Is there really a good reason to pay an automotive shop to have your check engine light diagnosed? If you Google “check engine light” you can find a lot of advice recommending you simply go to a local parts store, some of who will “scan” the code in the computer for free. Sounds like a good deal but is it really?
The problem I have with this method is that what you will get is a code number and a description of the code. For us technicians, the code leads us to further testing where we prove what is really wrong so that we can guarantee our repair and know that the check engine light will not come back on. The parts store might sell you the part that is mentioned in the description text, with the warning that it may or may not fix the problem. (I have to give them credit, it’s a great way to increase sales!)
For example, I once had a customer go to a parts shop and pull a code that read “EGR system low flow”. They suggested a likely cause was a defective EGR solenoid, and that they had one the shelf that cost about $350. My customer declined buying the part and instead came to me to have it diagnosed. The reality was that the EGR solenoid was a possible cause. What we found was that the EGR hose had come off the valve and this was the cause of low flow. In this case the cost of diagnosis and repair was less than the cost of the recommended part.
Another example is code P0174 – oxygen sensor stuck lean bank 2. The oxygen sensor could be defective, but it could also simply be responding to something as simple as a leaking vacuum hose and be stuck lean for that reason. Replacing the oxygen sensor in this case will result in the light coming on again with the same code.
Don’t misunderstand me, I think its fine to work on your own car. In fact it’s how I got started in this business as a young person. You must simply accept the fact that there is a learning curve and you may replace perfectly good parts accidentally. The key is that to learn how to fix a system, you must first learn how the system works. We do not yet live in a world where an inexpensive code reader will tell you what part to replace with any degree of certainty.
Brons Automotive has been repairing the true cause of why check engine lights come on for years in Olympia, Lacey, Tumwater, and Thurston County and backs their work with a 2 year/24,000 mile warranty.