Error Code U0100 - Drivetrain Malfunction

[kjdeion21]

Hello everyone, I recently put catless downpipes on my car. I have deleted the resonators and I am waiting on my JB4 tune to come in. I have also been driving the car with no issues for about a few days with the catless downpipes and it runs amazing. I am also waiting on the fabspeed muffler delete to come in for the car... the other day I was driving the car and I got on it a bit and got it to about 5000 rpms in 2nd gear and all of a sudden the car went into limp mode and immediately stated there was a drivetrain malfunction and it started behaving like there was a cylinder misfire. I safely got to my destination and it was turned off and detailed. When I started it back up there were no issues again while driving it, but when I gave it the beans again it did the same thing. Since then I have turned it off and on and it runs fine while driving normally around town and if i get on it a bit it is okay; however, as soon as I punch the throttle I get the same error code and the car goes into limp mode. I went to have the codes read as I thought I was experiencing a misfire, but upon getting the codes I noticed that I initially threw a code for Power Train system P0420 and in the Secondary DTCs the first code on the list is U0100 - Lost communication With ECM/PCM "A" and this seems to be the valid code...

Has anyone experienced this problem and if so what could it be, I have checked everything and it just doesn't make sense for what I am doing.

Any advice on this?

[ruben356]

Originally Posted by kjdeion21

Hello everyone, I recently put catless downpipes on my car. I have deleted the resonators and I am waiting on my JB4 tune to come in. I have also been driving the car with no issues for about a few days with the catless downpipes and it runs amazing. I am also waiting on the fabspeed muffler delete to come in for the car... the other day I was driving the car and I got on it a bit and got it to about 5000 rpms in 2nd gear and all of a sudden the car went into limp mode and immediately stated there was a drivetrain malfunction and it started behaving like there was a cylinder misfire. I safely got to my destination and it was turned off and detailed. When I started it back up there were no issues again while driving it, but when I gave it the beans again it did the same thing. Since then I have turned it off and on and it runs fine while driving normally around town and if i get on it a bit it is okay; however, as soon as I punch the throttle I get the same error code and the car goes into limp mode. I went to have the codes read as I thought I was experiencing a misfire, but upon getting the codes I noticed that I initially threw a code for Power Train system P0420 and in the Secondary DTCs the first code on the list is U0100 - Lost communication With ECM/PCM "A" and this seems to be the valid code...

Has anyone experienced this problem and if so what could it be, I have checked everything and it just doesn't make sense for what I am doing.

Any advice on this?

I would refrain from driving the car hard until you get your tune in. Possibly just happening because the car on the stock tune cannot compensate, or does not know the cats are missing. The signals between the catalyst or O2 module and PCM are inconsistent and possibly just flagged as a fault.

[kjdeion21]

Originally Posted by ruben356

I would refrain from driving the car hard until you get your tune in. Possibly just happening because the car on the stock tune cannot compensate, or does not know the cats are missing. The signals between the catalyst or O2 module and PCM are inconsistent and possibly just flagged as a fault.

Okay, this is the common idea that many of us are thinking... we think the tune is going to take care of the issue since we are having that issue once I did all this... so the fuel to air ratios and such are messed up. I did email the tuner and asked them if they have heard such a thing and if their tune will allow me to specify catless downpipes and such.

[M5_Raz]

It's not the tune, these cars run well with catless downpipes and no tune. I had a similar problem after going catless and spent a ton of money and time at various shops trying to find it.

Check your connections to the DMEs. I had a loose connection that would cause the car to buck and hesitate at higher rpms. This was because the wire was getting pulled out of its place. Also no codes, but an unrelated sensor one.

Hope you get it fixed soon.

[kjdeion21]

Originally Posted by M5_Raz

It's not the tune, these cars run well with catless downpipes and no tune. I had a similar problem after going catless and spent a ton of money and time at various shops trying to find it.

Check your connections to the DMEs. I had a loose connection that would cause the car to buck and hesitate at higher rpms. This was because the wire was getting pulled out of its place. Also no codes, but an unrelated sensor one.

Hope you get it fixed soon.

