P0540 code.

[ronsway]

2002, 2500HD, 4X4, auto - I am getting a P0540 code. I have heard that it is the IAH relay. What can I do to further determine the problem? Is this something a "bolt-on" mechanic is try to fix?

 

[Mike]

That could be anything from a bad fuse to a bad heater coil. Time for a volt/ohm meter.

 

[sweetdiesel]

That is what the code is for

If the temp of the truck is under 121f and or intake air temp is below73f it will kick on the heater coil

Check the voltage on the heater coil and that will tell us where to start,there is also a wire on the glowplug controller that need to be checked that will elimnate the wire to the plug being the issue

 

[sweetdiesel]

Check Ing 1 fuse in the under hood fuse block

 

[sweetdiesel]

That could be anything from a bad fuse to a bad heater coil. Time for a volt/ohm meter.

Also can mean a bad ECM

 

[Mike]

I didn't know that. Thanks

 

[sweetdiesel]

I didn't know that. Thanks

probably rare Mike,but it happend to a friend of mine

 

[Mike L.]

I took mine off. Truck runs better. No CEL but there is a constant memory code.

 

[bigblackbronco]

code p0540

OK, the most common thing that sets code p0540 is the air intake relay.

the thing most people don't realize is you don't have to replace this whole box
just take the top off, and what do we have

as you can see it is actually just two separate 70A SPST relays that can be had for $5 almost anywhere on the internet

I hope this helps, if you want to test the relay's there are plenty of how-to's on the internet, but I would just replace them both.