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nate
01-24-2005, 05:12 PM
PO720 - Output Shaft Speed Sensor Circuit

Anyone have more info on this? I was doing donuts on the ice and I got a CEL. Pulled the codes and that's what I got. I tried to clear the codes and it came back up. Drove home about 40 mins, and light went out later that night after a few restarts.

I did buy another speed sensor, since I was suspecting issues with it before (weird shifting). The wiring seemed fine as far as I could tell. For $35, it was worth the piece of mind IMO.

I was thinking maybe I "tricked" the tranny into throwing a code when doing donuts, but since it wouldn't clear afterward... hmm.

gearhead313
01-24-2005, 07:28 PM
what year do u have?

ELLLLLIOTTTTT
01-24-2005, 08:30 PM
i'm not sure what the huge difference is for the input vs the output speed sensor but my input sensor went out awhile back. I could tell it was acting up, wouldnt shift into 2nd until 3K rpm no matter how soft the pedal was down. Is yours acting funny? If I were you I'd disco the battery for a good while (20 min at least) to let everything uncharge and see if it goes away.

nate
01-27-2005, 01:56 AM
It's a 98. The output sensor was $12 actually, just picked it up today.

I didn't realize there was an input sensor as well. Is it located externally?


Tranny acts weird, doesn't shift when it should. Upshifts too early, downshifts too late.

ELLLLLIOTTTTT
01-27-2005, 02:48 AM
yea both of the sensors are external on the tcase.

nate
01-27-2005, 03:04 AM
Do you have a part number for it by any chance? I looked through the Jeep parts list and did a google search and didn't come up with anything.

Some good info here: http://www.rttransmission.net/42re%28a-500se%29.htm

Curve 4 in 4 Lo.. My T Case sensors aren't connected as it's a 231 from an XJ. Figured they were just for the 4x4 lights, etc so I didn't bother. I wonder if that's a problem?

I will check what the gov pressure is next time I drive it.. just to see. I think I can check the OSS RPM as well.

This is an ad for a tool, but good info on the same DTC I have:
http://www.gearsmagazine.com/2004-05/2004_5_48.pdf#search='42RE%20input%20sensor'

More 42RE info
http://www.asashop.org/autoinc/july98/techtips.htm

ELLLLLIOTTTTT
01-27-2005, 04:20 AM
http://www.wjjeeps.com/speed_sensors.htm

HTH

http://www.amghummer.com/Maintenance/SpeedSensor/image/SpeedSensorTcase.jpg

nate
01-27-2005, 05:29 AM
That's for WJs. :D
They have run the 545RFE and yes your correct, they have an input and output speed sensor, at least according to that website

The 42RE only has the output speed sensor as far as I can tell. I'm going to call a tranny shop tomorrow and find out for sure though.

ELLLLLIOTTTTT
01-27-2005, 01:22 PM
i know thats for WJ's but i coulda sworn its almost the same for zj's.

OverkillZJ
01-27-2005, 01:59 PM
i know thats for WJ's but i coulda sworn its almost the same for zj's.


It is, as far as I know :)

There's a shaft speed sensor on the back of the transmission, and the final speed output sensor on the back of the tcase (like in the picture)

nate
01-27-2005, 11:49 PM
Right.. but on the 545RFE, there's also an input speed sensor on the front of the tranny that the 42RE doesn't have.

OverkillZJ
01-28-2005, 12:39 AM
Right.. but on the 545RFE, there's also an input speed sensor on the front of the tranny that the 42RE doesn't have.


Ohhhhhhhhhhhhhhh

It senses the speed of the engine? That just seems so redundantly chrystler!