How can a signal error turn into a mechanical failure?

 

Because p0700 is a code transmitted by the tcm to other modules that indicates there is another code stored in the tcm.

For example. When my 6l80 ate a torque converter a month ago, it had a p0700 code. Then if you read the tcm it would show the other codes for pressure switches stuck on and stuck solenoids due to the metal clogging everything up.

Not saying there is definitely mechanical failure, but it is important to verify ALL of the codes before going on a wild goose chase. If there is a p0700 and the trans is in limp mode stuck in second gear there is most definitely other codes. P0700 alone is a meaningless code.

 

Stuck solenoids are easily restored with TRANS TUNE!
+Proper maintenance is the key to longevity!
++Monitor fluid color for fluid & filter change and/or flush to restore clean DEXVI fluid!

{{{{{{{BTW, OP posted:}}}}}}}
>>>>>>"A friend of mine took his scan tool, clear the code, and the Hummer ran perfectly fine again."

How does a mechanical failure repair itself?

 

A small failure in the tehcm due to debris sticking solenoid intermittently will throw a code and put it in limp mode until you clear it. If it keeps happening, there could be either a failure of something in the tehcm/valve body or a failure of something internally sending debris through the fluid that keeps sticking the solenoid or is clogging the filter and reducing pressure in the tehcm causing a code.

When my torque converter went out, it was the same thing. All the sudden, threw a code and went into limp mode and was so bad it would eventually stop moving. But if you shut the truck off for a minute and cleared the codes, the debris would fall out of the filter enough to unclog it for a few miles and it wouldn’t set a code until 3-4 miles down the road again.

Again. I’m not saying there is 100% a mechanical failure. But 9/10 times there is or at least an issue with the tehcm.

Finding an intermittent wiring issue takes a LOT of time. Always start with the easiest and the obvious. Easiest thing to do is first off, get a scanner that can actually read the codes. If theres a u-code, there’s a wiring or tehcm issue, if it’s a pressure switch, solenoid or tcc code, you need to drop the pan, check for metal evaluate the state of the tehcm and check your speed and range sensors.

These transmissions arent like the 4 speeds. The computer is physically inside the transmission. The only wires that come in and out of the trans are power, ground, can hi and low, selector sw signal, neutral safety, stop lamp, and an oss signal. If there’s an issue with one of these, it WILL throw another code than a p0700.