What is meant by the word limp in this/your case is that the throttle is being deactivated b/c of a siginal fault. [ limp] .
The Module shuts down the Electronic accelerator [ EA module]. So, one suspect could be a false or bad speed sensor or input/output sensor sig from conductor plate in the trans [ b/c that is a fault common to that trans]

..so , scanning the trans is the next step to verify or eliminate that likely possibility.
The "Limp Home " mode/feature is not what is meant by limp in this situation..you have drive by wire throttle and you have NO SIG to EA, so the trans has to be checked for speed sensor output from the trans conductor..................until that is done, you are not going to get a proper diagnosis or even a diagnostic base to work from. You may even have an EA problem, but I would suspect that would have shown a Power train code.
Early ASR traction controlled cars would restrict the throttle responce when ASR kicked in so that there would not be undue torque to the rear wheels..so, whenever there is a throttle responce problem in the pedal action, it is simply referred to as the pedal goes limp..it is just a term used for the pedal and is not the LIMP HOME MODE , it is just throttle responce terminology that is commonly used when there is a throttle problem..like in your case, where one would state, ..."The throttle goes limp"
Don't get hung up on the word limp, go get the trans codes. Once you have them, you will probably be able to find an answer in the Archives by plugging those code findings using the "Search Feature ".

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A Dalton