i got a request to repair a macbook pro model a1502 the keyboard and trackpad stopped working on. i did some testing hoping it was the “press this key 5 times to enable keyboard” kind of issue… it wasnt but i did notice the keyboard would wake it up from a deep sleep, so i thought maybe it was a software issue, cleared the pram and did a reset, nothing. i then also noticed the key combo for a forced restart worked… i had read about the ribbon cable connecting the trackpad and keyboard to the motherboard goes bad on these often, but i assumed if that was the issue key combos and stuff wouldnt be working!? next step a factory reset after i backed it up. nothing.
i finally decided after all this troubleshooting to lookup the ribbon cable and see how much it was $10 prime on amazon, ok i will give it a try. sure enough that fixed it.
if you have this issue and decide to replace the ribbon be sure to have a P5 bit and a T5 bit to get the case open, the bottom cover uses the P5 and the cover over one end of the ribbon cable uses the T5. i just grabbed a kobalt electronics driver set at lowes and it had everything in it to get the job done, even prying tools that are handy for popping the ribbon cable out and lifting the lever to slide the other side out. thanks for reading and good luck!