4runner transmission or ECM issue? (Aisin A340F trans, 4x4)
Bonner
my 1999 Toyota 4Runner (Limited trim, 4x4 automatic with O/D, 138K
miles).
First off, for 99% of the driving I do, the transmission shifts GREAT,
both up and down through the gears.
Problem #1: Shifting into reverse is harsh. Especially in the morning
after a cold start. It takes about 1 second to engage, and it does so
with a jolt. Not a big deal, but it's annoying.
Problem #2 (and this is the big one): After driving with the torque
converted in lock-up (above about 40 mph) for an extended period of
time (say a typical highway trip of 40 miles), and I come to a stop,
the transmission will act as though it's in neutral. Depressing the
accelerator just gives me revs. The best way I've learned to get it
back into gear is to manually shift down to low (1st gear). This
usually works, with about the same amount of "jolt" as shifting into
reverse. Then, I just shift up into drive once I'm moving, and all is
good again. If I've been on the highway for a LONG time (say, 200
miles without stopping), sometimes this symptom can happen at 2 or 3
stops, not just the first one. In all cases I need to shift down to
low to get it to engage in drive again.
Recent service (1,000 miles ago) included a trans fluid drain (about 8
quarts, said the trans tech) and filter replacement. I have noticed no
improvement in the problems. The fluid level is correct, having
checked it with the engine and transmission warm, idling in park.
Lastly, and perhaps most importantly, I noticed these issues not long
after having to replace the ECM in the truck. I went through an
automatic car wash and some pressurized water came in under the dash
and shorted something in the ECM. After taking that ECM out and
inspecting it, it's obvious it's seen plenty of water over the years
from this leak. So, I replaced it with an ECM out of the same year
vehicle. I had to have my transponder keys programmed into it by a
mobile locksmith, but it fired right up and has been running great
ever since. The only issue is this wacky shifting thing.
Any ideas? I've narrowed it down to:
1. ECM not sending the shift signal
2. VSS (vehicle speed sensor) not working 100% of the time
3. TPS (throttle position sensor) getting stuck after sitting at one
position for a long period (cruising on highway).
However, none of these (with maybe the exception of #3) seem to
explain why the truck shifts JUST FINE at all other times.
Thanks for the help!
jfran
The ecm on this truck is behind the glove box so i dont know what you
had replaced. You say that you have the trans serviced. Did they put
the right fluid back in it. That vehicle calls for dextron III. When
was the trans serviced before that? Is the check engine light on? Any
codes? Any of your ideas that you think it is will set a code.
Steve W.
I would probably throw a scan tool on it and see what program is in the
current ECM, it is possible that it is not programmed the same. Could
also be an issue with something in the trans shorted out when the ECM
went bad. Seen that more than once.
--
Steve W.
ben91932
> I would probably throw a scan tool on it and see what program is in the
> current ECM, it is possible that it is not programmed the same. Could
> also be an issue with something in the trans shorted out when the ECM
> went bad. Seen that more than once.
>
> --
> Steve W.
Can a '99 be reflashed or would the correct ecm need to be installed?
Also, I've never heard of a car wash shorting an ecm... has anyone
else?
Ben
ben91932
Touble codes??
Your A/T control circuit has 2 main grounds, g131 on the intake
manifold and g100 on the left front fender. I would do a voltage drop
across those before wigglig or disassembling to see if they drop less
than .05 volts.
Then I would sweep the tps and make sure it isnt sticking above idle
like so many Toyota's tps's have done since day 1.
Lastly I would drop the pan and ohm and wiggle test the 4 solenoids..
Hope this helps,
Ben
Steve W.
Should be able to be reflashed. By 92-93 most makers had switched from
the older EPROMs to EEPROMS and made the ECM field programmable with a
dealer level machine and code.
The OP said that water got behind the dash and into the ECM. I guess if
the glass leaked or there was a bad seam it's possible. Could even be
something like water that followed a heater line or something else
through a grommet in the dash. Many of the ECMs that are installed in
the interior are not potted like the under-hood units.
I've seen some real weird crap on cars over the years. Stuff that you
had to take pictures of because nobody would believe it was possible.
--
Steve W.