I swapped in a brand new SD harness and ECM into an '89 Trans Am.

Car is running great, but I have a couple of questions.

First, I do know that the main engine harness on a MAF TPI car has the window wiper motor connections integrated into the main engine harness. The SD harness does not have these provisions.

So, does the small engine bay harness (the harness that plugs into the firewall in conjuction with the main engine harness) on a SD TPI car have the provisions for the wiper motor? Or, is there another solution?

Also, since the SD swap, the speedo quit working. I installed a brand new VSS for a 91 SD car into the 89 car to see if that would correct the problem. Datamaster reads the speed just fine, but the speedo still doesn't work.

Is there a VSS buffer box somewhere on the 89 TPI car like the SD TBI cars have? Or is there something else I have to do to get the speedo to come alive?

Any help would be appreciated!

 

I've been working on the same MAF to SD transplant project more or less and have had some of the same results as you with the exception of the VSS speedo problem. My project donar car was a 91 GTA for my 87 IROC. The Camaro's speedo was cable driven so I had to convert to an electrical cluster (I used the donar car cluster to get it all up and running). I may have gone the hard way but, to get this done I also transplanted the entire interior wiring harness then, with the donar vin number I matched it to the correct VSS. No codes and speedo works.

The wiper motor function hasnt been resolved. I have one speed, and the arm will not return to park position until the brakes are applied. Even after changing 2 new style motors and trying to duplicate the same firewall junction block pin connection location from the donar. Not sure but think that a ground is missing somewhere. My next plan of attack is to find a 90-92 light and wiper motor harness and replace them since I havent located a firewall block schematic to reference from.

Havent really helped you out here but, just good to know that you are not alone.

 

Can anyone confirm that the side harness (headlight) harness in the engine bay of a 91-92 bird will work to get the wipers working again?

Also, is there a VSS buffer box in an 89 TPI firebird?

 

Your best bet is to check the wiring harness to make sure that you have the right connector hooked up to the wiper motor.
There is not a VSS buffer box in the 89 TPI firebird although there is one in the TBI firebird.

 

Then I'm stumped!

I can read the speed just fine on the scanner (Datamaster) though the ALDL/laptop , just speedo wont read at all. Is there something I have to bypass or re-wire?

 

I saw a 91 or 92 tbi camaro at the bone yard today and its wiper wiring is run from the headlight harness .... I know a 89 camaro tbi harness has the wiper in the main harness though

 

i just done the same i used all insides from 90 v6 firebird in 89 tpi t.a the headlight harness in 89 has the wiper conn the s.d 90 to 92 has it in the main harness just repin inside haress it pretty simple i will send schematic so you can get right hope this helps

 

If you can read the speed using Datamaster, then the ECM is receiving the VSS signal. The ECM sends two VSS signals, a 2000ppm and a 4000ppm signal.

B11 - GRAY - 4000ppm output
C1 - RED - 2000ppm output

Determine the signal your speedometer requires (probably 4000ppm...a service manual will tell you), then connect the signal from the ECM to the speedometer.

 

I used the VSS from a 91 car.

But, I also have the 89 VSS.

What one should I use?

 

Use the 4000 pulse per mile sensor (from the 91 car).

 

What wire (color and location) and on what side of the ECM do I connect to what color wire and where by the speedo?

I don't know anyone with a service manual for an 89 Formula.

Thanks for the continued help everyone! Pretty soon hopefully everything will work!

 

Please see three posts above. The ECM pin locations and wire colors are in my post. The back side of the ECM connector is labeled with numbers and letters.