P0740 TCC Failure - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 05-12-2009, 02:56 PM   #1
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Default P0740 TCC Failure

Hello All, I have at least two issues that I need to address. The P0740 code as well as a flashing ECC temp. First a brief history. Please bear with me as this is my first post beyond hello. Any and all suggestions are welcome. I recently purchased an Actron CP9145 scantool and am still trying to learn what all of the live info means. Also, I am not real clear on TCC lockup so I may confuse the terminology. These are the initial codes that I found:
P0406- Linear EGR- Pintle Position Error
P0640-Quad Driver Module QDM 1 Fault-check evap canister +TCC Apply Solenoid
P0740 TCC Converter Clutch Failure

Replaced the EGR with used one from J/Y
New BCS (after performing test per Tech info) Full boost now instead of 2 lbs.
Installed larger tranny cooler
Adjustable Vacuum boost modulator (btw, shifts out of first a lot sooner now, I turned it 1 1/2 turns clockwise)

Oh, I almost forgot, I recently replaced the heater fan motor due to excessive noise. The vacuum line going to the box on the firewall broke. I spliced it with some rubber hose and zip ties. Now whenever a vacuum hose is removed and reattached such as when I replaced the vacuum modulator a couple of days ago. I hear the vents on the passenger side creaking. There was a little tranny fluid in the old modulator. If I turn the key on but do not start the engine the creaking and flashing goes on for about a minute before it stabilizes. When I start the engine the creaking and flashing starts again. Once everything stabilizes I can change modes and vent positions with no creaking or any thing out of the ordinary. If I turn the engine off the whole process starts again when I start the car up again and hot air blows for a few seconds. From what I have read, which is a lot since I intend to at least skim all of the posts in this section (up to page 200 so far), I suspect that I will be looking at the Vacuum connections under the dash next. By the way, I have sprayed Carb cleaner around all vacuum hoses. supercharger base, etc, There was a leak where the EGR goes into the supercharger, I tightened it and no more leak there. I have not looked at the actuator arm to see if it moves or binds yet. I understand that there is a module that controls all of the vacuum lines which I have also not looked at.

About the TCC issue: Like many others everything seems to be fine until the car has been driven for 10-15 minutes. During that time I go WOT several times to try and aggravate the problem. I drive the same route to try and replicate the issue and it usually kicks out of overdrive about the same place. This is after WOT up a slight grade. I can stop turn off the ignition, open a door to kill all power, restart, come up to 65, engage cruise control and it will not lose overdrive until I disengage cruise control. I did record live info from the scan tool today. Also, the fluid was completely flushed two weeks ago, there is no burnt smell or brown color and the fluid level has not moved.

Stats on highway before loss of overdrive occurs:
LT Fuel trim 138, LT Fuel tr CL 16, Evap duty % 15, Cooloant 185, EGR vlv pos%(v) 4.3/2.8, Exhaust O2 Rich/Lean, IAC position 93, Loop Status Clsd, MAF 34/18, IAT 72, OSs (mv)53/838, TCC applied Yes/no mostly no, TCC duty cycle 78, TCC Slip RPM 155/220 drops to negatives when off throttle, TPS Sensor .84, Trans Temp 167, Average speed 65 mph, outside temp around 65 degrees.

Sorry for the long post but I am trying to include as much info as I can up front.
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Old 05-12-2009, 04:30 PM   #2
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I forgot to mention that when I have the scan tool on the car it sometimes loses the connection. I just press enter and it reconnects without having touched the ALDL. I just tested the Throttle Position Sensor and the voltage drops off badly so I am off to get another on. I am also going to clean the MAF sensor. Then I will test drive it and report back.
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Old 05-12-2009, 06:46 PM   #3
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The first thing I would suggest is check for vacuum leaks. These tend to throw all kinds of odd codes.
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Old 05-12-2009, 09:00 PM   #4
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Hey Danthurs, I have replaced all of the vacuum hoses or at least I think I have. I still haven't gotten under the dash yet. Was going to do that after I replaced the TPS but realized that it would be much easier to get to by removing the Throttle body. So....I went ahead and cleaned the Throttle body and am waiting for the new gasket to arrive on tomorrow. Once I get it back together and test drive it I will take a look at the vacuum lines under the dash.
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Old 05-12-2009, 09:15 PM   #5
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Don't forget to check the EGR tubes. If they crack you get a big vac leak and can be hard to find.
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Old 05-12-2009, 10:13 PM   #6
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Will do.
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Old 05-14-2009, 08:59 PM   #7
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You were right about the cracked EGR pipe. It was under the flange that goes into the supercharger. I sealed it with J-B Weld epoxy. It took care of that leak but she still drops out of overdrive and the ECC still acts screwy at startup.
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Old 05-14-2009, 09:26 PM   #8
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You should really replace the tube. It may not be totally sealed.
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Old 05-14-2009, 09:52 PM   #9
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I agree. I tried the dealer but they don't stock them anymore. If anyone has or knows where I can find one I am definitely in the market for it. The local J/Y has a couple of supercharged Bonnies and Ultra'* bodies but the engine bays are gutted.
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Old 05-14-2009, 09:53 PM   #10
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I was able to locate the lower tube on line but I haven't had any luck with the upper so far.
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