by Gary Hixson

Diagnosing complex vehicle issues is a common challenge these days for service professionals. One issue you probably encounter frequently is the vehicle that arrives with the check engine light on and several different DTCs present when you test it with your scan tool. What is your strategy in that situation?

There’s no doubt that with different vehicle systems being connected in new ways, diagnostics is getting more complicated. When you encounter multiple DTCs, how can you quickly determine which one to diagnose to get to the root cause of the problem? With so many components and systems on newer vehicles, you clearly need to avoid replacing every part the DTCs suggest might be faulty.

You probably turn to your repair information software to research the DTCs and see if a logical solution pops out at you. Drilling down to the correct component is often a process of elimination. Many technicians take the opposite approach and clear all the codes, drive the car to see which code comes back, and then diagnose that. This can be risky, as an intermittent problem may exist, or specific vehicle operating conditions may need to be met to expose the problem that caused the other codes to set.

We recently introduced ProView in ProDemand, a new feature that helps with this type of scenario. It’s another way of looking at DTC information that shows all the combinations of components that have ever been associated with the code (or codes) in our system. This allows you to quickly see the most commonly repaired components and plan a diagnostic strategy to resolve the problem.

To demonstrate the benefit, let’s walk through a real-world example. Imagine that a 2001 Chevy Tahoe pulls into your bay with the check engine lamp on and a couple DTCs – a P0442 (EVAP system issue) and a P0155 (HO2S voltage issue). You’ve cleared the codes and the P0442 has come back.

Starting with that code, ProView tells you that possibilities include the EVAP canister, fuel pump, EVAP purge solenoid valve, etc., but the most common culprit is the gas cap. However, the picture changes when you add the P0155 to the mix. You see that historically when those two codes are present together, the oxygen sensor is at fault (see figure at right). This would probably not have been the first thing you looked at when starting your diagnostic process.

The intent is not to imply that this is always going to be the definitive diagnosis. The oxygen sensor might not end up being the problem for this particular vehicle, but having this insight guides you in a direction that you can then validate with a guided component test.

SureTrack, the diagnostic module in ProDemand, is powered by millions of “Real Fixes” based on actual experiences and repair orders from professional technicians. SureTrack offers helpful tools like the guided component tests mentioned above, along with a library of more than 750,000 waveform and parameter identification (PID) graphs to help you troubleshoot a code or symptom with a diagnostic scan tool.

Other features in ProDemand that help save time on diagnostics include advanced 1Search™ technology that delivers verified real-world fixes together with OEM data, and a Top 10 Repairs List that displays detailed information about the most common component failures, DTCs, symptoms and lookups for the vehicle you’ve selected.

Whether you’re facing multiple codes or a “mystery” symptom, it’s good to know you can rely on your repair information to guide you in the right direction to an accurate diagnosis and successful completed repair.