PCM Modes of Operations

September 5, 2019


PCM Modes of Operations

by John Forro

Avoiding Typical PCM Pitfalls?

Well, the number one solution would be education. The more prepared you are on the subject the easier it is. Don’t forget to do proper research as well. Make sure you dig deep into the brand of car, common issues, wiring diagrams, how the vehicle is designed, and recent recalls the vehicle may have had. Every vehicle has some setting strategies or a shortcut tied to a power-train control module. These shortcuts are the insights to a quick diagnostic procedure.

Different Modes of Operation

There’s a whole arrangement of different modes of operation, closed-loop, closed-loop, and clear flood mode those are pretty much designed to work the same no matter what the name plate is on the fender of the vehicle. So open-loop is designed so that when you first start the vehicle that has a relatively cold engine it needs to try to get into the closed loop. Meaning the computer is in control of the fuel delivery as quick as possible. In the early days we relied on the exhaust gas temperatures to heat up the oxygen sensor. Nowadays we have heated oxygen sensors so we can obtain closed-loop status relatively quickly ,but notice the components that are displayed on the screen that the computers actually looking at while it’s in the open-loop status.

Changing Perspective

Let’s say there was a drivability problem when the vehicle is first started. The problem could be that the vehicle stalls out, and a inexperienced tech plugs a generic scan tool in because there is a check engine lights on. Now there is a trouble code for a faulty oxygen sensor thus this is where the automotive Common Sense comes in a play! Is the oxygen sensor even being looked at by the computer or does it display an unknown error code? Let’s say the computer sees the oxygen sensor. Maybe the oxygen sensor is bad and you could replace it curing that code; however if the drivability concern was something that was still in the open-loop status that oxygen sensors replacement will not work. This is a drivability complaint and that’s one of the key features that a lot of the younger or inexperienced technicians don’t really understand.

Think before you act

Just pulling codes out and attacking those codes may not always be your best route. Consumers have always complained about how their vehicle has been taken to a shop three or four times already and every visit takes two to three hours. Each of those shops charging them and their at your garage expecting to find another scam. So just think about it, instead of just replacements to their vehicle, find tools and resources to fill the gap in your automotive skills.


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