Dan’s 2005 GMC Yukon XL Passlock Fix

Dan Kirchheimer sent us his story in October 2014, about a year after his 2005 GMC Yukon XL started refusing to start. His version of the problem will be familiar to anyone who has lived with Passlock: completely random, never reproducible for the mechanic, and always at the worst possible moment.

Two hungry toddlers, fifteen minutes

“About a year ago I started having issues with my truck not starting with a blinking security light. It would be incredibly random and you’d never know when it would choose to act up.”

“I have two toddlers (2 and 4 years old) and one day my truck decided to leave us as we were preparing to go home to prepare lunch. The only known remedy: wait 15 minutes, cross your fingers, and try again. For those that don’t know what two hungry toddlers are like in a perfectly good car that won’t start for 15 minutes, this was a terrifying experience.”

That was the day he ordered. Not because the truck got worse, but because the wait-and-hope routine had just been performed in front of his children.

Too good to be true, at first

“I had assessed the situation as very bad after having called our local GM dealership and a handful of aftermarket alarm companies and thought Newrockies was too good to be true. I felt almost giddy at the thought that I could fix this problem and not add a year to our mortgage.”

“When the module arrived I was extremely impressed with the quality industrial feel overall and immediately went to work. I went into mad scientist mode in my garage and tore into the brain of my truck as if I were a highly trained surgeon (confidently guided by outstanding instructions).”

The thirty second phone-a-friend

Dan’s install did not go perfectly on the first key turn, and what happened next is worth recording, because it is the part most people worry about.

“When I started the truck I was terrified that it wouldn’t start at all. After checking my connections I Emailed Newrockes, who immediately responded and talked me through checking some switches. Within 30 seconds he had my truck up and running.”

Usually the culprit is a dip switch setting, and it takes moments to correct. The point is that nobody is left alone with a half-finished install.

A year later

“It has been nearly a year since I installed this module and I haven’t had to think about it since. This has been a true ‘cure’ and I have told every GM enthusiast I know, including my mechanic who still thinks it’s too good to be true. Thank you, thank you, thank you, it’s all I can say.”

Why the Yukon does this

On the 2003 to 2006 Yukon, Yukon XL and their Suburban, Tahoe, Avalanche and Escalade siblings, the Passlock sensor lives in the ignition lock cylinder. A magnet rotates past a Hall effect sensor as the key turns, producing a coded voltage the Body Control Module compares against a learned value. When wear makes that voltage drift, the BCM concludes theft, cuts the injectors, and flashes the SECURITY light. The truck cranks perfectly every time, because the starter is not the problem. Fuel is.

The randomness that made Dan’s truck impossible to diagnose is exactly what a drifting analogue value looks like: some mornings it lands inside the window, some mornings it does not. The NEWROCKIES PRO Module removes the comparison altogether, which is why the fix holds instead of resetting the countdown the way a new cylinder or a relearn does.

If you have one of these trucks

The BCM sits in the dash directly under the steering column. The full wiring, connector by connector, is here: 2003-2006 Chevrolet Suburban, Tahoe, Avalanche, GMC Yukon and Sierra, Cadillac Escalade, 2003-2007 Silverado Classic.

Related stories on the blog. Same family of trucks: Scott’s 2003 Suburban and Eric’s Avalanche, still starting two and a half years on.

Read more customer stories →