Intermittent SES

[tomtom72]

Glenn, Yes, from the FSM on DTC24 it looks like it could be the ECM or the chip ( MEMCAL or EPROM ). Do you have a stock EPROM that you could swap in just for a test? Maybe someone near you has a spare ECM ( known good ECM ) that they can lend you to just see what happens.

Also, on the shift to 3rd being smoother.....I'm a bit concerned for your clutch hydraulic system's performance. How old are the master & slave? What is the condition of the fluid? Usually balky shifts are a result of system degradation...usually. Check out the link to zfdoc.

http://zfdoc.com/ there is a good Q & A on diagnostics over at Bill's site.


Tom

[gbmidyear66]

Tom

Good observation on the clutch. I also replaced the clutch fluid while I was down there (color tells me it had been in there a while). This is probably why my shift into third is better. And yes - my slave is wet with fluid on it - looks like it needs to be replaced at some point (its a 91 style - has already been replaced).

I will swap the factory MEMCAL back in - it didn't help any when I was chasing the issue last year (before I fixed the TB and ported the top end).

Looking at the FSM - I think I will try disconnecting the ride control module - it also ties into the VSS signal . I doubt this is my problem (because my speedo seems to have no issue at all - so I think the VSS signal to the ECM is good). Even though ECM self check is good - this seems to be the most probable cause. I'm afraid that getting an ECM is going to be tough.....

[c4zr1]

I tried to find a used ECM for over a year. I finally sent my ECM to Tom Henry Chevrolet to get rebuilt. Good folks to work with and good turnaround time.

[gbmidyear66]

Originally Posted by c4zr1

I tried to find a used ECM for over a year. I finally sent my ECM to Tom Henry Chevrolet to get rebuilt. Good folks to work with and good turnaround time.

Do you recall the charge and turn time? I assume they send it out to someone - any idea who?

I have had two recommendations for the same ECM rebuilder - price seems reasonable (but I won't have a driveable car in the meantime).

Thanks

[c4zr1]

This was their response to me.
The ECM that you need is GM part number 88999186 and is list price $426.74 your price would be $266.71. $27.66 in freight .GM has no stock at any warehouse and there is no ETA. We ran the part number on a national locator with no results found.
GM has listed this item as a "Return for Remanufacture" part meaning that we would send GM your old ECM and they would remanufacture it. The time frame for this type of service is listed as 30-45 days from the time that GM receives the module. The above prices are plus any freight charges. We can not estimate shipping charges at this time because we don't know the destination zipcode for the GM reman facility.
We checked the aftermarket suppliers and found that White Racing Products of Tampa, FL. shows one in stock. Their contact information is www.whiteracingproducts.com 813-264-6368.
We hope this helps.
Thanks
Tom Henry Parts

[gbmidyear66]

Finally solved. Installed a replacement ECM today - all is good (guess I have a spare VSS sensor now too....). Very strange symptoms from my original.

Got the replacement unit from Whiteracing - could have had my original rebuilt a little cheaper - but would have had maybe 3 weeks of no car going that route.