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A Few Issues, Electrical or Other?

Dave01

Dave01

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Location
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My Suburban is running very well, no engine issues at all, so I'll just say that up front, nothing urgent about these problems.

My cruise control stopped working a few days ago. Last time this happened I had a bad battery and voltage was low, once I installed new batteries the cruise operated fine. I use it all the time. It won't engage at all.

Also, my high idle switches stopped working, probably related.

What would cause these 2 items to not work, but everything else to run perfectly? I'm thinking I need to pull the PCM and check connectors there, what else should I look at?

Thanks, David
 
I already checked some of the grounds, will look at more of them and report back.
 
Yes, I have a spare. But, with it starting and running perfectly, I can't see how it could be FSD related. Or am I wrong, are these functions somehow controlled from there, along with the PCM?
 
A failing FSD will cause problems with the cruise before you experience driveability problems. Not sure about high idle, though. Just a thought.:)
 
Do you have access to a scantool? Stored codes can/will affect both cruise and high-idle.

Coincidentally, disconnecting your batteries to replace them would probably erase the stored codes you had last time.

Take the truck to Autozone and check it for non-active history codes. It's free - can't hurt!
 
I have a code reader - didn't bother since the ses light wasn't on, but in the morning I'll check for stored codes. So, if I see some stored codes, should I disconnect batteries to erase them?
 
It's worth a try... definitely cheap (like free). Not all codes inferfere with cruise or high-idle, but some do.
 
Brake switch.

Go underneath the truck when the high idle is engaged and start wiggling sthings around the brake switch.

Same thing happens to me.

I guess there are 3 parts to the brake switch,

1 to PCM, 2 to brake lights, and 3 to actual brakes?

Something like that. I almost guarantee your problem is related to that switch.
 
And Matt wins the prize! Its brake switch wiring, just as you said.

I tried my spare FSD first, no difference, and I'd already looked at some grounds. Then I just moved the brake switch wires around until the high idle switched on, and then drove and the cruise was fine as well. So, I have no idea what wire or what connector is bad but for now its working and I know where to look when it fails again.

Tough area to get at! Its all I can do to get my hand up in there to wiggle the wires, I'd hate to have to change out the switch.

Thanks to everyone for the help with this! I use cruise all the time and really missed it the past few weeks.
 
damn right tough to get at.

Thats why I have not replaced mine... just deal with it when it acts up for now :)

Glad to help.
 
JiFaire said:
He shoots, he scores! Well done, Matt!
Click to expand...

Well out of 4000 posts a few are bound to land!

Dave, next time you are coming off the highway manually shift into 3rd on the offramp.

Now hit your brake pedal, and see if your RPM's drop to idle as the TCC releases.

For some reason, after I have been having this issue, when I hit my brake pedal, my RPMS DO NOT drop to idle, thus allowing me to tranny brake a little more than before.

See if yours does this, maybe we are on to some sort of free mod for OBD2 that allows engine braking a little more than factory.

Speaking of this issue, can this be changed in the PCM during reflash to not unlock the TCC when the brake is pressed?
 
Dave, next time you are coming off the highway manually shift into 3rd on the offramp.

Now hit your brake pedal, and see if your RPM's drop to idle as the TCC releases.

For some reason, after I have been having this issue, when I hit my brake pedal, my RPMS DO NOT drop to idle, thus allowing me to tranny brake a little more than before.

See if yours does this, maybe we are on to some sort of free mod for OBD2 that allows engine braking a little more than factory.
Click to expand...

I tried it this morning Matt. No, I did as you said, shifted down to 3rd, I was heading down a hill and about to slow down. rpm stayed at about 1,100 for maybe a second, two at most, and then dropped to idle. So, not sure that fuction is available or predictable. It would be great to figure that one out, since I've owned the truck I've wished I had more engine braking.
 
Dave01 said:
I tried it this morning Matt. No, I did as you said, shifted down to 3rd, I was heading down a hill and about to slow down. rpm stayed at about 1,100 for maybe a second, two at most, and then dropped to idle. So, not sure that fuction is available or predictable. It would be great to figure that one out, since I've owned the truck I've wished I had more engine braking.
Click to expand...

My RPMS don't even flinch when I hit the brake.... Not complaining, just curious why.
 
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