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2022 Ram 2500 Cummins - DEF Light and Reduced Power Mode

0

Mark S. · rep 0 · May 22, 3:36 AM · 1 replies · solved · Question

Vehicle: 2022 Ram 2500 Laramie 6.7L Cummins

Help! My 2022 Ram 2500 Laramie with the 6.7L Cummins just threw a 'Service DEF System' warning, followed by a Check Engine Light, and now it's in reduced power mode. I just filled the DEF tank last week, so I know it's not empty.

I'm currently on a road trip, and this is really inconvenient. What could be causing this? Is there anything I can check myself before I find a dealer? I'm worried about getting stranded.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:36 AM

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ClearTheCode admin answer:

Experiencing a 'Service DEF System' warning and reduced power mode on your 2022 Ram 2500 Cummins is a common, albeit frustrating, issue often related to the Selective Catalytic Reduction (SCR) system.

  1. Common Causes:
    • Faulty DEF Quality Sensor: The sensor might be misreading the DEF concentration or detecting contamination.
    • Clogged DEF Injector: Crystallization of DEF can block the injector, preventing proper atomization into the exhaust stream.
    • NOx Sensors: Malfunctioning upstream or downstream NOx sensors can trigger these warnings as they monitor exhaust gas composition.
    • DEF Heater Issues: In colder climates, a faulty DEF heater can prevent the fluid from thawing, leading to system errors.
    • Wiring/Electrical Issues: Damaged wiring or connectors to any DEF component can cause intermittent or persistent faults.
    • Contaminated DEF: Even if recently filled, using old, expired, or contaminated DEF can quickly lead to system issues.
  2. Relevant OBD Codes: When these issues arise, you'll typically see diagnostic trouble codes (DTCs) such as:
    • P20EE: SCR NOx Catalyst Efficiency Below Threshold
    • P207F: Reductant Quality Performance
    • P20E8: Reductant Pressure Too Low
    • P20BA, P20BD: Reductant Heater Control Circuit issues
  3. What You Can Check:
    • DEF Cap: Ensure the DEF cap is securely tightened, as a loose cap can sometimes cause issues.
    • Visual Inspection: Look for any obvious leaks around the DEF tank, lines, or injector area.
    • DEF Quality: If you have access to the DEF container, verify it's not expired and from a reputable source.
  4. When to See a Shop: Given that your truck is in reduced power mode and you're on a road trip, it's highly recommended to get it to a Ram dealer or a reputable diesel mechanic as soon as possible. Driving extensively in reduced power mode can be detrimental and might not resolve itself. A professional shop has the specialized diagnostic tools to accurately pinpoint the fault within the complex DEF system and perform necessary repairs, which often involve sensor replacement, injector cleaning/replacement, or software updates. Ignoring these warnings can lead to further damage and potentially leave you stranded.
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