my 99 superduty with the 7.3 has had the over drive light blinking so i checked the codes on it and p0720 came up which is the output speed center malfuntion. i was wondering where that is located and if it is the same thing as the vss. thanx

 

I believe it is. It is on the top of the differential.
Joe

 

The output speed sensor is on the rear of the transmission. The VSS is a different sensor.

 

P0720
Insufficient input from Output Shaft Speed sensor
<!---- code here to write warning text if needed. ----><TABLE style="OVERFLOW: visible; WIDTH: 100%" cellSpacing=0 cellPadding=0><TBODY><TR><TD class=messageMed style="FONT-WEIGHT: bold">Detailed Description</TD></TR><TR><TD class=messageSmall>The output shaft speed sensor inputs a signal to the PCM, based on the speed of the output shaft of the transmission. The PCM compares this signal with the signal of the VSS or TCSS and determines correct tire size and axle gear ratio.
</TD></TR><TR><TD class=tableHeader>Possible causes :-</TD></TR><TR><TD class=messageMed style="FONT-WEIGHT: bold"><LI class=bodyText>OSS sensor circuit short to GND. <LI class=bodyText>OSS sensor circuit short to PWR. <LI class=bodyText>OSS sensor circuit open. <LI class=bodyText>Damaged OSS sensor. <LI class=bodyText>Damaged PCM.
</TD></TR><TR><TD class=tableHeader>Diagnostic Aids</TD></TR><TR><TD class=messageSmall>Verify sensor signal output varies with vehicle speed.

</TD></TR></TBODY></TABLE>
Output Shaft Speed (OSS) Sensor
The output shaft speed (OSS) sensor is a magnetic pickup that provides transmission output shaft rotation speed information to the powertrain control module.
The output shaft speed (OSS) sensor is mounted externally on the top of the transmission case. The PCM uses the output shaft speed (OSS) sensor signal to help determine electronic pressure control (EPC) pressure, shift scheduling and torque converter clutch (TCC) operation.

 

thanx for all the info

 

how can i get to it?

 

Get under the truck, go to the back of the trans. The sensor is on the extension housing at the back of the trans.

 

I had this error on my 2000 bounder ford motorhome and replace the sensor as the error code was p0720 output speed sensor circuit and we took one trip and it started to happen again. The overdrive light on the shifter starts to blink then the check eng light soon comes on and I have very low power when stepping on the gas. It feels like it won't move. Does anyone have any other ideas that may be causing the problem? Thanks for any help.

 

The code doesn't necessarily mean the sensor is bad. It means the reading from the sensor is bad. It could be the sensor, the wiring to the sensor, or the tone wheel inside the trans that the sensor is reading.

 

Mark

Thank you for your help, Is there anyway of testing the tone wheel ?
I'm disablied and can only do so much under the motorhome. Any help with info would be great.

thanks again.

Marty

 

It isn't likely to be the tone wheel, but I threw it out there because it is possible. Usually these type of problems are damaged or corroded wiring.

Someone might be able to inspect the tone wheel by looking in the hole where the OSS goes, but the driveshaft would have to be rotated one entire rotation to see each tooth. The better way is to remove the driveshaft and the extension housing from the back of the trans.

 

Thanks for the input, I will check the wires first then I bought another sensor. I will see how that goes. Thanks again for the info.

 

where can i find the oss? every where i look just has the vehicle speed sensor

 

I'm sure a Ford dealer would have it.

 

mine 02 was throwing that code awhile ago every time i washed it with a pressure washer to get some of the mud from the underside! it would kill the motor everytime i stopped moving so i let it sit for couple hrs and everything would be fine! im guessing its a short somewhere