Intake Air Heater Circuit

[Miller Man]

I am worn out trying to navigate all these pages for a simple answer to this question - 2005 6.6L Intake Air Heater Circuit (code as displayed on scan tool P0540$10) - is the likely solution the replacement of the relay? If so, can anyone provide the location?

[More Power]

In the 2001 model year, the intake air heater receives power beginning at the 175-amp fuse located in the underhood electrical center - above the driver's side inner fender.

From there, power is routed to the Glow Plug / Air Intake Heater Relay Assembly (aka GPCM - Glow Plug Control Module). Inside the GPCM are two heavy-duty relays, one for the GPs and one for the IAH. The GPCM is located at the rear of the engine above the driver's side valve cover.

Using a multimeter or 12v test light, it's a simple task to verify whether the IAH is receiving power when the ignition key is first rotated from OFF to RUN. You can also verify whether the heater coil, that is the IAH, is functional by measuring the resistance of the coil - should be very low resistance.

[Willcoc]

The relay is located as described by "more power". Took awhile but removed the relay from the mount and did a full test with a meter and found no issue. Put power on the relay, still tested good. Put back in the truck and would not pass power under load. I founds the relay at DigiKey but have not installed. 2 relay abd shipping was $24. The replacement part at the local stores was $240 so a good savings. I can provide part numbers if needed.

[Henri Paul]

I keep getting the DTC P0540 I can clear it with my hypermax programmer, but it comes right back. Is this something I should worry about, or just deal with the annoying "service engine soon" light.

[More Power]

I keep getting the DTC P0540 I can clear it with my hypermax programmer, but it comes right back. Is this something I should worry about, or just deal with the annoying "service engine soon" light.

Have you put a meter on the Intake Air Heater element terminal to see whether it's getting power when it should?

If it's getting power when first rotating the ignition key from off to run, is the element heating?

The engine will run normally with this code. The only danger I can think of is that if the heater element is continuously powered (fused relay), it could burn out the element and cause it to disintegrate and be ingested by the engine. If you must run the engine when a DTC P0540 is present, I'd disconnect the electrical terminal at the Intake Air Heating (IAH) element and insulate the electrical wire connection so it can't short out on the engine.

A malfunctioning IAH could increase emissions at startup and/or it could produce hard starting or rough running in extremely cold temperatures.

Jim