RAM Fault Code
Free · no signupP229F
Check Engine Light; DEF/SCR warning on dash; Potential "Speed Limited" countdown (Limp Mode).
System
Cummins 6.7L
Symptom
Check Engine Light; DEF/SCR warning on dash; Potential "Speed Limited" countdown (Limp Mode).
Diagnosis & fix steps
NOx Sensor Circuit Range/Performance (Bank 1, Sensor 2).
LOGIC: The ECM compares the "Inlet" NOx reading to the "Outlet" reading. If the Outlet sensor (Sensor 2) provides data that is physically impossible or "stuck," this code triggers.
ACTION: 1. Check for exhaust leaks near the sensor.
2. Inspect the sensor wiring for melting or chafing.
3. Check DEF quality.
FIX: Replace the Downstream (Outlet) NOx Sensor and its attached control module.
Red Seal field insights
The "Moisture" Trap: NOx sensors are ceramic and run very hot. If you drive through deep water or snow while the sensor is active, the thermal shock can crack the internal ceramic element. Also, check the connector pins for "green crusties" (corrosion); these sensors are low-slung and catch all the road salt.
Same code keeps coming back?
That's a program problem, not a part problem. Book a 30-minute uptime review with Grant, a Red Seal Heavy Duty Technician.
Read before you touch anything
- This is general reference information, not a repair manual. It is for trained, qualified technicians.
- Fault codes, meanings and procedures vary by model, serial number and software version. Confirm the code and the procedure against the manufacturer's service manual before acting.
- Follow the OEM service manual, torque specs and your site's safety procedures: lockout/tagout, block raised equipment, relieve hydraulic, fuel and air pressure, and let hot systems cool.
- You use this information at your own risk. Adventure Mechanical and AM Fleet Integrity accept no liability for damage, injury, downtime or loss arising from its use.
- Not affiliated with or endorsed by any manufacturer. Brand names are used only to identify the equipment a code applies to.
Track this across your whole fleet
This code is free to read. AM Fleet Integrity lets your team log fault codes against assets, plus the full fault-code library, QR operator reporting, PM scheduling and predictive alerts. Start free — no credit card required.
Start your free trialRelated RAM fault codes
- P020FEngine "stumble" or miss; Knocking sound under load; Increased exhaust smoke; CEL on.
- P2563Exhaust brake stays on or won't engage; Poor throttle response.
- P229EMIL (Check Engine Light) & Potential Derate.
- Service Light Indicator
- P226CSlow boost response; Excessive black smoke on acceleration.
- P2262Low power; No turbo boost; "Service Electronic Braking System" message (sometimes).
- P20EE"SCR Efficiency Below Threshold"; Check engine light; Potential DEF derate timer.
- P208DDEF gauge reads empty when full; Service DEF system message; 5 MPH derate.
- P0880No Forward or Reverse / Defaults to 4th
- P0876Erratic Shift Stumble / 4th Gear Limp