CEL came on yesterday, 2006 ODB trouble codes

[2006Tahoe2WD]

Here's the updated part number for non-power-adjustable pedals (https://www.gmpartsdirect.com/oem-parts/gm-brake-light-switch-15128874).

The 25771554 part should work, but 15128874 is the latest part number:

View attachment 421686

From what I can tell so far is the 15128874 is no longer available. I went to the dealer and they said there is no indication when it would arrive. Looking online lots of NLA. I'm thinking going to have to go to Dorman/etc.

 

[Fless]

This guy is good and recommend by other YouTube mechanics as it relates to EVAP.

I think this confirms that the purge valve should go to zero when "sealing".
My theory to that Foxwell might be doing something valid was incorrect.
So, IMHO Foxwell has a bug or this is some sort of pilot error.

Yes, Mike's videos are good and he shows how it's done. I have to think that the Foxwell procedure seems to have a flaw.

 

[Fless]

More on this - What does a purge/seal test do?

Essentially it tests how tight the evap system is.

First, it closes the evap system (including the vent valve, fuel tank, canister, evap lines, etc.) except for the purge valve on the engine. With the engine running the purge valve opens to allow engine vacuum to draw down the pressure (pull a vacuum) on the closed system.

At that point a system without big leaks should cause the fuel tank (or system) pressure sensor to sense the pressure change (going negative as vacuum) and report it to the engine computer, and vacuum should continue to build.

Once the purge valve is commanded to "seal," the entire system should be closed, and only a small bit of vacuum decay should happen over a little time. The changes to the negative system pressure (e.g., decreasing vacuum) should be reported by the fuel tank pressure sensor.

 

[2006Tahoe2WD]

Essentially it tests how tight the evap system is.

First, it closes the evap system (including the vent valve, fuel tank, canister, evap lines, etc.) except for the purge valve on the engine. With the engine running the purge valve opens to allow engine vacuum to draw down the pressure (pull a vacuum) on the closed system.

At that point a system without big leaks should cause the fuel tank (or system) pressure sensor to sense the pressure change (going negative as vacuum) and report it to the engine computer, and vacuum should continue to build.

Once the purge valve is commanded to "seal," the entire system should be closed, and only a small bit of vacuum decay should happen over a little time. The changes to the negative system pressure (e.g., decreasing vacuum) should be reported by the fuel tank pressure sensor.

Exactly

 

[2006Tahoe2WD]

I put the graphing on for purge and venting and drove around. Pretty much the vent stays open and the purge command goes up and down - maybe going to zero at a stop and idle. I guess this means the a lot of air is pulled through the vent valve and then the charcoal canister most of the time when driving. Also meaning the purge valve (running on PWM) really gets a workout - not a surprise it needs replacing from time to time. When I looked inside the vent valve there was a lot of dirt - I'm thinking adding some additional filtering could be a good idea. The question is - what material to use. E.g. an old sock?

 

[Fless]

The vent valve has an integrated filter -- are you saying that it doesn't have a filter now? Some of the later years have a longer hose from the valve so the filter can be tucked out of the way a bit.

 

[2006Tahoe2WD]

The vent valve has an integrated filter -- are you saying that it doesn't have a filter now? Some of the later years have a longer hose from the valve so the filter can be tucked out of the way a bit

It has a rather wide open mesh type sponge filter inside the vent valve case. By the looks of it - it won't stop much in the way of fine dirt. I was thinking to improve the filtering by adding something.

 

[2006Tahoe2WD]

If you drive in a dusty environment e.g. on a farm or ranch I would expect a lot of dirt would get pulled into the charcoal cannister. I don't know how much dirt they will take before a code gets tripped.

For general reference... I think our layout is something like this.

 

[2006Tahoe2WD]

Minor update. I'm still waiting for the EVAP drive cycle(s) to complete. I don't see any new codes. Today I replaced the brake light switch with a new one (not OEM) it looks like they are NLA.
I used a new 2007+ clip to hold in the switch. That clip has a feature that might help get it off next time around. Until you get the hang of it - getting that clip off is a PITA.

I also took out the new aftermarket AL billet oil block off plate and put the OEM back with a new gasket from the dealer.

Somewhat new subject re. codes. I get a consistent B0229. Recirculation actuator signal. Using my two-way scanner I was able to move the other doors but could not get the recirculation door to move in any of the modes. I could hear faint noises but no movement. The recirculation door is to the right and behind the glove compartment. To get to the actuator it looks like pulling the top of the dash is the way to go. What is the correct pn for this? I have dual climate control with the knobs not levers.
Any thoughts? Thanks guys for helping me along on all this.

 

[2006Tahoe2WD]

I think the recirculation actuator is
GM GENUINE 1571845