Update: I did replace the sensor on the diff, but that didn't solve the problem.

On my truck the blinking was b/c the torque converter in the trans had failed. The T/C stopped locking up. I ended up having the trans rebuilt/replaced.

 

As a side note on reading transmission codes, the little Chinese ELM-327 code reader does have a way to read the extended codes, of which the transmission codes are some of.

These readers come as both Bluetooth, USB, and RS232 connection types. The Bluetooth works with tablets/phones and Bluetooth laptops. The USB works with laptops and PCS with USB, and the RS232 works with generally older PCs and laptops having RS232 connector.

Any of these are available for typically less than $10, and include software app or a place to download the app.

Further, they are simple to use, and will get you your extended OBD transmission codes.

 

Not for the OBS 7.3 Diesel...try again

 

I have a same problem overdrive was blinking shifting hard when I replace the tachometer sensor overdrive light is gone and shifting smoothly

 

Where is the Tach sensor ?

 

He probably means the abs sensor. It's a short term fix but will fail again.

 

Do you have a picture of this sensor or were its located by any chance.Thank you.

 

My 96 F250 7.3 had the overdrive off light flashing and hard shifting problem. I read forums about it and the only cure was go manual transmission. I finally saw a YouTube video about PSOM repair. Now this isn't just a 7.3 problem. Gas too. Take the psom out and send it to one of several companies that have made a business out of Fords error. I found two good ones on Google. One you can send in the whole cluster and get the lights updated.

 

Do not go see a transmission specialist. It will still shift hard. Psom repair.

 

flashing OD light is telling you there are diagnostic trouble codes stored in the computer. if the issue IS NOT the PSOM, than you just threw away a lot of money to fix something that did not need fixing. first thing to do is get the trouble codes read. they will tell you what the problem actually is.