a was under the intake manifold.

Was the car running/revving when reporting 0.0 from the MAF? Might be silly but rotated 180 degrees is the MAF still installed with the "inlet side" towards the filter?

Regarding the different MAF placement, once you get signal from it again it may be worth while getting a log of that data, install the stock intake and get that data to compare. I'd say keeping the stock sized housing around the MAF is more important than placement, but air speeds aren't uniform in the entire tube so not being in the same spot relative to stock could possibly affect things.


----------



## nekkidlad (Oct 4, 2013)

Yes, the car was running when reporting 0.0lb/m. Idle, revving and under load - same reading. I’ll try to make a video of the thing today if I can. Because it’s very exiting to see a measuring block not change reading.

A while back I had looked at the data(when I first bought the CAI) when the Oe intake was on because I wanted to see if/what difference the IAT would be when I finally installed the CAI. I scrolled through the thing, and I swear I remember seeing a reading on the MAF before. 

Also scrolled through when checking and verifying these codes before, again I remember seeing a reading but I just don’t remember what as I wasn't really looking for it, just checking there was one in there.

I’ll try installing the OE intake tube(at least till the MAF housing section) and check again.

Not looking forward to disassembling half the engine bay and wheel well to do it😩. O well.


----------



## nekkidlad (Oct 4, 2013)

Had been having issues after installing a CAI. Kept getting maf codes. Finally got around to testing rotating the maf 180* because I thought for some reason the maf was backwards than it should be, and my pocket code reader with data showed 0.0lb/m. 

After Rotating it it now shows hovering around .75lb/m at idle and has a reading at all points of rpm. Also noticed as soon as I started reading the maf the fuel trim went crazy lean for a while - STFT -25% for a while at idle(I’m assuming while it adjusted for finally reading a maf). Now it’s hovering around -7% at idle.

Car seems like it’s idling and running a bit smoother than it had been for the last while. Still have to take it on the highway tho, since I’m still at work.


----------



## nekkidlad (Oct 4, 2013)

Actually thinking about it, since the trims are negative, it’s actually running rich and it’s trying to lean it out.

Also, I just adjusted the maf sensor - because the sensor stand-off is rotated 180* when you try to fix it it has to sit at an angle is you want to use only one hold down screw - and it’s reading a bit better. Started it up let it warm up and checked the reading - was around .8lb/m, rotated it over and it was reading about .93lb/m. Just for double checking sake, put it back the way and it was and saw .8lb/m again. Then rotated it again to the other screw hole and back up to around .95lb/m. Also for kicks and grins, did a cap discharge after then test drove it for a few miles, but found nothing significant compared to driving home from work last night(after adjusting the sensor the first time).


----------



## nekkidlad (Oct 4, 2013)

So...after about 20 miles drive the engine light came on, p0172 bank 1 system too rich. No smoke or fuel smell from exhaust, runs smooth. So I went ahead and rotated the maf sensor back to the original direction I had it. 

Cleared the light, still reading ok, another test drive about 20 miles jic. No light. Great.

Now today I’m driving it again at work, has about 100 miles total since I cleared it. Engine light came on and saying p0172 system rich again. It doesn’t seem like it’s running bad, I don’t see any smoke or smell fuel from the exhaust, runs smooth.

Blah. I think I’m gonna get an injen intake when I get the chance. This one is turning out to be too much hassle. If anybody has one to get rid of, lemme know. 
Maybe we can trade for this gem🤣.


----------



## GTIVRon (Jul 24, 2009)

Unless you're affecting the position of the MAF in the air stream, rotation of it should not really influence the reading you're getting. That seems more like damaged wiring.


----------



## nekkidlad (Oct 4, 2013)

GTIVRon said:


> Unless you're affecting the position of the MAF in the air stream, rotation of it should not really influence the reading you're getting. That seems more like damaged wiring.


I looked at the wiring before all the way from the maf to where it goes into another wiring harness, but I’ll have to look at it again then, see if I find anything I may have missed.

It’s definitely not stretched out, it’s got enough slack for engine movement(which is already reduced by stiffer trans and dogbone mounts).


----------



## nekkidlad (Oct 4, 2013)

Checked wiring again found no issues from the maf to where it joins another harness at the firewall.

