In 2011, I had the transmission conductor plate replaced. All was fine after that.

Now 2015....car goes into neutral mode (rpm accelerates but no transmission) after sudden acceleration or shifting. Current fault code is P2500.

The ABS, ESP and SRS lights are also on.

When the xmission slips occurred, engine light was on...it also occurs when the engine light was off. Car is running fine now after the mech cleared the codes......the two ABS speed sensor codes were also registered.

IN ALL CASES, switching the car on and off, fixed the neutral mode problem.

At the time of the neutral mode, you cannot shift (using the tiptronic) and the car is actually like it is in neutral...rpm races but no power....scary.

I need to have the rpm ABS speed sensors replaced on both front wheels...this is the only solid evidence that MAY contribute to the problem....

Other possibilities:
a) xmission fluid...assume OK
b) contaminated connector harness ...assume OK
c) brake light Switch ......
d) ABS speed sensors......
e) ruled out shifter - no code
f) ruled out mass flow air sensor - no code

Comments.....thx!
Dr Ash

 

I think that you are confused between wheel speed sensors and conductor plate rpm sensors---my guess is that you have faulty conductor plate rpm sensor--which means new plate!!

 

At the moment the check engine light is not on. BTW, the display flashes BAS, ESP and ERL and the ABS light is on. I know my INDY(who is an honest bloke) showed me the codes (we spent an hr going for a test drive and checking codes after various runs)..that the speed sensors needed replacement. Since he did the conductor plate back in 2011, I will have him check the Connector and the TCU for any contamination. Could the speed sensors in the front L&R wheel wells have anything to do with the xmission slipping? Dr Ash

 

absolutely NOT!!

 

If it is a faulty conductor plate rpm sensor...what fault codes should I expect......I remember when the conductor plate was replaced in 2011 there were some additional P codes e.g. P0715 and at that time the shifter was not engaging from P.

Is there a specific code for the rpm sensors.....thx for your responses.

 

Is your mechanic scanning your vehicle with SDS or with a generic ODBII scanner?

 

He was using a larger scanning tool with SDS built in almost with help menu's similar to the Autoboss V30 or equivalent and he also used the OBD11 small generic scan.

As more info:
.........the car was with my mechanic for several days last week and he did not notice anything of the xmission slipping that I reported. So I visited him and we went on a test drive. When I was driving I noticed the car was in some form of a limp mode....pressed down on the gas with no or sluggish response....he could not believe it so we changed seats and he observed it as well....car would accelerate slowly even after gas applied on the highway. Then after driving it hard shifting and after sudden brake and acceleration..... the original symptom that I took it to him for happened...the car slipped into a neutral mode.....no response from the transmission rpm OK when the gas was applied....we pulled over and we turned the car on and off and transmission recovered. Back to the shop he pulled his SDS scanner and checked a few things and the sluggish response all went away after another test drive. He also plugged in the smaller OBDII scanner to verify faults..... The only thing is that it the car revs at 15K-20K on idle & N. He needs to reset the idle...all else is fine. I have driven the car for the past two days not hard but it is driving like a charm and no slipping except the high idle. Not convinced the problem is resolved....Dr Ash

 

If the speed sensors were a problem I would get the car in limp mode...the fact that it slips into neutral by the feel of it.....D on the display does not c
hange neither can I get the tiptronic to change gears.......means that the car is not in limp mode but in neutral since when this happens you hit the gas and the rmp ramps up...like in N.

Dr Ash