Broken, chipped, spun or cracked speed sensor ring.
Salvage output carrier assembly and restore normal operation by installing Sonnax output speed sensor ring.
GM 4L80-E and 4L85-E units commonly suffer damage to the output speed sensor reluctor ring such as cracks, chips or breaks. Failsafe mode and speed sensor codes can result when this occurs. Installing Sonnax output speed sensor reluctor ring 34880-01 allows salvage of the output carrier assembly and restores normal speed sensor operation.