Code P0720
 

While driving around this morning, I noticed the Check Engine light on. As soon as I had a chance, I connected the diag scanner and Code P0720 (output speed sensor circuit malfunction) came up. Erased it, started back up, one driving noticed my tranny shifts were sluggish and the same code came up.

Not sure where to start.

If I where to guess, I would probally start with the wheel speed sensor located in the rear axle. The problem is intermittent and doesn't effect my speedo just my first couple shifts when cold. Is there a way to test the sensor?

Help
thanks

SYMPTOM
P-0720 LOW OUTPUT SPEED SENSOR RPM, ABOVE 15 MPH

WHEN MONITORED
Continuously with the key on, engine running, and gear selector not in park or neutral.

SET CONDITION
This code is set if the vehicle speed (as determined from the vehicle speed sensor), is above 15 MPH , and the output shaft speed is below 60 RPM for 2.6 seconds .

POSSIBLE CAUSES

* Output speed sensor defective
* Output speed sensor ground circuit open
* Output speed sensor ground circuit short to ground
* Output speed sensor signal circuit open
* Output speed sensor signal circuit short to ground
* Output speed sensor wiring harness observable defect
* Park/Neutral switch code present
* Park/Neutral switch not operating properly
* Output speed sensor wiring harness intermittent defect (no code returned)
* Output speed sensor wiring harness intermittent defect (P/N switch code)
* PCM defective (output speed sensor signal ckt def)
* Powertrain control module defective (code returned)

The Vehicle Speed Sensor (VSS) is no longer used for any Dodge Truck.

Vehicle speed and distance covered are measured by the Rear Wheel Speed Sensor. The sensor is mounted to the rear axle. A signal is sent from this sensor to the Controller Antilock Brake (CAB) computer. A signal is then sent from the CAB to the Powertrain Control Module (PCM) to determine vehicle speed and distance covered. The PCM will then determine strategies for speed control system operation.

Testing for the Rear Wheel Speed Sensor can be found at Antilock Brakes / Traction Control Systems.

All other testing for the Vehicle Speed Signal can be found at Computers and Control Systems

http://i150.photobucket.com/albums/s...nfo/po7201.gif

http://i150.photobucket.com/albums/s...nfo/po7202.gif

http://i150.photobucket.com/albums/s...nfo/po7203.gif

http://i150.photobucket.com/albums/s...nfo/po7204.gif

http://i150.photobucket.com/albums/s...nfo/po7205.gif

I would guess that it' a sensor issue but IIRC you might have the vintage where the tone rings in the rear axle were failing.

Thanks JonnyC
The troubleshooting chart is awesome.

You guys are great... 2 responses to this guys problem within an hour.

Do you make house calls?

Darn, thought I could get by with a wheel sensor, buddy at a dealership sold me the sensor for $40. Unfortunatly, it did not fix the problem. Time to start troubleshooting.

Are your ABS lights on? Any ABS codes? Might need a Star Scan to find them, or a Solus or something to that effect.

On my 04 and 06 rocks and large puddles beat the crap out of the connection untill it came apart.:scared2: On the 04 it was in the dealership 4 times for that problem and they replaced the whole harness a couple times, then after accusing me of unpluging it:loco: they put a shield infront of it and that fixed it. On my current 06 it has gotten beat up and I tried to zip tie it back on but that didnt last long, and it needs to be fixed and a shield put on it.:argh:

My unit has a shield in fornt of connector and the harness connection looks good. Regarding the wheel speed sensor. If it is going out would the speedo dance all over the place. Mine is not.

The abs light does not come on, just the check engine light.

The problem I am expierencing is on the first shift into first gear the tranny "sticks" for a couple seconds then shifts. After the 1st time the problem goes away and the truck runs fine until I turn off the motor and restart.