2015 Toyota Yaris
Key Replacement - Save vs Dealer in San Diego

2015 Toyota Yaris Remote Head Key Replacement - Fast, Affordable & Professional

I got a call late on a weeknight from someone parked in their driveway off Bay Marina in National City. He had a 2015 Yaris and one key, and that key had stopped triggering the locks. He could still turn the ignition and drive, but the remote functions were dead. He figured the battery was probably the fix and asked if I could just swing by.

I told him to grab the battery cover off the back of the fob before I drove out. CR2016, flat coin cell. He had one in a smoke detector remote or something, swapped it over, same result. Nothing. So I headed out.

When I got there he had the interior light on and was comparing the new battery to the old one, trying to figure out if he had put it in backwards. He had not. The battery was fine.

I pulled out my programmer, connected to the OBD port, and read what the car was seeing. The fob was actually registering, but the registration had drifted. On these, if the remote gets triggered too many times outside of range, the rolling code counter in the fob and the counter the car expects can walk apart until they stop agreeing with each other. The car was not seeing the remote as valid anymore even though the transponder side still worked fine for starting.

Re-syncing the fob to the car took a few minutes. Locks responding, trunk release working, tested three or four times from across the driveway. Done.

He had almost ordered a replacement fob online before calling me. Would have been the same problem with a brand new fob if the root cause was not diagnosed first.

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