Transmission Sensor ?

I have a 2002 Elantra Auto...

I had a problem a year ago where i'd be driving at highway speed and the
transmission would drop to 3rd (fail safe) and would only return back
normal if i pulled over and switched off.. This turned out to be the pulse
generator.

A new problem is now effecting me... From switching on i drive from 1st to
2nd then high revs before jumping to 3rd.. Then i remain in 3rd when
speeding up or slowing down.

I switch off.. back on and it drives like normal.. I switch off back on
and the same error occurs. I've not determined if this is from a cold
start only but it's at the shop now so we'll see.

Any ideas what the problem could be?

 

The high revs are disturbing. That could indicate an internal transmission
problem. In any event, it's going into failsafe. The shop will check for
error codes (hopefully) and this will help them know what's going on.

 

I need to check and clean the pulse generator connection on a 2001
Accent AT. Is this a DIY or take to a service center?

 

You could probably do this yourself. If you've got a code P0722, there's a
reprogram available for this as well.

I'd recommend getting an account at www.hmaservice.com (if you don't
already have one; it's free) and checking TSB 03-40-016. You won't be
able to do the reprogram yourself, but it gives instructions for the
connector as well.

 

TSB 03-40-016 describes 2 procedures, pulse generator-b inspection and
TCM reprogramming. Are these 2 separate procedures which can be
performed independently?

Pulse generators break and connections go bad, I have no issues with
these types of expenses. But if the TCM reprogramming is needed to
address defects in the firmware design then Hyundai should provide
this at no cost to the consumer. My 2 cents.

 

Yes, you can do the inspection and cleaning independent of the reprogram.
It's my understanding that the reprogramming addresses the issue of
electromagnetic interference in the vehicle speed sensor signal and
reducing the computer's sensitivity when looking at the speed sensor. If
you're within the 5/60 warranty period, the reprogramming should be
covered by your new vehicle warranty. If not, you're out of luck. Sorry.

 

3. Locate the pulse generator under the battery tray. Disconnect the
pulse generator connector (blue) and remove the pulse generator male
connector (black) from the bracket.

The pulse generator-b is not as illustrated in TSB 03-40-016. Pulse
generator male connector is blue. It is not clear whether the bracket
and male connector is a single unit. Do I slide the male connector
off the bracket and pull the connectors apart or are they locked
together?

 

You'll slide the male connector off the bracket so you can get to it.
You'll need to pull the connectors apart (there's a little release tab)
and then check the resistance. Rather than trying to figure out which is
which, I just ohm test both.