Subaru Impreza — Immobiliser Fault
Found, Stripped, Repaired

Why a No-Start Isn't Always a Key Problem

A lot of "won't start" calls on modern Subarus look like key or immobiliser problems from the outside — engine cranks, dashboard lights up, but nothing happens. Most people assume the key's lost its programming, or the immobiliser ECU has failed. Sometimes that's true. More often, the fault is somewhere in the wiring between the ignition barrel and the immobiliser, and the dealer will quote a full module replacement when the actual problem is a corroded connector or a broken wire.

I start by reading the fault codes through the OBD port, then test the ring antenna around the ignition barrel, the wiring from the antenna to the immobiliser ECU, and the transponder signal from the key. The fault is almost always in one of those three places, and almost always repairable without swapping a module.

The Strip-Down Part

This Impreza needed the lower dash and steering column trim off to get to the immobiliser wiring properly — a strip-down the dealer usually skips because they replace the whole module instead. With the trim out of the way, the fault is visible and the repair is a much smaller job than the dealer would have you believe.

Classic Imprezas Aren't Exempt

The classic Impreza WRX / WRX STI uses the same ring-antenna-and-transponder principle as the later models. The wiring is older and more prone to chafe at the ignition barrel, but the diagnosis and repair is the same approach. Whether it's a 1999 GC8 or a 2007 blob-eye, the immobiliser fault is usually repairable without a dealer module.