Armored91Camaro

I have finally got a fix to most of everybody's speedometer problems, i'm new to posting but ill try to make this short, sweet and informative, along with pictures. I also have ECM 7730. Also I should mention 91-92 camaros that are TPI V8, MPFI V6 do not have a Vehicle Speed Buffer as the computer MEM CAL takes care of that. 91-92 camaros that are TBI v8 do have the VSS Buffer, which is a YELLOW box located on either the Passenger side behind the kick panel, or mounted to the computer, or could also be located in behind/beside the Gauge Cluster. I am not sure about 1990 models, i assume they all have the yellow box.


First of all, I tried reading any and all posts and to no avail i found nothing that was a sure fire fix. So i set out to fix it my self and create this post as I hope it help everyone else that is having the same issue(s) that I have had.

Second, I did a voltage check on PINs B10 yellow wire (vss positive input signal) and B9 purple wire (vss ground) to make sure my Vehicle Speed Sensor was sending voltage to the ECM. That Checked out. While I was there, I checked out PIN B11 grey wire (Speedometer signal wire) and nothing seemed to be coming out, so I did some research and found out that B11 receives signal from the Speedometer itself, B11 does not send signal it receives it.

After all of that, I went ahead and checked the Cruise control wire which I believe is 4000ppm. Everything check out very nicely. My cruise control always worked but I was confused as to why but I checked the wire anyways, which is the RED wire I have circled in red below:

From there I tested the Resistance of the Grey to make sure it was still a one piece wire and that nothing or no-one has cut it in half. It ringed out just fine. So I hooked up the voltage meter to the B11 pin on the ECM and drove the car around the block, no signal at all, ok, so I hook the voltage meter up to the grey wire on the back of the Gauge cluster and drove around still no voltage, the wire is circled in red below:

From there I preceded to take out the cluster and in spec the Speedometer itself. everything seemed fine. Then I remembered the speedo sends voltage to B11 so i traced the circuit board. All seemed good. The I randomly got board and started testing all of the resistors on the little mother board that is connecter to the Speedo shown below:

(ACTUAL resistance is 3.9ohm not 30ohm) "corrected 08/2019" If you notice I replaced a resistor that I thought was bad because it had no resistance, below is a picture of the bad resistor:

I did some color coding and found out it was 30ohms, so I took two 15ohm resistors and made 30ohm, i think the total readout was 30.2-30.4 ohms max. (Discovered by other members my mistake on the resistor actual resisrance is 3.9ohm)

While i was there i notice that a capacitor had blown out, so i replaced that as well, i do not remember what i baught but I got to from radio shack and it was a high capacity than the original, shown below:

Ok so i put everything back together and crossed my fingers, started backing the car down the driveway and i seen the speedo move slightly and i thought nah im seeing things. So I put It in 1st gear and boom I was showing speed! lol. It works great, today if i can get ahold of a GPS im going to try and see how accurate it is vs the GPS.

Thank you for reading and I hope this helps many many others.
Michael.
www.TheComputerArmory.com

Armored91Camaro

Ok today as i promised I used my aunts TOMTOM gps going down GA 400 hwy19 to work and the speedometer matched the GPS readout exactly even at 100mph I can't beat it.

zombienerd

Good find. Good Fix. Congrats!

Armored91Camaro

Thank You!

phasevariance

This turned out to be the exact problem with my speedometer and it was such an easy fix. Two 15 ohm resistors to replace one bad 30 ohm.

Thank you!!.

BluFBdy

iTrader: (1)

I'm having a similar problem but ky issue is slightly different, I'm recieving voltage on pin b11, the odometer is spinning but the speedo isn't moving the slightest bit, any ideas?

ibmtech

iTrader: (1)

Is your Speedo Cable driven?

BluFBdy

iTrader: (1)

Nope, I've done a full 90s swap, hence the post in the 90,91,92 speedo fix thread

ibmtech

iTrader: (1)

Sorry, didn't catch that, You stated that the odometer is changing but the speedo isn't moving. I can't get the schematics from where I am at until next week at best. I wish I could see the wiring diagram for that dash.

BluFBdy

iTrader: (1)

Atgo has wiring diagrams for the 92 cluster towards the bottom of the list

http://www.austinthirdgen.org/index.php?pid=44

abray1

I put a 140 cluster in my vert and wouldn't you know it; the speedometer doesn't work.

dads old blue 9

good stuff this site saved me alotof$$$$$$$$$$$ and great people!! thanks alot everybody . Does anybody know who started third gen ? I'd like to send him/her a dinner for two on me.

theurge

i did the same thing, the 30 omh resisters was gone, and so was the capacitor, i replaced both and still nothing with my speedometer, i got a new vss installed after the circuit board fix you shared, but still nothing, im going crazy, its been 3 weeks of playing around, everything checks out but i dont understand what the heck that needle wont move! would anyone one know where i can find that integrated circuit module on there i think its labeled DB9022M maybe if i replace that one too it will work? i searched online but no luck on finding it

Armored91Camaro

possibly a bad or rusted up needle motor. In my 91 the vss is built into the ecm. Sorry for being gone so long guys just completely got side tracked with new manager position, 2 yr old and wifes gecko business.

