Paccar MX-13 Forced Regen Fails - SCR Efficiency Low Derate

Question

My 2018 T680 is stuck in a 5 mph derate and won't finish a parked regen. It starts the process but kicks out after about 10 minutes with an SCR efficiency error. I'm worried the catalyst is face-plugged or the doser is acting up.

Kevin Tran · Accepted Answer

The issue was a crystallized DEF decomposition pipe and a failing DEF pump filter. I removed the 'L' pipe and chipped out a massive buildup of urea that was blocking the spray pattern. Replaced the DEF pump main filter (Part #2122902PE), performed a forced SCR crystals mutation burn via software, and the efficiency codes cleared immediately. Total cost was about $350 in parts and 4 hours of labor.

Ashley Park · Answer

Check your DEF quality with a refractometer first. If the fluid is old or contaminated, the SCR won't hit the conversion threshold no matter how many times you regen.

Sarah Thompson · Answer

You need to look at the SCR inlet temperature. If the DOC is fouled, you won't get enough heat to the SCR brick to satisfy the efficiency monitor during the test.

obd2_owl · Answer

Run a DEF dosing quantity test using DAVIE software. You might have a weak DEF pump that isn't maintaining the required 9 bar of pressure under load.

Paccar MX-13 Forced Regen Fails - SCR Efficiency Low Derate

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