A faulty glow plug control module will make it hard to start a diesel engine Jeep Cherokee in the morning. A sure sign something is wrong with the glow plug control module is when the engine light goes on and the Jeep takes a long time to start and it runs rough until the engine warms up. You should immediately go to an auto store to check the Jeep with a diagnostic tool to confirm your suspicions. Replacing the glow plug control module is a job most backyard mechanics can do themselves in an afternoon. If you have to replace the glow plug control module on a 2007- 09 diesel engine in a Jeep Cherokee, here is how you can do it.

Disconnect Battery and Remove Engine Cover

Take the negative cable off of the battery to stop the flow of electricity throughout the engine. Take off the plastic engine cover. The cover is held down with two 10 mm bolts. The bolts are located in channels on the top of the cover.

Remove Air Intake Hose

The air intake hose runs over the top of the glow plug control module and you need to remove it to gain access to the module. The hose is connected to the air filter and intake valve on the engine with hose clamps fitted with a 7mm bolt. Unscrew the hose clamps to loosen the hose and remove it. Make sure you disconnect the crank case ventilation tube from the hose. The tube is located by the engine block and will slide right out of the hose. There is also a bolt near the middle of the hose that has to be removed before you can take out the air filter hose.

Remove the Glow Plug Control Module

The glow plug control module is connected to a metal bracket right underneath the front section of the air intake hose. You should use an 8mm six-point socket to remove the four bolts holding the control module to the bracket. Unscrew and remove the bolts. You can now remove the bracket and the control module and reach the plugs for the wires running into the control module. Unplug all the wires and remove the control module.

Install New Module

Make sure you buy a new glow plug control module made specifically for the type of diesel engine you have in your Jeep. There is usually a sticker on the underside of the hood or in the engine compartment that will tell you what type of engine your Jeep has in it.

Connect the wire plugs to the new control module and bolt it and the bracket back in place. Clamp the air intake hose back into position and insert the crankshaft tube back into the hose. Replace the engine cover and screw the negative cable back on the battery. The Jeep should start right up now.