O/D off light flashing?

Mark Kovalsky · Nov 18, 2019

Since it works without the chip but sets a code when the chip is installed I suspect the chip is the problem.

Coolit · Nov 18, 2019

I just noticed today after driving it for a little bit without the chip in it will start coding/ flashing the overdrive off light I'm not able to scan it because as soon as i get down to 10 mph the overdrive off light stops flashing or while it's flashing if i kick it up in neutral and shut the engine off and restart it it turn off and does fine when it starts to code it is constantly going in and out of what seems like is overdrive but it's 3rd and then sometimes it goes into overdrive and 25 mph and it making lockup on the Tc, it's doing all kinds of crazy crap I get a good 1 - 2 shift then everything goes haywire but only when it's warmed up good. I hope all that makes since I know I shouldn't be shutting my engine off running 55 mph down the road but it's a long straight road and sometimes ya gotta do what ya gotta do lol. I'm starting to think I have a bad speed output sensor or on it way out completely at some point my theory is with the chip out the sensor works good enough until it gets good and warm the codes but with the chip in it's weak enough the chip just causes it to code as soon as it shifts 1 - 2 then codes I don't know I'm just guessing at this point I'm just glad there's folks around such as yourself to helps us numbskulls out that don't have a clue as to what we are doing.
Thanks for the help I really do appreciate it

Powerstroke Man 6.4 · Nov 19, 2019

Coolit said:
I just noticed today after driving it for a little bit without the chip in it will start coding/ flashing the overdrive off light I'm not able to scan it because as soon as i get down to 10 mph the overdrive off light stops flashing or while it's flashing if i kick it up in neutral and shut the engine off and restart it it turn off and does fine when it starts to code it is constantly going in and out of what seems like is overdrive but it's 3rd and then sometimes it goes into overdrive and 25 mph and it making lockup on the Tc, it's doing all kinds of crazy crap I get a good 1 - 2 shift then everything goes haywire but only when it's warmed up good. I hope all that makes since I know I shouldn't be shutting my engine off running 55 mph down the road but it's a long straight road and sometimes ya gotta do what ya gotta do lol. I'm starting to think I have a bad speed output sensor or on it way out completely at some point my theory is with the chip out the sensor works good enough until it gets good and warm the codes but with the chip in it's weak enough the chip just causes it to code as soon as it shifts 1 - 2 then codes I don't know I'm just guessing at this point I'm just glad there's folks around such as yourself to helps us numbskulls out that don't have a clue as to what we are doing.
Thanks for the help I really do appreciate it

Even when you shut it off and or stops flashing. The PCM will still store perm/continuous DTC's in memory.

Coolit · Nov 19, 2019

Ok thanks I'll take it and have it scanned again and report back.

lincolnlocker · Nov 19, 2019

Coolit said:
Ok thanks I'll take it and have it scanned again and report back.

Forscan should be able to read those codes.

Are you sure you got the correct matching pcm as the old one? Are yoy sure the chip connections in the pcm are correctly cleaned off and still have the tinning on them and or cleaned off too much where you can see the brass?

I had similar issues as you in my dually and one time it was the rear speed sensor and the second time i ended up havng to send the pcm in to get re-tinned..

live life full throttle

Coolit · Nov 21, 2019

It does the same thing without the chip in it

Coolit · Dec 8, 2019

I got the pcm that went with the engine and transmission they came out of a 2002 E350 ambulance we cleaned the pins to where it would make good contact no retinning necessary at first I was having problems with it dropping down to 2nd gear if I pulled over and pointed the truck uphill and turned it off for a couple minutes I could take off and it would work fine for about 4 or 5 miles so we replaced the pcm with the one that was in the ambulance which in a non intercooler vehicle the engine and transmission worked fine before we swapped them into my truck but once we figured out the pcm was the main problem it started coding for the output speed sensor we replaced that with a new one I decided I would put my chip back in then it started coding for both of the speed sensors P0715 p0717 and P0720 everyone was telling me these trucks are bad about the transmission wiring harness going bad so I changed that out still doing the same thing with the chip installed it does fine without it so it looks like I'm going to have to get the model number off the pcm and send the chip back to have it re-burnt that's the only other thing I can think of luckily I didn't have to buy any of the stuff speed sensors and wiring harness does anyone know of a place that rebuilds pcm's I still have my old one I'd like to have it for a back up.
Thanks