Yes, I have not installed the tune yet... this happened about 5 days after I had the downpipes installed... you are correct, these cars run perfect and should run well with the downpipes as I have a friend that did the same and has no issues and has been running it for 5000 miles with no issues, I did check the connections on the DME's but I feel limited in what to check... I can see the connections feel strong and I do not want to disconnect anything. I did have issues when plugging the ground back on when I first installed the down pipes and I was doing a test turn on, but we immediately discovered I forgot the grounds, and we put them on and the car started fine. Any other advice or ways to check the connections? Thanks I appreciate the help.

[M5_Raz]

Originally Posted by kjdeion21

Yes, I have not installed the tune yet... this happened about 5 days after I had the downpipes installed... you are correct, these cars run perfect and should run well with the downpipes as I have a friend that did the same and has no issues and has been running it for 5000 miles with no issues, I did check the connections on the DME's but I feel limited in what to check... I can see the connections feel strong and I do not want to disconnect anything. I did have issues when plugging the ground back on when I first installed the down pipes and I was doing a test turn on, but we immediately discovered I forgot the grounds, and we put them on and the car started fine. Any other advice or ways to check the connections? Thanks I appreciate the help.

My problem showed up a few weeks after installing the downpipes, which made me doubt it was even related. It's definitely not the tune, don't believe anyone that says a tune will adjust the air/fuel because the DMEs do that on their own.

Unfortunately that's all I was told by the shop, that a DME connection was loose. I took it to about 3 shops in total, one of which was a dealer, over the course of like a month. I was ready to sell it until the last shop found the issue. Where are you located?

[Kamate]

Just unclip your DME connectors and reinstall them, disconnect your battery ground first. When installing the connectors, push them fully into the DME without using the locking lever. If you use the locking lever to pull them together the plug will not fully engage the pins. The plugs must be fully pushed into the DME then locked with the lever!

[kjdeion21]

Originally Posted by M5_Raz

My problem showed up a few weeks after installing the downpipes, which made me doubt it was even related. It's definitely not the tune, don't believe anyone that says a tune will adjust the air/fuel because the DMEs do that on their own.

Unfortunately that's all I was told by the shop, that a DME connection was loose. I took it to about 3 shops in total, one of which was a dealer, over the course of like a month. I was ready to sell it until the last shop found the issue. Where are you located?

I am in Houston, Texas... I see what you are saying about the DME's but I have checked all that... well I went ahead and installed the tune a few days ago and I have driven nearly 200 miles on it with no issues and it actually runs smooth but I am waiting to really jump on it because it keeps giving me a misfire code under heavy load, well I got the NGK Laser Iridium 2 step colder plugs on the way, and Bosch Coils and I will install them next week and it should take care of the issue. Thanks for the advice... I think it is time for them to be changed anyway.

[kjdeion21]

Originally Posted by Kamate

Just unclip your DME connectors and reinstall them, disconnect your battery ground first. When installing the connectors, push them fully into the DME without using the locking lever. If you use the locking lever to pull them together the plug will not fully engage the pins. The plugs must be fully pushed into the DME then locked with the lever!

Isn't this a little dangerous to mess with those, I mean I have checked them over and over again and made sure they were lock tight and it seems fine, I just need new plugs and coils for sure, which are coming in next week and I will install them and in the mean time I just wont punch it past half throttle while driving around town just for a week and it drives beautifully. Thanks

[kjdeion21]

Originally Posted by M5_Raz

My problem showed up a few weeks after installing the downpipes, which made me doubt it was even related. It's definitely not the tune, don't believe anyone that says a tune will adjust the air/fuel because the DMEs do that on their own.

Unfortunately that's all I was told by the shop, that a DME connection was loose. I took it to about 3 shops in total, one of which was a dealer, over the course of like a month. I was ready to sell it until the last shop found the issue. Where are you located?

Oh wow really the DME's were loose.. they say to disconnect and reconnect but that makes me nervous playing with those, but I have checked them over and over and made sure they were plugged in and everything was good, so I think mine needs plugs and coils which are on their way and I will install next week. And you are correct mine showed up days later after the downpipes which didn't make sense for the downpipes to cause this... that being said when I installed the tune it has run so much smoother its amazing and I am only on a non aggressive map... thanks