Had some interesting things happen to the tahoe

[dropmech]

So two days ago, I lose my satellite radio. Won't even come up as an option for the source button. Then my traction control becomes disabled. Yesterday, I get my sirius back but the T/C is still going out on me. Last night, I go to start it up and my idle goes to 1500 RPM and the message center says "reduced engine power". I pushed the gas and the engine still stayed at 1500 RPM. So I let it sit overnight and start it today. Starts normally but now I have the engine shaped light on the dash. WTF is going on???

 

[ILLEGAL REGAL]

wtf?

 

[07Burb]

Can you verify that your alternator is good? Strange like this can be caused by your alternator going out.

 

[dropmech]

I'll check out the alternator. I found my OBDII reader and pulled 4 codes.

1st code0449 Evap emission control system vent valve/sol. malf........that one popped twice.

2nd code: P1516 Manf control Veh Spd idle speed cont. auxillary inputs

3rd code: P2108 TAC module performance

4th code: U0107 Lost comm with throttle control module.


I can clear the codes but on three subsequent starts, the Evap keeps illuminating the check engine light.

Is this stuff I can fix or should I take it in?

Side note: The fuel tank was about empty, as in on fumes, when all of this started happening.

 

[Jay]

What year is your truck?

Get the alternator and battery checked out first. Then trace down the ground connections to the wiring harnesses from both the PCM and body control module. It wouldn't be a bad idea to clean and di-electric all the connections you can reach while you're at it. The evap and TAC problems should be exclusive events under most cases, which is why I'm suggesting these ideas first.

If that checks out, the evap solenoid might be dead and *might* be causing secondary issues... these newer vehicles are made to flip out when an emissions system isn't functioning correctly. If you'd like to try the evap purge valve first, it's about a $30 part (make sure you clean out any dust/debris in the hoses). The evap system is designed to catch fuel vapors from the tank then release them at certain times into the intake to be burned when the engine is running. If the valve is stuck open then the PCM might be detecting what it senses as an intake leak. The fact that the satellite radio and TAC blipped out has me wondering a few other things we'll wait on for now.

If you have a 2005 or 2006 and the above things don't resolve the problem, it will be a good idea to get the battery control module checked out too (not present on 04-older)... it "throttles" the alternator output to match vehicle system load and battery's state of charge.

 

[Sweet_N_Low]

What year is your truck?

Get the alternator and battery checked out first. Then trace down the ground connections to the wiring harnesses from both the PCM and body control module. It wouldn't be a bad idea to clean and di-electric all the connections you can reach while you're at it. The evap and TAC problems should be exclusive events under most cases, which is why I'm suggesting these ideas first.

If that checks out, the evap solenoid might be dead and *might* be causing secondary issues... these newer vehicles are made to flip out when an emissions system isn't functioning correctly. If you'd like to try the evap purge valve first, it's about a $30 part (make sure you clean out any dust/debris in the hoses). The evap system is designed to catch fuel vapors from the tank then release them at certain times into the intake to be burned when the engine is running. If the valve is stuck open then the PCM might be detecting what it senses as an intake leak. The fact that the satellite radio and TAC blipped out has me wondering a few other things we'll wait on for now.

If you have a 2005 or 2006 and the above things don't resolve the problem, it will be a good idea to get the battery control module checked out too (not present on 04-older)... it "throttles" the alternator output to match vehicle system load and battery's state of charge.

I was thinking the exact same thing

 

[dropmech]

Jay, it's an 06. Thanks for the tips. I'm gonna try to start looking at everything you said tomorrow. i'll report back here with the findings.

 

[jdl_131]

What year is your truck?

Get the alternator and battery checked out first. Then trace down the ground connections to the wiring harnesses from both the PCM and body control module. It wouldn't be a bad idea to clean and di-electric all the connections you can reach while you're at it. The evap and TAC problems should be exclusive events under most cases, which is why I'm suggesting these ideas first.

If that checks out, the evap solenoid might be dead and *might* be causing secondary issues... these newer vehicles are made to flip out when an emissions system isn't functioning correctly. If you'd like to try the evap purge valve first, it's about a $30 part (make sure you clean out any dust/debris in the hoses). The evap system is designed to catch fuel vapors from the tank then release them at certain times into the intake to be burned when the engine is running. If the valve is stuck open then the PCM might be detecting what it senses as an intake leak. The fact that the satellite radio and TAC blipped out has me wondering a few other things we'll wait on for now.

If you have a 2005 or 2006 and the above things don't resolve the problem, it will be a good idea to get the battery control module checked out too (not present on 04-older)... it "throttles" the alternator output to match vehicle system load and battery's state of charge.

Where would I look for the ground connections? I assume somewhere besides at the battery?

 

[04SS99Denali]

REP mode is usually a lose harness in your engine bay. i used to get this in my silverado SS when it was stock. just go under the engine bay and check the big major harnesses. mainly the one that plugs in the throttle body and the one thats on the drivers side firewall its huge. make sure there snug. also REP mode might come up if you get even the slightest amount of water in the harness. if you were in some serious rain it may be the cause. little electrical gremlins can be caused be going alternators, batteries get yours tested at autozone or something