Hi everyone. I have a weird one. 16197427 computer, $8D mask. Converted to run a TPI. 4L60E transmission, 1995 with PWM.

Here's the issue: TCC locks up just fine, I have it set so it only locks up in 4th gear, it unlocks on decel, it unlocks when I downshift. All good there. The issue is when I tap the brake pedal, it won't unlock. When I connect the ALDL scanner to it, I can see the brake pedal toggle on/off on the screen, so the wiring should be good.

Any ideas?

I was hoping to find a flag in the bin that was unchecked, but no such luck.

Thanks!!!

 

$8D in a '7427 PCM?

$8D doesn't support unlock with a brake pedal input. There is a switch on the pedal that opens to remove power from the TCC solenoid.

RBob.

 

I'm sorry, typo there. It's a $0D mask, not an $8D.

That said, will the issue be the same, I need to remove power from the TCC solenoid with the pedal?

Thanks!!

 

Looked at a wiring diagram for a '94 G20 van, no pedal switch for the TCC. This is for the 4L60E ($0D mask) and the 4L80E ($0E) trans.

I'm not familiar enough with the $0D code to know what it is expected to do. So can't say that what you are seeing is correct or not (no TCC unlock on brake pedal input).

RBob.

 

TCC switch signal is an input into those TBI PCMs. Torque converter will not lock without 12 VDC applied to that PCM terminal. The TCC solenoid gets its pwer feed from the same pin as the shift solenoids. The PCM grounds the TCC solenoid and PWM solenoid if applicable to give lockup. The brake switch kills the lockup via the PCM.