Good evening all,
Today I started from scratch. I tested the front L/R ABS sensors and they tested good. And when disconnected gave me a code. The ABS speed sensor tested open in static mode like it is supposed to and has been replaced twice with a new one just to make sure. The ABS brake module has been replaced twice this week to try and insure a properly working unit. I ohmed out the wiring harness from the ABS speed module on the tail housing to the pin connector on the ECM. I disconnected the ground cables (three) of them from the chassis, ground the steel with a grinder and file before reassembly. I have a good circuit from the ECM to the ABS speed module on the transmission. At present I have a steady ABS light and a steady red brake light on. While driving the transmission works fine for about fifteen miles before issues arise. When the issues start, at idle with my foot on the brake, the speedometer will start to bounce from zero to almost seventy mph. If I try to take of while the speedometer is up there the transmission kicks in hard. I have no ABS brake function but the brakes work well with a good pedal. I have current codes of C0569 and C0550. I have tested each and every fuse under the hood and the dash. At this time the truck has had three ABS speed transmission modules and two ABS brake modules. I phoned the local GM dealer and was told that if I purchased an ECM programmed from them that the bill would exceed $1,000.00. I think that about covers what I did today. Thanks for any advice. Gary
Wednesday, September 2nd, 2020 AT 11:56 AM
(Merged)