Dealer not honoring warranty work..2018 5.3 Yukon issues

[smokey_mountain]

Thank you, I definitely now have electrical problems too B1325, U0415, U0121 were cleared but now vehicle has C0800, it all points that after last service some electrical connections were impacted... On top of my rough idle I now have electrical connections that are impossible to troubleshoot. I am taking it in on Tue again to address idle and to address now electrical. This truck is a royal pain...

 

[swathdiver]

Thank you, I definitely now have electrical problems too B1325, U0415, U0121 were cleared but now vehicle has C0800, it all points that after last service some electrical connections were impacted... On top of my rough idle I now have electrical connections that are impossible to troubleshoot. I am taking it in on Tue again to address idle and to address now electrical. This truck is a royal pain...

Are these fresh codes? Do you have a subscription to AllDataDIY? If not, why don't you sign up for one and check out these codes. Mine has some of them and they all point to a voltage problem which is usually a bad battery with a faulty cell. If we've all learned on thing on these forums with these trucks, a bad battery can cause all kinds of grief and mischief with the electrical system. Kinda like that guy Chaos on those car insurance commercials!

 

[smokey_mountain]

@swathdiver thank you, I wanted to ask for your help if possible with fuel trim data, I am seeing my LTFT all negative most of the time, I was wondering if the trims are OK or not (logs are here) https://docs.google.com/spreadsheets/d/1EbdAtrKXjTG0ujUXM6MsoTJqLzYeno1C82mWw76OVsE/edit?usp=sharing

As for electrical (5-6 codes appeared there after truck was from the dealer 12 days ago), no codes before
Codes found and cleared:
B1325 Control Module Power Circuit Voltage below Threshold
B127E Front Video Display Output Signal
U0121 Lost communication with Electronic Brake Control Module, Test Failed
U0401 Invalid Data Received from Engine Control Module
U0415 Invaid Data Received From Engine Control Module
Code found not cleared
C0800 Device power #1 (low current#1) circuit malfunction

Are these fresh codes? Do you have a subscription to AllDataDIY? If not, why don't you sign up for one and check out these codes. Mine has some of them and they all point to a voltage problem which is usually a bad battery with a faulty cell. If we've all learned on thing on these forums with these trucks, a bad battery can cause all kinds of grief and mischief with the electrical system. Kinda like that guy Chaos on those car insurance commercials!

 

[91RS]

Battery cable(s).

 

[swathdiver]

@swathdiver thank you, I wanted to ask for your help if possible with fuel trim data, I am seeing my LTFT all negative most of the time, I was wondering if the trims are OK or not (logs are here) https://docs.google.com/spreadsheets/d/1EbdAtrKXjTG0ujUXM6MsoTJqLzYeno1C82mWw76OVsE/edit?usp=sharing

As for electrical (5-6 codes appeared there after truck was from the dealer 12 days ago), no codes before
Codes found and cleared:
B1325 Control Module Power Circuit Voltage below Threshold
B127E Front Video Display Output Signal
U0121 Lost communication with Electronic Brake Control Module, Test Failed
U0401 Invalid Data Received from Engine Control Module
U0415 Invaid Data Received From Engine Control Module
Code found not cleared
C0800 Device power #1 (low current#1) circuit malfunction

Seem fine to me. Was that a drive or just idling and raising the rpms in park? Have you checked your grounds and the battery cables? It's common for the trims to be negative, up to -10 or so while idling and then it will attempt to get to zero and if you are driving at a steady speed for a while the computer will get there usually. Sometimes not but close. Depends on fuel, weather, driving habits, etc.

 

[smokey_mountain]

It was driving. I have checked the battery connections all seem to be tight. I thought about disconnecting every connection at the body but I will need to figure out which connections and wires to re-tighten.

Seem fine to me. Was that a drive or just idling and raising the rpms in park? Have you checked your grounds and the battery cables? It's common for the trims to be negative, up to -10 or so while idling and then it will attempt to get to zero and if you are driving at a steady speed for a while the computer will get there usually. Sometimes not but close. Depends on fuel, weather, driving habits, etc.

 

[smokey_mountain]

You are spot on, everyone suggests the cables and/or battery. I have called the local dealer, asked them if they would take the truck in and check it, they said "these codes are common and nothing to worry about" we would clear them for you...

Battery cable(s).

 

[91RS]

It isn’t just connections. The cables have high resistance internally. They are common but are something to worry about because they can cause problems such as just the radio screen going blank up to the engine stalling if they’re bad enough.

 

[smokey_mountain]

Yes, I will not take to that dealer for sure who spoke like that. I have scheduled with a selling dealer, so I expect them to help a bit more. All these codes appeared after selling dealer worked on the truck 12 days ago, they reflashed ECM. Now I wonder what they did.

It isn’t just connections. The cables have high resistance internally. They are common but are something to worry about because they can cause problems such as just the radio screen going blank up to the engine stalling if they’re bad enough.

 

[smokey_mountain]

This is how truck shakes when is fully warm, stopped in D in idle. Running 93 Octane Exxon. Bottle test shows the pattern of shaking if you watch carefully. BTW, if I put Regular gas - shaking pattern is the same except amplitude is wider.