Piston Slap: The Body Control Module Electric?

Sajeev Mehta
by Sajeev Mehta
piston slap the body control module electric

Gary writes:

Good Afternoon,

Today when I got into my 2002 Saturn SL2, the power door locks started chattering. Each door, over the space of about 45 minutes, had the same thing happen. Sometimes it would be one at a time, other times it would be two or more. I also noticed that the inside locks – the “up/down” button, not the little lever you use to manually unlock the car – would not work, only later to work. For now I have removed the lock fuse and that stopped the problem. I wait and plug the fuse back in, and the sporadic chattering once again begins. Sometimes it is completely quiet. Any thoughts?

Thank you!

Sajeev answers:

Whenever a problem like this occurs, I blame something Body Control Module like. When guidance systems break down? When there’s a struggle to exist? To resist? That’s not a mere switch panel or short in chassis wiring. Oh no, Son, this is some heavy duty FAIL right here.

A body control module that’s scared out of its wits is the only culprit behind such berserk behavior. My apologies to the TTAC mothership (and all Torontonians) for such a shameful riding of RUSH’s coattails.

If I’m right, the video (below) is helpful. Ditto this Saturn forum link, complete with the body control module’s pinouts for your testing pleasure. A replacement is over $200 at Rockauto, rebuilders on eBay want over $150 for the privilege. So you’d be wise to test the wiring, get a factory shop manual and perhaps learn the proper BCM diagnosis method.

And don’t forget the BCM recall, too!

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.

Sajeev Mehta
Sajeev Mehta

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  • Kyree Kyree on May 27, 2015

    Oh yes, that will do it. I've seen body control modules fail on lots of General Motors vehicles, mainly Pontiac G6s for some reason. One indication from outside the car is when the brake lights stay on while driving, but turn off when the brake pedal is depressed.

  • Felix Hoenikker Felix Hoenikker on May 27, 2015

    Anybody know why are these modules keyed to the car's VIN?

    • See 1 previous
    • SCE to AUX SCE to AUX on May 27, 2015

      Some of them also control the odometer, whose reading needs to be implanted into the new BCM. As you know, the odometer reading is an Important Thing.

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  • Spamvw Three on the tree, even Generation X would have a hard time stealing one of those.
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