My wife was driving the other day and the engine light came on, car lost power and ran very rough and the PRNDS on the dash display started flashing. She was close to home and was able to get back to the house. I looked at it that evening and when I started it up the idle was very rough. I had a new coil so I replaced each one with the new one and found that the idle smoothed out when I replaced the one in the rear cylinder. The PRNDS would still flash each time it was started. I disconnected the battery for 15-20 minutes hoping that would clear. It did not. Today I replaced the remaining coils and the spark plugs and seems to run OK. I drove around the block and the PRNDS stopped flashing within the first minute. No check engine light. My question is could a coil going bad cause the transmission error that she encountered? Or is it just a coincidence and from what I read is the TCM about to go out?

 

What transmission cvt, tiptronic, manual.
No there shouldn't be a relationship unless it's an electrical issue. I'd get the car scanned

 

Sorry, should have included CVT as the transmission (or should I say "notorious" CVT). I asked to have check engine codes checked at the auto parts store but the check engine light was not on so they wouldn't do it. I have one of the off brand VAG COM cables that worked for me in the past but I upgraded my PC and the newer VCDS software will not work with it anymore. There is a euro car garage close by so I could take it there for the scan.

 

I don't think that's a transmission error. I believe the flashing PRNDS indicates the car is in "limp mode"--probably from the multiple misfires. If it's running smoothly and you're not getting an MIL after replacing the spark plugs and coils, you should be fine.

 

Yeah, like he said!

When the ECM detects an engine fault, such as a severe misfire, it will also do other things like put the trans into default (limp-in) mode to prevent possible damage. Most likely the cruise, stability control and traction control were also disabled during that time. The PRNDL flashing is the trans in default mode. It does this because all it knows is the engine is misfiring and has reduced power. it does not know why or what is causing it so it errs on the side of caution.

Now that it sees the fault is no longer present after a couple drive cycles it goes back to normal.

In other words, everything is good now!

 

Thanks for the info. That is good news.

 

Not so fast. After driving it for two days without any problems, I get in it this afternoon and as soon as I shift it into reverse the PRNDS starts flashing and the check engine light comes on. It runs fine on the way home but the gauge flashed the whole way. I went and had the codes read and have P0706 code. I start it up and the PRNDS was not flashing any more.

 

The mil comes on at the request of the transmission.... The Flashing PRNDL is indicating a limp home condition due to a failure in transmission. The randomness of it is telltale of a faulty module... It may have felt like a misfire but most likely a bucking from erratic shift patterns. Misfires throw codes.... They have to per government regulations. The PRNDL won't flash due a misfire

 

^^^This^^^ misfires almost always throw codes. You need to pull codes before guessing at expensive parts.


Here's the RossTech Wiki on that code. Sounds a lot like your symptoms.


17090/P0706/001798 - Ross-Tech Wiki

 

Here is the latest. I tore into the transmission and sent the TCM to Module Repair Pros for refurbishment. I reinstalled it with a new external filter, new trans mount and fresh CVT fluid. I did not replace the internal filter as that looked like more of a job than what I wanted to tackle. I hope it does not come back to haunt me. Here is what I need help with. I have a knock off VAG cable (K+CAN, 2007 A4 is supposed to be CAN) that I can connect to the vehicle with either VCDS Lite or Commander 1.4 but I have not been able to get the transmission temperature readings so that I can do the final fluid level adjustment. I don't want to go through all this and trash the trans due to the fluid level being wrong. Everything I read says to make sure this is correct. With VCDS Lite I cannot access the transmission at all and with Commander I can get some information but I have not found the temp reading and I do not know how to use the software. Anyone have any suggestions on how to access the info that I need? My other option is to take it to a local German car repair shop and have them do it for me. There is one a couple miles from home. I did drive the car around the block to check it out and it seems to run better than before (no hesitation or jerking) but I am not ready to make it the daily driver until I can get this finished. Thanks.