OBD 1

[LanceW]

Had the 4L80E go "hard-shift, limp mode" yesterday. Shutdown and restarted, and all worked normally after that.

First chance to check for codes was this morning, and when I did all I got was "DTC 48 (Intake Air Temp Sensor Circuit High- low temp indicated)". It kept repeating it as long as I left the key on.

Kennedy's tech tips on reading codes (thanks, JK) says I should have gotten 3 12's, then the fault, then 3 12's again. Should I be concerned about the OBD's behavior? Also, if a code is set, how long does it remain before it is cleared? No sign of any more trouble from the transmission.

Thanks,

Lance

[Jim P]

My truck is a 95 and whenever is has any codes stored, the dtc 12 does not show up. Only the actual trouble codes.

Jim P.

[Diverguy]

Hi Lance;
The computer will store the codes for 100 start cycles. You can clear the codes with the scanner or disconnect both batteries to clear the memory.

[ucdavis]

Mine is the same; no Code 12 if there is a DTC present. Just repeat of each code 3 times for infinity.
Clear process for mine doesn't work by disconnecting battery. I have to undo the jumper on diagnostic connector so codes won't flash, key off, key on (but don't start), depress brake & hold, depress gas & hold & count ten seconds, release gas, release brake, & check codes (will get 12 if codes cleared). If it didn't clear, repeat, counting 15 seconds. Note: I might have brake & gas swapped.
BTW, I had similar thing w/4L80E twice. Fired up rig & got on the road & it wouldn't shift (stuck in 2nd); tranny shop reported no codes, & on shut-down/restart it worked normal. Must be Microsoft driver for the TCM functions or something similar that needs rebooting periodically for self-assurance.

[LanceW]

Thanks, gentlemen. Appreciate your help.

Lance

On Edit: No way it's a hacker. Why on Earth would George Jetson bother to hack Barney Rubble's truck?

[ 09-13-2003, 02:10 PM: Message edited by: LanceW ]

[Cowracer]

It is common for the transmission input speed sensor to get flaky and cause this condition. It is a magnetic prox sensor and the iron filing in the tranny will stick to it giving a false signal

Cleaning it sometimes will help, but I reccomend replacing it

It is an easy $30 one bolt fix.

Tim