O/D light flashing
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From: Morgantown, WV
O/D light flashing
On the way home tonight, the O/D light started flashing. I happened to have the Bluetooth OBD adapter with me, so I plugged it in and opened Torque. It comes up with a "pending" code of P0743. After a little bit, the light quit flashing so we drove the last mile home. The O/D light began flashing again the last couple hundred feet before our driveway. There didn't seem to be any loss of power or anything like that the whole time.
After we got the kids to bed I went back out to check the fluid level. (It had cooled some, so I let it run a bit before I checked it - the light wasn't flashing this time.) The level is at the second dot, right below the crosshatch. It's almost transparent, but I don't know when it was last flushed (if ever).
From what I've seen on here, I'm guessing this is an electrical short somewhere?
After we got the kids to bed I went back out to check the fluid level. (It had cooled some, so I let it run a bit before I checked it - the light wasn't flashing this time.) The level is at the second dot, right below the crosshatch. It's almost transparent, but I don't know when it was last flushed (if ever).
From what I've seen on here, I'm guessing this is an electrical short somewhere?
Frmr Ford Trans Engr
Joined: Aug 1999
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From: SE Florida
P0743 means an electrical problem with the torque converter clutch control solenoid electrical circuit. It could be an open or a short. It could be a bad solenoid or a problem with the wiring between the PCM and the solenoid.
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From: Morgantown, WV
TIP: Many times a simple fluid and filter change will take care of minor transmission issues. There’s nothing to lose with a fluid and filter change. Notice I say change and not a fluid flush. A fluid flush on a high mileage transmission may cause further damage. Also, for a transmission that is slipping I recommend Lucas Oil Transmission Fix. I am not endorsing the product nor am I getting paid to use the name. But it works!
In addition to suggesting that a fluid flush could damage a transmission, I like how he "recommends" a product but is somehow "not endorsing" it. It may be true that he's not receiving anything for his recommendation, but that's a technicality.
He also says "Note: This may well be an intermittent condition and may not show up again, so clear the code and keep monitoring." Is this advisable? Can I drive it to test as long as I have the Torque app monitoring trans temp to make sure it doesn't overheat?
I'm going out now to see if I can track down any obvious electrical issues. (Someone on the Expy forum found that the insulation next to the exhaust had melted off the wire and allowed it to ground out.)
Edit: Can't see much, and nothing obvious from what I can see. It does appear one of the O2 sensor wires is wrapped around the shift cable, but I don't think that is related.
Frmr Ford Trans Engr
Joined: Aug 1999
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From: SE Florida
It's not a bad idea to clear the code and see if it comes back. Once in a great while the code will set and not set again. If there is really something wrong it should come back pretty quickly.
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From: Morgantown, WV
Well, it's not a fluke. I cleared the codes and took it for a drive. The light stayed off for a while but eventually came back. After the light came on, there were times I could feel momentary lags in the transmission while it was driving. I believe the first on I felt was the first time the torque converter locked up (torque slip went from readings in the hundreds to readings near zero). I felt the same thing after that when shifting gears.
We let it rest for a little while before returning home. The O/D light was off again when we started. After we drove for a little bit it started flashing. A little while later it went out, but then returned again - this time with the SES light. I canned for codes and now it is showing two:
Current Fault:
P0743 - Powertrain
Torque Converter Clutch Circuit Electrical
(same as before, except it was previously a "pending" fault)
Pending Fault:
P1744 - Powertrain
Torque Converter Clutch System Stuck in Off Position
At this point, I guess I'm going to call some places in the morning to see if someone can look at it.
We let it rest for a little while before returning home. The O/D light was off again when we started. After we drove for a little bit it started flashing. A little while later it went out, but then returned again - this time with the SES light. I canned for codes and now it is showing two:
Current Fault:
P0743 - Powertrain
Torque Converter Clutch Circuit Electrical
(same as before, except it was previously a "pending" fault)
Pending Fault:
P1744 - Powertrain
Torque Converter Clutch System Stuck in Off Position
At this point, I guess I'm going to call some places in the morning to see if someone can look at it.
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From: Morgantown, WV
So far, it looks like the earliest I can get someone to look at this is Wednesday. Is it safe to drive until then? I hate to run the transmission right now, but my other car is on jack stands until a couple bolts arrive.
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Frmr Ford Trans Engr
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From: Morgantown, WV
I found a transmission shop that had time to look at it this afternoon. They are checking it out now and showed me the codes their system was able to pull:
P1000 - OBDII System Checks Incomplete
P0741 - Torque Converter Clutch System Stuck Off
P0705 - Transmission Range Sensor Circuit Fault
P1702 - Transmission Range Sensor (TRS) Circuit Intermittent Malfunction
P0740 - Torque Converter Clutch Fault
P0743 - TCC System Electrical Fault
P1000 - OBDII System Checks Incomplete
P0741 - Torque Converter Clutch System Stuck Off
P0705 - Transmission Range Sensor Circuit Fault
P1702 - Transmission Range Sensor (TRS) Circuit Intermittent Malfunction
P0740 - Torque Converter Clutch Fault
P0743 - TCC System Electrical Fault
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Senior User
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From: Morgantown, WV
Not looking good. The shop owner called and says they've checked through the electrical options and it checks out. He asked if I had changed the fluid filter because it looked so clean (I have not). It seems to run fine until the fluid warms up. Now he's looking at the converter itself.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,704
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From: SE Florida
There is no way that the torque converter can cause an electrical code. There is something wrong with the electrical circuit. It could be the wiring, the solenoid, or the computer. I listed those from most likely to least likely.
Junior User
Joined: Apr 2008
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From: Jonesville, NC
Mark, any advice on troubleshooting these codes would be very welcomed.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,704
Likes: 2,625
From: SE Florida
My advice is to get a wiring diagram. I don't know how to check circuits without a diagram. The P0743 code can only set from an electrical fault. That must be either the wiring, the solenoid, or in very rare cases, a bad computer.
Post Fiend
Joined: Mar 2009
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From: Mt. Shasta California
Agreed, the physical part of the converter won't show up in any codes.
Junior User
Joined: Apr 2008
Posts: 66
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From: Jonesville, NC
BTW, I do have an extensive trouble shooting background. I've been in industrial maintenance trouble shooting/repairing/rebuilding CNC machining centers and lathes for over 20 years and am also a licensed electrician. Basically I'm wondering if machine quality electrical prints are available for the automotive world. The ones in the Haynes manual helped me find my head light problem but there are no transmission wiring diagrams there.