Ammonia Odor From Tailpipe?

Keith Browning · July 23, 2015

A 2013 F550 6.7L came in. Complaint was that there was a strong ammonia odor that the two municipal "workers" reportedly became light headed and sick. I never verified the odor. These guys reportedly took a trip to the local ER and the Hazmat team was called in... their sniffers detected nothing.

I verified that the DEF was good. Then I pulled DTC P20EE from the PCM and replaced the NOx sensor then performed a manual regen as the DPF was 95% full. I wanted to make sure the aftertreatment system was clean and working 100% before releasing this truck back to the town.

I am not necessarily calling bullshit here but do you think it is possible for the system to load up the SCR with DEF and cause an ammonia odor? I am thinking it is possible. This happened on a 95 degree day with high humidity as well.

Bruce Amacker · July 23, 2015

I'd probably also check the reductant injector for leaking/flow test like in the WSM/IDS. Some other vehicles (Dodge Cummins, maybe?) have an ammonia sensor in addition to the other sensors, I'm not sure what it's used for but to prevent odor might be the idea.

:grin:

Keith Browning · July 23, 2015

A DEF pump line or injector issue would likely set a code.

Cummins runs with a NOx and a NH3 sensor at the SCR outlet. I need to look this up in my training materials but I think its going to be required in the future. My memory is a little fuzzy but the NH3 sensor can check the SCR efficiency but I recall something about excessive heat converting the gasses back into NOx and NH3 under certain conditions... or something *like* that. :scratch:

cbriggs · July 24, 2015

I had a friend of mine complain about an ammonia type odor from his 2012 last year. I verified it, at idle it smelt heavily of a chemical of some sort from the tailpipe. No codes were present, I told him to try a different kind of def for his next fill, and never heard back from him. I did replace the def pump on it a few months later for a low pressure concern/ code, not sure if it was at all related.