Speed Sensor R&R, or "I may be the worst DIY mechanic on the planet"

OK, so I had intermittent speedo on my '91. Did the requisite search here on Prime, did some investigation on which part I needed (thanks, Larry B and other Prime posters!), ordered the speed sensor, found some threads here that said "5 minute fix".

Not for me. Not EVER for me. I dunno, I used to be good. I've replaced the head on a '74 Pinto, rebuild Holley carbs, did timing chain and removed the heads on Ford 302 , often change the brakes on the Track Rat Miata, did my own Leatherseats.com install on my NSX, re-adjusted the window regulators on my NSX, rewired all lights on a travel trailer, etc., etc. I'm not completely unfamiliar with a wrench. But every once in a while a seemingly simple endeavor absolutely kicks my ass. This is one of those.

(Yeah, I know. The older I get the [multi-select from the drop-down list of values: faster; smarter; better looking; thinner] I was.)

Tools/items needed:
1. 10mm socket
2. Short extension
3. Ratchet
4. Jack and stand
5. Patience
6. Curse words when run out of (5)
7. Thick bearing grease
8. Optionally, circuit tester
9. Optionally, drill-driver
10. Fender cover
11. Flashlight

OK, removing the old sensor is easy-peasy.
1. Disconnect the harness up near the fender so when you stick your left arm down to the speed sensor you don't tear up the fleshy part of your forearm. You'll know which one when you try this repair.
2. Disconnect the speed sensor harness
3. Remove the two 10mm bolts on either side of the sensor
4. Remove the sensor. Take care of where the small orange o-ring gasket and the sensor drive shaft end up. They are awfully small parts.
5. Pick up the sensor cover from the garage floor after it invariably falls

So far, so friggin' good.

The manual is so, how shall we say it, full of bull. Or, as in the title, I am the world's worst backyard mechanic.

See, the manual says to reverse the steps to re-install. Yeah, right. What the manual doesn't say is that the cover goes between the tranny and the sensor, its center of gravity is such that it doesn't want to stay lined up, and that you probably need two hands down there but only one fits. And don't forget about trying to get the tiny drive shaft to engage.

After an interval of time that I will only admit to being "more than 5 minutes", the sensor, including cover, was in. Finagle, cajole, use up 90% of patience, consume a few of the curse words I had in reserve, and it's in. Test drive the car. Speedo does not move. Consume some of the more robust curse words.

I broke out the manual. Did the tests on the harness. Black to ground, continuity, uh-huh. Yellow-red and Yellow-black, with ignition on, showed 12v and 5v, per the manual. So, what is the problem? Per the manual, if electrical tests pass, the sensor is bad. But I just installed the new sensor.

OK, removed the sensor, and connected the harness. This is I got creative and where the drill-driver comes in. Turned on the ignition, hooked up the drill to the drive shaft of the sensor, inserted the shaft in the sensor (which is in my hand, not on the car), and spin it clockwise with the drill. Hmm, speedo registers all the way to 100MPH. Use another of the more interesting curse words, sorta along the lines of "well, [insert very blue action verb here] me." Must not have engaged the shaft properly when installed it in the car.

OK, opened a new can of patience and analyzed what I had done. Here's what NOT to do:

- Don't leave the shaft in the transmission
- Don't try to install the sensor, cover, and bolts all at once

