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  #1  
Old April 27th, 2019, 21:11
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yossarian19 yossarian19 is offline
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AW4 TCC / Brake switch circuit

I'm reading the FSM and fairly sure I understand, but, if anyone can hold my hand and tell me one way or the other it'd help.
I think what I'm reading is that on the brake switch connector, pin 5 is power in, it's normally "open" to pin 2 (brake lamps). Pin 4 is ground, normally closed to pin 3 (K29 TCM / PCM brake switch sense)
Push the pedal, you close circuit to power the brake lamps and break ground connection to the TCM, which unlocks the converter.

Correct?

I'm putting an AW4 in my FSJ and need to get the last couple wires connected to the TCM before it'll move.
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Old April 28th, 2019, 10:37
lawsoncl lawsoncl is offline
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Re: AW4 TCC / Brake switch circuit

I believe that's correct for the older AW4 setup, but might have changed in 98? What year tcu are you using? There was a pullup resistor wrapped up in the harness near the TCU that would pull the voltage up to 12-volts if the ground connection at the pedal was broken by pressing the brake. It's backwards from what you'd expect if they just hooked the sense wire to the brake light circuit.. When I did my manual to aw4 swap, I didn't track down the switch and just used a small relay driven by the existing brake light switch.
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Old April 28th, 2019, 10:39
lawsoncl lawsoncl is offline
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Re: AW4 TCC / Brake switch circuit

The trans computer on the older Renix setup also wanted the Throttle Position Sensor voltage opposite of normal, which is why they had the dual output TPS sensor. Later years flipped that and just tapped into the existing signal that goes to the engine computer.
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Old April 29th, 2019, 09:20
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yossarian19 yossarian19 is offline
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Re: AW4 TCC / Brake switch circuit

It's a 1995 trans / TCU
I think I'm going to go to the wrecker and pull the brake switch and clip the pigtail, then wire per 1995 FSM
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Old August 5th, 2019, 19:13
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yossarian19 yossarian19 is offline
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Re: AW4 TCC / Brake switch circuit

Conclusion: I dug around on the internet for a while to find a threaded dual-throw brake switch, then promptly lost the part number. The XJ switch won't fit an FSJ
I did, however, have the wiring scheme correct in my original post.
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Old August 5th, 2019, 21:33
lawsoncl lawsoncl is offline
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Re: AW4 TCC / Brake switch circuit

When my tcc switch disintegrated, I used a small relay that's switched by the brake lights instead.
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