Chevrolet Diesel Repair and Maintenance

Bays Complete Auto Repair is Phoenix’s Top Shop for all lightweight and medium duty diesel engines. We have expertise in Chevy’s Duramax and are excellent at diagnosing and repairing diesel engines. From problems with the Duramax high pump system to water pump failure, we are your one stop diesel mechanic in Phoenix.

Below is a list of common issues we run into quite frequently:

Fuel Starvation and/or Air in the Fuel Lines

A common problem with the Duramax diesel is air getting in the fuel lines and starving the engine of fuel. More often than not, this problem can be attributed to the poorly designed fuel filter housing and also because Duramax does not use a lift pump. After time, a the fuel filter housing will develop a crack and/or the o-ring will go bad and allow air to enter the system. Lb7 fuel filter housings in Duramax years 2001 thru 2004 seem to be the most problematic.

Water Pump Fail

Unfortunately it is a common occurrence for water pumps to fail before 100k miles. Seems Chevy didn’t engineer the water pump to have a long life and unfortunately when it goes bad it needs to be replaced immediately.


Duramax diesels before 2005 tend to have overheating issues when hauling loads during the summer months. Duramax solved this problem for 2006 and older models by engineering in a larger radiator and fan. Other typical reasons for overheating are fan clutch failure, dirty or clogged radiator, thermostat failure or a coolant leak.

Fuel Injector Failure

Fuel injectors was a problem for Duramax between years 2001 to 2004 due to faulty design. The problem was fixed after 2004 with a new injector design. Buyer beware, if you are purchasing a used Duramax; not all engines have been retrofitted with the new injector design. Even though the new injector design performs much better then the old, they are still susceptible to premature failure if proper maintenance is not performed.

Injector Wire Harness Failure

Fuel injector wiring harnesses chafe over time. Exposed wires can cause a myriad of problems such as lack of power and no-start or running poorly. Often a check engine light will tell the technician which injector has the open circuit causing the problem. The fix is generally a wire harness repair unless the harness has more damage and may need replacement. Simply wiggling the wires around the injector will detect if the harness is the culprit. Be mindful that if you wiggle the wires and it solves the problem it is only a temporary fix and you risk damaging the rest of the expensive harness.

Glow Plug Problems

The 2006 LLY and LBZ Duramax are known to have glow plug problems that often caused catastrophic engine failure. The tips of the glow plug would deform and break off in the engine due to the glow plug module over cycling the glow plugs. A simple glow plug module flash reprogram will fix this problem if it’s not already too late to repair.

PCV – Turbocharger Oil Ingestion

Duramax poorly designed the PCV to vent crankcase pressure into the intake. This process forces engine oil into the turbocharger which over time coats the intercooler and it’s tubing. When enough oil has accumulated in the intercooler boots the boots themselves will breakdown and cause turbo problems. Have no fear as there is a fix which reroutes the pcv line away from the turbocharger.

Limp Mode; Allison 1000 Transmission

Limp Mode is a good thing as it is safeguarding your transmission from complete failure.  Even though limp mode may not seem like a good thing, keep your head up because it most likely is saving you from a costly repair.  If the Allison 1000 transmission senses any abnormal slipping; it will enter limp mode which disables reverse and locks into 3rd gear.  Sometimes however the limp mode can incorrectly engage when under a heavy load and downshifting to pass.  If your diesel is performance tuned this is even more common.  Unfortunately you will need a scanner to take the transmission out of limp mode and it is very likely the transmission will need to be replaced soon.  Replace transmission fluid when the manufacturer recommends to give you the longest life possible.

Emission System debacle; 2011 LML DEF and SCR

In 2011 the LMO Duramax came fitted with an over-engineered selective catalyst reduction (SCR) emissions system. This SCR emission system needed a constant supply of diesel exhaust fluid (DEF) and had a plethora of reoccurring failures. Constant failure of NOx sensors, DEF pumps and DEF tank heaters clearly showed this new system needed to be redone. And a redo in 2012 fixed most but not all of the problems.