Q: no power to pcm

asked by on January 03, 2017

1990 Ford E350 Short School Bus, Diesel 7.3 liter The transmission works fine and then all of a sudden it goes in to "limp mode". It is an e40D transmission and the PCM (powertrain control module, aka, the TECA) is not getting power for some reason. The transmission itself is shiny and definitely has been removed,cleaned, and replaced at one point, hence why I would be willing to bet it was rebuilt. When it works, it works great. When it doesn't work you have to shift it manually from 2nd to drive.

My car has 238000 miles.
My car has an automatic transmission.

Hello. Thanks for writing in to YourMechanic.com. Unfortunately, this model of Ford bus is not among those we service. In most cases, when a transmission is damaged, or electrical harnesses are faulty, it will trigger and error code which as a default, triggers the limp mode. The best way to resolve this is to check all connections and sensors to determine if the error is caused by these systems. Otherwise, you’ll most likely have to remove the transmission and inspect internal parts to determine why it’s entering limp mode.

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