1990 Oldsmobile 88 Speedometer short

LAZARUS4

MEMBER
1990 OLDSMOBILE 88
6 CYL
FWD
AUTOMATIC
150,000 MILES

Recently has an 80K engine put in. Since then I've had intermittent operation of the speedometer while driving. I replaced the VSS since I was also replacing Cam and Crank sensors as well.

My speedometer still fluctuates randomly.

Where should I next check? I'm guessing somewhere in the harness.

3 Replies

JACOBANDNICKOLAS

MECHANIC
108,289 POSTS

If you replaces the VSS, chances are the cluster itself is the problem. It was common for them to short.

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Friday, December 18th, 2009 AT 1:28 PM

LAZARUS4

MEMBER
3 POSTS

Thanks for the insight. My logic is:
The speedo only started acting up after the new engine got put in. When it works is acts like a very touch wire connection (which of course could be the cluster) What I was sort of hoping to do was get a harnass diagram check to make sure that all the connections are solid, before I start pulling out the dash.

So, Does the feed to the Speedo come from the computer directly? Is there a connection that I can check to ensure proper installation?

Tks

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Friday, December 18th, 2009 AT 2:50 PM

JACOBANDNICKOLAS

MECHANIC
108,289 POSTS

I have a copy of the schematic, but you will need to enlarge it to read it. Here is what you are looking for. From the VSS, there are two wires, a purple one and a yellow one. Both go to the ECM numbers B9 and B10. From the ECM, number B11, a signal is sent to the speedo through a dark green wire. A red wire, B12, is for the cruise control. Here is the schematic. I hope it helps.

I hope it helps and you can enlarge it. Looking at it as a map, go to B-5.5.

Let me know if it helps or if you have other questions and thanks for using 2carpros.com.

Joe

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Friday, December 18th, 2009 AT 11:22 PM