Armored91Camaro

Also I have a Tach thread somewhere as well

Armored91Camaro

Welcome.

AGearHead4life

Great write up man. Thank you for sharing. It takes a lot of time to write something up like that and I am appreciative.

Armored91Camaro

Your welcome, also my trip meter started to randomly work about 2 weeks ago back in july, i took out the speedo one more time to line the cluster with aluminum tape to help make it more reflective with the LED strips i was installing, anyways i had driven about 70 miles before i noticed it was working, so possibly bad connection cause iv had it out atleast 50 times and never could get it to work, so i have no clue as to why it started lol.

studebaker60

got a 91 firebird, 305 cid TB. Speedo worked fine with a bad transmission (3-4 clutch packs out). Paid a shop to R&R the trans. The rebuilt trans that I bought had the steel wheel for the speedometer, wiped out the plastic gear. Bought a new gear, removed the drive gear from the old trans and broke the clip. Ordered a new clip and put it all in. The speedometer takes about 10 -15 miles before it works. Some times it will start working by it's self and other times I bump it into neutral at 75 mph, tach drops to idle (800 ish rpm) then the speedometer starts working. I tested a new sensor for the trans, I get about 7 volts AC with a Ryobi cordless drill. Got about 6.5 volts AC with the old one. Took the cluster out, disassembled it, blew the dust out and reinstalled. Same problems. First question is does the clip that holds the speedometer drive gear go in the hole closest to the drive shaft or towards the front of the car. the gears seem to be engaging fine, but not sure. Second, what do I chase, check or replace next? Thanks in advance.

Armored91Camaro

The clip i have no clue about i have never disassembled my tranny yet, also if the clip is in the front now put it in the rear and see what happens, or the reverse. If all else fails the rebuild could have slight play in it somewhere.

92lpeb4c

Just finished fixing my speedo using this method. Thank you Armored91 for taking time to put this write-up together. Cheers

Armored91Camaro

Your welcome, took me a while to figure it out myself, thats when i decided to make the post noone else had made one yet either.

B1CrwDwg

GREAT INFO...although being stationed in Japan it was a nightmare trying to decipher where to find the parts I needed so I ended up sending my speedo and circuit board off for overhaul/recondition, but the info you posted pointed me in the right direction. THANKS!!!

If anyone is interested here's the place I sent my speedometer and circuit board to:
Hawks Third Generation
1-864-855-2694 Ext:11
www.Hawksthirdgenparts.com

Armored91Camaro

Yes, they are very awsome i have used them for years with no issues ever.

domprim

Does anybody know where i can purchase a brand new Speedometer circuit board for a V8 1992 Z28 Camaro?

Armored91Camaro

http://www.camarocentral.com/product_p/das-460.htm

also i just found this website now,
http://www.wc-autoparts.com/1990-92-...circuit-board/

White92RSVert

This thread is still going strong. The board fry of the resistors and capicator was exactly the problem with my speedometer. Thanks!

studebaker60

After rechecking all of the electronics, Figured out that there are at least two different housing for the speedo with different depths. Put about a 3/8 inch spacer between the gear and the generator and it works great all the time. Something to consider if you replace your 700R4 trans.

Armored91Camaro

You very welcome.

92camaro350

I went to try and do this fix because my speedo wont move at all and when I took apart my speedo gauge it had different resistors than what you have in your pictures. According to the color bands mine is only a 3.9 ohm resistor in that location. What would be the reason for this? I have a 92 rs, originally it have a 305 tbi

Armored91Camaro

Im not sure as to why the huge difference but i do have the 110mph gauge cluster, and are you sure that you read the numbers to the colors correctly?

Armored91Camaro

Holy crap I just realised that i made this thread 2 years ago, man how time flys.

oldmotorhead64

Armored91Camaro,
Thank you for an interesting thread read and pics. My question is odometer related. I have a 92' RS Camaro, analog gauges, with only 15K original miles. My speedometer and all other gauges work fine, but last weekend while driving my odometer just stopped working. I was wondering if that would also be an electrical issue like your speedo was or do I look another direction like a mechanical/cable issue? If you can provide any input on where to start it would be appreciated. Thank you!

