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Still throwing up P0740 code


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As the title states, I replaced my duty b solenoid with a unit from a 96 legacy outback. Tested it, it clicked, and the tranny fluid from donor car was clean, and not burnt. Car did have, 185000 on it though.

I pulled the pan off mine, and noticed it was glued on (nasty pinkish Rev, and that the magnet was full of metal. I put the new solenoid in anyway, and refilled the trans with Castrol dex-merc(?), and a quart of lucas trans conditioner, and a quart of stop leak. It still throws the Code.

Is it toast? Or is it something down the line? I also changed the TPS and it made the check engine light go out. But no change in shifting. Please help. Thanks.

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every connector starting at the rear of the engine, passenger side.

the largest connetor goes to the trans.

check the pins.

follow the wiring back toward the middle trans, driver side.

look / feel for rodent damage, check the pins in the next connectors.

follow it all the way back to where it enters the trans.

was / is the trans pan dented?

was the wire in good condition inside the pan?

 

when the description uses the word ''circuit'' always check the wiring first.

 

P0740 Torque Converter Clutch Circuit Malfunction

 

Read more at: http://www.obd-codes.com/p0740

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I

every connector starting at the rear of the engine, passenger side.

the largest connetor goes to the trans.

check the pins.

follow the wiring back toward the middle trans, driver side.

look / feel for rodent damage, check the pins in the next connectors.

follow it all the way back to where it enters the trans.

was / is the trans pan dented?

was the wire in good condition inside the pan?

 

when the description uses the word ''circuit'' always check the wiring first.

 

P0740 Torque Converter Clutch Circuit Malfunction

 

Read more at: http://www.obd-codes.com/p0740

 

Pan wasn't dented, but now that you mention it, the harness was tampered with it seems. I noticed the brackets that hold it to the tranny are loose. I've traced the harness to a big black plug on the passenger side, but can't find anything on drivers side. So just basically pull the connections apart, and check the pins? Anyone got a pin out so I know which pins to check? Also, would this make the awd not work? I had the car's front end completely jacked up, and put it in drive just to see if it would try to move. Only the front wheels spun. Unless this is normal?

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Also, would this make the awd not work?
would what make the AWD not , bad wiring? yes.

bad duty B solenoid? no.

 

lots of things will cause the AWD to not work right.

bad speed sensor

bad transfer clutch plates

busted transfer clutch drum

bad TCU trans computer (pretty rare, look elsewhere)

no drive shaft

busted rear axle

bad or stuck duty C solenoid

to name a few.

 

the ones in red will usually cause NO AWD.

the ones in black will usually cause torque bind,

which is like driving a 4wd truck on dry pavement with the hubs locked.

very unpleasant.

 

the main harness for the trans enters on the driver side (for left hand drive cars, USA).

start at the drain plug and look up on the side and maybe to the rear??

you will need a light.

there are also connectors on top of the trans / bell housing under the fire wall,

just behind the fire wall trans mount.

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would what make the AWD not , bad wiring? yes.

bad duty B solenoid? no.

 

lots of things will cause the AWD to not work right.

bad speed sensor

bad transfer clutch plates

busted transfer clutch drum

bad TCU trans computer (pretty rare, look elsewhere)

no drive shaft

 

 

busted rear axle

bad or stuck duty C solenoid

to name a few.

 

the ones in red will usually cause NO AWD.

the ones in black will usually cause torque bind,

which is like driving a 4wd truck on dry pavement with the hubs locked.

very unpleasant.

 

the main harness for the trans enters on the driver side (for left hand drive cars, USA).

start at the drain plug and look up on the side and maybe to the rear??

you will need a light.

there are also connectors on top of the trans / bell housing under the fire wall,

just behind the fire wall trans mount.

 

OK, I checked the connections, and the ones I could get to I did a continuity test. All the wiring seems ok, so where do I go next? Tcm? Or complete tranny swap? I'm almost ready to scrap the car already. This is frustrating.

