ABS issues

[Backlash2032]

Alright. So here's the deal. This is my first Supra with ABS, and I'm having a little trouble. My last car was an N/A shell, which I swapped over a full GTE swap, with R154 trans. I've since swapped the engine and transmission (along with some other bits and pieces..) to a 89 auto turbo targa shell (with ABS). So my current car has a 7M-GTE, R154, M/T ECU and harness, along with whatever ABS computer came with the car.

The first thing I notice on my very first drive is the antilock light came on. I did a brake check, and sure enough, no ABS. So I pulled the codes from the ABS ecu and it says there's a fault with the rear speed sensor. Now in a factory car, I would be sure that the problem lies with the rear speed sensor; I would replace it, and be on my way. HOWEVER, since I have no idea what ABS ECU is in the car (or if theres even a difference from M/T to A/T), I don't know if it's trying to find the signal from an A/T rear speed sensor (I KNOW that is different...), and it sees the signal from the M/T rear speed sensor and it just throws the code because it's different.

SO my questions are.. Are the signals from the A340E speed sensor and the R154 speed sensor different? And if so, will replacing the ABS ECU with a R154 ABS ECU fix my problems, granted my rear speed sensor IS good...)?

 

[Maple191]

If im not mistaken, the rear speed sensor is different from A/T to M/T.

 

[Backlash2032]

I already know that. I want to know if the signals are different.

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[Maple191]

accordin to the EWD they are the same
http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=110

 

[Backlash2032]

That just tells me that it's wired the same, not that they're the same signals.

Edit: The TSRM gives me the idea that between the R154 and A340E the sensors are the same. But I'm still not certain.

 

[jetjock]

Look in the TSRM...

 

[Dirgle]

The signals are the same. So is the Skid Control Computer.

Are you sure your R154 has a rear speed sensor?

edit: Sorry JJ didn't see you had posted already.

 

[Backlash2032]

I did check the tsrm, maybe I missed something. That's the main reason I came here.

So my rear speed sensor must be kaputt. Makes sense with the car it came off of....

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[jetjock]

I did check the tsrm, maybe I missed something.

You did.


It's OK Dirgle. I prefer not to simply hand it to them but that's just my style.

 

[Dirgle]

It's OK Dirgle. I prefer not to simply hand it to them but that's just my style.

I know, and I agree with the "Teach a man to fish...." style. I usually try to give some time before I say something if you have pointed them in a direction. That usually lasts until I start having visions of everything that could be missed, overlooked, or even made worse, and I end up saying something.

 

[Backlash2032]

Well.. since you're both all for teaching a man to fish, why not point out what I missed in the tsrm so I know more of what to look for next time?

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[jetjock]

That would be handing it to you. Look again...

 

[IJ.]

Tooth count on the rear reluctor wheel...

 

[Backlash2032]

Well, when I get to a computer I definitely will look again.

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[Dirgle]

Did you get connector 'B3', connected properly during your swap?



The small connector.

 

[Backlash2032]

So I'm bringing this back from the dead. With all the talk about the signals being the same I just assumed a bad speed sensor. I finally got around to replacing it and sure enough, it made no difference.

The B3 connector is connected correctly, and this issue has plagued me over two harnesses.

I've checked the TSRM again, and noticed two things. For the rear speed sensor, it shoes four wires. An ECT wire, an rr+ and rr- wire, and I believe a signal wire. Could be wrong though. Also, it shows for auto trans there's the neutral safety switch, and two terminals going to the ABS ecu from that. I doubt my issue stems from that, however, as it's only showing a code for the rear speed sensor.

I would also imagine that it's not wiring, as I assume the ECU would instantly illuminate the ABS light if it were. However, I have to drive a little ways for it to come on. Earlier, IJ. commented that the tooth count on the reluctor rings could be different. Obviously, this would send a different speed signal depending on transmission, which would imply there needs to be transmission specific ECUs. However, JJ and Dirgle both say that the ABS ecus are the same...

I'm honestly at a loss now.. Any help would be much appreciated.

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[Backlash2032]

Bump

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[Backlash2032]

Anyone?

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[Backlash2032]

Bump, still having issues

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[Nick M]

In the real world, this is a quick and easy check. Rotate the tire and watch the voltage. A scope is even better. Good to go? Then you have a harness/ECU problem based on your testimony earlier in the thread.