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Ask Ryan Schott Your Own Question
Ryan Schott
Ryan Schott,
Category: GM
Satisfied Customers: 82
Experience:  technician at Demarois Buick Gmc
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Have a def issue on a 2012 duramax 6. 6 JA: Thanks.

Customer Question

***** ***** Have a def issue on a 2012 duramax 6. 6
JA: Thanks. Can you give me any more details about your issue?
Customer: It wont clear keeps telling me that speed reduced to 55 mph No engine light is on and no faults
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Submitted: 8 months ago.
Category: GM
Expert:  Ryan Schott replied 8 months ago.
What did you fix initially? if you had a DEF heater fault you would have to cycle all heaters with a scan tool for 30 seconds, if it was a fluid quality issue you would have to run a RFQFT with a scan tool. Def codes may not re-run and fail for a while if you cleared it but it will remain in tamper mode until it is repaired and passes certain tests. If nothing was replaced do you know the original fault?
Customer: replied 8 months ago.
Well yes it had a heater problem replaced the heater reservoir and check the rest reasembled unit clear the faults bht the def symbol still blinks in the dash but there is no engine light or anh code faults but the truck is limited to 55 mph
What kind of tool do i need for this besides a scan tool cus y tried it all ready with it unless i need to run it with alldata
Expert:  Ryan Schott replied 8 months ago.
You need a scan tool with bi-directional control of the glow plug control module. Cycle each of the def heaters for 30 seconds. I would run a service regen afterwards but the heater cycles will clear it. I will send you a copy of the tamper procedures in the morning, if you can't get a tool for it you can print that and take it to a GM dealer and show them do this exactly and it should be cheap. Or just hit the back door and offer a tech a 20$ it takes 5 min with a tech 2. But I'll get it sent to you in the morning I suspect most tools can output to the heaters. I have a tech 2 but I will try it with a solus in the morning for curiosity. But the longer you drive the more tamper will cut your speed till you can barely get anywhere and it will get harder to clear.
Expert:  Ryan Schott replied 8 months ago.
heres the normal clearing strategy, i'm looking for that other document about running the heaters but i know you will need to cycle all three heaters.
Customer: replied 8 months ago.
Got the file yoh sent but does not match with the problem i have
Expert:  Ryan Schott replied 8 months ago.
here it is,Repair VerificationNote: The reductant or diesel exhaust fluid (DEF) and ambient air temperatures must be greater than −7°C (19°F) before proceeding with this procedure.Install any components or connectors that have been removed or replaced during diagnosis.Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.Clear the DTCs.Ignition Off, all vehicle systems OFF, this may take up to 2 minutes.Ignition On, command the Reductant System Leak Test On with a scan tool. Allow the pressure to build for 30 s. Observe the scan tool Reductant Pressure sensor parameter. The reading should be between 425–575 kPa and there should be no leaks in the system.Engine idling, command each GPCM Reductant Heater 1, 2, and 3 ON for 10 seconds with a scan tool. If that does not do it follow that first flow chart based on what your initial issue was, i know the warnings are off but they get stuck in reduced power if you don't jump through all of the hoops after the repair. i assume you had one of these codes DTC P20B9-P20BF or P20C0-P20C4
Customer: replied 8 months ago.
Yes the P20B9 this is all done
Customer: replied 8 months ago.
So i guess send it to the dealer
Expert:  Ryan Schott replied 8 months ago.
Sorry, Emissions regulations made them do all this extra tamper warning BS, i wasn't able to do it with a snap on solus but their newer tools might have control over gpcm outputs, but yah a tech 2 is the only guaranteed route.