2001 4.0 Flashing O/D Off Occasionally...

[Sephiroth]

I own a 2001 Ranger XLT 2WD with the notorious 4.0 SOHC engine. However, I'm at almost 350,000mi and the engine is fine, but I am becoming concerned with my transmission. Twice now, at the same part of highway, I got the dreaded flashing "O/D Off" light. Truck continued driving and shifting fine, so I went home both times and turned the truck off. After the first time (two weeks ago) it did not happen again until today. It happens on the same stretch of road, which makes me wonder if somebody has a high output RF transmitter that may be tripping out the PCM, but let's throw my conspiracy theory away for now.

After the first occurrence, I hooked up my laptop and data-logged a trip using FORScan. Things look okay to me, but I do not know what they SHOULD look like. I attached the FORScan log (live data stream) so those with proper knowledge can get an idea of how the truck is behaving. Is my TCC gone? The valve body? Is this just a sensor error? The truck has no codes or warnings and never has. Oil and filter are changed at the dealer every 5,000mi. I just did all six plugs (they needed it badly) and the engine air filter this past week. Transmission oil is in the proper range on the dipstick and is still red or pink in color. It shifts smoothly. We know it shifted, but it's a smooth shift, not hard.

Thanks for any help you can offer.

 

[RonD]

Welcome to TRS

What code did you get?
I won't download and open a zip file, my conspiracy theory, lol

TCC is torque converter lock system
If there is a code for this it would mean engine RPMs and input shaft RPMs were different after TCC was engaged, so could be torque converter issue or TCC system issue

Flashing OD light just means Computer sees a problem at that time, no its not from an outside source
Difference in engine RPM and input shaft RPM above 30MPH would cause Flashing OD light and reference to TCC

What MPH are you at when you get the flashing?


4.0l SOHC is a good engine, earlier models, 1997-2003, did have issues with the original long chain tensioners, but the tensioners were redesigned
Never a 100% failure rate, just higher than it should be so redesign was in order
But these should be changed every 100k miles just as preventative maintenance, but not required

 

[Sephiroth]

I forgot the code, it is P0741, the dreaded code. No engine light at this time. Drives fine though, for its age and mileage. It is a daily driver, but bone stock.

I thought that all of the 4.0 SOHC motors had the chain issue, but I guess I am mistaken. At 350,000mi, should I be sweating bullets or doing a rebuild of the chains?

You can always upload the zip file to Virus Total if you are worried. They allow any file up to around 700MB. They unzip it in a VM on their end and scan the zip contents with about every virus scanner on the planet. I use it regularly as I am in IT and need to download files from others regularly. I do NOT blame you for being concerned about a file from a total stranger online though!

 

[RonD]

TCC has these general codes
P0740 Torque Converter Clutch Circuit Malfunction
P0741 Torque Converter Clutch Circuit Performance or Stuck Off
P0742 Torque Converter Clutch Circuit or Stuck On
P0743 Torque Converter Clutch Circuit Electrical
P0744 Torque Converter Clutch Circuit Intermittent

P0740, 743 or 744 would be wiring or solenoid issue
i.e. computer "sees" the solenoid, electricity is passing thru it, and it is getting the feedback pulse when its activated, or it would set one of these codes

P0741 would be valve issue or torque converter issue
What it "sees" is that the engine RPMs and input shaft RPMs are not "locked" together when TCC is ON, slipping is occurring in torque converter, because its old or because valve is leaking
No way to tell which one from the code

Does transmission/torque converter also have 350k miles?


There were no issues with the timing chains or the guides in any year 4.0l SOHC, only issue was the tensioners, if one failed it allowed the chain to bang on the guide at start up and break the guide, this caused "the death rattle", damage done, have to pull the engine to repair
The two tensioners are external so not hard to change, one takes 1/2 hour, the other 1 hour, only use Motorcraft, if you feel the need

The tensioners are hydraulic(oil pressure) but have a strong spring inside, spring is only needed at start up before there is oil pressure
Original design had issues with the springs failing, as said not 100% failure, maybe 20%
If a spring broke then on start up the chain would bang on the guide and over many startups, break the guide, there is no warning, no sound you would hear because starter motor is too loud
Redesign has better springs

 

[Sephiroth]

The tensioners scare me. My old roommate had a 2001 4.0 SOHC also, and his had a chain jump a sprocket and damage the engine at around 149,000mi. Is there a way to test the tensioners without a tear-down?

As for the TCC, I believe it's original. I know that 741 is mechanical failure, which is why it worried me. Is there a way to know if it is a valve issue or worn clutch without disassembly? I ask because if I have to remove the thing and split it, I may as well rebuild it, right?

On the brighy side, I have not had the flashing light since my initial post on this thread. Doesn't mean the old thing isn't going out, but it's running good.

I just had a thought. Since the transmission is shifting smoothly but the TCC fails to lock at times, would the be indicative of a bad TCC? My assumption is that, if the valves were going, the shifts would be very hard.

 

[RonD]

Tensioners are external no tear down needed

4.0l sohc is an interference engine so can bent valves, but that usually doesn't happen

Each solenoid has its own valves, so TCC valve can be an issue and wouldn't effect shifting

 

[DILLARD000]

...Is there a way to test the tensioners without a tear-down?...

Not really a practical\formal way to fully test the 2 OilPressurized TimingTensioners,
other than taking them out & feeling if they are "crusty\crunchy" when being compressed in your hand.
If they've been in an engine for a 100kMiles or longer, especially without regular Oil+Filter changes,
they will definitely be sludged up & feel crusty\crunchy when you try to compress them.
Usually if you spray some CarbCleaner thru them & then some fresh oil, they will loosen up;
though if you've got new Tensioners on hand, don't recommend re-installing the old ones.
Click here for more on OilPressurized TimingTensioners for the V6~4.0L~SOHC.

 

[ekrampitzjr]

If that transmission and torque converter are original and made 350,000 miles, I'm very impressed. Newer stuff (new cars and trucks) isn't able to do that. Ditto for a lot of engines now.

I'm suspicious of the torque converter in particular on yours.

 

[Sephiroth]

Me too. It's a clutch. I figure it's on the way out. Guess it's time for a rebuild! Thank you for the information!