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William B. Cushman

Extreme on MR2 - power steering and ABS

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Hi everyone, I'm installing a G4 Extreme on a '93 Toyota MR2 with the 3S-GTE engine (turbo). The old (stock) ECU has two inputs/outputs for the power steering control module, and one for the ABS module. I also have the 'Electrical' manual for this car, but in the case of the power steering two different diagrams show the signal flow in two different directions. So my first question is, does anyone know whether these signals, 'PS' and 'PSCT' go in to the Extreme, requiring a DI input, or out of the Extreme, requiring an 'AUX' output? I think there is one of each, but which is which? The second question is: what are they for? My guess is that the input signal to the Extreme, whichever that one may be, is simply to 'idle up' and compensate for steering load . . . but the output from the Extreme has me baffled. I'm also guessing that 'ABS' is an input to the Extreme, but what is it for? Thanks for your help! BillyDoc

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Hi William.

I love my MR2's, and going from what I looked in to with mine, the 'PS' was not used (thin black wire with 2 dots), and the PSCT (thin blue/yellow with 2 dots) was the one I used going to a DI.  The DI was set to power steer, and the signal went low to show as 'on' (loaded PS pump for PS Idle up as suggested).

For the ABS, we do not need to see this signal, so can be left out of the loop.  I can only assume that as the OEM ECU would work differently to the Link, they may have liked to know when ABS was active to pull timing out to help with engine braking possibly... No idea really, but a good chance.

The ABS has it's own control unit (funny enough so does the power steering), and is controlled and operated independantly from the ECU.  The Link does not need to see this signal, but maybe you want to take advantage of it for some reason.  If this is the case, I once again will only assume this is a DI also, and most likely will go low for 'on' and high for 'off'. 

Maybe there is an ABS light on the dash this operated, allowing you to have an unessesary light on the dash you could now use for something meaningfull like knock or RPM shift?  Once the car is running, it might pay to just tentitively check the ABS in a safe area to see that it is operating normally, because I really don't know what that wire is for.  Let us know if you firgure it out.

Jurgen

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Hi Bill.

Mine was JDM, and technically a GEN I SW20 as was Sep '92.  However I had a weird cross over model mix with differnt wiring, GEN II OEM ECU, and GEN I engine (on the cusp of the change over and the worst cars to figure out what parts you need!).  I have noted several different variatoins for SW20 as far as wiring goes, so my car will not have been the best example.

Good luck with testing the AUX... I would be inclined just in case to fuse that wire so if the AUX pops out +12v and the pump grounds it you are not going to damage anything.  Use a 5A fuse or similar. 

I know that Link do not do anything with this wire, and can only assume the wire was the ECU sniffing when the pump was on, as apposed to controlling it, and the wire also doubles to the power up relay for the pump based of hard wiring for example. 

These are all guesses, so hook it up, start it and turn the steering wheel... It should be immediately apparent if it's not working I would imagine :)  Let us know how you go, and don't be letting out that magic smoke out.

Jurgen

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