Wiring issue? - temp gauge stuck on max

[Mos]

The temp sensor at the front of the engine with the green plug and brown and blue/red wire is the temp sensor for the engine ECU and not the cluster - running the brown wire from the cluster to this brown wire is not appropriate (it's the ECU signal ground that's grounded inside the ECU, and therefore isolated from any currents running through any other grounds).

The cluster temp gauge has a 12V feed inside the cluster, a brown reference ground wire that runs to the grounding point on the head (that you broke), and a yellow/green wire running to the temperature sender (which is a single pin device grounded on the water neck). By cutting the brown ground wire the gauge had no ground reference, and the internals of the gauge caused the 12V reading on that pin on the cluster.

So... while your repair made the gauge work, it wasn't the correct way.

And the most important thing, don't EVER assume that the same colour wire IS the same wire!!

Mos.

[Ribfeast]

Aha! Explains why the engine light came on when I tried to start the car! I'll pull the dash out and re-attach the brown wire under there I reckon. Thanks heaps for the advice

Anyone know what code 47 is on a 1JZ? Along with the expected code 22 when the temp sensor wasnt connected, I got code 47, and the car stalled very quickly after starting up.