The Check Engine light refers to the engine and engine performance / emissions problems. The yellow ABS light refers to the optional anti-lock brake system. Between the two systems, there's over two dozen sensors. Are you saying someone blindly replaced all of them without diagnosing anything? If that is what happened, a whole lot of new variables have been added to compound the problems. If the brake warning light is red, that refers to one of three relatively minor problems, but it will usually trigger the yellow ABS light too since the minor problem could prevent the anti-lock system from performing properly.
The first step with any warning light related to a computer-controlled system is always to have the diagnostic fault codes read and recorded. The people at most auto parts stores will do that for you for free, but there's some things to be aware of. First, many of them use relatively low-cost code readers that only communicate with Engine Computers. Once you get those code numbers, you can go here:
https://www.2carpros.com/trouble_codes/obd2/p1700
to see the definitions, or I can interpret them for you. If they are able to retrieve Anti-Lock Brake system fault codes, I can look up those definitions for you.
The second thing to be aware of is the people at auto parts stores are in the business of selling parts. No diagnostic fault code ever says to replace a part or that one is defective. If a sensor or other part is referenced in a fault code, it is actually the cause of that code only about half of the time. This is why you'll often read that someone replaced a sensor two or three times and the fault code keeps coming back. Fault codes only direct us to the circuit or system that needs further diagnosis. First we have to rule out wiring and connector terminal problems, and mechanical problems associated with the part before we spend a customer's money on that part.
Once you've written down the fault code numbers, ask to have them erased. That will turn off the warning lights for now. Some of those codes could have set in response to replacing sensors. We want to see which of those codes comes back later.
You can sometimes get a general idea of what's being detected by when the warning lights turn on. Both should turn on for around six seconds when you turn on the ignition switch, as a bulb check during the computers' system self-check. The lights will go off after that six seconds. If one of them turns back on right away, it suggests a wiring problem or defective sensor has been detected. If the yellow ABS light turns on only after the vehicle starts moving, a mechanical problem related to that sensor is the better suspect. If the Check Engine light turns on after driving for a few minutes or longer, that much time was needed before the defect showed up or it took that long before the computer initiated one of its system checks that it runs without you knowing.
The severity of the problem can be measured by observing if and when the Check Engine light goes off. With intermittent problems, if it's very minor, it will go off while you're driving, and only turn back on if the problem acts up again. If it's a little more severe, even if the defect clears up momentarily, the light remains "latched" on for the rest of that drive cycle. It will turn off when you turn the ignition switch off, then restart the engine. For more serious defects, the Check Engine light is on any time the engine is running, even if the problem hasn't acted up in some time.
The most serious is when the Check Engine light is flashing. That means you must stop the engine as soon as it's safe to do so. Too much unburned fuel is going into the exhaust system where it will burn in the catalytic converter, overheating and destroying them. That's a very expensive repair if you keep driving that way.
A common misconception is there's no diagnostic fault code(s) to be read if the Check Engine light is not on. In fact, the Engine Computer can detect and set fault codes for over 2,000 things. Only about half of them refer to things that could adversely affect emissions. Those are the codes that turn on the Check Engine light. The other codes can be set, and are vital for telling us where to start the diagnosis, but the Check Engine is not turned on for those.
Let me know when you have the fault code numbers, then we'll figure out the best course of action.
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Thursday, October 20th, 2022 AT 6:40 PM
