Simple Diagnostic Tricks to Keep Work in Your Bays

By Vanessa Attwell for Motor Age Magazine

Even though newer vehicles can be complicated to diagnose and repair (and very expensive to misdiagnose) it’s still very possible – and often profitable – to do the work yourself rather than send it along to the dealership to be fixed.

True, dealership technicians often have access to special tools and help from technical assistance centers to make diagnosing and repairing challenging problems easier, but quite often seemingly complicated problems can be repaired successfully without going to the dealership by using a good scan tool, detailed service information and with vehicle-specific wiring diagrams, if you’ve prepared for the challenge and done a bit of research beforehand.

It is possible and people do it successfully every day.

Yes, it’s complicated, but it’s still quite possible to repair many problems yourself rather than sending a vehicle off to the dealership to be fixed. (Photo source: Motor Age)

Obviously that doesn’t mean it’s a good idea to just open the hood and start stabbing connectors wildly, hoping for the best – in fact, quite the opposite is true. Understanding how possible problems could develop in a system and then understanding what it takes to fix them is now more critical than ever. For example, some newer high-end vehicles will need to have every single one of their modules reprogrammed if the vehicle’s battery goes dead, which can take hours. Yikes! So knowing what you’re getting into is critical to keep work on track and problem-free.

But if you’re facing a diagnostic challenge, and you’ve got a systematic plan of attack, good diagnostic tools and a few clever tricks at your disposal, you may well be able to diagnose and repair the vehicle right in your own bay – profitably and without undue stress or aggravation.

Here are a few tips to help out along the way.

Preliminary checks

True, there are times when sending a vehicle to the dealer is the smartest move – for example, when a special tool is needed, and you rarely service that type of vehicle so it’s not worth purchasing it or getting involved at all – that’s an easy situation to pass on.

But in other cases such as failed emission tests, MIL lights illuminated or communication issues on relatively common vehicles, it’s wise to check a few things before passing on the job. Even a 10-minute inspection can be well worth the trouble.

For example, a minivan came in with an airbag light on and a code stored indicating a problem with the passenger seat sensor. Quickly inspecting the area revealed a water bottle had been jammed underneath the seat, pressing upwards on the sensor, which created a negative pressure signal and set the code. Removing the stray bottle solved the problem. Easy.

In another instance a small, high-end import came in for a complaint of no power on acceleration. A quick check revealed a rodent’s nest in the air filter compartment (a common event for farm vehicles, but this vehicle was always parked indoors at a downtown condo). No sign of the critter, but clearing out the nest and installing a fresh air filter fixed the problem quickly and effectively. Gross, but also an easy fix to complete.

So in other words, it’s worthwhile to quickly ensure there’s no obvious problem with the vehicle before simply closing it up and sending it away. After all, you never know — you may get lucky and find the problem right away.

The tiny warning light on this 2017 Audi A4 Quattro indicates a problem in the forward warning system – part of the pre-collision system. It’s worth having a quick look around before sending this off to the dealer for repair since it might be a simple fix. (Photo source: Motor Age)

In particular, during your inspection ensure that any sensors exposed to the elements are intact (not cracked), securely mounted and free of mud and debris. Since so many newer vehicles have plastic front bumpers that catch on concrete curb stones used in parking lots, this is a fairly common area to find cracked or damaged sensors or mounts that affect system operation. Quickly looking at the front of the vehicle can be well worth the time.

And since poor-quality replacement windshield glass can cause problems ranging from noise and leaks to cruise control malfunctions, it’s worth checking for signs of recent replacement if the problem you’re chasing is related to systems that use sensors or cameras in that area. Unfortunately however, fixing the problem involves replacing the windshield again, using parts that won’t interfere with the system operation – not likely something the customer is going to want to hear.

Also look for any recent repairs including any suspicious-looking replacement parts or harnesses routed at extreme angles that just don’t seem right. If the repairs weren’t done correctly or poor-quality replacement parts were used (or wrecker parts that don’t quite match the system or vehicle) that may indeed be the cause of the troubles. Newer vehicles have very strict tolerances and even tiny differences can affect system operation.