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420A Possible Limp Mode?

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Skyline-Tweak

Proven Member
64
2
Nov 11, 2012
Kunkletown, Pennsylvania
So this is the one thing that got me good. I believe my Talon is back in Limp Mode. This was the original state I bought the car in and the Limp Mode actually blew a hole in my block from pressure build up while driving it home. From that point my brother and I have rebuilt another engine and bought a transmission from a salvage yard. We hooked it all up and started the car. It worked correctly, began shifting, and everything was ready. I was so thrilled that my car was finally complete. Then my brother and I took the car out again yesterday to make sure everything still ran properly before prepping it for paint and the speedometer has stopped reading and the car will not shift again. I've just about had it with these problems and am ready to do a 5-speed swap unless anyone knows a solution. I've researched online about it and I've read it might be the output speed sensor but I've already replaced it. Any help would be appreciated.
 
We've got both an auto and a 5-speed. They both have their own issues, so swapping to a 5-speed will not end your challenges.

As you probably read, your car will go into limp mode for a variety of reasons; some having to do with the transmission, and some having to do with information its getting from the engine.

The transmission has its own control box (tcu) to make the shifts happen. You might try a simple swap of the tcu to a known good one to eliminate that as the cause of the limp mode.

Others can chime in, but we will need more information about the engine, and any modifications, if it turns out to be more than the tcu.
 
The engine is a Chrysler 420A and the transmission is an A604/41TE. After the rebuild we had used the same wiring harness and same ECU. Everything else was replaced. It did run correctly after the rebuild. Shifted and all. But next thing we know it started having this issue again. Could the ECU be causing this?
 
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