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Aftermarket Alarms Ruin Catalytic Converter?


WarrenJ

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Every once in a while I stumble over something unexpected while researching another topic entirely. Bulletin #02-06-05-004A - (Jan 9, 2004) is one of those little gems.

I'm posting it here without any real expectation it will solve someone's problem. Rather, I'm posting it because it's just so darned interesting (to me, at least). I hope you won't yell at me if you don't share my fascination. It's edited for brevity.

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Info - Misfire DTCs P0300, P1380, P1381 and Catalytic Converter Damage Due to Installation of Alarm Systems

General Motors Engineering, in an effort to determine the root cause of catalytic converter damage, has determined that aftermarket alarm systems incorrectly installed in vehicles have the potential to cause misfire codes and damage to the converter. These alarm systems use a circuit interrupt which utilizes the ignition circuit on the vehicles.

These alarm systems utilize mechanical relays and normal vehicle movement can trigger these relays to engage and disengage the ignition circuit while the vehicle is in motion. These disruptions of the ignition circuit, which occur in milliseconds, may cause more fuel to be commanded. Over time, this dumping of fuel on and off again can cause misfire codes and ultimately damage the converter assembly.

Important

Engineering could not identify any alarms that utilize solid state circuitry that would eliminate this concern. Because of this, it has been determined that all alarm systems must be routed through the starter circuit in order to avoid this condition.

Dealers must be aware of this issue and take note of the wiring on vehicles with alarm systems that come in for repair, particularly for catalytic converter damage that seem to have no known root cause.

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Whodda thunk it?

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There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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I think it is a gimmic, a coverup. I had alarms and starters in every car I owned before these 3 vehicles, and the only reason why I dont now is because the they arent necessary for my cadillacs and my truck is a manual, and doesnt need an alarm.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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If an alarm system causes intermittent interruptions to the spark signal of a running engine, it can do just what the bulletin says. Messing with the spark of a running DFI engine is a well-known no-no, particularly when running in open loop or high throttle. The best way would be to send a "kill engine" signal to the PCM over the car's network. Second best, and more feasible for aftermarket systems, is interruption of the FI signal. Since most aftermarket systems can interrupt the starter solenoid actuation circuit right out of the box, that is probably the best solution, just as the bulletin says.

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  • 2 weeks later...

My first inclination when I hear a car alarm is to put a .44 magnum projectile through the battery of the offending vehicle! :ph34r:

Some of them are set so sensitive that a strong breeze will set them off.

We had a car left in our parking lot at the airport that was going off every 30 minutes or so. We finally had the local police come out. They unlocked the car with a slim jim and popped the hood. We disconnected the battery. End of problem! :yupi3ti:

When he came back in a couple of weeks, we hooked the battery back up for him.

We also suggested what he could do with that alarm, and it wasn't pretty! :fighting0025:

Britt
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My first inclination when I hear a car alarm is to put a .44 magnum projectile through the battery of the offending vehicle! :ph34r:

:D :D :D

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There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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