Hey bro_KEN RE:Speedometer

[-=Jeff=-]

Ken,

I was reading about your journey in the off topic section and wanted to ask about your Speedo problem.

First I was not sure which ECM system you are using.. is it still the Stock one? or did you go to the Speed Density system?

Does the VSS on the trans work? is it even the Stock one? The VSS is wired Directly to the Cluster to display speed. If Chris was scanning the car and was registering speed it is getting to the ECM so we know the signal is good

BUT:

If it is the Stock ECM in the car the VSS wires to the Cluster with is a 4Kppm signal, it is then converted to a 2Kppm signal to go to the Stock ECM. If you swapped to the Speed Density System using an GM ECM, the newer ECM (assuming a 7730 from an Fbody) is setup for the 4Kppm directly. so it could very well be that the wiring is no longer connected to the Cluster for Speed.

Just a thought

 

[69MyWay]

Jeff,

You are right on target. He has a 1990 style speed density computer.

The computer is getting a good clear signal from the trans and is reading very accurate.

The signal is dead to the speedo gauge. They installed an all new replacement harness for the engine/computer.

I told him he would most likely need a Dakota Digital calibration unit that could cut the signal coming out of the newer computer to the right signal for the gauge.

 

[-=Jeff=-]

Jeff,

You are right on target. He has a 1990 style speed density computer.

The computer is getting a good clear signal from the trans and is reading very accurate.

The signal is dead to the speedo gauge. They installed an all new replacement harness for the engine/computer.

I told him he would most likely need a Dakota Digital calibration unit that could cut the signal coming out of the newer computer to the right signal for the gauge.

Nope he does not even need that dakota box.. all he needs to do is add wire from the 2 VSS leads on the ECM to the correct pins on the connector to the cluster connector and it should work.. The Vss for the 87 and 90 are the same and his Speedo just needs to be directly connected to the VSS.

My friend has this in his 85 vette with the 90 Speed density ECM and that is what he did.

 

[69MyWay]

That is great news.

His builder/installer in California had been working on this, but they ran out of time before his road trip.


I was looking at his harness. At this time, it is not clear what wires coming down out of the dash are the correct ones/one for the speedo gauge. It is possible that the entire cluster may have to come forward to get a better look behind and track the correct wires.

The new computer has been installed and some of the old harness removed.


What we need to know is the color of the VSS wires to the gauge. Then, we have to verify the pin location and wire colors coming out of the aftermarket harness and make the connection. Or, like you said, just jumper straight from the sender wires coming off the trans to the gauge.

My other question is will this make the cruise work, or is the another jumper position for that?

We really ran out of time.


When I put a 93 LT1 into a 1989 truck, I HAD to get the Dakota splitter to translate the signal. I assumed (you know what happens when we do that) the same problem was present here.

 

[Ken]

Thanks Jeff, I'll be keeping my eyes on this thread.

_ken

 

[-=Jeff=-]

I know the 84-89 Cluster pinouts are basically the same.. I also think that once the Speedo is working the cruise will.

I will check my 89 Shop manual for the correct pins..

Also.. where is the new ECM at? stock location or under the hood..

Chris, since you might have seen this.. is it the under the hood ECM like your '90 or is it a silver ECM with 3 connectors.

let me know and I will get pin locations for that too.

 

[69MyWay]

I know the 84-89 Cluster pinouts are basically the same.. I also think that once the Speedo is working the cruise will.

I will check my 89 Shop manual for the correct pins..

Also.. where is the new ECM at? stock location or under the hood..

Chris, since you might have seen this.. is it the under the hood ECM like your '90 or is it a silver ECM with 3 connectors.

let me know and I will get pin locations for that too.

Good call Jeff. Your suspicions are correct. It is a silver box three connector (like a F body). It will be mounted back in the stock 87 location as soon as the speedo portion is ironed out.

 

[Ken]

Gee, I don't even have to participate in this thread...

