Red Flash

Dear All

So, I'm looking at the work shop manual (28-74) and don't understand something entirely. I have the following info there:

For 928 GT : 928.618.124.22 (EZK Control Unit Cut-off 6800)
For 928 GT : 928.618.123.14
For 1991 GT : 928.618.123.26

Am I to understand that:
a.) The first part above (.22) will only work in 1989 and 1990 cars?
b.) The second part (.14) will work in 1989 and 1990 cars
c.) But if you want the diagnostics to work properly on the 1991 cars you will need the .26 box. But, if you don't care about the diagnostics, the other boxes will work in a '91 GT too?

Thanks for any input.

John

ROG100

928 618 124 22 EZK Option M639 1989 GT
928 618 124 22 EZK Option M481 manual trans. 1990 GT & 1991 GT
928 618 123 14 LH Option M637/M639 CS/GT - 88SE/CS, 89GT & 90GT
928 618 123 26 LH Option M481 1991GT

Diagnostics work through the plug by the side of the passenger seat 89 to 95. 88 works via a different plug and if IRRC 87 also with updated chips - although the depth of interrogation may be limited.

John Speake

There are small changes in the software between the various versions of LH ECUs listed above - mostly to do with diagnostics. e.g. with the introduction of the digi dash in MY 89.

The fuel maps are identical for all intents and purposes.

worf928

What about the diagnostics available from the coded flash of the CEL light first available in my '91?

Is it safe to assume that swapping '91 'proms into a '90 LH would be sufficient?

John Speake

That would be OK, the main difference between non- digi and the 90 onwards is the additional code for the "ignition protection relay" device in the Porsche diagnostic tool menu.

So I think '90 chips with a '91 digi dash would also be fine.

worf928

'89 has IMS too.

If you put '91 proms in an '89 can you get codes from the CEL?

John Speake

Yes, from MY89..... the software in the CEL is totally separate to the LH ECU software. No electronic linkages.