What ultimately worked for me:
- Put a dab of thick wheel bearing grease on the drive shaft and inserted it into the sensor. The thick grease, besides lubing, helps hold the shaft in place since the shaft hangs down and is prone to fall out. Before you do this, put the shaft in the tranny to see how it is oriented so when you put it in the sensor the tabs on the sensor line up in the tranny.
- Put the orange o-ring on the shaft. (OK, c'mon guys, get your minds outta the gutter!!!)
- Install the sensor WITHOUT the cover. This will ensure you have lined up the shaft and the bolts, and have truly engaged the shaft between the sensor and the tranny.
- Optionally, drive the car to interim test it. (Don't forget to re-hook up the harness you had removed to give your arm room.) Don't drive too far, just a few feet; don't want to get the engine compartment hot.
- OK, here's the tricky part, at least for me: the cover. Loosen the bolts holding the sensor in place JUST A LITTLE BIT, just enough to be able to float the sensor, enough so that the cover tabs fit under the sensor. Completely remove the sensor bolt toward the back of the car. Leave the other bolt in place to maintain engagement of the drive shaft.
- Jack up the car (with jack stand of course!)
- From underneath, cajole, finagle, slide the cover in between the tranny and the sensor on the side that doesn't have the bolt.
- Go back up-top and install the bolt. Leave it a little loose.
- Remove the other bolt.
- Go back underneath and slide the other side of the cover between the tranny and the sensor.
- Go back up-top and install the other bolt.
- If the stars are aligned, and you have been good all year, and the shade tree mechanic gods are in a good mood and are done screwing with you, the shaft will still be engaged with the tranny.
- Tighten the bolts
- Hook up the sensor harness
- Hook up harness you had removed to give your arm room
- Remove jack and jack stand
- Test it. Celebrate, smile, consume some of remaining curse words you had set aside, something like "[insert appropriate gerund here]-right, man!!! It's [gerund]-fixed!"

:biggrin:

hmmmmm........that's strange..........it only took me 5 minutes

Dhalsim said:

hmmmmm........that's strange..........it only took me 5 minutes

Click to expand...

I KNOW, right? Hence, the sub-title.

Replace the word "patience" with "beer."

Update:

I changed out the sensor on Friday. On Saturday morning I left to do the Exotic Car Toy Rally for Toys for Tots. When I put the car away on Friday the speedo was working and I had declared victory. Of course Saturday morning it was NOT working again. It exhibited the same behavior as with the "old" suspect speed sensor in the car: on first use it would either not work or work only up to about 20 MPH, then drop to zero, and then when I got under five MPH would then work a bit until around 20 MPH, then drop to zero, then eventually work for the remainder of that trip.

Any ideas? Of course, if it is electrical with a break in a wire somewhere, diagnosing it would depend on being able to replicate the failure, which as of now is annoyingly intermittent, although happily intermittent enough to be not working only as long as it takes me to get out of my neighorhood.

Things I can think of:
- Speedo at the instrument cluster is bad
- Connection of the harness at the instrument cluster is bad
- New speed sensor is bad, although I highly doubt it
- Engagement of the sensor shaft is wrong, althoug I also highly doubt that, too
- Some wire between the harness in the engine compartment all the way to wherever it goes has a slight open in it
- Harness the speed sensor plugs into in the engine compartment is bad

Any thought of where I should look next most appreciated. Without a solid recommendation at this point I am inclined to leave it until it fails permanently so I can then diag it. So far, while it fails it has never not eventually worked. Frustrating.

Thanks for any help you guys can offer.

Assuming you still have the old sensor, disconnect the speed sensor harness and connect it to the old sensor. Connect the old sensor to a battery-operated drill or battery-operated Dremel-type grinder tool. Turn on the drill for a moment to see if the speedometer indicates 100 MPH, or whatever is appropriate for the drill speed.
Wiggle the speed sensor harness (and speed sensor & drill) around to see if the speedometer does its crazy dance. If not, go to the next step.
Now, the crazy part. Securely duct tape the drill to something so you can turn it on and drive the car. Then go for a drive. If the speedometer does its crazy dance, you now know its not the sensor, engagement of the sensor shaft in trans, trans drive gear, etc. Vibration is causing the speedo, instrument cluster, wiring, etc to act up. Go drink a beer or two. Now you have narrowed down the problem, but it still will be ugly to find the cause.

ftuhy said:

Assuming you still have the old sensor, disconnect the speed sensor harness and connect it to the old sensor. Connect the old sensor to a battery-operated drill or battery-operated Dremel-type grinder tool. Turn on the drill for a moment to see if the speedometer indicates 100 MPH, or whatever is appropriate for the drill speed.
Wiggle the speed sensor harness (and speed sensor & drill) around to see if the speedometer does its crazy dance. If not, go to the next step.

Click to expand...

