So I'm having trouble with my 99 Ranger (4.0 4x4). My ABS light and check gauge light come on after the trucks ignition is shut off. When it start the truck, the lights go off. I had my usual mechanic tell me it was my GEM module, so replaced that at the dealer, still have the issue. Dealer "electrical guru" thought it was a bad instrument panel, I replaced that since it was cheaper and easy, still have the issue. Checked the brake fluid reservoir and verified I've got the proper level in there. Went ahead and replaced the rear ABS sensor but lights are still on. Maybe the master cylinder? Could it be an electrical issue? Thanks in advance.

 

Welcome to the forum

2 wheel ABS(RABS) or 4 wheel ABS(4WABS)?
It matters

Most warning lights on the dash have 12v with key on
For the bulb to be on it needs to be Grounded by its "device"

Check Gauge light has no connection to RABS or 4WABS
Or GEM module for that matter

GEM does activate Door Ajar Light, one wire, grounds that bulb when a door is open
And in 1998-2000 Rangers GEM is also connected to instrument panel via one Speed wire for speedo/odo signal
So just those 2 wires

Check Gauge light comes on when one of the 4 instrument gauges are high or low or disconnected, Volt, Fuel, Oil, Temp gauges
And it is powered by a Key On fuse, so shouldn't be on with key off
Do all 4 gauges work as they should?

Pull fuse 11 in cab fuse box and see if Check Gauge light goes off

Same fuse 11 also powers ABS light and Parking Brake light
Fuse 11 should only have 12v with key On

If pulling fuse 11 shuts off the lights then test fuse 11's fuse terminals to make sure neither shows 12v with key OFF
If one still has 12v, or any volts, lol, then that's the problem, could be ignition switch or fuse panel issue
OR
A short to Fuse 25 wire on back of cluster, Fuse 25 has 12volts all the time, after pulling fuse 11 out and lights are still on pull fuse 25 and see if lights go off