We had a customer come in with a 2003 Mercury Sable that had an engine randomly stalling. The customer would be waiting at a light and the engine would randomly shut off. We started by scanning the power train control module to see if there were any codes.
Misleading Engine Codes
We found a check engine code for the coolant temperature sensor. It had a fault for voltage too high. In these cases most people would assume that the sensor went bad and all we have to do is change the sensor and problem solved!
Proper Diagnosing > Guessing and Throwing Parts
Now that we had the coolant temperature sensor fault we have a lead to further investigate! We now need to test and confirm that the coolant temperature sensor is indeed bad. We check the voltage readings and it read fine.
So we proceeded to check the wiring as NYC has a rat infestation problem and we have seen many cars get check engine lights for chewed up wires.
The wires visually looked okay, but we decided to take a deep dive. While reading the signal off the coolant temperature sensor we jiggled and strained the wires that connected to the sensor. Then we found that the reading from the senor jumped all over the place, and caused the engine to stall!
Why Proper Diagnosing is Important!
After confirming that indeed the wiring had gone bad we were able to replace the wiring and connector. If our shop would not have taken the proper steps to diagnose the issue, the coolant temperature sensor would have been changed and the customer would still have the same engine stalling problem!
This is a perfect example as to why connecting a scanner and pulling codes is all mechanics do. A proper technician pulls codes to have a direction in which to start diagnosing. Once we have an idea of what the issue may be we then have to test the components and replicate the customer’s complaint. Once we can effectively replicate the problem and tested the components in question then we can proceed with the repair. This is also why there is a diagnostic fee for scanning and running tests on the vehicle. Proper diagnosing takes specialized tools and years of experience.
If you have an Asian, Domestic, or European vehicle in need of diagnosing, maintenance, or auto repair feel free to Contact Us @ Tolima’s Auto Center !
Here you can see a video about how we diagnosed the issue with this 2002 Mercury Sable!
