I swapped a Ls1T56 into my 1990 RS that was originally a 305 tbi 700 r4 car. I did the harness myself using Pocket's walk throughs and felt I did a good job. Now post swap I have no tach, speedometer, oil pressure or fuel gauges. I have taken the c100 apart and cleaned the terminals and that didn't do anything, I also pulled the cluster and cleaned the printed board as well as the dash connectors.

Any ideas folks?

 

Some aditional info:

With the key off and the parking brakes on all of the dash back lighting works. When you turn the key to run, the bulb to the right of the speedometer goes out.

 

Tach

Did you change the settings in the PCM?

If not, did you build a pull up circuit so the signal is strong enough for the factory tach to work?

Speedo

Did you bypass the VSS buffer box the TBI cars have? If not, then the speedo won't work.

Fuel

Did you swap tanks? If so, did you mod the sending unit to read 0-90 ohms?

If its the factory tank and sender, perhaps the float is stuck. Especially if you dropped it and swapped the pump out.

Hope that points you (and others) in the right direction

 

I had Hawks tune the ecm and they were supose to fix the tach signal.

I did indeed bypass the buffer box for the vss

I am using the factory sending unit and it worked before the swap. In fact I did not even drop the tank because I already had a high pressure pump I had installed in it.

Banging on the dash doesn't even get a thing to move and I have pulled the cluster and flared the connectors a bit to no result.

I'm leaning toward a ground problem because when I press the clutch the security light barely glows. This is odd being it is only wired to the ecm and the safety switch. Non of which go through the cluster.

Does anyone know where the cluster grounds?

 

Resolved!

It was indeed a ground problem. It was the black/white wire that went to C207. The csm is worthless in that it identifies the colors but not where they go. While I had the cluster out I found a pinout on tgo and ran a continuity test on each ground wire.

 

Thanks for posting the solution to your issue

Hopefully it will help others with their issues.

 

No problem, thanks for your suggestions! I hate when I'm searching threads and find one on my problem but the op never posted their resolution.

 

Odd

The gauge cluster ground wire goes through the C100 for 90-92. On 82-89 is a C207 pin

Glad it was something simple

 

It's a 1990 RS tbi car originally. The pin out has 4 grounds on the gauge plugs. The missing one was blk/why so I checked continuity to the blk/what in the C207 and it beeped. Made me really happy.

The C207 seems to have a few different pin outs from tpi to tbi to v6.