Code P20b9 and “service exhaust system” warning on

Tiny
CHARLIE1229
  • MEMBER
  • 2015 GMC SIERRA
  • 6.6L
  • V8
  • TURBO
  • 4WD
  • AUTOMATIC
  • 42,000 MILES
Will installing a new DEF heater resolve this issue or is there other steps I should look into first?
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Thursday, November 7th, 2019 AT 7:28 PM

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Tiny
JACOBANDNICKOLAS
  • EXPERT
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
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Friday, November 8th, 2019 AT 6:15 PM

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