I just replaced the reservoir heater in my DEF tank on my 2014 Silverado. The check engine
light is off but the "service exhaust
fluid, speed reduced to 4MPH" will not reset. Is there a manual way to reset it or how do I get the warning to reset?
JA: Diagnosing the correct check engine code is the key to getting a quick fix. Fortunately, the mechanics we work with have tons of experience dealing with this type of thing. Are you hoping to fix this yourself?
JA: Great! What have you tried so far?
Customer: I had a P21DD code and replaced the reservoir heater. The engine light is now off. I drove the truck for about 10 miles to see if it would reset itself like it normally does. It didn't. Now I'm down to 5 miles before going to 4MPH.
JA: Is there anything else important you think the GM Mechanic should know about your GM?
Customer: 125,000 miles on it. Never had a mechanical problem of any sort.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the GM Mechanic about your situation and then connect you two.