Servicing Check Engine Light Conditions on 2020 Models

GM requires that technicians document the causal Diagnostic Trouble Code (DTC) that leads them to a vehicle warranty repair. The DTC is to be documented in the “Cause Comments” section of the repair order (job card), along with any other diagnostic results. The cause comments from the technician are uploaded with the warranty transaction to GM and help quality engineers understand what repairs are being performed to vehicles and why.

For the 2020 model year, documenting the correct causal DTC and clearly identifying it on the repair order is increasingly important as the DTC will help a dealership’s service team identify proper warranty coverage on the following models:

  • 2020 Chevrolet Corvette
  • 2020 Cadillac CT4
  • 2020 Cadillac CT5

The new Corvette, CT4 and CT5 operate on GM’s Next Generation Digital Vehicle Platform. With the new architecture, there are several vehicle components that are referred to as mixed-use parts, which means they control both emissions-related (Fig. 19) and non-emissions-related features on the vehicle. Therefore, depending on the malfunction of that part, warranty coverage may be emissions warranty related, or it may not.

Fig. 19

Mixed-Use Components on 2020 Corvette, CT4, CT5

  • Body Control Module
  • Blower Motor
  • Heating and Air Conditioning User Interface Control
  • Transmission Control
  • Ride Control Switch
  • Battery Monitor Module / Intelligent Battery Sensor
  • Vehicle Stability Control System Switch
  • Evaporator Air Temperature Sensor
  • Programmable Temperature Value Actuator

Validating and Diagnosing a Check Engine Light

No Check Engine Light — If there is NOT a check engine light illuminated when the vehicle pulls into the service department, there is no need to do anything differently to help your service team identify warranty coverage. If one of these components is affecting vehicle emissions, it will illuminate the check engine light.

Check Engine Light On — Perform a normal DTC scan. When viewing the DTC Display screen, a new yellow Malfunction Indicator Light (MIL) symbol may be seen next to select DTCs. (Fig. 20)

Fig. 20

After running the DTC scan, follow the diagnostic steps listed in the appropriate Service Information to determine the causal DTC, and document it on the repair order as you normally would.


New Requirement for 2020 Model Year

If the causal DTC was emissions related, identified by the MIL symbol next to the code, document it as part of the repair by printing out the Vehicle DTC Display screen and attaching it to the repair order as an easy method of verification.

Knowing the causal DTC, along with if the MIL indicator appeared next to it in GDS, will help warranty administrators to properly submit the warranty claim. For future claims beyond the Bumper-to-Bumper Warranty (or Canada’s Base Warranty), the causal DTC will also be critical in determining warranty coverage on the repair.

– Thanks to Patti Marino

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