Hi All, Our 98 Accord EX v6 sedan began shutting down and not always starting. It happens when the green key light (immobilizer system light) is not flashing. When it flashes, the car will start. Sometimes, we jam the steering column up and down and the light comes on. We started with replacing the fuel pump. We later learned that the immobilizer system disables the fuel pump, so this problem may have started earlier than we thought. Then, we replaced ignition switch, relays, fuses, and finally we installed a used immobilizer. When the dealership mechanics connected the computers to reprogram the immobilizer, the computer would not read the ECU at all. The dealership recommends doing a diagnostic, but the diagnostic computer is not able to read a connection from the car’s ECU. They say it could be anything, maybe a short, bad ECU, or what? Can we put a used ECU from the same car where we got the used immobilizer, same car, same year, and will we have to get a new key programmed to the immobilizer or can the original immobilizer be used with the replaced ECU . If we use a used ECU does it have to be reprogrammed to the car? Thank you for your time, please help if you can.

 

You can put a used PCM in with your original immobilizer. It will need to be programmed with HDS. For VIN and immobilizer set up.

Test to see if this solves the problem before going to dealer by;
Plug in used PCM. Plug into obd2 port and see if you can communicate with the new one.

 

If you're already using the same immobilizer you got from the same car you're getting the ecu from then you just need to have the dealer reprogram keys for the vin that you're getting the car from. You should then be good to go. The ecu and immobilizer will already have the same codes. You just need keys with the same codes.

http://www.hondata.com/immobilizer.html

 

Ya, those posts help. We will get the ecu from the same car we got immobilizer from. Sounds like we need the vin from the parts car, right?

What would cause HDS (Honda dealership?) diagnostic tool to not even read my car's ecu?
The dealership said they tried three separate devices.

 

If you can't communicate with ecu you have an issue with your ecu. Either missing a power/ground (check at ecu for this). You have a shorted/open comm. line, or you have no power to obd2 port. If you have another ecu, swap it in And see if you gain comm.

 

We had a Honda main relay replacement because the after market main relay that had been installed went bad. the car starts every time now and stays on!

We have a problem now with the transmission, maybe. We drove today going 65 mph and when we slowed to below 60, the engine rpm increased to 5,000 but would not shift gears for a delay. When I let up the gas, it shifted, and then the shift in gear jerked the car.