Pulled on the wires to see if any loose pins at connector or broken wires, flexed them around to see if the insulation was broken or breaking. Plugged in my reader and checked maf readings while wiggling and pulling on wires. Readings stayed pretty much constant, they did vary a bit but nothing significant.

Still having the stft go way out to -25%. Before it went there but then came down to about -7% or so after about 10mins. Now it’s just staying there and not moving. Im almost starting to think maybe the O2 sensor may be going bad. I checked the readings for it voltage and MA. Of course I don’t remember now what they were, but they vary and didn’t seem like it’s flat dead or pegging out. I’ll check again later and update with the actual O2 volt and MA readings jic.


----------



## GTIVRon (Jul 24, 2009)

That all is very odd. remember though small change scale.. not seeing large change with a measure of 1 g/s change at 3-4 g/s idle is a lot if you scale it as a percentage at, say 180 g/s.

And the fuel trims....

If you unplug the MAF the ECU will substitute a data table of what the reading should be. I'm not sure if fuel trims will be active but short term corrections should still happen based on O2. Taking out the O2 sensor (MAF plugged back in) it's likely going to assume lean and run a richer fuel map.

I suppose you could unplug the O2 sensor and see if the car feels like it's operating differently. If it's weaker and smells richer it may be an indication the O2 sensor is OK.

I would unplug the MAF at this point. Clear codes, warm up, and monitor fuel trims/corrections. See if trims work to begin with and log fuel correction and compare to with the MAF plugged in. All this assumes you have the stock intake manifold and throttle body and are tuned for stock IM and TB. If the trims look better or the car just runs better overall, I'd say the MAF is the issue.

Did you ever run an oiled air filter on that MAF?


----------



## nekkidlad (Oct 4, 2013)

Unfortunately lb/m is al I have available because I just have a matco pocket code reader with live data...

I’ll try checking data with the maf unplugged and/or the 02 unplugged. I meant to do the maf disconnected before but just didn’t. Don’t ask me why, I shoulda known better..lol

Also I bought the car used and had the oe intake, I doubt it ever had another kind. I’ve never put on an oiled filter and the one I have on is a dry style cone filter. So I know there’s no oil on the maf from me.

I do have a UM stage 1 tune and it’s supposed to be for a cai and exhaust(which I still need to get). But I don’t think that would make it so rich out of the blue ONLY after installing a cai.

It has the original intake manifold and tb as far as I’m able to tell, doesn’t look like it’s been replaced or removed. Only real difference is the cai. I started having troubles only after I started moving stuff around and tried to install the cai the first time, so I’m pretty sure it’s somehow related. But the issue is the codes keep changing. First it was maf and/or map, now rich code.


----------



## nekkidlad (Oct 4, 2013)

Ok so checked the fuel trims, O2 and maf readings today at idle and while cruising around 65mph on cc.

-Stft was between -1% and +2% during cruise and around -3% at idle
-Ltft was pegged at -18.8% the whole time I looked at it
-Maf was fluctuating around at cruise, and at idle it was around .73lb/m, +/- .2lb/m or so

Upstream O2 at idle
-.060/-.033ma and amps goes up w rpm up
Downstream O2 at idle
.8-.810v and voltage goes down w rpm up 

So far 314mi since last code clear and no codes yet, not trying to jinx it. If the mil comes on again I’ll start unplugging things and testing some more, for now I’ll leave it alone.

Being the ltft isn’t changing at all, I would almost think the downstream o2 is malfunctioning, but the readings from it vary...(but it could be out of range...)


----------



## Ichabod0525 (Feb 11, 2018)

Not sure about your Amps reading on the upstream. A normal upstream sensor operating on a warmed-up engine will constantly switch between 0.1 Volt to 0.9 Volts DC.


----------



## nekkidlad (Oct 4, 2013)

Ichabod0525 said:


> Not sure about your Amps reading on the upstream. A normal upstream sensor operating on a warmed-up engine will constantly switch between 0.1 Volt to 0.9 Volts DC.


Unfortunately upstream MA and downstream V is what I can read as far as O2 reading, can’t switch them around. I know the downstream should be pretty steady since it reads mostly catalyst efficiency, and the upstream should vary in voltage as it’s the one before the cat reading directly out of the engine.

