Differing Trouble Codes

[imp]

Can anyone help me understand how the several types of trouble codes other than emission-related (which turn on MIL light) differ in the way one captures and views them?

Specifically, flashing "O/D OFF" light is initiated by PCM, just as is "Check Engine", but is not "stored" for future reading, I think. In my case ('04 Explorer 5R55S transmission), tachometer suggested torque converter clutch (TCC) not engaging. I had dealer read code; he came up with P1744 "TCC solenoid circuit error or stuck off".

Each time the engine is shut down, the flashing light is deleted, only to return after a speed is reached sufficiently high to call for TCC to engage. If driven slowly, like on our dirt road, 20 mph, the light will never come back on.

My code reader has not been able to duplicate the dealer's result, showing only "error".

Do I need to go beyond the "KOEO" (Key On, Eng. Off) test mode to read such a trouble code? imp

 

[javer]

"TCC solenoid circuit error or stuck off". that means no movement so it could be a fuse or a relay try and remember if you had a short circuit or jumper cables touching. anything that causes sparks could damage a fuse or relay.

 

[imp]

"TCC solenoid circuit error or stuck off". that means no movement so it could be a fuse or a relay try and remember if you had a short circuit or jumper cables touching. anything that causes sparks could damage a fuse or relay.

Thanks for your thoughts! No work of any kind has been done to the vehicle in the 3 months I've had it.

I can see how the PCM can "tell" the Torque Converter Clutch is not engaging: it "looks at the transmission input shaft speed sensor and compares that reading with the engine speed. If the 2 are the same, the TCC is engaged. What I do NOT understand is how PCM can differentiate between possible causes: If the solenoid is "stuck" and cannot move, how could the PCM possibly know that without sensors on the solenoid to "prove out" whether it moved or not. If solenoid coil BURNED OUT, no current would flow through it; PCM could monitor that.

This stuff is getting pretty hairy! imp