For the past two mornings on cold startups the check engine light comes on. The first day it did it I checked the bin on the chip and the first few lines just FF. I reprogrammed it and checked it, put it back in and it still came on. The scanner just said no communication so I couldn't check the code. After driving it for about 10mins. the check engine light went off and it drove fine but showed a prom error code. I erased the codes and though all was fine until this morning I went to start it and check engine light came on again. Could the 29C256 just be sensitive to temperature or something? Once I had been driving it and the light had gone off it didn't come on again till this morning. I'm lost.

 

i cant say ive had this trouble.would seem sort of odd. i thought the whole idea of using eproms eeproms flashproms over a system thats was floppy based was due to the fact that it could withstand greater changes in temps and handling. im in michigan and the mornings have been in the low teens i have zero issues. if anything id maybe suspect condensation ?? hard to say for sure.and im using the 29c256 with a moates adapter. email criag see what he has to say.or you could just have a loose memcal or a goofy ecm.

 

Might have nothing to do with the weather but I jut noticed how cold it was these past couple of mornngs. The thing I though was wierd was the fact tht I have programmed it and checked it before installing it in moates adapter and it checks out fine. After starting it and getting a check engine light I brought the prom back in and read it and the first few lines were FF. There is no way the ECM could rewrite it is there? Also, after about 10 min. of driving the light went off and data displayed it had a prior "promm error". Clear codes and drive it all day just fine. I though if the prom was on the fritz it could be just showing no data sometimes. I have been messing with this prom off and on for about a month and a half with no problems until the past couple of days and I haven't changed anything in the past couple of days either.

 

it is entirely possiable for the ecm to write data to the erpom if 5volts is getting to the vpp pin of the eprom. the only thing i could think of is a bad chip with an internal short or the ecm has a short that is passing 5volts onto the vpp pin and allowing a back flow of current to wipe the chip. replace the ecm and see what happens. or try another eprom.

 

The commercial version of the Atmel AT29C256 has a rated operating temp of 0°C to 70°C, while the industrial version is rated from -40°C to 85°C.
In extremely cold climates, I would opt for the industrial version, although they do seem to be a bit harder to find..

 

Temp has been getting into the upper 20's lower 30's F. so that might explain why it has a prom error until my heater in the car warms up somewhat to get the temp up. The it works fine.

 

Even with the rather limited advertised operating range, I have not heard of too many problems with low temperature yet. I suspect you just have a sligtly more sensitive chip. Perhaps just try swaping it out for a new one. Worth a try anyway....

 

Another thing I noticed is that all of my VE cells have been changed and I have only messed with about 10 of them total, that I know of. If I compare them to the original bin file they have all been changed a few points. Is this something Tunercat does by averaging or did I do it somehow and not realize it?

 

Another thing I noticed is that all of my VE cells have been changed and I have only messed with about 10 of them total, that I know of. If I compare them to the original bin file they have all been changed a few points. Is this something Tunercat does by averaging or did I do it somehow and not realize it?