hi there i am having a problem with my truck[:@][:@], it is a 1999 dodge ram 1500 laramie sle 4x4 automatic without abs. The check engine light came on the other day and the truck was acting weird so i had the code pulled today and it is p0720. the symptoms i have notcied are when im at a complete stop and the vec. is in gear (drive, reverse) the speedo reads twenty ish km. When im coming to a stop the spedo will drop down to zero but once i've reached a full stop it bounces back to twenty, when i start to accelerate from a stop the speedo instantly drops to zero and goes up as i increase speed, seems to be working properly when accelerating. However there is a slight hesitation, almost a clunk when I begin to accel. If I put the truck in park the speedo drops to zero but if i depress the brake pedle while in park it sits at about twenty again, if I release the brake it drops back to zero as long as it is in park. The other symptom is if I have my foot on the brake and im at a stop and I shift into neutral i can hear a clicking noise (and kinda feal it in the pedle) it clicks about 10 times then stops, once i shift back into drive it does the same thing, about ten clicks. Also when I am applying the brakes while moving i hear the same noise however it continues clicking untill I come to a full stop or release the brake pedle, and the speedo seems to bounce up and down slightly on decelaration when i hear the clicking. The truck also seems to be late shifting, it actualy wonldn't shift out of first gear for awhile today, then it started shifting again. Any suggestions would be great, is there any way to acutaly test the output speed sensor? i hear this is a common problem associated with this fault code. How about the entire circuit? thanks in advance -dan
[align=right]
(in reply to MagnumVP) [/align]

 

SYMPTOM
P0720-OUTPUT SPEED SENSOR ERROR

WHEN MONITORED
The transmission gear ratio is monitored continuously while the transmission is in gear.

SET CONDITION
If there is an excessive change in output RPM in any gear. This DTC can take up to five minutes of problem identification before illuminating the MIL.

POSSIBLE CAUSES[*]Output speed sensor signal circuit open[*]Speed sensor ground circuit open[*]Output speed sensor signal circuit short to ground[*]Speed sensor ground circuit short to ground[*]Output speed sensor signal circuit short to voltage[*]Speed sensor ground circuit short to voltage[*]Output speed sensor[*]Powertrain control module[*]Intermittent wiring and connectorsi cen get you a full flow chart on how to check it out if you wish

 

does anyone have a quick link pic of where the ouptu sensor is for a 1999 5.9 4x4

 

the speed sensor is in the rear of the transmission (or t-case?) i think transmission. it's got an electrical plug on it. its pretty simple, just a magnet that monitors a tone ring or something. check your wiring and connection before you replace it, only about $15-20 at any parts store.

just fyi, there is a second sensor involved in the speedo, its the rear abs sensor on the top of the rear diff. it can also cause the speedo to malfunction.

 

Speed sensor goes in the hole to the right...



Thought I had of photo of it installed from rebuild, but don't see it.

Go to FAQ/DIY section and download service manual. Trans section is real good.

 

Hey,

I just had the P0720 code come on and replaced the Output Speedo Sensor on the transmission because of all of everyone's helpful information on this site. But when I pulled the old one there was a slight drip of transmission fluid (maybe 10 drops) and the tip of the old sensor had a bunch of tiny metal shavings on it. Could these shavings be causing the problem in the first place? (The $18 part was worth it, I know). But my bigger question is... could the shavings be signs of transmission wear, and the beginnings of the transmission problems that these trucks are known for?

'99 Ram 1500, Reg Cab, Short Bed, 5.2 V8, 4x4, Automatic

 

Yeah, that's a pretty good sign that you are going to be looking at a rebuild in the pretty near future.....

 

I have the same code and I changed the sensor. It didn't fix it. It runs fine and shifts fine but the speedo still don't start working until about 25 mph and the code is still there. Any ideas what it could be would be appreciated.

 

Hey Tod King, I'm pretty sure other people on this forum have spoken about a secondary speed sensor on the rear axle. My issue was fixed with the sensor at the transmission, but I guess sometimes you have to replace both. I don't really know anything else about it, but it's a place to start.

 

I like old threads that cover the common issues. This thread and this post.

This morning my CEL came on. I was like.....wut?!?!? Not Skookum! lol (thx Merc!) It's 100*F this weekend and so I didn't mess with it till a bit ago.

Picked up the sensor for the tranny about $12 from Napa.

Replaced the old one, cleared code (which must be done with key in ON, not Start position), then started and drove around. All is good.

However, I think I'll be doing first fluid/filter change sometime soon.



No other symptoms going on at all....