Oxidation Catalyst Efficiency Below Threshold
The BOBCAT-P0420 (Bobcat) diesel fault code means: Oxidation Catalyst Efficiency Below Threshold. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- advanced
- Estimated cost
- $1,500-$4,500
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Common Symptoms
- DPF regen more frequent
- Slight power reduction
Probable Causes (Ranked by Likelihood)
- DOC substrate aged / contaminated with fuel Likely
- Leaking injector raw-fueling the DOC Possible
Step-by-Step Diagnostic Procedure
Check DOC inlet vs. outlet temperature delta during regen.
Inspect for injector copper washer failure that raw-fueled DOC.
Frequently Asked Questions
What is Bobcat code P0420?
Bobcat P0420: Oxidation Catalyst Efficiency Below Threshold. This code is reported on Bobcat equipment running the described engine family.
Can I keep working with Bobcat code P0420?
Usually drivable short-term, but fix soon to avoid derate or DPF issues.
How much does Bobcat P0420 cost to fix?
Typical repair cost: $1,500-$4,500. Off-road diesel shop labor runs $125-$175/hr in 2026. Dealer diagnostic software (Bobcat Service Analyzer) is usually required.
P0420 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown: