Code PO720 -

1st Gen Durango 1998 - 2003 Durango's

Code PO720


Old 08-08-2005, 03:01 PM
mcdelaware is offline
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Join Date: Aug 2005
Posts: 1
Default Code PO720

I have a 98 D with a PO720 code (output speed sensor circuit malfunction). Is this just a speed sensor on the trans, or could it be something else?
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Old 08-13-2005, 01:56 PM
kingburnett is offline
Join Date: Aug 2005
Posts: 1
Default RE: Code PO720

My Durango just did the same thing as yours. The Check Engine light came on yesterday. Went to the local AZ and had them test with their OBDII scan tool. The only code found was P0720. Their printout says "The pcm has determined that a malfunction exists in the electrical curcut for the output speed sensor." I looked in the H manual and it says in the index and emissions and engine control systems "vehicle speed sensor (1997 models only) check and replacement" Not to hijack your post, but does the 1998 Durango have a vehicle speed sensor? Let us know what you find, soon. so I can fix mine too.
BTW my durango is 1998 4WD 318ci autotrans.
AZ has a Wells part # SU1034 OEM#4412879, 4800879 for $23.00
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Old 08-15-2005, 11:00 PM
DebbieB is offline
Join Date: Aug 2005
Posts: 1
Default RE: Code PO720

I drive a 98 Dodge Ram 1500 V6 and my check engine light came on today. Went to AutoZone and they ran a check. Got a PO720 output speed sensor circuit malfunction. I see from the posts this is nothing new but how much is Dodge generally charging to fix this? Or ballpark repair figure. Thanks
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Old 05-12-2006, 11:56 PM
Russd is offline
Join Date: May 2006
Posts: 1
Default RE: Code PO720

We have a 2001 Chrysler Sebring.

The first indication we had was that - The Speedometer read 0 (zero) nothing, and the transmission would not shift out of first (sound familiar?). We weren't to far from home (less than 2-miles) so we returned home, during the drive home after a minute or so the dash board finally displayed a 'Service engine soon'.

We did a Google search for 'sebring speedometer not working', and did we get a lot of hits. H'mmm not quite to the point of a recall I guess.

The short side of the story was: Our answer came from a forum called Automotive helper - 'Speedometer reads 0 transmission wont shift out of first', the link was

It took me longer to write this message up than it did to fix the actual problem and saved us over $300. The dealers said understandably "it could be anything but it is most likley the transmission control module (TCM) $300".

It mentioned the Output Speed sensor as a most probable culprit. We looked and found the part on AZ online, in our case a WELLS Speed Sensor Part#SU1034 Output Side $26.99.

Understand we did not get to the point of using an OBDII tester to confirm the service engine light or find this forum until later. We did not have a tester nor did we want to drive the car to our local AZ who was over 10-miles away. Note that your friendly AZ will gladly help you out by using an OBDII tester right out in front of most of their store(s) if your able to get the car to them, we did not want to take that chance.

Here is what we did. hopefully it will help others out too.

In reading the above forum link we discovered it was probably the 'Output Speed Sensor' located on the transaxel that was causing our problem. Seems like it's the culprit on a lot of Chryslers and Dodges.

Anyway here is what you need for tools: One 1" Offset wrench, Ratchet wrench, or 1" semi-deep socket, drop light or flash light, and a med or small flat head screw driver (just for kicks - you'll see).

The sensor on a Sebring is white plastic, (2" long, about 3/4" around) with a 2-pin keyed connector. It's located on the transaxel (to the right of where the battery is located underneath). To access the sensor jack up the car on the driver side, although you may find you may not need to it's easiest with the drivers front wheel removed.

Pull the small mud guard located under the car behind the bumper between the nose and the driver front wheel well. The whole piece is only about 1 foot large with two pop in place inserts to hold it up in place, this is the peace that exposes the underneath part of the battery, you'll see it.

Use a drop light/flash light and locate the 'Output Speed Sensor', it's on the side of the transaxel towards the front. Disconnect the two wire connector by lifting the locking tab (up) and gently pulling it out. Here is where you may want to gently lift using a med or small flat head screw driver to lift the locking tab (be gentle). OK - Here's the fun part, use either and offset 1" box wrench, ratchet wrench, or 1" semi deep socket and remove the sensor (standard CC Loosen, CW to tighten). It's just close enough to the frame that it may be difficult to use an open end wrench and certainly wont take most short sockets.

