ECU Tune and Limp Mode

[sandcam]

Quick question... I've had an issue with my MTM tune where almost every 2 weeks the tune just turns off and the car goes into a non boost limp mode. I finally gave up and started to work on a custom tune with a local Audi/Porsche tuning shop. We are still running into the same issue where every 2-3 weeks the car goes into this non boost limp mode. We looked into it being mechanical but everything checks out ok. It's almost like the ECU after a certain amount of time is overriding or somehow bypassing the tune and going into a safemode. Scanning for codes gives us nothing.

[ben916]

What do you have for mods?
Please list everything...

What does VAG-COM say?
ECU = MTM
TCU = ???

[905084]

Need more data...heat, time, cycles...........and how do you get it out of limp mode?

[JSRS6]

Need more data...heat, time, cycles...........and how do you get it out of limp mode?

I'm guessing redneck reset...

[sandcam]

What does VAG-COM say?
P0601 Internal Control Module Memory Check Sum Error (only when it goes into limp mode)

ECU = MTM
It was MTM but went back to stock and then am working on a custom Tune to rule out MTM's tune but still having same issue.

TCU = ???
Yes, I currently have an MTM TCU

Need more data...heat, time, cycles...........and how do you get it out of limp mode?
I'm in the northeast so heat is not a factor as it has not been over 55 degrees while this problem is going on. Time, is roughly 2-3 weeks of good boost and then it just cuts off. I have been counting cycles on this last reset and I am up to about 10 full cycles (15min or more run time) and about 10 small cycles (4min or less). My guess is I'll get close to 20 full cycles in 2 weeks and then it will go into limp mode and throw the check sum error code. How I get it out of limp mode is good old fashioned redneck reset (unplug ECU) and then reflash it with the custom tune.

To give you more info we also had data written on the ECU to allow for program mode switching on my iphone www.speedport.us (http://www.speedport.us) We felt this data might be getting written over after @2 weeks or 20 full cycles give or take and then throwing the ECU into the check sum error and limp mode. We just reflashed without the iphone switching and just the modded Tune (no switching between stock, valet and tune modes this time) and we'll see if it stays away from limp mode.

[marklar182]

Could be a cold solder joint on the ECU board. Maybe remove the ECU and run a heat gun over the board IC's to reflow the solder and test again.

[905084]

I always have the internal memory checksum error. Product of the Sportec tune. Boost and checksum error are unrelated on mine. Are you just losing boost and then checking for codes? or do you check for codes even when it is working well?

[sandcam]

There are no codes when the boost is there. I only get the checksum error when the boost cuts out after about two weeks. This is the same symptom with the MTM tune and the custom tune. Both work fine for about two weeks and then the car goes into limp mode.

[JSRS6]

Sounds like a problem with the hardware, not the software...

[skribe]

Have you logged requested vs. actual boost? Is it possible your car is overboosting due to physical wastegate problems? Have you checked vacuum lines to the wastegates? Have you replaced your N75 valve?

Did you de-solder the MTM chip from your ECU? Wasn't aware you could flash over a physically chipped ECU if you didn't. Early MTM tunes did give checksum errors... but that should go away with the tune... but if you didn't physically remove the MTM chip, I would think that file would still override whatever is flashed to the stock ECU, and still deliver checksum errors.

Hoppen can update your MTM file for $100 if you send them the chipped ECU.

[sandcam]

requested and actual boost are spot on. Replaced the N75 valve, redid all hoses/vac lines

MTM chip was de-soldered as we thought that might be causing the issue.

Today is officially 2 weeks since we reflashed and roughly 20 full cycles (10minutes of drive time or more). Went right back into no boost mode today. I am completely scratching my head on this one. I'm thinking maybe it's some type of a bad ECU that goes into this limp mode ever 2 weeks or 20 cycles.

[sandcam]

Ok Car is back to bone stock and we're going to see if limp modes shows up in about 2 weeks or 20 full cycles.

[ttboost]

Any update on this? I suspect overboost? Do you have some boost spikes in your logs?

[skribe]

My car was doing the same shit. Just replaced the ECU with a factory fresh one. Will let you know if that cures it.

[sandcam]

Here's the update. We flashed it back to bone stock and the car has ran perfect for Over 6 weeks. My shop that did the custom tune did find that there is some type of tuning protection built into this ECU. After about a 2 week period the ECU checks itself for overboosting. If it recognizes that the car (with the new tune) has been requesting more boost and delivering more boost than stock....viola...limp mode. They are working on writing code right now to trick that part of the ECU. This custom tune is significantly faster than my MTM tune so I need to figure out a way to get this thing running full bore as doing a redneck reset every two weeks is painful.

Skribe, are you running an MTM tune with the limp mode issues?

[lswing]

Here's the update. We flashed it back to bone stock and the car has ran perfect for Over 6 weeks. My shop that did the custom tune did find that there is some type of tuning protection built into this ECU. After about a 2 week period the ECU checks itself for overboosting. If it recognizes that the car (with the new tune) has been requesting more boost and delivering more boost than stock....viola...limp mode. They are working on writing code right now to trick that part of the ECU. This custom tune is significantly faster than my MTM tune so I need to figure out a way to get this thing running full bore as doing a redneck reset every two weeks is painful.

Skribe, are you running an MTM tune with the limp mode issues?

Um, don't be so sure about what they are telling you. I've been running with way more boost than stock for a year now, no limp mode yet....

Are they saying it goes to limp because the actual numbers are not near requested, that makes sense, maybe some air leaks or something in your case?

What boost numbers are you getting, timing?

[ttboost]

I had been chasing this problem for months now also...done... tired...quit. I couldn't seem to find a correlation of when it went into limp mode as I have also had SAI issues and CEL's for that.
I have since recently reflashed it with a less aggressive tune and it's been fine. Don't even notice the 2PSI loss. My thought is: it goes into limp mode if it sees more "actual" than "requested" for a fixed period of time, a few times?

[4everRS]

My thought is: it goes into limp mode if it sees more "actual" than "requested" for a fixed period of time, a few times?
Mike, this is exactly it. If the ECU is getting more than it wants, it protects the engine by going to limp. Let's say that a piece of hardware fails, it kills the turbos to stop things from getting really bad. Did you recently have your tune brought down a little? I remember in the log you sent me, your actual was well above your requested. Made me think you had one of those fancy N75 valves. I know you said you didn't.

sandcam, I seem to remember that you had an MTM ECU. If so, MTM soldered chips onto the ecu for a while and if that what you have, your problems will likely persist. If I am mistaken, and you don't have a soldered-on chip, then I think you may need to consider a different tuner.

[skribe]

Skribe, are you running an MTM tune with the limp mode issues?

I was. The brand new ECU fixed it. 500 miles and no limping. Believe it or not, the ECU was still under the 8 year factory warranty for emissions controls -- my car was sold in April '04, manufactured in '04, sold as an '03 model.

I miss the extra 50hp but will live with the stock tune for a while. May try an APR or custom tune this summer if i do meth and piggy pipes.

[ttboost]

Yeah, we just put in a "production" flash. My flash was massaged.....car runs awesome now...