So I was out running errands and turned off the truck for a minute and started it back up. It went into limp mode. M+S lights flashing and no acceleration.


No codes from U/G pending or otherwise. No SES light. Just for grins I "Cleared check engine light" on the U/G and M+S turned off and truck drove fine.


Any thoughts?

 

Mine did this after mudding it was the maf because it would start then if you accelerated it would bog down then just die. if this is what happened to you try cleaning your maf haven't been in limp mode since (i drove it home in limp cleaned then it started fine)

 

Sounds familiarly like the xyz rotary switch on the side of the autobox. There are other conditions that throw up the M&S lights as well. Once in M&S the truck via the BCU automatically goes into limp home mode until the fault is fixed.

The other scenario is that the software and electronics sometimes throws a 'wobbly' and invents conditions and faults and often self corrects.

 

check all you body grounds and your charging system before you start replacing parts

 

Has not happened since. I just thought it was strange that clearing a non-existent check engine light "fixed" the limp home mode. I guess I'll have to wait for it to happen again to try and figure out what happened. 14.2 for voltage from U/G. Grounds were all cleaned up before winter. May have just been a fluke.

 

Is your 14.2v while running or while cranking?

A low battery will do this, watch the UG to see if it pulls low while cranking.

 

14.2 is while running. How do you watch the ultra-gauge while cranking? Battery is less than 6 months old.