Hi I have been looking thru this site for quite some time and have learned alot of valuable information from the many posts i have read. I hate to make my first post a beg for help but here it goes

I have a 2001 250 crew cab with 7.3l 4x4 with 165000 miles i have not ever had any major problems with this truck and i tow a 32ft travel trailer all over wv and ohio in the summer

the issue i am having is a blinking od light at a stop with foot on the brake and also when i put the truck in park i get a rev of rpms when this light is flashing. I took it to a local garage and they scaned it and came up with p0720 oss intermittent problem i think is what they said. anyway they replaced the sensor on the output shaft of tranny and said that should do it. well a couple days later it started again. i have replaced both batterys and new alternator, also have checked all grounds on truck, have checked harness for bad places and found none. i have replaced the vss on rear end and also about a year ago i changed trans filter and drained tc and refilled with new dexmercIII also added the small inline filter from ford to the cooler line.

this problem is very intermitant. it may go days without doing it then one day i will be a a stop and the od light will start flashing and it will go into limp mode i assume and then goes away after up to speed.

any help would be apriciated. i love this truck and would love to figure it out before camping season rolls around

 

welcome to the forum matt i had na similar problem with my 93 f250 a couple years ago it has a 7.3 and e4od trans i would let off acell and od light would blink back on the gas and it would go off then noticed my tach would drop to 0 at idle but would work when you give it gas finally tach got real erratic and started shifting rough turned out to be the tachometer sensor put on a new one work fine ever since.hope this helps.

 

Mine only does it when I am at a complete stop it has never started blinking while moving. Where is the tach sensor. Is that the same as the vss on the rear end? Thanks for the info I will look at that

 

I had a friend that his was doing the same thing and it turned out to be the torque converter. He bought a additive, can't remember the name, and put in his and problem went away. He pulled a race car with his. Maybe some here will know the name of the additive.

 

my tach sensor is located on the cover of the gear that drives the injector pump right behind the oil fill but mine is a 93 yours may be diffrent

 

Moved to the 1999 - 2003 7.3L Power Stroke Diesel forum.

 

I'd pull the OSS and check the following:

- corrosion on connector to OSS

- chafing (resulting in intermittent shorting) on harness from the OSS to the PCM

- failure of OSS sensor (unlikely, but possible...particularly if they replaced with an aftermarket sensor)

- I have heard, but am not certain that extremely high RF (radio frequency) transmissions can cause an P0720 code somehow. This would point towards an alternator which has gone buggy.

One of the first two are what I would bet on...


Here is a thought from our own PaysonPSD:

The OSS and TSS are interchangeable. Swap them and see if you get a code for the TSS.



Might just be a bad sensor, dirty sensor or loose connector or wiring.

 

I can't imagine this contributing, but FYI, you need to use Mercon V fluid. Recommended for a few years now.

 

I believe the sensors are interchangeable, but only if it's a non-PTO 4R100.

Yours probably is not a PTO-type, but thought you ought to have the caution, just in case.

Pop

 

I will be looking into the problem more tomorrow and i will post any finding i have. i am going to look at all the recomendations and this will give me something to go by. I cant say enough how much i appriciate all of your input. I will let yall know what i find in a couple days

 

Took truck to ford shop and they had it all day yesterday and they said the new (napa) alternator that I put on is bad throwing a rf signal. I'm gonna try a ford alternator and take the napa one back. Hope they are right.

 

Ok wasn't alternator they now think it is cable going from alternator to starter?