Emergency Brake Light comes on when truck shifts between 3rd and 4th. Only in 2H



I have a 1991 Chevy 1500 step-side 4x4 pickup automatic transmission . About 3 months ago while traveling down a California highway a short somewhere was created after driving over a large bump in the road. This blew the ECM fuse. Since my traveling companion and I were stranded on the side of the highway late at night with much need to get somewhere safe to investigate we immediately replaced the fuse with another and were able to continue. Early the next day we brought the truck in to a mechanic. He went through all that he could think of to try to find the original short location and any problems associated. No luck.

Since this incident there has been no other short and the truck has returned to it’s ‘running like a champ’ self. However, ever since the short/highway mystery the emergency brake dummy light comes on every time the truck shifts from 3rd to 4th gear only (now this is the real mystery) if the truck was started with the transmission in 2H. If the truck is started while in 4H the emergency brake light will NOT come on, at anytime even if after starting truck it is then put back into 2H.

Other possible points of interest: we had the transmission replaced a month before incident, they mentioned something about replacing a brake sensor in the cab for some reason after replacing the transmission; have had all brake systems throughly looked at and received a clean bill of health; had the rear drum solenoids replaced for good measure.

Any ideas?


Have you checked the brake fluid level?


Yes, system was flushed, refilled, bled and topped off. Level has maintained correctly.