Yes it's easy to overlook things AND to over complicate a repair. I had an ABS light come on - spent almost two weeks troubleshooting the entire system to no avail. My son mentioned that my third brake light bulb was out. BING it dawned on me, when I was replacing bulbs in the instrument cluster I inadvertently plugged the Light Failure indicator bulb into the ABS slot. DUH ME

86 Isuzu Trooper TD 5 speed
82 Isuzu Diesel I-Mark
86 300 SDL MB 126
85 300SD MB 126
82 300 D MB 123