98 S10 4x4 P0740 code.

[Terrybg]

Just bought a 98 S10 4x4. It has a code P0740 and when I reset it it comes right back. The truck runs great but gets horrible gas milage. Any ideas wherew to start. I took it AAMCO and they said they wanted a $500 deposit just to look at it, it shifts good, makes no unusal noises. I feel like thay are trying to screw me. Any advise would be great.

Thanks,
Terry

[j cAT]

Originally Posted by Terrybg

Just bought a 98 S10 4x4. It has a code P0740 and when I reset it it comes right back. The truck runs great but gets horrible gas milage. Any ideas wherew to start. I took it AAMCO and they said they wanted a $500 deposit just to look at it, it shifts good, makes no unusal noises. I feel like thay are trying to screw me. Any advise would be great.

Thanks,
Terry

the torque converter is not locking up. this could be low expense or much more. droping the pan and making an inspection would be required. loosing pressure or electrical problems can cause this.

the 500.oo to check it out sounds too pricey to me. 200-300.oo is better.

most times old contaminated fluid damage , to the internal valves causes this problem.

if the valve bodies are worn it will take a good amount to replace everything. 1200.00 or so.


you should get about 18 MPG max with this vehicle. V6.

[Terrybg]

So you think I should flush the trans and change the filter to start. I have read stuff online and my truck is acting fine other than the low gas milage and CEL on.

[j cAT]

Originally Posted by Terrybg

So you think I should flush the trans and change the filter to start. I have read stuff online and my truck is acting fine other than the low gas milage and CEL on.

what is the gas MPG ?

the code you gave refers to the torque converter not locking up.

replacing the transmission fluid and filter is a good idea but I doubt that this would correct this.

flushing is not recommended with these GM transmissions.

FLUID EXCHANGE IS WHAT IS USED TO REMOVE ALL THE OLD FLUID.this is where the transmision circulation is used to remove the internal old fluid as you add new fluid back into the transmission fill / stick tube.

so the transmission shop shop be used to determine why you have a 740 code. post back what they found that was worn . how much to repair, and make sure you get a 1 year warrantee on the repair .

[Terrybg]

Its getting 10 or 11 miles a gallon. The trans fluid is clean and smells good, it looks like it may be over filled could this be the problem. Anyone live in MD that would like to take a look at it lol.

[FishFind]

Originally Posted by Terrybg

Its getting 10 or 11 miles a gallon. The trans fluid is clean and smells good, it looks like it may be over filled could this be the problem. Anyone live in MD that would like to take a look at it lol.

Overfilled will cause it but to check it proper you need the engine at temp hold the brakes on and shift it through each gear for at least 3 seconds. then check the level.

I had this same problem and fixed it. I can help you all the way through this from fuses to the wires involved.

First thing is is the p0740 the only code that you have??
A p0740 is a electric fault and you are not getting overdrive. It may also feel that you are in second gear from a take off. If a p0740 is your only code then more then likely it is a fault to the ground wire. The tcc Solenoid is fed power from a harness in the pan that feeds power to all the Solenoid. If a fault in power you would have more codes unless the tcc Solenoid is bad it's self but not likely.

My guess is that you have a short in the ground. The ECM tells the tcc when to ground so you have a wire that is a tan wire with a black stripe on it that comes off the wire harness on the top of the tranny. It then goes to the ECM on the BLUE wire harness. It is the #10 pin.



You can connect a wire to this wire and then to a toggle switch. run the other end to the neg battery post. Go start you car watch the rpm flip the switch and see if it drops in rpm. FYI don't put it in gear or it will stall. It would be the same as putting a manual in 5th gear and taking off from a stop.

If you can make the rpm drop when you do this then I am guessing that the ECm has a short and is not able to ground the TCC.

If the rpm does not drop then I am guessing that you have a broken wire between the harness and the blue connector.

I have the full testing repair guide. If you want it pm me

[j cAT]

Originally Posted by Terrybg

Its getting 10 or 11 miles a gallon. The trans fluid is clean and smells good, it looks like it may be over filled could this be the problem. Anyone live in MD that would like to take a look at it lol.

check the fluid after a 10 mile ride on level ground, should be slightly below the full mark, also the fluid should be a solid red color with no air bubbles in the fluid. air means the level is too high and this will cause pressure loss and slippage, tranny will soon fail.

if too high use a hand pump with a length of 3/8 in tubing and suck out using the dip stick tube.

[xgiovannix12]

any chance you can send me the flow chart you have? i grounded the wire and no rpm change