Reductant Heater A Control Circuit Performance
The YANMAR-P20BA (Yanmar) diesel fault code means: Reductant Heater A Control Circuit Performance. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- advanced
- Estimated cost
- $300-$800
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Common Symptoms
- Cold weather DEF system fault
Probable Causes (Ranked by Likelihood)
- DEF tank heater failure Likely
- DEF line heater circuit open Possible
Step-by-Step Diagnostic Procedure
Ohm-test DEF heater circuit.
Check heater fuse and relay.
Frequently Asked Questions
What is Yanmar code P20BA?
Yanmar P20BA: Reductant Heater A Control Circuit Performance. This code is reported on Yanmar equipment running the described engine family.
Can I keep working with Yanmar code P20BA?
Limited operation only -- finish the current task then shut down for repair.
How much does Yanmar P20BA cost to fix?
Typical repair cost: $300-$800. Off-road diesel shop labor runs $125-$175/hr in 2026. Dealer diagnostic software (Yanmar SmartAssist / YDT) is usually required.
P20BA on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown: