P1516 and other random errors

[jpkc97]

Hi all, Had this 2003 GMC Sierra Denali Quadrasteer for a couple of years and chasing some random issues.
The latest is the dreaded P1516 TAC error. It seems to be happening more often. Once I get it, I can pull over and reset the error with my scan tool and it runs fine.
I've read about bad grounds being a big issue, so I started chasing ground connections. I've heard a big issue is the one on the back of the passenger cylinder head.
I went in there yesterday to replace my valve cover gaskets, but while I was there I intended to check this ground. However I discovered there was nothing bolted to the back of this head.
The only connections I could find was one in the middle/back of the block and on the driver cylinder head. Both were very secure and almost impossible to reach, if I wanted to loosen and clean.

Any other suggestions? I hate to start "pull and replace" parts but might try some used stuff from the pick and pull...
Also, the horn only works if I turn the wheel to the right about 1 o'clock. I've tried the common fixes (extend contact) and still does the same...wondering if a new clock spring will fix but everything else on the wheel works fine.

Also, basically everything electrical seems to act up upon random starts...sometimes no fuel readout, sometimes security, sometimes rearview mirror compass...ect. If I shut off and restart they usually function...
Feels like a ground issue to me ...could it be something with the column or canbus? PO told me his "mechanic" said he needs a new column but not sure what that meant.

 

[99Sierra2500]

Welcome from Indiana, that is a nice looking truck. There is another ground from the frame to the cab underneath. Connectors can get corroded at the plug, and that causes an intermittent short.

 

[jpkc97]

Welcome from Indiana, that is a nice looking truck. There is another ground from the frame to the cab underneath. Connectors can get corroded at the plug, and that causes an intermittent short.

Thank you, yes I've checked the 2 bolts right under the driver door to the frame. I loosened them, cleaned and rebolted but no go.

 

[ORVietVet]

The hard to get to grounds should be done. You need to ELIMINATE possibilities and approach methodically. That Throttle Actuator Control is at the firewall on the d/s area. IIRC. Sometimes just unplugging connections and plugging back in can clean a dirty connection. BUT, if you do unplug, LOOK at the connections. Connections at the throttle body and at the throttle pedal controller need inspected as well.

 

[Tonimus]

Welcome to the forum! When doing connectors, I like to hit them with some electrical contact cleaner or DeoxIT. Then plug and unplug a few times. Helps greatly with tarnish that can build up. As ORVietVet says, you need to go through all the grounds and connectors before moving on.