Armored91Camaro

If i remember correctly, the speed sensor would be the first location to check. The sensor should send voltage to the ecm, i think but if i remember correctly the speedometer takes the ALTERNATING current that the sensor gives out and converts it into a DIRECT current that the ecm understands. I could be wrong as it has been 2 years since i fixed my issue and havent had to look back.

tonys91rs

iTrader: (17)

well maybe someone here can help me. I have a 91 tbi that was converted to a 92 tpi using the 92 harness. after a while the speedo quit. I have the yellow buffer box under the dash. I replaced the speed sensor with another and the speedo still does not move. should I unplug the buffer box or leave it connected? where do I go from here?

BluFBdy

iTrader: (1)

The tpi system would have made the buffer box obsolete, there should be a simple repinning procedure to correct it

tonys91rs

iTrader: (17)

does anyone know what this repining procedure is? how come my speedometer worked for a while after converting the tbi harness to the tpi?

jonny_z9

I got the board pulled out on mine to see if i have the same problem. The resistor on mine looks different than the bad one you had, its brown and had a reading of 3 or 4, i dont remember exactly. Im going to go to radio shack today and try to find a replacement resistor anyways to see if that was my problem. My capacitor held charge so its good, i also used a 9 volt and connected it to the pins on the back of the speedo and the needle moves. Do you think my problem is elsewhere besides the speedo itself?

Bradlyj8Z28

iTrader: (2)

Wow. So my speedometer acted wierd a few times before my LS swap. After LS swap no speedo. I have tried to figure it out off and on and it should be working. Hope this works for me too. Thanks for the in depth write up.

Dougs91Z

iTrader: (1)

The two 15 ohms resistors fixed my speedometer on my 91 b4c, took a a few miles before is started reading! Thanks for the thread!

tonys91rs

iTrader: (17)

I had attempted this fix prior to learning about repining the ecm and eliminating the buffer box. I had completed the repining and the speedometer still does not move. I switched out the gauge panels for another. again no functioning speedometer. I switched out the vss and still nothing.
I took apart the gauge panel to check the speedometer circuit board. I found that it was fried. honestly I don't know if it was like that or I did that as I was repining the ecm. previous owner said the speedometer worked fine.
I discovered that the two speedometer circuit boards were slightly different. the connectors are not the same.
below is a picture of the two circuit boards. you can see where the unmodified board burnt out. the other board was the one I modified with the resistors.

does it appear that I have the correct resistors on it?

obeymybird

iTrader: (4)

So when your speedos die are they at 0mph? cause mine died at 40mph and hasnt moved since its a 92 tbi 5spd factory i swaped in 350 tpi 6spd speedo worked before and after the swap and was trying to get the dakota digital box setup when it stuck at 40 any ideas?

FryeDaddy

iTrader: (1)

What's the difference between this and transmission speed sensor? My speedometer slowly went out, now rarely bounces back up to correct speed but then sometimes drop again.

775carguy

So i searched a ton of threads about this issue. This was very informative even though i have a V6. i actually did this with 2 clusters and it still didnt work. I pulled the cluster out 1 more time and looked closely at the Plug itself. I had already tested it with the tires off the ground to make sure i was getting A/C voltage. What i didnt notice was that someone had pinched the terminal down on the gray wire. It wasnt making contact when the cluster was pushed back. I used a small pick tool to push it back up a little. Installed the cluster and wouldnt you know it. BOOM speedo works. Now i just need to get the Odometer working. Thank you very much for the assistance.

Oncea3fan

Well I pull my speedo, and checked all the connection and cuircut board everything checked out.
I noticed some corrotion on the contacts so I used contact cleaner and a Q tip.

so far it is working again, this may be why it was working on and off.

Armored91Camaro

Wow i never thought my thread would get this large, anyways on the original resistors there should have be color coded lines just follow them. for the other guy yes corrosion can be a cause for it to not work, i sprayed my trip meter with wd40 and it started working at random.

Oncea3fan

just did a 2 hour trip , working great

sabien

I have an even stranger problem than most. I pulled the engine and the ECM out of my 1991 TBI, 5-speed and stuck in a warmed over 350, carbureted. My speedometer works, but not after 75MPH. That is as fast as it will register no matter how fast I push the car. This is a 140 MPH gauge cluster swap. Any ideas why it will read ok until 75,and will go no higher, or should I be glad that my speedo is working at all given there is no computer.

junior419

I did this and fixed my speedometer and odometer, thanks alot. I do have an issue though and would like some feed back. It's a stock 92 tbi. Speedo says it can go 110mph. my speed is off by about 15-30mph. For example I will be going 60mph according to gps but my speedometer is sitting at 90mph. the problem I am having is once my speedometer hits 110 my camaro bogs down and has no throttle response. When I'm probably going 70mph or 80mph. could this be the result of a bad speed sensor at the tranny?

jfreakofkorn

this is a helpful thread, thx =0)