What Scanner Do I Need For A Duramax? GM mechanic says…


Working on a Duramax is not for the faint-hearted, but you already know that. I’m a GM-trained technician, and I’ve worked on a ton of Duramax trucks. Most days, I love them, but some days…. aghhh …they make me so grumpy.

The best scanner for a Duramax is the Autel MaxiCOM Mk808. The MaxiCOM performs simple tasks such as reading and clearing fault codes, resetting service intervals, codes injectors, keys, performs relearn procedures for transmission, throttle, steering angle sensors, codes new batteries, performs DPF regens.

In this post, you’ll learn why I like the Autel MaxiCOM for the Duramax. You’ll also learn some of the common issues I met as a Duramax mechanic working at the dealership.

What You Need From A Scanner

Duramax is a no-nonsense get her done kind of engine, and in my experience, the owners tend to be of a similar build – hard-working, DIY, salt of the earth, no BS, get her done types.

Tools that are up to the job are important. At the dealership, I used the bulletproof GM Tech2 handheld scanners for the older trucks. The newer vehicles used the wireless MDI system.

The old GM Tech 2 scanners were tough, no doubt about it. I witnessed an apprentice test drive a truck with a Tech 2 trailing from the door jam. Nice!

But the problem with the old Tech 2 is they were clunky and slow to use, the new system is great, but it’s a laptop/desktop-based system with a wireless interface and spendy to buy.

The tool I recommend for your Duramax is the Autel MaxiCOM MK808, it’s competent, does almost everything a DIYer needs to do, it’s robust, and is easy to use.

If you simply want to read powertrain fault codes, that’s fine. Autel has a less expensive reader for that too.

But, if you need to go delve deeper and run more sophisticated tests and adaptions, you’ll need a bidirectional scanner.

You can check out all scanners here on the Mechanics tools page.

Why I recommend the Autel

The Autel MaxiCOM has a good range of functionality without costing a ton. I’ve used their tools for years and trust them.

That said the MaxiCOM won’t solve all your Duramax problems. If you are dealing with a more complex problem you’ll need a bidirectional scanner. Bidirectional tools are pro tools and you already know these guys are typically not cheap.

The extra functionality of the pro-type bidirectional tool allows you to operate components from the scan tool, capture live data, and adapt components after fitting.

For most DIYers the Autel MaxiCOM is great.

  • Strong and reliable – I’ve been using Autel products for years and have yet to break one
  • Easy to use – Hook up and finds your vehicle automatically, color touch screen with big big clear buttons
  • Range of functions – It reads codes and live data on all systems not just the powertrain. Resets service intervals, codes injectors, keys, performs relearn procedures for transmission, throttle etc. steering angle sensors, codes new batteries, performs DPF regeneration and a ton of other good stuff.
  • Range of vehicles – Works on nearly all vehicles, new and old and that’s important. It means you can work on multiple family vehicles without buying another scanner.

Common Duramax Problems

The Duramax engine is a serious thought unit, but it does have some weaknesses, and like all motors, it needs love from time to time. In our dealer workshop, the harder working Duramax engines were actually less trouble.

The most problematic Duramax tended to be the barely worked school-run truck. They would typically come in with blocked EGR cooler issues or DPF and SCR sensor issues.

Your Duramax is a great engine, well designed, tested, and fit for purpose. But use caution if tuning the motor. I’ve worked on a few coal burners, and it hasn’t ended well. I’ve stripped motors with cracked pistons and broken cranks. These are expensive failures that could have been avoided. 

Here are some common Duramax problems I would regularly see. Some issues are very common, and as a Duramax owner, you may already be familiar with one or two of them.

The most common failures include:

  • Injector failure
  • Fueling issues
  • Head gasket failure
  • Water pump failure
  • Egr cooler failure
  • Fuel pump failure
  • SCR system faults
  • Manifold faults
  • Engine harness failure

The Autel MaxiCOM will be invaluable when diagnosing and repairing these types of Duramax issues. However, for some, you may need a bidirectional scanner. You can check out the MaxiCOM along with a ton of other tools here on the Mechanics tools page.

Fuel Injector Failure

Fuel injector leaks internal and external. That’s not unusual. Having the tools to diagnose the root cause of the fault is crucial to nailing the repair the first time out. Incorrectly calling failed parts on these trucks can be expensive. A single injector alone can cost $400 plus. 

But not finding a leaking issue can be even more expensive. A leaking injector will dilute the engine oil and possibly cause a catastrophic engine failure.

Running an injector balance rate test is easy with the Autel. The balance rate is a measurement of fuel delivery across all injectors. A significant difference between the cylinders means you likely have an injector issue.

Injector issues are common across the LB7 and LBZ engines.

Fueling Issues

Duramax employs a lift pump, also known as a low-pressure pump, to move diesel from the fuel tank to the high-pressure pump. The fuel filter housing seal lets go and allow air to sneak in, this commonly contributes to fuel starvation.

Water pump failure

Water pump leaks are common, too, across all the engines. Replacing a water pump is a maintenance issue with all engines. But with these big V8s, we need to be careful of overheating the motor, especially when towing.

Faulty fans and dirty, clogged-up radiators are common causes of overheating too.

Head Gaskets Faults

Blown head gaskets especially tuned engines. The gasket commonly fails across the back of the motor at the firewall, where exhaust heat increases gasket stress.

EGR cooler failure

EGR cooler leaks are a motor killer. The EGR cooler can fail to allow coolant to enter the intake and the motor, which doesn’t end well. Keep a sharp eye on coolant levels, investigate coolant loss immediately.

SCR system faults

The SCR (Selective Catalytic Reduction) system is designed to make our world cleaner…well, it certainly made GM technicians a touch grumpier. The system was fraught with issues from NOx sensor failure to DEF fluid freezing, DEF pump, and fluid level sensor failure.

The Autel MaxiCOM, unfortunately, does not command test SCR heater circuits.

Fuel pump failure

High-pressure fuel pump failure is uncommon with the exception of one pump. The Cp4 Bosch pump fitted to LML engines. It’s particularly prone to granding, lack of lube, usually poor quality diesel.

Replacing the pump may not be the end of the expense, metal filings from the pump are distributed throughout the fuel system – rail, injectors and it can cost a packet to put right.

Engine harness failure

The V8 vibration has a knack of chafing the wiring harness loose and eventually rubbing a wire and shorting to chassis ground. Engine bay real estate is tight in a Duramax. Harness rubbing is not unusual as no matter which path a loom takes, it’s never far from a chafing hazard.

Motors that have had significant work seem to be more prone to chafing as looms may not be secured or routed correctly.

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John Cunningham

John Cunningham is an Automotive Technician and writer on Rustyautos.com. I've been a mechanic for over twenty-five years, and I've worked for GM, Volvo, Volkswagen, Landrover, and Jaguar dealerships. My passion is cars. I use my knowledge and experience to write articles that help fellow gear-heads with all aspects of car ownership, including buying advice, maintenance, and troubleshooting.

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