View Full Version : Removal of ABS harness

09-02-2015, 08:26 PM
I just completed the conversion to vacuum brakes, deleting the old abs system in my 89 SC. I no longer have the ARC shocks either. Can the harness be removed from the engine bay without affecting anything else? It looks like it goes all the way back to the abs computer in the rear without a connector in between (looking at the EVTM). There are a few connections on that harness that did not go to the old abs system, but connected near the main bulkhead connector. I left them disconnected and have not noticed any ill effects so far. Can anyone provide insight if there is anything else in this harness that needs to be connected or can the whole harness be removed?


09-12-2015, 07:56 AM

Fog Lights:
While removing this harness from the car, I found that part of the harness runs under the passenger seat. This part of the harness goes to the fog light and firm ride switches in the center console. In order to maintain the fog light functionality, I unwrapped the harness between the fog light switch connector and the two connectors by the ECU. I then removed the needed wires. The fog light switch has three wires going to it. One is the power wire going to the switch (when low beams are on), another is power going to the fog lights, and the third wire is the ground to make the light inside the switch work. I was able to remove all the other wires out of the two connectors by the ECU without cutting the harness. I used a small flat piece of metal (one side of a pair of tweezers), pushing in from the wire side of the connector to release the locking tab inside. I also kept the firm ride switch connector and its two wires in case I wanted to re-purpose that switch in the future. The two wires going to the firm ride switch go all the way back to the ride control computer, so i just cut those two wires where they joined the main harness. That should make it easier to re-use the firm ride switch later.

Variable Assisted Power Steering:
I forgot that (on the SC and XR7 models) the ride control computer also controls the EVO solenoid on the power steering pump. So deleting this harness will remove that functionality. My understanding is that this feature makes it easier to steer at low speeds and tightens up steering at higher speeds. I drove the car for over an hour on the back roads to see if I could tell a difference... and either I am oblivious or something, but I didn't really notice anything different.

ABS light:
The ABS light went out when I disconnected those two connectors by the ecu. This makes sense, but I did not expect that. Now I don't have to pull the cluster to remove the bulb!

XR7 Dave
09-12-2015, 08:31 AM
It's possible your variable assist steering wasn't working in the first place. The EVO removes boost from the system when conditions of speed are met, and the re-enabled if steering angle exceeds a specified number, or if your turn the wheel at a high rate. So for the most part the system should operate the same with or without. The big difference is that above the cutoff speed, under normal driving conditions the steering effort is increased, road feel improves, and tracking is more positive. It's subtle but very noticeable if you know what it feels like.

XR7 Dave
09-12-2015, 08:34 AM
We recently did this same procedure only we kept the speed sensitive steering. To do so only required keeping about 6 wires altogether. Since the steering wires mostly go through the dash and out the driver's side, we were still able to remove 95% of that big harness and all the wires from the engine bay (passenger side).

09-12-2015, 10:32 AM
Thanks Dave. I will give this a shot for now. If I find that I don't like it, I will figure out how to add it back. The EVTM is very helpful do do things like that.

For those who are interested, the ABS computer, Ride Control computer, 4 relays (two in package tray, two on the firewall), and harness weighs about 14.5 pounds. I read somewhere else that the difference in the old ABS unit to vacuum brake booster and MC difference is about 10 pounds. I don't really care about the weight savings, but saving 25 pounds is a nice bonus in addition to ditching that expensive old leaky system.

Now I need something to plug up the hole in the firewall. I glanced at McMaster Carr for some kind of plug and did not see one right off. Any suggestions?

XR7 Dave
09-12-2015, 02:47 PM
Non ABS cars have a properly formed rubber plug for that hole. Check the junkyards.

09-12-2015, 02:51 PM
Seems so obvious now that you mention it and yet it never crossed my mind. thanks!