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Old 08-02-2012, 11:25 AM   #8
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 43,465
 

2003 L-Series 3.0L Sedan
Default Re: Passlock / Ignition Problems

Passlock is GM's theft deterrent system and indicates when its ON/flashing/OFF for status. If OFF during start then its not Passlock related (the security indicator is a LED). Post what you see when starting.

A worn key interferes with the lock cylinder, a mechanical issue. Replace the worn key from GM using the VIN. Its not advisable to make a copy of a copy from the hardware store.

With security OFF while starting, there are two issues to deal with; crank position sensor and ignition control module (for spark). First check for fuel and pressure at the fuel rail's test valve; with ignition ON the fuel pump runs (with a faint hum/hiss) for 2-seconds, remove the schrader valve cap and depress the valve stem (cover with a rag) expecting a spray. If you can test for spark, remove the plugs and reassemble them with the ignition coil pack/icm and ground the plug bases to the engine block. Have someone crank the engine while you observe for spark. No spark usually points to the cps while the ignition control module (sitting in the coil pack, aluminum finned box) is a close second. The cps can be tested for resistance (700-1200 ohms) before replacing it. To be sure its a faulty cps, measure it again while immersed in boiling water and after rapping it on the table a few times as this duplicates the engine environment. Any open reading means failure. The cps is next to the starter.

The icm is the second most failure prone part of the ignition system after the cps.

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