I also tried the torque bind best, and nothing. Idk if it's because the awd is dead, or working.

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Here's a thought:would one of the speed sensors going bad cause the car not to lock up? I also apparently have no abs (almost rear ended a car the other night in the rain), so module? Or roll the car into the street and light it on fire?
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I also apparently have no abs (almost rear ended a car the other night in the rain),
do you have an ABS light on??

the ABS system in 95 - 99 is not speed sensor sensitive.

 

Or roll the car into the street and light it on fire?
.

make sure you have ''comprehensive'' auto insurance,

and a good alibi.

or maybe drive it to baltimore for the weekend.

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I would get the DTC code list and go through the suggested item checks.

I've had this code twice, once because the tach was acting up and once because the tranny dipstick was slightly bent( not really detected by looking at it) and was grounding out the duty solenoid when it was inserted! (I removed the tranny pan to eventually discover this.

Sure you replaced the solenoid correctly?

The DTC codes are in the fsm.

 

O.

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I would get the DTC code list and go through the suggested item checks.

I've had this code twice, once because the tach was acting up and once because the tranny dipstick was slightly bent( not really detected by looking at it) and was grounding out the duty solenoid when it was inserted! (I removed the tranny pan to eventually discover this.

Sure you replaced the solenoid correctly?

The DTC codes are in the fsm.

 

O.

 

Just push it in, correct? I'm going to drop the pan again, and recheck everything again.

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I'm a subaru tech and my girlfriend drives a 97 legacy gt that throws p0740. Its been a lg ongoing mystery at our dealership and I've changed the solinoid, converter, flushed 4 times, checked all wires ect. Also checked the dipstick for grounding out the duty c and today I'm replacing the entire transmission.

The tcu calculates the tcc lockup by checking engine speed vs. Vehicle speed and if they don't jive then it assumes a tcc issue. I'm not the best trans guy in the shop but I know internally worn valve body parts,clutch or band slip and/or clogged valve body from dirty atf causes this code and it's almost never a easy fix.

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I forgot to mention a bad vacuum modulator can cause funny shifting too.tps installed with volt meter? How does it shift exactly?

 

No, I didn't put a voltmeter on the tps , I will though. I replaced it about three weeks ago with a unit from an older legacy, and the light went out,but came on later. It shifts....ok I suppose. Where is said vacuum modulator? What other sensors are in the circuit for the tcc? I want to pull the trans last if I can. Is there a way to manually bypass the tcc? Like run a switch or rheostat and splice into the harness, and control it there? I saw this once on a Dodge cummins website, and they installed a rheostat in the trans harness, and you could control what speed the tc locked up. Been on my list of "what if" fixes.

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Sorry I've been busy the last few days with my sti, but your problem is a tps that isn't set up right. If the ecu doesn't see .45-.55 volts when the throttle is closed,then the ecu and TCU will try and determine throttle open or shut voltages and give you 100% full line pressure when the throttle is open and zero line pressure when throttle is closed causing some crazy shifting. Voltage is taken at the white wire coming out of the tps.
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Set the tps right today, but car still has problem. Went to the junkyard, snagged another tcu, and threw it in. Still has the problem. Tried to do the connecter diagnostic test (black plug with two pins), and no codes. Tried doing the secret handshake, no codes. But at oil temp light still keeps blinking. The car will be hauled off sometime next week. Done screwing with it.

But just curious as to why it won't pull any codes? I haven't given up on subaru, just this particular nightmare.

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Tried to do the connecter diagnostic test (black plug with two pins), and no codes. Tried doing the secret handshake, no codes. But at oil temp light still keeps blinking.
if the AT Temp light is blinking you have a trouble code.

you are just not pulling ti correctly.

 

i do not know what the car cost,

or how much to have spent trying to fix it.

but before you throw it away,

you might try spending $75 - $100 at the dealer.

they can read the code with the ''select monitor''.

then you can use that knowledge to fix it your self,

pay them to fix it,

or walk away.

 

good luck.

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