Electrical Wiring Experts

GM Passlock Electrical Wiring Short Automotive Robo Tech was called to a shop on a 2003 Chevy Van G2500, with a 4.8 liter engine, experiencing a security light on followed by a no start situation. For some reason, the shop replaced the crank sensor. Because is was a no start, they reason it was probably the crank sensor, and of course, it wasn’t. They eventually saw the security light on, and figured out that it was a Pass-Lock system issue. They next replaced the Pass-Lock key cylinder, with no luck either. At this time, the shop decided to call me in for assistance. They simply didn’t have to scan tool to access the BCM or body module for this problem. When I arrived at the shop, the tech gave me a briefing on the vehicle, and also said that the vehicle would start once in a blue moon. Ok, that was probably some kind of clue. I started my diagnostic by performing a general code analysis. I did get code P1632, or Theft Deterrent Fuel Disable Signal Received from the BCM. There were no other codes present. I knew it wasn’t the key cylinder, since it was already replaced. There are steps to take in all Pass Lock diagnostics before condemning a component. In this particular GM, the signal from the ignition system is controlled by a resistor embedded in the Pass Lock module, which is part of the ignition switch cylinder. In these systems, any key that will allow the cylinder to be turned to the on position will work, the only condition that must be met is that the cylinder …

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