The General has published a service advisory outlining a solution for some 2021 Cadillac CT4
small luxury sedans that may be impacted by an inaccurately calibrated Engine Control
Module (ECM) that is possibly unable to detect and/or identify catalytic converter issues.
In certain situations, wireless over-the-air upgrades may appropriately recalibrate
the ECM software without requiring dealer repair, however potentially impacted 2021
Cadillac CT4 cars should still be checked to confirm the issue has been resolved.
If there is a defect or failure in the car's catalytic converter in 2021 Cadillac CT4 units
with an inaccurately calibrated Engine Control Module, many difficulties may occur.
The ECM may fail to identify the defect by not lighting the Check Engine light,
may diagnose the catalytic converter problem inaccurately, or may fail to establish
Diagnostic Trouble Codes (DTCs) so that diagnostic procedures do not discover the error.
This issue only affects Cadillac CT4 cars powered by the turbocharged 2.0L LSY I4 gasoline engine,