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Unread 02-15-2006, 11:22 PM   #1
mongerryan
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P0740 Code - TCC Circuit Malfuntion

Hi All,

I've had my check engine light on for a while on my 01 grand Cherokee, and I finally was able to get a OBD tool to check it. It gave me a P0740 Code - TCC Circuit Malfuntion code. From a search on this forum:
"P0740 (M)

Torq Con Clu, No RPM Drop at
Lockup

Relationship between engine and vehicle speeds
indicated failure of torque convertor clutch lock-up system
(TCC/PTU solenoid)

I'd ask here about symptoms of a bad Torque Converter."
and
It's one (or more)of, probably, three things:
- Bad torque converter (blew the lockup clutch)
- Bad lockup solenoid
- Bad wiring from the PCM to the lockup solenoid
- Very remote possibility, but possible none the less -> Bad PCM.


You *MUST* fix this before driving on the freeway, or at freeway speeds, as you can burn up your transmssion by driving at freeway speeds without the toque converter locked up.

- Oh, forgot, could be the speed sensor also, but that's a little doubtful.

If it turns out to be a bad torque converter (blown lockup clutch), the transmission will have to be taken apart and checked, as, more than likely, lockup clutch material would have made it into the tranny,

I'ld start with the wiring itself. Check to make sure that it looks ok at the electronic solenoid itself.
So...my question is...what should I do about this? Would a regular mechanic be able to take care of this, or should I take it to the service at a jeep dealership?


Anything else I should look for from this problem? Anybody else had this problem and fixed it?

Thanks ahead of time for your comments!


Ryan

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Unread 02-16-2006, 06:05 AM   #2
greasefingers
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I am not aware of any danger if you continue to drive this way. You will however see a drop in gas mileage. I believe your solenoid is fried.
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Unread 02-16-2006, 06:14 AM   #3
michiganmaveric
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I don't think you havew to take it to a dealer. A good transmission shop should be able to fix it.
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Unread 02-27-2006, 07:07 PM   #4
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Turn your overdrive off
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Unread 02-28-2006, 12:20 AM   #5
Ross
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I just got this pcode today. It will stall if I don't keep the engine speed up. If I turn off the o/d it seems to idle but not very smooth and eventually die.

Is there anyway to get a little better handle on what is going on other than the shop?
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Unread 02-28-2006, 05:50 AM   #6
greasefingers
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Your VSS is bad. The PCM needs to know how fast the vehicle is traveling. Instead the PCM will use one or other sensors to try and determine the vehicle speed. Doing it this way is not accurate enough and the engine is not performing properly. Replace it and your problem should go away.
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Unread 02-28-2006, 09:10 AM   #7
Ross
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Quote:
Originally Posted by greasefingers
Your VSS is bad. The PCM needs to know how fast the vehicle is traveling. Instead the PCM will use one or other sensors to try and determine the vehicle speed. Doing it this way is not accurate enough and the engine is not performing properly. Replace it and your problem should go away.
Tahnks for you help. Is VSS Vehicle Speed Sensor. If so I found a write up for it being changed on a 95 grand. It seems like it is the component that the speedo gear is attached to, if it is anything like the right up says. I have changed the speedo gear on my TJ and that was a 3 minute job. Do I have it right or am I heading in the wrong direction?

Another thing I have noticed. When I first start it its fine. It is revving at about 900rpm like it should but it doesn't drop in rpms when I shift into gear. After I have driving, and go to stop, the rpms will fall put it will ussally die unless I give it gas. Even if I shift into neutral or park the rpms will still drop and the vehicle will die unless I give it gas.

Thanks again for the help. It is pooring rain and the jeep is outside. I am heading for work. I shouldbe abel to get under it tonite.
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Last edited by Ross; 02-28-2006 at 09:24 AM..
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Unread 02-28-2006, 09:28 AM   #8
greasefingers
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Yes thatís correct. However I do not know where yours is. It will either be on the tranny or the transfer case. First make sure that it is plugged in and that nothing has flown up and damaged the wires.
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Unread 02-28-2006, 09:33 AM   #9
Ross
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Quote:
Originally Posted by greasefingers
Yes thatís correct. However I do not know where yours is. It will either be on the tranny or the transfer case. First make sure that it is plugged in and that nothing has flown up and damaged the wires.

Thanks for the help, My wife is about seven and a half months pregnant and can't get in and out of my TJ very easy, becasue of the lift, and I hait leaving her with out a vehicle for very long.
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Schitzangiggles: We used to teach our children to fight evil, now we teach them that fighting is evil.

2001 TJ, 33 trxus MTs , W, locked, belly up, some armor.

"If you aim at nothing, you will hit it every time." Zig Ziglar
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Unread 02-28-2006, 09:53 AM   #10
Woody
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Grease, the WJ's don't use a VSS. They get speed from another source. I'm not sure what offhand though.
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Unread 02-28-2006, 11:49 AM   #11
Ross
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Quote:
Originally Posted by Woody
Grease, the WJ's don't use a VSS. They get speed from another source. I'm not sure what offhand though.

I called the dealership. They are too different sensors it MIGHT be one measures wheel speed and the other measures transmission out put speed. I assume it is the later of the two. I am not sure were they are located on the vehicle but I am going to go to the dealer and hopefull they have a diagram I can look at.
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Schitzangiggles: We used to teach our children to fight evil, now we teach them that fighting is evil.

2001 TJ, 33 trxus MTs , W, locked, belly up, some armor.

"If you aim at nothing, you will hit it every time." Zig Ziglar
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Unread 02-28-2006, 12:44 PM   #12
greasefingers
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Quote:
Originally Posted by Woody
Grease, the WJ's don't use a VSS. They get speed from another source. I'm not sure what offhand though.
Ahh sorry if I mislead anyone here??
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Unread 02-28-2006, 01:19 PM   #13
Ross
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Quote:
Originally Posted by greasefingers
Ahh sorry if I mislead anyone here??
Its a different part but you lead me in the right direction. Thanks
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Schitzangiggles: We used to teach our children to fight evil, now we teach them that fighting is evil.

2001 TJ, 33 trxus MTs , W, locked, belly up, some armor.

"If you aim at nothing, you will hit it every time." Zig Ziglar
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Unread 03-01-2006, 03:43 PM   #14
Ross
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Went to the dealership and talked with a very helpful Mech. He said 0740 is the code for the torque converter lockup switch ( I may not have the tech name). You have to drop the pan to get to it, but should be easy to get to. I going to have it done, I am about to put my house on the market and don't need a oil stain on the garage floor.
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Schitzangiggles: We used to teach our children to fight evil, now we teach them that fighting is evil.

2001 TJ, 33 trxus MTs , W, locked, belly up, some armor.

"If you aim at nothing, you will hit it every time." Zig Ziglar
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