DTC P0740

TUFFTRUX · October 4, 2006

Hi everyone,

A new problem started in my van yesterday. The SES light was on and I pulled the code P0740 with my scanner. It is a Torque Converter Clutch Circuit Malfunction. So far the van runs fine and seems to shift fine but I will do a more in depth road test on Thursday. Any ideas on how serious this problem is and any ideas as to how to correct it? Hope the trans. doesn't have to come out. Thanks in advance for the help.

Vehicle Info: 2000 GMC SAVANA 2500 5.0L V8 and remanufactured 4L60E trans.

Luke

GM-Tech · October 4, 2006

The trans should not have to come out for this. This is an electrical fault in the TCC circuit. Could be the TCC solenoid, wiring, VCM, etc. This needs some in depth diagnosis and if the fault isn't a hard failure, it could be difficult to find.

I'm almost positive that this is not a power problem to the TCC solenoid. The power that feeds the TCC solenoid branches off inside the trans and feeds all the other solenoids in the trans. If you had no power to the TCC solenoid, you'd also have no power to the other solenoids and you'd have a handful of codes related to all the solenoids.

So, that leaves the control side of the solenoid. The VCM controls the solenoid by grounding the control side. The VCM monitors the voltage on this circuit and if it sees battery voltage when it should be 0 (or vice versa) it will set this code.

The trans should shift just fine except that you won't have TCC engagement. If I had to guess, I'd replace the internal harness in the trans. There's not much to it.

If you want to go all out, replace the TCC solenoid at the same time. Can't say whether or not this will be a total waste of money.

Is this reman trans a GM SRTA? If so, did you purchase or have it installed at a GM dealer? It has a pretty good warranty if so.

TUFFTRUX · October 4, 2006

Thanks GM-Tech,

My transmission is not from GM, its from a local transmission shop in NYC, and I installed it myself. They do warranty it for 1 year and they scheduled a check up on the problem this Saturday. They told me they replaced the entire harness in the transmission so maybe there was a problem with the new electrical harness. Thanks again for your help, I wouldn't want to take that transmission out again so soon.

Luke

TUFFTRUX · October 8, 2006

Problem Solved, Thanks GM-Tech,

Took it into the transmission shop yesterday and they verified the code yet they couldn't find the problem. Told me to come in on Monday but thanks to your advice I don't think I have to. I had replaced the van's VCM and I guess the TCC solenoid wire/connection pin at the VCM was loosened and pushed back out of the plug so the PCM couldn't send any signal to the solenoid. With the wire connection tightened at the VCM everything works great, even the trans. seems to be shifting smoother.

Thanks Again,

Luke