COStruck

At first I thought my torque converter clutch had a problem, as the manual says the test is to cruise at 50 and tap the brakes, which should result in a 5 second increase in RPMs, but nothing happens when I tap the brakes. After observing the TCC activating and deactivating in Forscan, and then realizing that the trans does seem to go into "fifth gear" when I accelerate to highway speed from a stop, I'm pretty sure the TCC is working just fine except it isn't releasing when I brake. I read that brake light bulbs can pose a problem, so first I pulled the topper off and replaced the third brake light bulb but that didn't help; then I replaced the EP27 flasher relay with the factory one and that didn't help either. Putting the only LEDs I have, which are the front TS lamps, back to stock seems like a stretch but I'll try that next. What else could be keeping the TCC from releasing when I brake?

COStruck

This truck came with a Hopkins Impulse brake controller. Could that be a problem? It lights up "13" (or the readout is upside down and it's "E1") whenever I brake.

EDIT: I just tested again with the brake controller unplugged - still no TCC release.

Bluegrass

The signal comes from the operation of the brake pedal switch.
If you have a dash Tachometer, do the test again and watch for about a 300 rpm rise, then a fall back if the TCC unlocks and locks up again.
You should see the TCC unlock in OD with very light throttle loading , as well.

COStruck

Thanks, Bluegrass. That's what I've been trying and the tach has no response at all. The manual specifies to left foot brake, which I assumed meant to hold steady throttle, but I just noticed in the wiring diagram a note that the PCM may ignore the brake pedal signal if throttle position "signal is above the closed signal", so I'm going to try again at closed throttle coast.

white89gt

It has to be unlocking at some point, or the motor would kill on you when you come to a stop.

COStruck

Yeah, it is definitely unlocking (if it's actually locking), just not by the brake trigger. There are 4-5 other signals involved, like MAF and TP.

raysorenson

What manual are you using? Not all calibrations unlock the converter with BOO. My guess is that they quit using BOO at some point and instead started relying on more a sophisticated use of TP info to decide if the TCC unlocks in order to prevent driveline clunking. I see ~half dozen TCC lock/unlock w/closed throttle modifiers but zero for BOO controlled TCC unlock in my '04 Mustang definition file.

COStruck

Factory FordWhat's BOO? Another name for BPP (Brake Pedal Position)?

COStruck

Neither the incandescent front TS bulbs nor the closed throttle made any difference. I'm kind of glad about the former, too, because those amber bulbs sure are ugly! :P Back to LEDs.

Bluegrass

Converter lockup is a function as far back as 1984 in the Bronco and Rangers and even in the A4LD transmissions.
The Throttle has to be at min and road speed up in normal cruise range. A speed --throttle non normal condition recognized by the PCM.
This 'sudden' throttle release at road speed is a signal to unlock by the position of the TPS..
The brake signal should keep the unlock, if applied.
The reason for this is to help shorten stopping distance in a Panic stop situation.
It prevents the drive line and motor from adding momentum, countering braking efforts to avoid a possible unpleasant situation.
A small help but it it has some value.