90 SI 2.1 Honda Prelude


Old 04-23-08, 04:15 AM
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Question 90 SI 2.1 Honda Prelude

Hi! I just brought a 90 Honda prelude and I'm having problems with the speedometer. The speedometer intermittently stops working, and at the same time the S3 light starts flashing on the dash. How do I troubleshoot and repair this problem?
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Old 04-23-08, 04:31 AM
the_tow_guy's Avatar
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Must be too early in the morning, but what's the S3 light?

Speedo problems like that are often the vehicle speed sensor (VSS) which is generally mounted in the transmission. I'm not sure there's a troubleshooting procedure for the sensor short of replacing it other than checking connections for security/corrosion/broken wires.
Old 04-23-08, 11:39 AM
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1. locate speedometer sending unit on the transmission
2. it should be attached in place with one bolt, usually 10mm head. if you have electric connector on top of sending unit, unplug and clean/lubricate with dielectric grease. check if it came back to life. no can do for cable type speedo.
3. for cable type speedo or for one with electric connector, if step 2 did not help, losen the bolt to the point that you can wiggle sending unit. tilt it towards the driveshaft center. sending unit is, usually, on the firewall side of the driveshaft, where driveshaft enters trannie.
4. i, usually, jackstand front for this test, so that i can start the engine and put trannie into D. then i tilt sending unit towards the driveshaft center. this means: part that is INSIDE trannie has to be tilted towards driveshaft, while part that is OUTSIDE away from driveshaft. if speedo came back to life, plastic gear on the sending unit shaft, that engages with gear on the trannie output shaft, is worn out and needs to be replaced. if you can't jackstand the car, jamm something to keep sending unit tilted that way, and drive for some time. i drove for long time with sock jammed between trannie and sending unit once. please, make sure that you do not have unit pulled out too far, or you can spill trans fluid.
5. if that's the case, pull sending unit out, remove plastic gear, and replace. in my case, was roughly $10, vs $800 plus for alleged repairs and 3 days without car (xxxxxxxxxxxxxxxxxxxxxxxxx)
if this test, if done right, as you have to tilt sending unit the right way, does not restore speedo, then you have something else going on. if it's electrical sending unit, rust/corrosion on both unit AND inside the instrumental cluster is possible. for cable driven one, if the cable goes bad, it'll start making choo-choo noise driving, chah, chah, chah. cable rubbing inside the housing. get one off junk yard and replace.

Last edited by carguyinva; 04-23-08 at 11:44 AM. Reason: Bashing not allowed.

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