Jump to content

speed error


harry yarnell
 Share

Recommended Posts

I have now gotten my '90 running!!! However the speed is all wrong. Did you know the max speed reading on a '90-91 Reatta is 158 MPH? Thats what mine reads max when I'm just getting up the road.Probably about 20 MPH. This is with the '93 Riviera speedo cluster. I've got the '90 Reatta VSS, BCM, a '89 Riviera ECM. Why is the speed WAY off? Both the '90 Reatta and the <BR>'93 Riviera use a 40K cycles VSS; that signal goes to the BCM, then to the ECM, then to the dash cluster. I can't see why the speed is so far off. Any ideas?

Link to comment
Share on other sites

Does sound like a calibration error but not mph/kph - 158 kph would just be around 98 mph and we know the fuel cut of is at 125. (210 kph). So if the ECM thought you were going 150+, the fuel would shut off.<P>First question - when it does come up, is it linear ?<P>I suspect the problem may be the 89 ECM and 90 BCM. The MPH reading is developed in the ECM but is picked out of the ALDL serial stream by the BCM and converted to the IPX reading.<P>If the 89 and 90 ECM data streams are in a different order then the BCM may be picking up oil pressure and interpreting it as mph. Have you tried a 90 ECM prom in the ECM ? (I may have one around here you could borrow - would need to check). Does it read zero when the car is stopped ?<P>Way to find out is to use something like the DIACOM (www.rinda.com) software/cable and extract the two serial data streams. Another way is to connect a good scan tool and see if the MPH is different if you tell it the car is first an 89 and then a 90.<P>Too bad you are not closer to Orlando: have all the tools and now the back garage is cleaned out.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...