Yeah, I already had done this as part of my original diag. What I maybe didn't do enough was wiggle the harness around to see if I could duplicate the intermittent part. I was focused originally on whether I had engaged the sensor shaft. Good thoughts for diag on the engine compartment wiring.

ftuhy said:

Now, the crazy part. Securely duct tape the drill to something so you can turn it on and drive the car. Then go for a drive. If the speedometer does its crazy dance, you now know its not the sensor, engagement of the sensor shaft in trans, trans drive gear, etc. Vibration is causing the speedo, instrument cluster, wiring, etc to act up. Go drink a beer or two. Now you have narrowed down the problem, but it still will be ugly to find the cause.

Click to expand...

Also a good thought but struggling to picture how I would accomplish this. I'll give it some serious thought.

any updates on this troubleshoot?

nikey22 said:

any updates on this troubleshoot?

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Inconclusive. Since the initial install and problem next morning, it has not failed since.

Doug, your problem is that you're not used to working while looking at something upside down, in a mirror, with one eye closed. Oh yeah, don't forget using a electric drill spinning at 300,000 RPM.

Strange, who in the world needs to see something to change it - or use two hands to hold only a couple bolts, a cover and speed sensor while trying to install some bolts and line up a gear with a shaft???

Great write-up!

Sounds like you got some faulty wires or connections.
And since the ECU seems unaffected by the problem it would seem the problem lies in either the speedo, or wiring to it. The speedo and ECU shares the signal from the speed sensor, and if it had been the sensor itself you should get code 17 on the CEL.

I would gain access to the connectors into the instrument cluster, spin up the speed sensor as you've done before and "wiggle" the wires that goes into the instrument cluster connectors.
It could also be caused by some bad soldering inside the instrument cluster.

1026 rpm on the speed sensor = 60 Mph

I had this problem with the speed sensor as well.. Assuming once your speedo jumps and drops to zero a couple times then the tcs light pops up.. Turn off car let it sit then another test drive works fine.. Has happened a few times. bought a new sensor but have not replaced old one yet since the problem hasn't came back 2 months now since.. Was your sensor still working prior to replacing it?

1stwife said:

I had this problem with the speed sensor as well.. Assuming once your speedo jumps and drops to zero a couple times then the tcs light pops up.. Turn off car let it sit then another test drive works fine.. Has happened a few times. bought a new sensor but have not replaced old one yet since the problem hasn't came back 2 months now since.. Was your sensor still working prior to replacing it?

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I don't know whether the speed sensor was working prior to replacing it. Considering that it behaves exactly the same with the new sensor, I would have to guess that there was nothing wrong with the speed sensor at all.

No, I never got a TCS light. I tend to believe what A_J has posted. (Thanks A_J.) I'll see if the problem returns then try to chase it down, or do as A_J and others have suggested, by working the sensor with a drill driver and monkeying with the connections at the engine compartment harness and at the speedo.

Maybe I'll make some time tomorrow to mess around with it. If the weather is good (i.e., finally not raining in South Florida), I may even take it out for a drive. :smile:

Entertaining read!

Next week I will be in your shoes - speedo died this AM on my '92 together with his 2 friends: CEL and TCS light. I just bought one, not sure I want to get myself into this DIY...

HDA said:

Entertaining read!

Next week I will be in your shoes - speedo died this AM on my '92 together with his 2 friends: CEL and TCS light. I just bought one, not sure I want to get myself into this DIY...

Click to expand...

Not sure if the speed sensor on the tranny is what u need if the tcs and cel light are on. Dont have complete access to the materials to look it up but before you dive i you might want to research further . I am thinking if u got tcs and cel u might need a wheel speed sensor not the speedo sensor on the tranny.

dquarasr2 said:

Not sure if the speed sensor on the tranny is what u need if the tcs and cel light are on. Dont have complete access to the materials to look it up but before you dive i you might want to research further . I am thinking if u got tcs and cel u might need a wheel speed sensor not the speedo sensor on the tranny.

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That is a good point. Many threads talk about the speed sensor without specifying which one is it: Wheels? Trans?...

After a nice 0-80mph on the highway I parked the car and this morning no speed and TCS and CEL: car drives fine.
NSXwiki does not mention anything on it

Thanks for anyone who can chime in.

http://www.nsxprime.com/forum/showt...s-to-zero-Check-Engine-and-TCS-lights-come-on

dquarasr2 said:

Not sure if the speed sensor on the tranny is what u need if the tcs and cel light are on. Dont have complete access to the materials to look it up but before you dive i you might want to research further . I am thinking if u got tcs and cel u might need a wheel speed sensor not the speedo sensor on the tranny.

