91 rally sport

iTrader: (2)

hey I have an 85 I rocz and I swapped an 91 wiring harness for the whole car. but now I cant get the speedometer or odometer to work. im getting the signal up to the computer because I have and ebl-p4 and that reads the speed. but the gauge wont. I tried a good know speed and nothing I have also tried a new printed circuit with no luck so I moved on to trying to find a bad resister on the circuit board. I found one, changed it and still no luck. any ideas?

OrangeBird

iTrader: (1)

I'm no expert here and won't pretend to be one . The one thing that came to mind is that I think earlier cars like your 85 may have had a "VSS buffer" in between the VSS and the speedometer gauge and that later cars like the 91 that the harness came from didn't ? If your speedo was looking for a signal from a VSS buffer but was seeing one directly with no buffer involved could that make sense as to why it doesn't work ?

91 rally sport

iTrader: (2)

Yes that does seem like it would effect it. But I forgot to mention that I am using a cluster from a 91 camaro so all the electronics should but matching up perfectly I would think.

John in RI

iTrader: (167)

Didn't the 90-92 TBI use a VSS Buffer,... but TPI and MPFI just used the ECM ??

91 rally sport

iTrader: (2)

Ur right but I bought the harness from hawks and that what they sent me so I assumed I needed it to recieve the signal from the vss

John in RI

iTrader: (167)

?? I can only assume that you really meant "ALL the wiring" ,.... was it all from a TPI car and are you still running TPI ??


Are you using the 90-92 VSS ?

91 rally sport

iTrader: (2)

The engine harness is but the interior is feom a tbi it has the buffer box that im guess has to be bypassed

birdtojag

iTrader: (1)

91 TBI cars had speed sensor buffer and TPI is internal to ECM. The body harness does not match up with the TPI engine harness. The way to tell is the red wire coming from the engine harness that connects to the body harness is on the engine side and not the body side. Bypassing it will not allow the cruise control to work due to the cruise getting signal from the sensor buffer.

John in RI

iTrader: (167)

+1

The C100 diagram shows the TBI Dash harness is expecting the VSS Speedo wires at D4 and E4 to the Buffer, then from Buffer to the Cluster. ( Pin C, TAN wire )








Meanwhile the TPI ENGINE harness expects the speedo wires to feed directly to the ECM @ pins B9 and B10, then out to the Cluster. (pin D of C207 )


Looks like you've still got a little re-wiring to finish before the speedo will work properly. It should be modified to be the same as the TPI design as the TPI ECM needs the speedo info.


Here is how the TBI speedo is wired:



Here is how the TPI speedo is wired:


Good Luck !

91 rally sport

iTrader: (2)

I tried that today with no luck

Bradlyj8Z28

iTrader: (2)

Did you look at this thread yet?

https://www.thirdgen.org/forums/elec...92-camaro.html

Just something to get the brain stimulated and hopefully come up with some more ideas.

John in RI

iTrader: (167)

If you've corrected the wiring incompatability correctly ( re-wired to be EXACTLY as shown in the schematic for TPI cars ) then it seems like your gonna' have to remove the VSS and check if the speedo gears are still mounted correctly on the VSS and that the DRIVE gear is still intact and mounted properly on the tranny tailshaft inside the tail housing......

91 rally sport

iTrader: (2)

I probably rewired it wrong. But I connected a lap top to my ebl p4 and it read the speed from the computer its just not getting to the speedo

91 rally sport

iTrader: (2)

ill be honest im not the best at wiring. and this is confusing me very much.

camarotucker

iTrader: (2)

85 TBI converted to 91 TPI, (91 TPI engine harness and computer) (85 TBI interior harness)

speedo, Pin D "GRY" of C207 (clear side) must move to pin k "BRN" (clear side).

cruise, pin E (buffer box) must connect to C207 pin P "red" (black side) (may have to run your own wire for this)

Connect pin F to pin C (buffer box) box can now be removed if desired.

91 rally sport

iTrader: (2)

Actually its a 91 tbi interior harness with a 91 tpi engine and computer.

camarotucker

iTrader: (2)

Same procedure as above

91 rally sport

iTrader: (2)

I rewired it like you said and got the odometer working again . but the speedometer is still not working

91 rally sport

iTrader: (2)

I was out fooling with the speedometer today. And I got it to work. I cant thank you guys enough!

tonys91rs

iTrader: (17)

I have it wired exactly as it's posted. Still no speedo or odometer. I'm using another cluster where the speedo work.
I moved the pin d grey to the pin k brown black side. I ran a wire from the buffer box connector pin e to pin p black side then. I connected pin f to pin c on the buffer box connector. The buffer box was removed
This is correct?

camarotucker

iTrader: (2)

speedo, Pin D "GRY" of C207 (clear side) must move to pin k "BRN" (clear side).

Should have been moved on the clear side of the connector?

tonys91rs

iTrader: (17)

sorry typo. the pin d GRY (clear side) was relocated to pin k (clear side). there was nothing in pin k, but it now (gry wire) connects to a brown wire on the black side through the clear connector.
was the other wiring correct? I basically ran a wire from the buffer box harness pin e to black side pin p.

"Connect pin F to pin C (buffer box) box can now be removed if desired. "
-does this mean pin f from the clear side of the harness, black side, or the buffer box connection?

"cruise, pin E (buffer box) must connect to C207 pin P "red" (black side) (may have to run your own wire for this)"
- I don't have cruise control. do I still need to run this?

tonys91rs

iTrader: (17)

I reedited the above post. also is there a way to test the vss itself?

camarotucker

iTrader: (2)

If you don't care about cruise, leave it alone. The cruise circuit has no effect on any other circuit.

The PCM (TPI) is now doing the job that the buffer box was doing. So, the buffer box is no longer needed, however, the VSS signal is still being routed through the buffer (signal from PCM (input) pin c, signal to gauge (output) pin f). Simply cut the wire to pin c and the wire to pin f and connect the wires to each other. The buffer box itself is dead to you, if you want you can literally throw it in the trash.

Pin C and F are at the buffer box itself.

post #9 showing pin F as "BRN" pin C as "Tan"

tonys91rs

iTrader: (17)

as I shared in a private message with CamaroTucker, im posting to share with everyone else and hopefully get this resolved. I do appreciate his help in this.

I believe I have everything wired correctly, but its still not working. I switched out vss sensors, and nothing. I switched out gauge assemblies and made this discovery. although the gauge panels were identical, even the year and code on the back, the two speedometer boards have different connectors built into them they were not able to be switched.
one board you can see the visible damage. the other one I attempted a resistor repair, prior to the repining in this thread. I do not know if it was successful or how to test it. I don't know if the damaged board was prior to install.
you can see in the second picture the difference in the connectors and the damage.
what I think I need is another speedo circuit board.