Another E4OD flashing OD light thread

94NAIDI

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I know this has been discussed over and over again. I tried my best to not start another thread. I read through so many different threads on this site as well as the other diesel truck sites trying to get advice without creating another thread on the same issue. But all the other threads either had different symptoms or the resolution they came to didn’t work for my truck. So I apologize in advance for yet another repeat of the dreaded flashing OD light.

1994 F350 7.3 IDI 4x4 crew cab E4OD transmission.
Here are my symptoms. Truck runs perfectly fine. Transmission seems to shift fine. I can drive the truck for two or three days with no issues. Then randomly the OD light will start to flash out of no where with nothing unusual happening prior. Then of course it goes into limp mode and shifts like crap. Usually if I continue to drive the truck, the OD light will eventually go out. I drove a 4 hour trip last week and the light came on and went back off 3 different times throughout that trip. Also if I shut off the truck, the light goes off and does not come back on when I drive it again. Then without warning, a couple days later it appears. Sometimes, when the light comes on, if I manually shift into first, then second, then drive taking off from a stop light the light will go out. I do this a lot when the light comes on to avoid it slamming itself into gear in limp mode. I don’t know if that is telling us anything or it’s just purely coincidental. I did notice today that the shift to 3rd and then 4th happen really fast. Almost so fast you don’t notice 3rd at all. I’m staring to question if that is normal or not. My truck will literally be in 3rd for maybe a second or two at most. And usually the shifts take place simultaneously to where you don’t even notice 3rd at all. I have to watch the rpm gauge to even notice the 3rd shift and it immediately goes to 4th. I don’t know if I’m just getting overly sensitive to the tranny at this point or if that is a legit symptom.

Here’s what I have done to solve the issue based on my research of other threads. Replaced VSS. Replaced the 100uf capacitor that is known to go bad on the PSOM. Unplugged, inspected, cleaned, applied dielectric grease, and plugged back in the connectors at the VSS, the transmission selector switch, the solenoid pack, and the TPS. I also adjusted the TPS to 1.2 volts at idle. It was at 1.08. I unplugged and checked every fuse in the cab as well as in the distribution box. Did a tranny fluid and filter change. All the above seemed to help my tranny shift even better. But unfortunately I am still getting a random flashing OD light. I ran the codes just today and came back clean. 011 no codes found. That was KOEO and KOER tests. Both found no code. The only thing is my light is not currently flashing. So I don’t know if the light has to be actually flashing for a code to be pulled. I will keep the code reader with me to run them next time it happens. Because the flashing goes away a lot of times before I even get home.

I have done everything I can think of, and everything I found in my research. Does anyone have any other tests I can do or advice. This is an extremely challenging issue for me to fix. I don’t mind spending the money to fix it. But I don’t want to waste money either. I need to find the smoking gun so I can get it fixed once and for all. I appreciate any help and feel free to ask questions. There may be more symptoms I’ve forgotten
 

Cant Write

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Being in the rust belt, it sounds like you might be fighting an intermittent “break” in the wiring.....?

Wish I could be more help. Will be following along until you find the solution.
 

Nero

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You will need to scan for codes as the codes are there. Be careful driving with a flashing OD light, it forces it to go full rail pressure. Prolonged driving like that will blow out the front main seal.
 

94NAIDI

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I have a back up truck. So I can stop driving it for now. But I love this truck so I definitely need to get this figured out.

My scanner isn’t seeing any codes. Is there a different type of scanner I need?
 

Nero

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Just the basic obd1 Ford scanner. Sometimes the codes can be a bit of a pain to show up, been there done that.
 

94NAIDI

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Ok. I’ve got a pretty nice scanner. Not one of the cheapies. I’ve had it for years. Usually works fine for me. I’ve ran the codes on this truck twice in the past week. Both times comes back 011. Which means all good. No trouble codes found. I’m not sure what else to do to get the codes.
 

94NAIDI

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Yes. Sorry I forgot to include that in the initial write up. I did check and even cleaned the brake light sockets
 

94NAIDI

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I sure will. I’m going to keep the reader in the truck with me. Unfortunately I leave tomorrow for a trip to Texas. So I’ll be gone f for 4 days. Obviously not tanking this truck. But it will be at least 4 days before I’ll have a chance for it to fail again. So I won’t be getting odes until after that.

If anyone else has other suggestions though, I’d like to come back from my trip with some ideas to look at and test.
 

94NAIDI

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I could also have my son drive it while I’m gone and see if he can get me t to read codes once the light starts to flash.
 

94NAIDI

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Ok. I decided to drive it to the airport so I could pull the codes. The OD light started flashing about 30 minutes into the drive. I pull over to read the codes. Hook up my scan tool, OD light still flashing. As soon as the scan tool starts the test (getting cylinder ID) the OD light stops flashing. I continue on with the test. Results 011 system passed. I disconnect everything and start back out on the road. OD light starts to flash again within a couple miles. I pull over again. Connect scan tool, same result. Get back on the road and the OD light remains flashing for the next 30 minutes of the drive. It was all interstate so I didn’t get a chance to notice any shifting issues. But I was obviously in limp mode. I’m sure it would have had a hard shift condition if not on the interstate.

By the time I get into town, the light goes off and everything seemed to be shifting fine. No limp mode.

It wasn’t until I get to the airport parking lot that I notice anything unusual. Cruising around 5 mph in parking lot the truck was surging like the torque converter was locking up instead of slipping. Kinda like letting off the clutch on a standard shift truck at to low of rpm. The truck would surge forward then release.

I don’t know if that was from driving in limp mode so long or if this is a symptom of what’s wrong.
 

94NAIDI

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Is there a trick to getting these codes? I’ve used this same scan tool for many years on multiple vehicles in the past. Never had any issues pulling codes. This is the first time I have not been able to see the codes. I assume a code exists since the OD light is flashing. I just can’t wrap my brain around why my scan tool isn’t picking it up.
 

Greenie

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Key on engine off for the OBD1 I have. When you shut off the engine maybe the codes go away? Maybe the next time the OD light flashes find a safe place to stop and leave the engine running but pull the fuel shut off wire off the pump and then run the OBD1 test. The throttle needs to be held open for the test, BTW. I went through a summer of what you're going through, sometimes it takes a while to figure it out. The RPM sensor wires and connector in good shape?
I ended up refreshing all the grounds, replacing the TCM with a rebuilt Napa TCM, and the alternator... I found an AC ripple which may have been causing some issues.. With the engine running around 1,500RPM check the alternator output with a meter set to 20 volts (+/-) AC. You can test from the battery terminals too. There should be less than .25 VAC present - if more the alternator needs to be replaced.
 

94NAIDI

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Good suggestions. I actually did perform the test this morning with the engine still running. I didn’t want to risk turning off the engine and losing the code. But the darn light goes out as soon as the scanner communicates with the truck. My scanner only has me hold the throttle open in the KOEO test mode. Which I did previously. This morning I was doing the KOER tests. No holding the throttle open in those tests. I was doing KOER because I wanted to perform the tests while actually having a blinking OD light.

I will definitely check the alternator when I get back from Texas on Friday.

The grounds are a good call as well. I live in the rust belt and my truck does have some rust. Not as bad as most. But none the less it’s there. I read where someone suggested running a new ground from the battery negative to the bell housing. If that’s worth trying, I’m willing to do it. It’s a safe bet I have some rusty/bad grounds.
 
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