No speedometer when cold, flashing S4

Third Generation Honda Prelude topics

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jhcowboy
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No speedometer when cold, flashing S4

Postby jhcowboy » Sun Sep 06, 2015 12:34 pm

Hello all, new Prelude owner,
1990 auto SI 2.1 engine, no modifications.

I'm reading a code 17 out of the vcm and just four flashing codes on the transmission module?
I know 17 is the speed sensor or a connection so I removed and tested. Zero ohms with no magnet and 105 near the magnet, so what number should I see?

Before checking the sensor it would shift a little rough between 1st & 2nd and a fairly hard down shift when turning corners. Since checking sensor, problem changed and now it shifts at 4000 rpm or you can let off the gas it and shifts. Could I have damaged the sensor by getting the magnet to close?

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spiffyguido
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Joined: Fri Nov 11, 2005 2:55 am
Prelude Model: 1991 SE-SR
Location: Alberta, Canada
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Re: No speedometer when cold, flashing S4

Postby spiffyguido » Mon Sep 07, 2015 9:57 pm

A quick read of the service manual indicates that you are correct to suspect the speed sensor as the source of the problem. 4 flashes on the S indicator can be caused by problems with the speed pulsar.

I wasn't able to find any resistance specifications in the service manual. The procedure suggested actually suggests just measuring the voltage across pin A6 on the transmission control module while the ignition is on (but engine off). Voltage should alternate between zero and 5V as a wheel is turned.

See page 9-14 and 9-24 in the service manual.

Can't tell you whether you may have damaged the sensor. I'm not sure if they would be susceptible to an overly strong magnetic pull.

jhcowboy
Prelude Enthusiast
Posts: 2
Joined: Tue Aug 18, 2015 4:41 am

Re: No speedometer when cold, flashing S4

Postby jhcowboy » Wed Sep 16, 2015 9:56 pm

Just a little feedback would be helpful. Following the trouble shooting guide in the service manual and wiring schematics, I've identified my problem as the plus generator VSS. It was strange that the manual lead me to replacing the transmission module, lucky enough it was only $45 on eBay, so no great loss. Once I eliminated it, I just started isolating each circuit and as each one passed, it lead back to the to VSS.
Now, it discontinued at Honda, can't find one anywhere? OEM part number 28510TR0013.

Any suggestions, other than a manual transmission?

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spiffyguido
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Posts: 2196
Joined: Fri Nov 11, 2005 2:55 am
Prelude Model: 1991 SE-SR
Location: Alberta, Canada
Contact:

Re: No speedometer when cold, flashing S4

Postby spiffyguido » Sat Sep 19, 2015 1:36 pm

Auto wreckers have always been my most reliable source for discontinued parts. If there is a Pick-N-Pull or similar self-service wrecker in your area I'd check there.

Otherwise, eBay, but such an obscure part won't come up that often.




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