ABS Question
Thread Starter
Suckin' gas, haulin' ass.
Joined: Apr 2010
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From: Newport News Virginia
ABS Question
So my 89 track car is nearing completion. All that's left (yea right, lol) is wiring, corner weighting, alignment, and tuning.
I'm running a carb setup, and rewiring the whole car since the PO decided to play cut and splice. Basically I'm removing every wire that won't be used. I just want a little info on the ABS, since I'd like to keep it.
If I'm reading the FSM correctly, it looks like I need to keep the Lateral Acceleration Switch, an Ignition On input, a brake applied input, and power on the wire from the fusible link. Does that about cover it? I don't really see the need for lights, but if they are required, I can put some in.
What do you guys think?
I'm running a carb setup, and rewiring the whole car since the PO decided to play cut and splice. Basically I'm removing every wire that won't be used. I just want a little info on the ABS, since I'd like to keep it.
If I'm reading the FSM correctly, it looks like I need to keep the Lateral Acceleration Switch, an Ignition On input, a brake applied input, and power on the wire from the fusible link. Does that about cover it? I don't really see the need for lights, but if they are required, I can put some in.
What do you guys think?
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Most people don't understand how ABS works much less the question you have. 
I'm no as familiar with the 89 Version of the ABS system but I am with the later one.
I would think if you have a brake fluid level input you would need that.
Indicator lamps? Those are technically outputs. IDK if you NEED them? Helpful, to know if there is an issue.
Are you taking cruise control off? I would assume so.
Does the EBCM need RPM input?
EBCM ground, you need that.
Obviously, you need the wheel speed inputs.
You may need serial data line? Then again NO On Board Diagnostics on 86-89 ABS systems so probably no.
One nice thing about C4's is most of the systems are stand alone or can be easily made to. Unlike C5's and later which have much more integrated systems, which are less costly, weighs less, less complex, you can easily modify the car heavily and still retain the ABS for example. A lot harder to run a carb on a C5 and still retain ABS than on a C4.
If you have a online version of the FSM wiring diagram for your 89, I could take a better look.
I'm no as familiar with the 89 Version of the ABS system but I am with the later one.
I would think if you have a brake fluid level input you would need that.
Indicator lamps? Those are technically outputs. IDK if you NEED them? Helpful, to know if there is an issue.
Are you taking cruise control off? I would assume so.
Does the EBCM need RPM input?
EBCM ground, you need that.
Obviously, you need the wheel speed inputs.
You may need serial data line? Then again NO On Board Diagnostics on 86-89 ABS systems so probably no.
One nice thing about C4's is most of the systems are stand alone or can be easily made to. Unlike C5's and later which have much more integrated systems, which are less costly, weighs less, less complex, you can easily modify the car heavily and still retain the ABS for example. A lot harder to run a carb on a C5 and still retain ABS than on a C4.
If you have a online version of the FSM wiring diagram for your 89, I could take a better look.
Last edited by 93Rubie; Feb 8, 2012 at 08:26 PM.
Thread Starter
Suckin' gas, haulin' ass.
Joined: Apr 2010
Posts: 1,100
Likes: 8
From: Newport News Virginia
Thanks for the reply. I spent most of the day hacking about 50 lbs. (literally) of wire out of the car. I had a friend who is more literate with wiring diagrams than me. What it came down to was it needed a power input, via the "J" fusible link, it needs the lateral accelerometer, a brake input via the brake switch to the 3rd brake light, wheel speed sensors (obviously), and an ignition on input.
It was pretty easy once I got to looking at it. Basically all that was needed was about 5 wires out of the entire body harness. I kept aft end of the car harness. (Lights, fuel pump, fuel sending unit, ABS, brake lights, defroster, hatch release, etc.).
And yes, you are correct that the unit is stand-alone. The diagnostic for the early ABS plug in-line with the module harness and the module. Now I just hope the ABS actually functions.
It was pretty easy once I got to looking at it. Basically all that was needed was about 5 wires out of the entire body harness. I kept aft end of the car harness. (Lights, fuel pump, fuel sending unit, ABS, brake lights, defroster, hatch release, etc.).
And yes, you are correct that the unit is stand-alone. The diagnostic for the early ABS plug in-line with the module harness and the module. Now I just hope the ABS actually functions.
Thread Starter
Suckin' gas, haulin' ass.
Joined: Apr 2010
Posts: 1,100
Likes: 8
From: Newport News Virginia
I will for sure. My friends are wiring up the car while I'm out of town for work. When I get back, I'll test it out and post up the results. I'll also add pictures of the needed wires. I couldn't believe how simple it was. Basically it was 1 power wire, the lateral acceleration module (2 wires) and a brake wire.
