justyntime

HI, CEL came one, code said ECU going bad. I got another one and installed it not realizing it didnt match up with the transponder key. I put the old one back in and now the radiator fan doesnt come on so when I use the A/C it over heats.

Took it to a reputable shop and they told me I need to take it to the dealer to have it re-flashed because I took it out. Seems like thered have to be another way.


2004
Jeep Grand Cherokee Limited 6cyl

Radi

Did you disconnect the battery first? If not you may well have corrupted the programming making a reflash necessary. Not awfully likely but it does happen. More often a pin in the connector slips or gets bent. Can you drive it with the new one installed, ignoring the transponder issue for the time being? I'm not sure if you mean a security transponder or a remote door lock?

justyntime

I did disconnect. New ecu only allows the car to start for 3 seconds and shuts off, lighting up the key with a line through it on the gauge cluster

cruiser54

Security system? Lock and unlock the driver's door with the key and try again.

Carl48

The shut down after 3 seconds is probably a transponder key issue...IIRC the dealer needs to program the new computer to work with the key otherwise the SKIM will shut down the vehicle as you describe.

As far as the radiator fan not working now with the old computer, my guess would be a pin on the connector that got bent or pushed back.