Hi all,
Have recently lost 4WD on my 2003 Tahoe Z71. Had had the red "neutral" light in the 4WD module lit for a couple days, and wouldnt go into 4wd. Then the module just became inactive and service 4Wd message came up. Had Advance put it on their scanner and these are the codes:

CO291 Park Brake relay short or open
CO226 Left speed sensor
CO222 Right speed sensor

Feel like its odd that both sensors would go bad at once. Cant find where the park brake relay is on the schematic for fuses. Hoping the one relay is causing both sensor codes.

Any ideas where to look first, or where to find the park brake relay?. I know Auto 4WD cant work unless it can sense wheel speeds, so figured thats why whole unit shut down. Any help appreciated!
Thanks, John

 

The codes you received do not necessarily mean that the speed sensors and/or the parking brake relay are bad. It is just an indication that there is something in that system that is causing the code to be set. It could be a bad connection at the speed sensor for instance.

 

Ok, so I will check the two connections for the speed sensors tomorrow. Any idea where to find the "Park Brake" relay?

 

Relays are usually located in the fuse centers.