The Pump Mounted Driver (PMD) is a set of resistors that control the fuel injection pump on General Motors (GM) 6.5-liter diesel engines manufactured between 1994 and 2001. The PMD produces a considerable amount of heat, and it sits in one of the hottest places in the engine compartment. It relies on contact with the fuel injection pump to cool itself but is prone to failure, often due to overheating. Some replacement PMDs come with cooling fins; mount these PMDs away from the injection pump in a cooler location to prevent overheating.
Unscrew the air filter assembly with a wrench, and lift it from the top of the engine.
Locate the injection pump under the air filter in the valley between the two cylinder banks. The PMD is the black box about 2 inches wide mounted in place by four bolts on the driver's side of the injection pump. It attaches to a wiring harness.
Unclip the wiring harness, and use an Allen key to loosen and remove the four attachment bolts on the PMD. Remove the PMD from the injection pump.
Place the new PMD in position on the fuel injection pump. Install and tighten the four attachment bolts with an Allen key wrench.
Attach the wiring harness to the PMD.
Place the air filter assembly in position over the intake manifold, and tighten the air filter nut with a wrench.
