Will installing a new DEF heater resolve this issue or is there other steps I should look into first?
Nov 7, 2019 at 7:28 PM
Code P20b9 and “service exhaust system” warning on
2015 GMC SIERRA
CHARLIE1229
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Hi:
I believe that code is related to the DEF system running it's own self test and not the heater. Try this. An onboard test must be commanded using a scan tool. A fluid quality test or a forced REGEN will make the monitor run and the messages should clear and the system should return to normal. Basically, you need to force a fluid quality test using a scan tool.
Try this and let me know if it helps.
Joe
I believe that code is related to the DEF system running it's own self test and not the heater. Try this. An onboard test must be commanded using a scan tool. A fluid quality test or a forced REGEN will make the monitor run and the messages should clear and the system should return to normal. Basically, you need to force a fluid quality test using a scan tool.
Try this and let me know if it helps.
Joe
Nov 8, 2019 at 6:15 PM