The thing is, VPW J1850 is not new. If a reader worked on the 2002 Tahoe, it should work on 2003 Silverado. I think there's something corrupting the Class 2 data bus which is causing the present concern. If that were the case, an emissions testing that checks the OBD readiness monitors would fail. It'd be best to take it in for service, besides. It'd be a shame to have an accident because of the lack of ABS/TC.
Ok took it to my son-in-laws brothers speed lube....They too had difficulty with the professional computer...only code was p1571...However the speed sensors on the ABS read correctly to the speed of the car...so they are good...Still have ABS and Check brakes message...His mechanic suggested maybe a reflash of ECU...But now we are lost....
Yea, I know, however I know the mechanic (not a lube guy) and he did run the tests. I guess next thing is to pull the PCM and check all grounds and wiring....Something just doesnt fly. The equipment he used cost over $4k and has capability to read everything...He was able to determine that the speed sensors were reading correctly and match wheel speed....
OK bad news, we took the pCM out and checked all of the pins, everything looked fine...also took the fuse panel apart and check all of the wiring for whatever....Car still will not communicate....So its off to the Dealer on Monday....Be interesting to find what is going on. The mechanic suggested a reflash of computer at the Speedy Lube. we'll see.
OK the solution....Gm in their wisdom created a radio system that incorporates the warning lights in the vehicle with the radio...The radio died and was replaced with an aftermarket radio that required an interface module to allow the warning lights to work...Well the interface box failed and caused the diagnostic interface to not work...one wire removed (orange) and the diagnostic plug works...Good job Government Motors....thank you Local Chevrolet dealer for finding this after two days...I commend their troubleshooting, my friend and I were definetly lost without schematics.
Thanks for the update. Though I can't say I agree with your sentiment. You had some aftermarket module that crapped out and was corrupting the Class 2 data bus. It could've been worse, how about some aftermarket alarm or remote starter system that takes forever to figure out?