Vent Valve Issues 2012 Chevrolet Malibu

Michael Mobile Technician Clinton, Utah Posted   Latest  
Case Study
2012 Chevrolet Malibu LS 2.4L (1 LE5) 6-spd (6T40)
P0446 - EVAP System Vent Control Circuit

Got a call to come program a PCM on a Chevy Malibu. The customer had stated that they had replaced the vent valve and a code still existed. Seeing that it was a circuit failure, I doubted that it would do any good. I went ahead and updated the calibration to the latest. As expected the code remained.

Looking at the wiring diagram, I saw that there was one wire from the trunk fuse box that fed the vent valve and another that went from the vent valve to the PCM. Before lifting the vehicle, I disconnected the battery and checked continuity to the fuse and the fuse itself. It was all good to there. I then measured the resistance from the positive lead to the White vent valve wire at the PCM. It was showing "OL" or out of limits. I surmised that there was an open based on information so far. The vehicle was then raised with the battery connected and Ignition on. At the vent valve there was a few hundred millivolts. At the body connector X413 there was 12.5 volts. So it appeared there was a problem in the wiring between the vent valve and the body connector X413. Further inspection of the wiring revealed the culprit. The winter's snow and ice melt found a chink in the wiring's armor. I had the technician helping me pull on the wire. It broke easily. What was once nice Copper was now Green powder. The wire was repaired and codes cleared. No return of the code.


Geoff Diagnostician
Lahaina, Hawaii
Geoff Default

There's a couple guys that make good diag videos and they use the term "green crusties" when wiring corrosion sets in.

+3 Default Ð Bounty Awarded
Abe Technician
Monticello, Minnesota
Abe Default

We call it the green monster...

0 Default Ð Bounty Awarded
Michael Owner
Pelham, Alabama
Michael Default

One of my early mentors referred to these as "nose goblins"...

0 Default Ð Bounty Awarded
Abe Technician
Monticello, Minnesota
Abe Default

What terminology do you use?

0 Default Ð Bounty Awarded
Hollis Technician
Boulder, Colorado
Hollis Default

Verdigris-a-fication, Y'all :O)

0 Default Ð Bounty Awarded
Ric Owner/Technician
Hooksett, New Hampshire
Ric Default

We call it 'green death'. :)

0 Default Ð Bounty Awarded
Stuart Mobile Technician
Blue Island, Illinois
Stuart Default

Thanks for sharing​.​GM does have a history of putting critical electrical components in places prone to the hazzards of road crud.

0 Default Ð Bounty Awarded
George Owner/Technician
Skagway, Alaska
George Default

This totally blows me away too. Every time I deal with something like this I just have to shake may head and thank the engineers for such a good pay check

+1 Default Ð Bounty Awarded
Ricardo Diagnostician
Plymouth, Michigan
Ricardo Default

When I see wires like these I remember when used to work at the gm plant and seeing that every harness comes in a box with a big warning sticker that says " do not use sharp objects to open box" or something like that, can you guess what every worker on the line uses to open the box ? Yep : utility knife

0 Default Ð Bounty Awarded
Mark Owner/Technician
Monterey, California
Mark Default

Thanks for your case study. This is why piercing wires is such a bad idea.

+2 Default Ð Bounty Awarded
Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default

Hi Mike: The owner of the shop, where I worked on Peugeots, used to say that the eyes are a mechanic's best tools. Good grab. BTW, it appears there is some consistency here. The white wire looks like it's been stabbed also. Guido

+1 Default Ð Bounty Awarded
Steven Instructor
Cumming, Georgia
Steven Default

Mike, Nice case write up! I will surmise most of us believe connection resistance and wire probing issues will continue on a steep growth curve! Even today, I still see wire "stabbing" tools included in electrical testing kits.

0 Default Ð Bounty Awarded