DEF Tank Heater
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The Problem: P20BA (Reductant Heater A Control Circuit
Performance)- My F250/F350 is in limp mode. When this code occurs, you will notice that the truck is in reduced power mode or limp mode. Although you can drive with this code on, this is something that should be fixed relatively quickly. We typically see this code come in in colder conditions as your DEF fluid is compromised of 67.5% de-ionized water and 32.5% urea. When the temperature drops below 35 degrees, this heater turns on to keep the def fluid from freezing. If your heater is operating properly it won’t be able to thaw out your fluid. If this happens your truck may go into a speed-reduced power mode. If this happens your speed will be limited to 50MPh after 100 miles of driving eventually dropping your maximum speed to 5MPh. Should this happen, drive to your nearest diesel repair shop and have the problem fixed. Our recommendation is that if you go beyond the 100-mile limit, do not turn the truck off until you’re ready to leave it where it's parked. In most cases, the truck will not limit your speed to 5MPH until the truck is restarted.
The Fix: In most cases replacing your DEF tank heater assembly will fix this problem but in cases where more than 1 code is present, you will need to test the DEF tank harness & the harness to the GPM (Glow Plug Module) to confirm it is still in good working condition. This process typically requires a multimeter where you are able to test each wire from pin to pin. This will require some electrical knowledge. We recommend leaving this repair (def tank heater and harness) to the professionals. Some of the things to watch for if you do plan to do this repair yourself:
o These components and connectors are very fragile. Most commonly the def pump injector nipple will break off if you aren’t careful with it. Should this nipple break you’re looking at replacing a 500$ pump. Our recommendation here is to spray out all connectors with brake parts cleaner to loosen things up. Make sure to wear eye & hand protection while doing this.
o Make sure and pressure wash your tank assembly off before removing any of the components. Should dirt or debris get into your tank it could clog your DEF injector line or DEF injector thus causing more headaches and issues with your DEF system down the road.
o Make sure that your fill and return lines are not kinked where they bend at the tank or over the frame rail. Make sure if you remove these lines (recommended) that you re-install them in the exact same fashion and position they came off in. A good way to ensure this is by marking the location of the line on the tank and the line itself to ensure it’s installed the same way.
o The large gray plug is in a bad position and can be difficult to re-install. Take your time with it and make sure that the connector is cleaned out on both ends to ensure it is clipped back in. When removing the connector for the first time, a straight pick tool may be helpful as it is a sea-saw-style clip. This means that you can simply pry upward on the retainer to pull the 2 apart rather than pushing on the opposite end of the clip to get them to separate.