Chris knows as much about my car as I! :L

It dawned on me this morning after I left here and was on my way to my mechanic's; I forgot to tell you Chris that I had Terry fax a copy of the GM PORT FUEL INJECTION ECM CONNECTOR IDENTIFICATION sheet. It contains voltage information for the circuit, the pin, the wire color and the circuit number and is used by TPiS for their street rod harnesses. Richie asked me to have them fax it so I hope it helps him sort it out.

Part of me still wants to do that analog conversion though. Then my dash could resemble yours.

_ken

 

[-=Jeff=-]

BB9 and BB10 of the ECM in Ken's Vette are for the VSS (located on the 24 pin connector)

BB9 Purple (VSS Low)
BB10 Yellow (VSS High)

CLUSTER:

D11 = Yellow (VSS High)
C15 = Purple (VSS Low)

I *THINK* it is the 32 pin connector to the Cluster.

 

[Ken]

BB9 and BB10 of the ECM in Ken's Vette are for the VSS (located on the 24 pin connector)

BB9 Purple (VSS Low)
BB10 Yellow (VSS High)

That's what it says here on the id sheet, but there is also a back view of the 24-pin A-B connector that shows a couple of triangles, one with BB1 in it pointing to a pin in the top of the connector and one with BA1 in it pointing to a pin in the lower part of the connector.

CLUSTER:

D11 = Yellow (VSS High)
C15 = Purple (VSS Low)

I *THINK* it is the 32 pin connector to the Cluster.

I'm clueless as to the above information. :confused

_ken

 

[-=Jeff=-]

When you pull the cluster there are 2 connectors.. they look like your ECM connectors.. One 24pin and one 32pin.

 

[Ken]

Yes, I am aware of that--had it in and out many times. I thought that was referring to something else I guess. Obviously I'm not very good at this.

_ken

 

[-=Jeff=-]

Yes, I am aware of that--had it in and out many times. I thought that was referring to something else I guess. Obviously I'm not very good at this.

_ken

Gotcha..

I would suggest ohming out both lines from Cluster to ECM..

I am guessing somewhere they got disconnected.

Worst case you can just run each wire new..

Too bad you did not live in Chicago.. I would be there to help you out

 

[Ken]

Too bad you did not live in Chicago.. I would be there to help you out

We never know do we?

_ken

 

[-=Jeff=-]

We never know do we?

_ken

I guess I would when I would see your rig outside my door

 

[69MyWay]

Purple and yellow are usually the standard colors for these wires.

I was reading my 1990 schematic and it referrenced a green wire as the key feed signal to the cluster. This really confused me for obvious reasons. Then, I noted a green wire in the TPiS harness that the installer had nipped out, attempted to put a splice on, then nipped that off and had it singled out from the rest of the wires.

That is where I backed off until getting more info.

You can usually identify antilock brake and speedo signal wires as they are twisted together in a braid. This will carry through to the cluster in most cars.

I could not locate a braid anywhere in the harness either. The twisting of the wires is good to keep the signal shielded, etc. from outside currnet/referrence current.

Ken, if Jeff is right, that speed should be working fairly quick, and that is great news. The analog gauges are cool too, but your current cluster appears to be in good clear bright colored working order, and it would be a shame to kill it off when it is otherwise in such great condition.

 

[Ken]

...current cluster appears to be in good clear bright colored working order

It should be--it's brand new! :L

_ken

 

[-=Jeff=-]

Chris,

The 90 is a different set-up then Ken's 87

on the 90-96 the VSS Purple and Yellow wires go from the VSS to the Following: CCM, ABS ECM, and Selective ride control.

The speedometer on the 90-96 is fed directly from the CCM, since the CCM is just sending a Serial signal to be converted by the Integrated circuit mounted within the LCD panel to display the speed.

 

[69MyWay]

Chris,

The 90 is a different set-up then Ken's 87

on the 90-96 the VSS Purple and Yellow wires go from the VSS to the Following: CCM, ABS ECM, and Selective ride control.

The speedometer on the 90-96 is fed directly from the CCM, since the CCM is just sending a Serial signal to be converted by the Integrated circuit mounted within the LCD panel to display the speed.

That explains why nothing added up. That is also why I stopped dead in my tracks before jumping any wires based upon the info I had in front of me.