General question about the A604/41TE

I have a simple question: Are 2nd gear and/or reverse "hard coded" into the
valve body of the transaxle meaning that "Limp Home" mode is simply the TCM
saying "I give up!" and cutting all power to the solenoid pack? The reason
I ask is that a few months ago I got a call to work on a '96 Caravan 3.3 and
they told me over the phone that the speedometer didn't work and it was
locked in 2nd so I immediatly thought a simple output speed sensor was the
problem. After starting the van and putting it in gear I noticed that all
of the squares on the digital shift indicator were lit up which had me
thinking PRNDL switch. After about an hour of checking and cleaning
connectors it still didn't work so I decided to start checking fuses and
found that the TCM fuse in the underhood box was corroded due to battery
acid so I swapped in a spare and it fixed the problem. I even ran it up and
down through the gears about a dozen times with the front wheels off the
ground to be sure. Then about an hour ago I read this post elsewhere: "as a
test... I removed the EATX relay for a test run... and it was Instantly in
2nd gear, from 0mph"

I hope that someone can give me a definitave answer because I already know
how to properly treat this trans to keep it healthy and happy but I am
trying to learn more about the theory of operation etc.

 

Essentially 'yes' for 2nd gear. I just looked at the logic table for
the solenoid pack in the FSM on an LH car (42LE tranny - I assume its
the same control-wise), and all solenoids are de-energized for 2nd gear.
For reverse, one solenoid is energized - but that particular solenoid
just locks the torque converter cluth, so in limp mode, reverse works,
but the TC is not locked (degraded mode)

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Thank you bill, I had seen the solenoid pack truth chart before but didn't
fully understand it. Thank you for answering my question.

 

You're welcome!

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')