So I recently replaced a blown 4.3L in my '99 Blazer with a 4.3L from a '98 Blazer. The engine is in and runs great, but now the transmission isn't shifting past second gear. Could anyone tell me why this is happening? Also, the ABS and check engine lights are on and the speedometer is stuck at 100 even when turned off. None of these things were happening before the swap.

Thanks everyone,
Joe

 

You'll need to have the EBCM, (Electronic Brake Control Module) scanned with a capable scan tool. For the transmission to shift properly, the PCM needs to receive the VSS data, (Vehicle Speed Sensor). The data is collected by the EBCM, and shared with the other modules when they request it. If there is a problem with the VSS, or its wiring, the ABS light will come on, and the transmission will not shift properly. Speedo stuck at 100 is fairly common if you disconnect the battery for an extended period of time. If the VSS or its wiring are the problem, after you repair it, and drive it, the speedo should start operating correctly. If not, you'll need to access the IPC, (Instrument Panel Cluster module) with a capable scan tool, and command the speedo to zero mph.

 

Thank you so much! My brother who works at Autozone is getting me a scanner now.

 

Powertrain scanner will not access the EBCM. Needs to be ABS capable scanner.