Howdy everyone, please go with me as I try and track down why my beloved beater with a heater is misbehaving. I chased wiring diagrams replaced parts and tested several things but what and why its doing this is beyond me... so I present my case in hopes that the Accord gods will smile down on me and provide me with direction.
First time poster long time lurker.

Here we go, 2000 accord f23a1 with manual tranny, this adventure started one day when my tach and speedo both stopped working at the same time. They would both come back at random and stop working at random, the cruise control and Vtec would still function as normal even if the tach and speedo weren't. I checked grounds and fuses (with multimeter) I found nothing wrong. I then looked through the wiring diagram and decided that the multiplex had went bad as on this combo that's the only thing that both of them run through. The tach would lay on the needle and the speedo would read 40 MPH whenever the car was running.

I ordered the multiplex and while waiting for it to arrive I replaced the the VSS on the back of the tranny. After replacing the VSS I lost cruise and Vtec (stupid me I pitched the original VSS). Upon replacing the Multiplex I regained the tach function but still no speedo, cruise or Vtec. I thought well I might have gotten a dud right out of the box on VSS so I ordered another one of a different more reputable brand, the only change is that the speedo no longer reads 40 mph whenever the car is running it just reads zero now. I haven't been able to find the specs I need to test the wiring to VSS.

My thoughts were also that well whenever whatever was intermittent was working they functioned normally because they would both work. I'm at my witt's end chasing this. I drive 100 miles a day for my work commute and driving my cummins is killing me in fuel bill.

 

Was any work or other issues previous to the speed/tach problem showing up?

It is probably more important to get the car running properly by fixing the VSS first without the cluster signals, so you can still drive and use the CC.

The original VSS was probably working properly, because your cruise control worked. Replacing the VSS is pretty simple, so only a few items could go wrong on the install. I'd fix the VSS issue first, then work on the orignal. There is a plastic gear inside the transmission that drives the VSS and could have come out with the original VSS. Look at an oem parts site like hondapartsnow.com to see what I'm talking about. If you did any electrical testing on the VSS electrical connector, you could have spread out the female pins and now have a poor connection. You can close the gap with a pick or a mini screwdriver. Was the new VSS a Honda OEM part or aftermarket?

As for the original problem, your VSS and tach are unrelated electrically, so your original problem likely lies in the instrument cluster or a faulty electrical connection/wiring to or near the cluster.

I'll suggest getting a shop manual for your car if you don't have one. automanualsource.com has an OEM pdf of the 98-02 for ~$22 that help a lot for DIY work.

 

Thanks for the reply, the second VSS is a BWD as OEM is discontinued. I haven't pocked around the VSS connector yet with the MM. As far as work done yes I pulled tranny and reshaped the sycnro dawgs as I lost IIRC 3rd and reverse ( I bought the car at auction assumed a kid was driving it and chewed the syncros up pretty badly), but that was about 100k miles ago. I cant find the plastic gear in any of the parts diagrams. most of the internal parts for this trans are discontinued. I might have to stick a bore scope down there and see what I can see.

 

hondapartsnow.com has the VSS and components shown under manual transmission, then MT clutch release. I don't know what items come with the new sensor, but you should have an idea of the items that drive the sensor. I just remember reading that a small plastic gear can come out with the VSS and it is easily overlooked.

 

The new sensor comes with the shaft and gear shown on the parts diagram. I'm going to have to get a look down into the tranny to see what drives the sensor. I'm thinking I can pull the sensor and have someone sit in the car with it running and spin the VSS sensor shaft with a drill and see if the speedo responds to verify function.

 

Update, The multiplex was the reason the speedo and tach were dropping out at random. The reason my cruise control and Vtec still worked was because my VSS was good, like a moron I replaced the VSS before I replaced the multiplex to verify the fix and caused myself more heartache with 2 bad VSS's in a row (different brands and price points).

Thanks for the help guys.