Posessed Speedometer

[2bigtanks]

My father-in-law has an 04 leSabre and appears as though the speedometer has a mind of its own. It does not return to 0 and it starts at 40mph. It functions correctly if you do the math though. If you are driving and the speedo says 105 the GPS says that you are traveling 65 (105-40=65).

I read another thread where this question was asked but there was no solutions posted so I thought I would ask again.

Any Ideas?

Cheers,

Derek

[HotZ28]

Unfortunally, this sounds like the IC will have to be replaced.

[2bigtanks]

Thanks for the reply. Is the thought that there is a short in the cluster?

Does Buick have the internal diagnostics? i.e. on some vehicles if you hold the trip computer button for 20 or 30 seconds it runs a diagnostic test on various components to the PCM by flashing signals on the IC and scrolling codes on the odometer or some other display.

If not is there some other way to check this out to verify that the IC is bad?

Cheers,

Derek

[Smith1000]

I have put salvaged instrument clusters in both of our '97 Lesabres. One had a speedometer that would jump around. The tach would jump too. The other had similar problems, but I believe it was just the tach. The one with the bad seedometer always registered the correct miles on the odometer. That might be something to check. I suspected the vehicle speed sensor, but the odometer worked fine.

This problem will not set a code, so diagnostics, unfortunately, will not help.