I just don’t think the ltft should be stuck on -18.8% at all times, and what could be the reason? I wish I had a better scanner but I kinda have to work with what I have. I wonder if that’s something in the tune, tho it’s changed from -25% like it used to be when I first installed the cai, adjusted the maf and cleared codes.


----------



## GTIVRon (Jul 24, 2009)

-18.8% may eventually trigger a cel. I think over 15% either way. 

If there's bad data or the tune is way off the number won't freeze, it zeros out. The more miles you put on the more steady that value. Think of it as a constantly running average, values swing around a bit, but as you populate more data the average overall becomes fairly consistent. I wouldn't be alarmed by that. 

What I would do next, though, is clear codes (erase fuel trims), unplug the MAF and see if LTFT starts to populate. If it does, drive until you have enough miles for the LTFT value to stabilize. If it gets closer to 0 good chance the MAF is reading high, and likely indicative of a problem with the intake. (Size or shape of housing and relative position of the sensor in the air stream. 

Sent from my SM-G950U1 using Tapatalk


----------



## nekkidlad (Oct 4, 2013)

GTIVRon said:


> -18.8% may eventually trigger a cel. I think over 15% either way.
> 
> If there's bad data or the tune is way off the number won't freeze, it zeros out. The more miles you put on the more steady that value. Think of it as a constantly running average, values swing around a bit, but as you populate more data the average overall becomes fairly consistent. I wouldn't be alarmed by that.
> 
> ...


The tube itself is around 3” (I’ll have to measure for an exact size, it matches the TB outer diameter - whatever that is). I wouldn’t doubt it’s actually the same size as oe size tubing, just metal and different routing. If I had to say, it looks smaller than the injen intake I had on my 09(but that one didn’t have a maf).

Maf location is about the same distance away from tb as oe, but the standoff for it is about 1/4” taller than oe and it’s 180 degrees compared to oe(hence I have the sensor actually at an angle because I rotated it around to oe direction plus/minus a bit to be able to still use one retaining screw).

I’ll check the codes see if anything shows pending. If there is or sets a mil, I’ll unplug and test.

Thanks for the help so far guys. Just for info, I was looking at o2 sense pricing and WOW they’re expensive...

~$70/ea for an economy one!? Jeez
~$180/ea for oe...🤯


----------



## GTIVRon (Jul 24, 2009)

Yeah unless you run a shop and have the parts, the days of "throwing parts at it" for testing are over, ha ha.


----------



## nekkidlad (Oct 4, 2013)

You still can, it’s just expensive


----------



## nekkidlad (Oct 4, 2013)

Ok so I finally got the mil back on.
Checked code again running rich(figured as much).

Disconnected the maf sensor and started it up, instantly got codes p0102 maf sensor low input and p0113 iat sensor high input - no surprise, it’s unplugged.

Checked the fuel trims and sure enough stft is at -8.6% at idle and between -6% and -8% at cruise, ltft is 0% always.

So I’m thinking the maf just went bad. It’s just weird to me that it went bad exactly when I installed the cai(unless of course something I did is what made it go doa).


----------



## GTIVRon (Jul 24, 2009)

Did you try driving it? Need to be over I believe 166°F coolant temp and have reached 3k rpm. Possibly less. See if it starts to populate anything.

I still think your intake is the problem. With 0 ltft and your short term at only -8% it's a lot closer than it was (with -18% ltft already applied before short term corrections). Also, with the IAT also not getting a signal you'll be running a slightly richer mix since it's going to default to lowest ambient temp map (meaning negative trims will happen). I think you're seeing better values because the map the car defaulted to for MAF data is closer to actual than the bad data due to the intake.


----------



## nekkidlad (Oct 4, 2013)

I drove it about 45miles from work to home when I was getting those readings.

The iat showed -40f...
I left the logger on to see if it changed and kept monitoring it, but it stayed constant as long as I wasn’t going up/downhill too much.

If it IS the intake I would say it doesn’t surprise me. It’s just too much hassle so far to make it fit and work if it’s “designed for this year make and model”.

I emailed bsh before trying to verify if it’s theirs(as it was claimed in the sell ad to be a bsh intake, but no reply). Also the seller says he had it installed on his car but the tubing was way too clean and the hardware didn’t look used thinking back...just the filter itself looked like it had SOME use.

