GM has released a service update for certain units of the 2020 GMC Sierra 1500, 2021 GMC Sierra 1500, and 2022 GMC Sierra 1500 Limited over an issue related to the pickups’ heater auxiliary coolant pump.
The problem: units of the GMC Sierra 1500 affected by this issue are equipped a manual HVAC system (RPO code CP4) and HVAC Control Module (RPO code K33), the latter of which may not activate the auxiliary coolant pump during an engine auto stop event. The pump is required to maintain cabin heater temperature.
The hazards: this particular issue does not pose a safety hazard. That said, it may affect passenger comfort.
The fix: GM technicians are instructed to reprogram the HVAC Control Module with updated software to correct the issue.
Affected components: HVAC Control Module (RPO code K33).
- 2020 GMC Sierra 1500
- 2021 GMC Sierra 1500
- 2022 GMC Sierra 1500 Limited
Number of affected vehicles: it’s unclear how many vehicles are affected by this GM Service Bulletin.
Owners should: GM will notify owners of affected vehicles and advise them to make an appointment with their local dealer in order to correct the issue. Owners who are unsure if their vehicle is affected by this service bulletin can reach out to GM directly with questions or concerns by using the Service Update number and contact information listed below.
- Service Update number: N222375000
- GMC Customer Service: 1-800-462-8782
As a reminder, the 2020 GMC Sierra 1500, 2021 GMC Sierra 1500, and 2022 GMC Sierra 1500 Limited were offered with a wide range of powerplant options. Among these is the atmospheric 4.3L V6 LV3 gasoline engine, turbocharged 2.7L I4 L3B gasoline engine, atmospheric 5.3L V8 L82 gasoline engine, atmospheric 5.3L V8 L84 gasoline engine, atmospheric 6.2L V8 L87 gasoline engine, and 3.0L I6 LM2 turbodiesel Duramax engine. Under the skin, the GMC Sierra 1500 rides on the GM T1 platform.