Help Code P0540

[sdtplus3]

I just bought a 2006 GMC K3500 with the LBZ and 114000 miles on it .I have put about a 1000 miles on it and now have a engine light with code P0540 Intake Air (IA) Heater Feedback Circuit.I did a vin check and found out they replaced the glow plug controller right before I bought it ,does the glow plug controller also control the intake air heater? How long does it take to set a code if someone reset it, I was wondering if the person I bought it from knew anything about it?

[More Power]

The IAH is operated from a separate circuit - other than the glow circuit. This is why you'll see your voltage gauge on the dash stay below 12 volts after a cold start for a few or more seconds, but the "wait to start" lamp (glow plug light) isn't on.

First, check your fuses, then make sure the IAH hasn't been tampered with, and that the electrical wires are in-fact connected. If so, check for continuity across the IAH heater coil. Should register just a few ohms. If the fuses are good, the IAH ohms OK and the wires are connected, the next possibility includes the IAH relay.

Jim