The sensor should come out easily with a blue 'o'-ring attached, ensure the blue 'o'-ring is removed as ours stuck to the transaxel case (no big whoop). The sensor will come with a new blue 'o'-ring attached. Note that the sensor will be oily as it is in the transaxel case but it is below the fill line so don't worry.

Note, we did find some minute sluge on our sensor and one or two minute filings (tran breakin and wear) on the end when we pulled it mixed with the oil. Sense the sensor is magnetic one can only wonder if it might have caused the sensor to appear faulty? I did attach an oscilloscope to the sensor and when waved in front of metalic objects did find it to react/be active (sensing).

Clean the transaxel sensor mount with a clean rag and ensure there is no debris.

Insert the new sensor and tighten snuggly, re-attach the sensor connector housing (note it is keyed) and is attached securley.

Replace the mud flap cover underneath, catching the cover lip and re-inserting the two plastic push pins.

Mount the front tire again (if removed) and that's it...

We took ours for a short test drive and - YES IT FIXED IT !!!

OK don't get to overjoyed after all your not the only DIY.

We were told that to extinguish the SERVICE ENGINE LIGHT we would:
1. Have to go to a garage or mechanic with a system
2. The old "Disconnect the cars battery for about 20-minutes".

Concerning step-2 - Yes may lose the cars favorite radio stations, but no big deal. and yes 'on some cars' it may scare the hell out of some people when they turn the ignition back on a number of the dash board lights will light but keep reading.

We opted for step-2 "Disconnect the cars battery for about 20-minutes". Here's a little shortcut for you, we choose not to
disconnect the cars battery from underneath the car where Chrysler so wisely placed the battery but rather to "CAREFULLY" remove or disconnect the battery at the POS terminal lug up top, under the hood near the FUSE Panel and Air Cleaner (where they recommend Jump Starting the car). After loosening and removing the terminal lug we carefully isolated the POS cables (battery plus two others) and left the battery disconnected for about 20-min.

You may find or want to go shorter but in talking to several mechanics and understanding something about electronics we opted to wait the 20-min to ensure the memory properly dissipated in the cars onboard computer (aka forgot things and heopefully would reset). You can find something to do for that long, take a break you deserve it, plus you can walk around and do the rooster strut like Mick Jagger, tell your loved one how you may have just saved over $300. OK - Come Back - Reality Check !

After 20-Min carefully re-attach the battery cables, the terminal lug nut, and it' (red) saftey cover.

When we turned the key to our delight the SERVICE ENGINE LIGHT was extinguished. YAY !

Now our mechanic friends told us on some cars a number of other message lights may come on and that you may have to let some cars run as long as (15-20 minutes or so) so as the systems car computer can relearn or calibrate itself - OK point taken.

In our case the SERVICE ENGINE LIGHT was extinguished immeadiately and there was no other lights or messages to extinguish.

In fact I may be off here but I swear some of the cars other systems are running even more efficient than before. The cars electronic radiator fan - variable speed control seems to be running more efficient, even the radio's speaker system (balance) sounds better, h'mmm that's odd no one touched any controls. Best yet even though the cars radio clock did show 12:00 (OK easy fix we reset it to the current time) all the radio stations were still preset.

When all else fails nothing like a good old fashion system COLD REBOOT I guess. After all it is a computer !

Time total: 15-min worth of labor (jacking up the car, wheel and sensor removal and re-attachment) + 20-30 minutes worth of battery disconnect time = all told 45-minutes of time and $26 for the Output Speed Sensor.

Told you - It took me longer to write this message up than it did to fix the actual problem.

Hopefully this will help others along the way - Keep contributing everybody it's worth the time and helps others !


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Old 08-03-2006, 04:48 PM
honden is offline
Join Date: Aug 2006
Posts: 1
Default RE: Code PO720

You ROCK !!!!!!! Thanks so much for the concise reply. It saved me ( as well as others I hope) alot of headache and cash. I especially thank you for the statement regarding the sensor still being magnetic. It saved me alot of peace of mind after I replaced it but before I test drove it.

I took the battery out prior to replacing the sensor so that I wouldnt have to wait as long. Yes It has taken me longer register and post this than it took to replace that sensor.

Thanks again
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Old 08-04-2006, 01:23 AM
spectre184 is offline
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Join Date: Dec 2005
Posts: 47
Default RE: Code PO720

May want to read this thread. My reply is half way down. OBTW I did read thru all those 8 pages I linked to off of that thread.

*oops * -edit- Our D had check engine light come on and come to find out it was the tranny sensor. Replaced and ops check good
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