FIXED: GNX Dash Wiring

[rick j.]

Does anybody have a photo/know location of the '87 analog dash's factory brown wire to the ECM's A10 Terminal, and the input wire going to the Cruise control module?

I think they're around the factory green VSS buffer, with a 3-wire white plug and a 1-wire black plug attached to it.

I'm trying to finally get my GNX dash's speedo, cruise, and TCC lockup fixed. Built a "The_Six" harness combining Caspers' VSS Sender and Tach Module; The_Six has a great tutorial found here .

But because it's been 10 years since the original pieces were removed, wires have been cut and I don't know where to start looking.

Still need to hook up the VSS signal wire to the ECM's A10 wire, and the Caspers Tach Module's yellow wire to the cruise control module input wire.

I'm thinking the white 3-wire connector is at the right of the attached photo, with the red quick connects on it.

 

[rick j.]

5/19 Update: Still not working after my wiring marathon Sunday, have a few pics attached.
Found what I think is cruise module in lower right of dash area. This module only had one red wire, assumed it was the Cruise Module speed input wire to Speed Sensor Buffer wire, but couldn't see if it was in terminal number D from Cruise Module wiring schematics? So...

1. Connected Caspers' Tach Module yellow wire to "supposed" cruise module red input wire. Had to lengthen so it shows white wire in photo.
2. Connected Caspers' Tach Module black and red wires to ground and IGN power terminal in fuse box. (The_Six used pink/black stripe wire in 3-wire harness in photo for power; wonder what's the difference here, if any?)
3. Still not sure which wire is A10 to ECM but connected white VSS Signal wire from my new harness to brown/white stripe wire in 3-wire harness. There are two brown/white stripe wires in this harness.
On startup check engine light, and still no speedo, TCC lockup, or cruise.
Ideas?



Edit: FYI Caspers' VSS Converter 102046 installation instructions show that the tach module's Black/Red/Yellow wires only connect the yellow one, black and red aren't. The_Six's harness connects the VSS Converter and Tach Module together, so it appears that he uses the Tach Module's Black as ground, Red as 12v power for the entire harness, see green pic.

 

[rick j.]

Update: Fixed!
The green speed sensor buffer had been relocated to almost behind the radio and wasn't visible.
Once found I got the two wires connected: Casper's yellow tach module wire to the red cruise module input wire, and the vss signal to ECM to the brown A10 ECM wire.
Speedo works like a charm now; no cruise or TCC lockup yet but need to check fuses. Finally!

 

[GNRick]

Rick- keep us updated. For TCC lockup, first thing is check the brown wire in the upper left position in the 4 prong plug in the side of the transmission. Should be hot with key on engine off (or on). I have a thread on chasing a gremlin in this wire. Also make sure the white brake switch is adjusted correctly. If you have power there, hook up your scan tool and see if the TCC light comes on at about 45 mph. This should tell you if the ecm is commanding lock up and if the wire is good going to the ALDL. You can also jump the upper left and upper right ports in the aldl to ground the wire going to the transmission, forcing lock up. Are you still writing magazine articles?

 

[rick j.]

Will do Rick, thanks for the TCC tips. Spent 3 days digging through wires so this feels nice. Prob only put 5,000 miles on it since the stock dash was replaced but so nice to have that sweet Perf Instruments GNX dash all functioning.
Yep still do the occasional GMHTP story; here's the latest about Dave Sapper's (sold) amazing GN: http://www.gmhightechperformance.co...buick_grand_national_black_reign/viewall.html
Something to aspire to!

 

[GNRick]

Looks like that is quite the car.

 

[rick j.]

It really is. Wish I'd seen it in person but the lucky photog got that treat