Click to expand...

Just for reference if it were a wheel speed sensor, you would also have an ABS light.

Regards,
LarryB

Larry Bastanza said:

Just for reference if it were a wheel speed sensor, you would also have an ABS light.

Regards,
LarryB

Click to expand...

Thanks, Larry.

Update on my original situation: This past weekend I took the NSX out, and of course, the speedo was not initially working. So, at the end of my street I stopped, got out, opened the engine compartment, and jiggled the harness and wiring leading to the transmission sensor. Hmm, immediately after that the speedo was working. So, while I can't imagine many others of us would have the same issue, I am pretty sure I have a problem in the wires leading to/from the speed sensor, or the harness on the car has a problem.

But at least I seem to have narrowed it down. Until it fails again and this process doesn't fix it puts me back to square 1. :biggrin: When I have time I will mess around with the wiring and harness in the engine compartment and report back.

Just saw this, you was able to get to your speedo sensor from within the engine bay? i'm guessing you have to reach down next to the throttle body? Is it obvious what sensor it is on the gearbox?

Does this apply for the second gearbox sensor on the later cars? can i do the same reaching down from within the engine bay?

Thanks.

jaffaz32 said:

Just saw this, you was able to get to your speedo sensor from within the engine bay? i'm guessing you have to reach down next to the throttle body? Is it obvious what sensor it is on the gearbox?

Does this apply for the second gearbox sensor on the later cars? can i do the same reaching down from within the engine bay?

Thanks.

Click to expand...

Yes you can. I typically change the speed sensor from the top. Remove the entire unit, then replace the drive pin and sensor on the unit, on the bench, then reinstall. The entire speed sensor is held in the trans case by one bolt.

HTH,
LarryB

At the connector itself, push the wires inward toward the sensor. Sometimes, over time, the pins inside the connectors come a little loose - I've solved many an intermittent issue doing only this. I know it's not scientific, nor does it narrow down the exact problem, but its easy, quick, and free and if it solves the problem - awesome. If not, I don't envy you. I HATED chasing electrical gremlins when I was wrenching on cars for a living.

jaffaz32 said:

Just saw this, you was able to get to your speedo sensor from within the engine bay? i'm guessing you have to reach down next to the throttle body? Is it obvious what sensor it is on the gearbox?

Does this apply for the second gearbox sensor on the later cars? can i do the same reaching down from within the engine bay?

Thanks.

Click to expand...

Btw, second sensor (small one, more towards the top of the trans, is used for the EPS) would seem to be ok, unless you also have an EPS light. And, yes you can get to it from the top.

HTH,
LarryB

Fast forward to this Labor Day weekend.

Since I first reported this problem and worked on it by replacing the speed sensor with a Honda OEM unit, the speedo would behave exactly as it would with the original sensor, that is, would not work the first few minutes then by the time I got out of my neighborhood, about a mile, then would start working and would stay working until parked. Next time I used the car it would do the same thing, sometimes, even when the car was still warmed up.

Last week, it took longer for the speedo to start working. On Saturday, I did a whole outbound trip, about 15 miles, did not work. This is the first time it did not eventually start working. It started working only about 1/2 way back to my house. Today, it didn't work again until I was almost back to the house on a similar round trip. Was working when I pulled in the garage. I did the diags, and got continuity on the ground at the sensor harness, and the proper voltage on the other two receptacles in the harness.

Let the car sit for a while, and drove it up the street. Speedo was not working. Tested per the manual, and again, got continuity on the ground and voltage on the other two wires. I then connected the original sensor that I had replaced, and hooked up drill driver and spun the shaft. Speedo no workie.

So, I don't understand what could be the source of the issue. It could be:
1. The replacement OEM sensor is also bad. I would discount this being the issue.
2. The speedo gauge in the dash has a problem. I did not find in the manual how to troubleshoot the actual gauge. Any hints?
3. There is a break in some wire somewhere between the sensor and the dash.

Are Honda speedo gauges usually points of failure?

Is it possible to run new wires straight from the sensor to your speedo? you would have to remove the speedo to gain access to the harness. Seems like quite a bit of work but it might help.