Chipped ecu

[sr-rompa]

I have a group n chipped ecu but it is throwing code55 Engine Control Unit (ECU) fault Renew Engine Control Unit (ECU) iv swapped the chip over to another ecu which I had run on my 2.0 xe with no faults and straight away the management light came on and code 55 came up again . I have no running faults when the chipped ecu is on any body have any ideas why it keeps the light on and puts code 55 on ????

[A11VXL]

The genuine group N chips almost always did this, they were written by Geoff More of MBE for Atkinsons Motorsport, and we had a license to sell them from MBE. There were 3 EPROMs written to cover the range of Motronic 2.5 ECU's. The very first ECU which if my memory serves me correct was an ident FE which has an additional 4 screws on the top and a EPROM ident of 26RT3xxxxx did not put up TC55 however all the other did, I will explain what TC55 relates to.
TC 55 is basically a check sum error message. When you turn the ignition on (but not do the engine is running) the ECU does a check sum calculation, this means it adds up all the hex numbers (mapping address's) which comes to a total, when you change a value to (to increase the fuel for example) the numbers change and the check sum total changes, MBE did not do a check sum correction in the EPROMs as rally cars do not tend to sit around with the ignition on, and if you go from ignition off straight to cranking the check sum calculation is cancelled so the light will stay off.
So with a Grp N EPROM installed you need to go from key off to cranking to cancelll out the check sum calculation and all will be fine. There is one previso though due to the change Bosch made to the ECU one EPROM will not work in all the different Motronic 2.5 ECU's hence why 3 different versions were produced.
Hope this helps explain TC55, cheers Jon

[sr-rompa]

Yes mate helped alot thank you

[Nobby]

The genuine group N chips almost always did this, they were written by Geoff More of MBE for Atkinsons Motorsport, and we had a license to sell them from MBE. There were 3 EPROMs written to cover the range of Motronic 2.5 ECU's. The very first ECU which if my memory serves me correct was an ident FE which has an additional 4 screws on the top and a EPROM ident of 26RT3xxxxx did not put up TC55 however all the other did, I will explain what TC55 relates to.
TC 55 is basically a check sum error message. When you turn the ignition on (but not do the engine is running) the ECU does a check sum calculation, this means it adds up all the hex numbers (mapping address's) which comes to a total, when you change a value to (to increase the fuel for example) the numbers change and the check sum total changes, MBE did not do a check sum correction in the EPROMs as rally cars do not tend to sit around with the ignition on, and if you go from ignition off straight to cranking the check sum calculation is cancelled so the light will stay off.
So with a Grp N EPROM installed you need to go from key off to cranking to cancelll out the check sum calculation and all will be fine. There is one previso though due to the change Bosch made to the ECU one EPROM will not work in all the different Motronic 2.5 ECU's hence why 3 different versions were produced.
Hope this helps explain TC55, cheers Jon

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