Cold Case #1 {2013 Chevrolet Equinox)

Not every car I do a diagnostic scan on gets authorized for further work but I still have the scan with no follow up. What if I explain what would be the next steps if the steps were made? Contrary to what you may see or hear, a diagnostic scan is not a diagnosis. It is a first step in making the journey to a diagnosis, and repair. Bear in mind, the car is no longer here but I have the scan. 

2013 Chevrolet Equinox 2.4 {186,372 mi}

I have 7 stored engine codes. 

 P0030, P0031, P0053, P0135, P0138, P0300, P0455 are the stored engine codes. 

P0030, P0031, P0053 and P0135 are all indicating a problem with the front O2 sensor heater circuits. That can be tested further by using a scan tool to command the heater circuit on or off and testing for power, ground and resistance at the sensor. Further testing would be based on the results. But we are forming the overall strategy at this time so let's consider the P0138. There we would want to monitor the rear O2 sensor voltage while engine is running and see just what the high voltage actually reads. If it is simply the sensor is indicating a high voltage due to a rich condition it could be related to the front O2 problem causing a loss of fuel control. A look at freeze frame data for the P0138 might also be helpful as this was a snapshot of the conditions present when the code set,. P0300 is a misfire code. What we should do from that is take a look at misfire history in the scan data and see if this is any particular cylinder(s) or spread throughout. If it is several cylinders involved it could also be related to the O2 problem. We also want to inspect the spark plug condition while looking for the misfire problem. Our job during the diagnostic phase is to find the items that are needed so be able to advise the customer of the best course of action. The P0455 would lead me to do an inspection of the EVAP hoses and connections, gas cap, evap vent and purge solenoids looking for any obvious problem. 

At this point we know:

 we need to inspect spark plugs and look for more misfire information

we need to test the front O2 heater circuits

we need to look at an obvious EVAP system problem (an EVAP problem has potential to cause a fuel control problem)

Once we have found and repaired the front O2 problem and misfire problem we can retest the rear O2 voltage to see if it is now good, or address that problem further if it still exists. Also, if the car did require a new front O2 sensor you must do a heater relearn reset so the car can adapt to the new sensor.

That may leave the P0455 for further diagnosis if the problem wasn't found on inspection.

Thanks for reading

Kenny@GGAuto.Repair