Persistent codes preventing state inspection

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jbeazell

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Hello all,

I have two codes that I'm curious if anybody has some steps for me to test and resolve.

P0440 (Evaporative Emission Control System Malfunction). I've already replaced the gas cap. I did some work to drop the gas tank. I replaced the wiper arm on my fuel sending unit to fix a faulty gauge. The fuel gauge now works, but I'm getting this code. I think I might have been a bit too rough with one of the Evap lines, but I can't see any breaks or disconnects.

P0741 (Torque Converter Clutch Circuit Performance or Stuck Off). I am going to do a filter change, along with some fluid and maybe some Lucas Oil Automatic Transmission Fluid Conditioner, but I'm hoping that I don't need to tear into the trans on this one.
 
Hi !
Code P0440
Look for a loose or damaged seal at the gas cap, or any of the associated hoses for the EVAP system, including the fill hoses and seals, Also check EVAP vacuum lines for good connections or damage. The EVAP canister could also be damaged. The solenoids around the EVAP canister have also been know to get dirty when driving on a lot on dirt roads. A 'smoke test' may be required to detect these leaks, but once this is done the leak should be obvious . Code names a particular sensor or component, it does not mean that sensor or component is bad. Proper diagnostic procedures (such as a smoke test) may need to be performed to find the root cause of the problem.
For information purposes :
The fuel tank pressure sensor is located above the gas tank, on top of the fuel pump assembly . The EVAP canister is mounted just in front of the fuel tank

Code P0741
This code says that you have internal sensor problem. The only way to really checks this trans and in the internal sensors is with a high end scan tool that can read real time trans data.
These sensors are inside the transmission, but before I would replace the trans or tear the old one down, this vehicle is know for wiring issues. There is a big wire harness that runs across the top of transmission that connects to the transmission. This wiring harness carries the signals for the shift sensors inside the trans. Check this harness for any broken wires or wires that are shorted against anything metal. 90 percent chance you don't have a internal trans problem, more than likely just a wiring problem .
You will need to remove the plastic conduit covering from the wiring harness and inspect the wires all the way back to engine control module under the air filter box . These wires allot of times will break, get shorted out from the constant movement of the engine and trans over time and miles.
 
Great, thank you! Looks like I'll need to bring it in for a smoke test. I'm pretty sure I made something unhappy when I dropped the tank. That is great information about the Trans code.
 
So, here's a random question. The TCC circuit is connected to a brake switch that I assume tells the TCC to disengage because the driver is hitting the brake. What if I short that circuit so that the switch is constantly 'on'. Will that tell the transmission to never engage the TCC, or will it throw a different code?
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To answer, no, it does not keep the system from using the TCC. It also does not throw a code. I still get the same old P0741 :)
 
I did a bit of digging, and found that the switch is wired open when the brake is depressed, so by shorting the connectors, I was basically telling the trans that I never hit the brakes. I've just unplugged it to see if the code comes back. This should tell the trans (and the cruise control circuit) that I'm always hitting the brake.

We'll see if this prevents the car from trying to engage the TCC.
 
jbeazell said:
I did a bit of digging, and found that the switch is wired open when the brake is depressed, so by shorting the connectors, I was basically telling the trans that I never hit the brakes. I've just unplugged it to see if the code comes back. This should tell the trans (and the cruise control circuit) that I'm always hitting the brake.

We'll see if this prevents the car from trying to engage the TCC.
Click to expand...

to report back, no, it didn't. The TCC code returned. At least doing this disabled my cruise control. So there's that. Oh well, looks like I have a transmission rebuild in my future. All wiring seems solid.
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