In 2003, Chevy only offered the turbo-charged 6.6-liter Duramax Diesel engine in the 2500 and up series, which have been known for being good reliable trucks. Regardless of how good a truck is built or how well it is taken care of, the possibility for failures is always there and random stalling or no start conditions aren’t exempt. Finding the culprit causing your diesel engine to stall or not start can be like finding a needle in a hay stack, but there are a few common things to look into before diving head deep into said hay stack.
One of the most common problems with the 03 Chevy Duramax engine is fuel filter blockage. The fuel filter is located on the right -- passenger side -- valve cover and is secured by a single bolt. Fuel goes into the filter and then on to the fuel rail and injectors. The clogged filter can prevent the engine from starting or can block fuel flow while driving, leaving you helpless in the middle of the road. Separate the filter housing and swap in a new filter, they are inexpensive and should be done on a regular basis. Some guys swear by changing the filter every other oil change or around 7000 miles. Also be sure to check all fuel lines and hoses for damage, leaks or kinks and replace as necessary. Any restriction between the fuel tank and injection pump will create drivability problems that could likely leave you stranded. If the filter was recently replaced, there could be air in the system or a leaking connection on the back side of the filter. You can pump the primer on top of the housing three times to re-prime the filter, but any more than three times will damage the fuel system.
Check all of the electrical connectors for the fuel injectors and glow plugs. Check that your battery terminals, on all batteries if your truck has more than one, are tight along with the connectors for the alternator. Any sudden loss of power supply will cause the engine to shut down and could make it hard to start back up again. Older Chevy trucks had a problem with the ignition switch terminals wearing out, leading to a lost connection between the ignition and the vehicle's switched power that could cause your engine to shut down as well. If the ignition switch is faulty, you will lose power to multiple components at once when the key is on or the truck will act like the key is off even while it is in the on position. A loose or bad ground can also cause your engine to randomly stall or not start. There are two troublesome ground points that should be checked; the first connects on the driver-side below and behind the power steering pump and a silver ground strap that attaches to the rear cylinder head below the glow plug control module.
Aftermarket equipment that claims to help increase gas mileage and horsepower can also have a negative effect if they happen to fail or have become subject to moisture. Even remote starter modules can go bad or short out and cause intermittent stalling, a no-start condition and other problems. There have been various complaints about certain aftermarket chips that had a manufacturer defect that would cause Duramax-engined Chevy trucks to not run at all. It was commonly found that when the chip was removed, or the box under the dash was unplugged, the engine and vehicle would operate fine; in most cases, the manufacturer would supply a replacement product in return for the faulty one. Your best bet is to unplug an aftermarket remote starter or performance tuning equipment to see if that solves your stalling and failure to start problems.
Use a scan tool, one with the capability of reading freeze frame data and look for any stored trouble codes and freeze frame data. If the vehicle will run set the tool to its in-transit repair mode, as directed by its operating manual, and have an assistant ride along to view data as you drive. If you can replicate the scenario with the scan tool connected, you will be able to see what is changing within the engine and computer at the time of stalling. Engine fuel delivery is controlled by the PCM, but it uses information from the crankshaft position sensor to know how and when to fire the injectors. Check the connection at the crank position sensor. Replace the sensor, if it is damaged or you believe it may be faulty. The sensor is on the passenger side of the engine and the mounting bolt should be tightened to 71 inch-pounds.