Not really related to the codes n such but also ever since I installed it it just doesn’t sound right, I’ve had cai’s on all my cars before and this one just doesn’t sound the same, honestly it sounds like the stock intake. Doesn’t have that distinct sucking/induction noise. And (on a good note) doesn’t have that loud vacuum cleaner SAI startup noise either. I really do think when I have money again I’ll just ditch this one and buy an injen one like I had on my old jetta.


----------



## GTIVRon (Jul 24, 2009)

Probably your best bet to replace it yeah.

May not notice much of an induction noise due to the poor intake manifold design. If it chokes flow that much maybe sound with it? Possibly part of why it was made this way. Still have the stock airbox on ours so not sure.


----------



## nekkidlad (Oct 4, 2013)

I’m not too familiar with the 08 and earlier 2.5, but the 09+ have a very noticeable sound difference with an intake installed, specially at high rpms.

I can’t imagine it to sound any different tho since it’s the same intake design, just adding a maf.

Here’s a video (from inside the car), for reference - it’s from my first 2.5 jetta with an intake many years ago.
https://youtu.be/qiJFOuOJDb4
And here’s one of cold start under the hood.
https://youtu.be/3ZTkO4kmKu4
Here’s a stock vid under the good for comparison.
https://youtu.be/qVS12lr4ysM


----------



## nekkidlad (Oct 4, 2013)

So one update is I had been driving around with the maf unplugged for a few weeks(seemed to make my fuel last a bit longer).

About 2 weeks ago my battery finally gave up, so put a new one in. In the process also plugged in the maf again just for kicks to see if it made any difference. Now my mil light keeps coming and going, haven’t had the chance to plug the reader in because I took it back to storage. It’ll come on for a few days, turn off for a few days.

When I plug in and see what the codes and data are I’ll update more.


----------



## flowmastergfunk (May 31, 2007)

Granted, I haven't read every word of this thread...but since you still appear to be having issues... did you ever realize your MAF sensor was installed backwards? They are certainly directional, and I can see that it is backwards in the first picture that you shared.


----------



## nekkidlad (Oct 4, 2013)

Maf direction already been addressed.
The design of my CAI tube won’t allow me to fix it(properly), so it’s kinda diagonal a bit now, but at least heading in the correct direction.

Last night I got the data looked at, even tho there is no current mil light on, it says there’s a hard code(still p0172 bank 1 rich).

At cruise(~45mph) found stft stil rich and is reading “better” at -14.1%. Ltft is -5%, maf read around 1.10lb/m.
Also while at storage picked up the maf section of the Oe intake and going to(when I have time) to just install it as a temporary “short ram intake” and see what that shows.

On a completely unrelated note, bought some oil and filter(for an oil change), and also bought a can of seafoam intake spray stuff(probably won’t fix it but, but I’ll pretend it did SOMETHING).


----------



## GTIVRon (Jul 24, 2009)

Careful with the seafoam if you have nosy neighbors. Not the last time but previous time I treated my Corrado local fire department showed up.


----------



## nekkidlad (Oct 4, 2013)

So a few days ago, had a misfire on my way home from work. On my 1hr drive home about 2 miles from home it starts to stumble. Awesome.

I limped it home and parked it, looked into it the next morning cyl2 misfire. Figured it’s either a coil pack or plug so swapped coil to cyl3 and plug to cyl1. Started it up and it ran smooth and fine. Drove around theneighborhood and was just fine, took it to the main road and put try e floor down, and it fell on its face , misfires and mil starts to flash. Pulled codes and found cyl5. Wtf? Had too many other things to do and go to work, so just parked it again for another day.

Next day again, cleared codes left it as is and drove it around again, all smooth til the main road again. Same thing,fall on its face misfires mil flashes. Pulled codes again this time it shows cyl3. Jic to make sure it isn’t tricking me I swap the coil again to cyl1 and drive again. This time right away it jumped to cyl1. Ok good, it’s official coil was bad.

So check into rockauto for a return - because I just put in a set or coils and plugs from them about 8 months ago and a bunch a maint stuff when I bought the car. So because of the holiday season and delayed shipping it’ll take around 2 weeks to get a warranty exchange. So in the meantime went to advance auto and bought a coil there, slapped it in and it drives fine now.

Hopefully when the new ones comes in from rock auto I can return the one to advance no problems and then it’s just a warranty free replacement like it should be.


----------

