PACCAR Fault Code P3969: NH₃ Sensor – Internal Error

Code details

Manufacturer

PACCAR (Kenworth & Peterbilt)

Applies to

PACCAR MX-13 (2013–2016)

Fault code

P3969

J1939 SPN

5848

FMI

4 — Voltage below normal, or shorted to low source

Truck models in source

Kenworth T680, T880, W900, T800; Peterbilt 579, 389, 567, 367

What to do next

• Read active and inactive codes with the OEM service tool and note the occurrence count.
• FMI 4 tells the shop the type of failure to test for: voltage below normal, or shorted to low source.
• Have a heavy-duty diesel technician confirm the fault against the engine or chassis service manual before replacing parts.

Related fault codes

• PACCAR Fault Code P3969 — EAS-4 Sensor Power Supply – Voltage Too High or Short Circuit to Supply on ECU (D442) Pin (14)
• PACCAR Fault Code P3811 — Heater Element PM Sensor – Voltage Too High or Short Circuit to Supply, Low Side
• PACCAR Fault Code P3815 — Heater Element PM Sensor – Voltage Too Low or Short Circuit to Ground, Low Side
• PACCAR Fault Code P3821 — Sensor Circuit PM Sensor – Voltage Too High or Short Circuit to Supply
• PACCAR Fault Code P3951 — CAN Communication – Timeout From DEF Quality Sensor
• PACCAR Fault Code P3955 — Exhaust Gas Temperature Before DOC – Data Valid But Too High
• PACCAR Fault Code P3962 — DEF Quality – DEF Concentration Too High
• PACCAR Fault Code P3963 — DEF Quality – Abnormal Rate of Change