2004.5-2007 Dodge 5.9L Cummins Grid Heaters

Grid heaters on the 2004.5-2007 Ram 5.9L Cummins

The intake air grid heater is an electric element that sits between the cast aluminum air horn and the intake manifold, right in the path of the charge air coming from the intercooler. It warms incoming air for cold starts. On the common-rail 5.9L, pilot injection works well enough that Cummins made the block heater optional, which leaves the grid heater as the primary cold-start aid. Power reaches it through a relay and heavy wiring, with a fusible link in the circuit. Because the heater is part of the intake path, the joints around it have to seal like any other intake joint.

What goes wrong

The most predictable problem here happens during service. The air horn and grid heater must be unbolted for injector work, and the gasket tears easily on the way off. A torn gasket lets unmetered, unfiltered air in at the horn-to-head joint, which skips your air filter entirely. If the grid heater itself stops doing its job, trace the whole circuit (the grid, the relay, the relay-to-grid wires and the fusible link) before buying parts, since each one is a separate piece you can replace.

Stock replacement vs. upgrade

There is no performance angle on this page. The goal is a heater that works and a joint that seals. For the horn joint, use the heat-resistant gasket: Cummins 3969988 replaced the old pink 3938158, and because it tears so easily, it pays to keep a spare on the shelf. On the wiring side, the XDP parts are heavy-duty versions of the relay-to-grid-heater wires and the relay fusible link wire, a sensible choice when the factory pieces need replacing and you want heavier wiring in their place.

What we carry

This collection holds the XDP XD440 heavy-duty relay-to-grid-heater wires (listed for 1998.5-2007 5.9L), the XDP XD442 heavy-duty grid heater relay fusible link wire (listed for 2003-2018 5.9L and 6.7L) and the MAHLE G32749 intake heater grid gasket (listed for 1989-2007 5.9L). The heater grid element itself is in the main air intake collection for this truck, and everything else for the engine starts at our Cummins hub.

Fitment notes

The air horn is held by four 10 mm bolts plus the dipstick-tube bolt and a band clamp, so plan the job before you start: horn off, grid heater out, new gaskets in. A 2004.5 truck is titled as a 2004 model year. On a 2007, confirm the engine is the 5.9L; trucks built after January 1, 2007 got the 6.7L Cummins. The year ranges on these parts are wide, so read each listing and verify by VIN if you are unsure.

Frequently asked questions

Does my 5.9L need a block heater if the grid heater works?

Not necessarily. Pilot injection on the common-rail 5.9L is effective enough that Cummins made the block heater optional. That leaves the grid heater as the primary cold-start aid, so it is the part to keep working.

Do I have to replace the grid heater gasket after injector work?

Yes. The grid heater comes out with the air horn for injector service, and its gasket should be replaced. Cummins 3969988 is the heat-resistant gasket that replaced the pink 3938158, and it tears easily, so have one on hand before you start.

What happens if the horn gasket tears?

You get an air leak at the horn-to-head joint, and that air is unmetered and unfiltered. Dirt that skips the filter goes straight into the engine. Replace the gasket rather than trying to reuse it.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.