The DEF light is the one that turns into a derate if you ignore it. We come to the truck, test what’s actually in the tank, check the pump, heater and sensors, and fix it there if it can be fixed there. Available 24/7, call (403) 969-3600.
Roadside diagnosis
DEF tested before anything is replaced
Refractometer and laptop on every service truck
What’s in the tank
Bad fill, frozen line, or a sensor that’s lying
Fix the fluid first
Here’s the thing about DEF. It’s two-thirds water, it freezes at minus eleven, and it goes off if it sits in a jug in the cab for a season. So before anybody talks about replacing a pump, we check the fluid. A refractometer tells us in ten seconds if the concentration is right. Wrong concentration or contaminated fluid, we drain it, flush it and refill with fresh, and a lot of the time that’s the whole job.
If the fluid’s fine, then it’s the hardware. The tank header holds the heater, the level sensor and the quality sensor in one unit, and when the heater fails the fluid stays frozen and the pump can’t draw. On some trucks the header comes out from the top. On others the tank has to come off, and that’s a shop job we’ll tell you about on the phone, not after the drive.
DEF system
From the fill neck to the doser. If it’s on the DEF side of the truck, we’ve probably had it apart on a shoulder somewhere.
Refractometer test, then drain and refill if the fluid is off. The most common fix and the cheapest one.
Heater test in cold weather, header replacement where it comes out from the top without pulling the tank.
The ones that make a full tank read empty. Replaced where accessible, faults cleared and re-checked.
Pressure test, filter, and pump replacement when it isn't building pressure.
Crystallized or stuck doser cleaned or replaced, lines checked for the blockage that got it there.
It happens on night shift with two blue caps. Don't start it. We drain the system and check what it reached.
Live Dispatch Desk
Call before the derate does. Tell us the message on the dash and where you last filled DEF.
Clear Answers
Usually, yes. Nine times out of ten it’s the level or quality sensor in the tank header, or fluid that’s gone off. We test the fluid first, then the sensor. If the header has to come out and the tank has to come off to do it, that’s a shop, and we’ll tell you before we leave the yard.
No. Frozen DEF is normal and the truck expects it. The problem is when the heater doesn’t thaw it. If the light stays on after twenty minutes of running in the cold, the heater’s probably done and the derate will follow.
Don’t start it. If you already have, shut it off. Diesel wrecks the pump and the doser and can get to the catalyst. Call us, tell us how much and whether it ran, and we’ll come drain it.
Yes, with the laptop, after the fault’s gone. Clearing the code without fixing the DEF just gets you a few kilometres before it’s back.
