1990 G30 5.7

**Andy** · 10-17-2014

I wonder if anyone can help me with this, My van is a 1990 G30 5.7 tbi with a TH400.
I had problems with idle some time ago and a mechanic here in the UK tried to fix it.
Unfortunately, he took the engine service bulb out after switching my ECM.
I now have a 1227747 ecm with the original chip...he says.
I am trying to buy from the US another correct ECM & chip but I have a feeling it should be a 1228747
I don't know what ECM came with the van from new.

The reason for changing is that the engine runs badly, is terrible on mileage and after replacing the bulb the engine service light keep flashing fast.
When I get the code I get 51 ECM fault.
I have another problem in that the van has no injector spray just suddenly & won't start, I don't think this is related, probably fuel pump just gone.

Could you tell me if I should get the 1227747 or 1228747?
Also is the ebay remapped chip for the 1228747 any goon in case my chip is no good?

I really want to get this running well as I have a list of mods I want to do.
Many thanks.
Andy.

**dave w** · 10-17-2014

I think the Vehicle Identification Number (VIN) for your G30 Van should be decoded by a GM dealership to figure out what the Original ECM and PROM Chip Broad Cast Code (BCC) was.

dave w

**fastacton** · 10-17-2014

I think the main difference between the 8747 and 7747 is the type of EGR valve used. That might help you figure it out too. Can anyone verify this or am I wrong?

**dave w** · 10-18-2014

Usually the '8747 is used with the TH400, and the '7747 is used with the TH700R4.

dave w

**Andy** · 11-02-2014

Thanks for your help, I have now fitted a reconditioned 1228747 computer with my original prom AKWA and the engine light has stopped flashing all the time!
No fault codes either but I now have the original idle problem again so will be rebuilding the tbi, replacing the IAC valve and will try to reset the idle.
I have also just received my cable to be able to log data from my van, hopefully this won't be too difficult.

**dave w** · 11-02-2014

Originally Posted by Andy

Thanks for your help, I have now fitted a reconditioned 1228747 computer with my original prom AKWA and the engine light has stopped flashing all the time!
No fault codes either but I now have the original idle problem again so will be rebuilding the tbi, replacing the IAC valve and will try to reset the idle.
I have also just received my cable to be able to log data from my van, hopefully this won't be too difficult.

Thanks for the update.

dave w