Piston Slap: Xterra's External Air Bag Influencers?

Sajeev Mehta
by Sajeev Mehta
piston slap xterras external air bag influencers
Mike writes:

Ok Sajeev, I got one for you.

I own a 2009 Nissan Xterra 4wd X model. It has nearly 100k miles on the clock. In the past week, whenever I start the vehicle, I hear a chattering noise coming from the passenger side dashboard. The noise persists as long as the passenger air bag light is lit; when that light goes off, the chattering stops. So I took the truck to my local Nissan dealer, whom I trust, and I was told that the problem is the passenger side blender door of the HVAC system – apparently there are gears in this assembly which are not moving freely or properly.

The cost to repair is estimated at about $600 because of the necessity to remove the whole dashboard. The dealer’s service people told me to do nothing until the HVAC system fails to function properly, and it is currently functioning properly except for the above described noise. My question: how is a bad blender door mechanism linked to an airbag light? Can airbags chatter on vehicle startup?

Thank you as always for your excellent advice.

Sajeev answers:

First try resetting the air bag light. If that doesn’t work, let’s trust your trusted dealer on the blend door actuator, and allow me to meander as I cannot Google a precise explanation.

I have a similar problem with my (now fully restored) Lincoln Mark VIII after suffering a front-ish fender impact (i.e. airbags didn’t pop). Now the air bag light/buzzer triggers if the headlamps are on during start up. I disabled the automatic headlights and delayed my knob twisting, keeping the Air Bag Diagnostic Monitor happy.

Which makes me happy, and I’ve invested in a set of factory shop manuals. (You should too!) So let’s see how two seemingly unrelated items are linked:

After starting the Mark VIII, fuse #10 juices up several things, including that Air Bag Diagnostic Monitor (second box from the left on the bottom). So when I crank on the headlights “too early” after startup, the circuit (in the multifunction switch?) drops the amount of juice (voltage?) which upsets the Air Bag Diagnostic Monitor’s 22 year-old circuits. My logic is pathetic, but the result is clear.

What’s the point? Air Bag health indicator modules are, as they age, hyper sensitive to external influences.

If anything looks wrong, the system is engineered to assume the worst and get the owner into a repair shop. This ensures [s]fewer manufacturer lawsuits[/s] the air bag system will never be neglected and always save lives.

Just buy the shop manuals with wiring diagrams, please!

[Image: Nissan, Sajeev Mehta]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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2 of 19 comments
  • Lorenzo Lorenzo on Dec 30, 2017

    Since sensors and switches go bad, automakers should make an effort to make them easy to replace. I smell a class-action suit, and/or government regulation! Oh, wait! These are out-of-warranty cars, and regulations are being slashed as we comment. We'll have to depend on the hackers for quick fixes, and follow shop manual instructions for extensive disassembly of, er, assemblies.

  • Olddavid Olddavid on Dec 30, 2017

    I don't care where I read it - seeing Mark VIII in print anywhere warms my heart. I just spent three of the holidays stripping every usable part from a low mileage '97 base. When one of these with an operable blend door, a tight steering column and charged airbags comes to a PickNPull I should just move to the closest motel. I'm wondering if your car is fully restored one weekend at a time or all done at once? Doesn't matter. The two door V8 rear drive cruiser is fast achieving unicorn status. Or fellow sufferer. I cannot decide.

  • Redapple2 C2 is the best. C3 next. Then C7 (looking at you jimII).
  • Jeff S Vulpine--True the CAFE rules are for ICE.
  • Gray I grew up in the era of Panther and Fox platforms. If only they developed a good looking two door Conti. The four doors became a cult in their own right. And kept the 351W as a top line option.
  • Vulpine ABSOLUTELY YES!!! Bring back the TRUE compact trucks. The demand for them is far higher than the OEMs want to admit.
  • Brn More likely, with Google having troubles, the money tree isn't as ripe as it once was and cutbacks are needed.I hope the overall industry continues to evolve. When I get the the point I can't easily drive, I would still appreciate the independence that autonomous vehicles can bring.