PACCAR PX-9 CM2350 (2013-17) Fault Code:3543 PID:SID 115 SPN:4094 FMI:31 NOx Limits Exceeded Due to Insufficient Reagent Quality – Condition Exists

Reason:
NOx Limits Exceeded Due to Insufficient Reagent Quality – Condition Exists. The diesel exhaust fluid quality is not sufficient enough to provide adequate NOx reduction.

Effect:
Possible reduced engine performance.

Circuit Description:
The engine control module (ECM) monitors the NOx concentration in the engine’s exhaust gases using an aftertreatment intake NOx sensor and an aftertreatment outlet NOx sensor. By comparing these two values, the ECM is able to determine the conversion efficiency of the SCR catalyst and dosing system.

Component Location:
The SCR catalyst is located in the vehicle’s exhaust system, after the diesel particulate filter and decomposition tube.

Conditions for Running the Diagnostics:
This diagnostic runs after the diesel exhaust fluid tank has been refilled. Specific engine and aftertreatment conditions must be met. NOx sensor data is gathered over varying engine speeds and loads. When enough data has been gathered, the diagnostic will run, make a pass/fail decision, and begin to gather data again.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the NOx conversion across the SCR catalyst was less than expected, and the diesel exhaust fluid tank has recently been refilled.

Action Taken When the Fault Code is Active:
1) The ECM illuminates the amber CHECK ENGINE lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
2) Engine torque will be severely reduced.

Conditions for Clearing the Fault Code:
It is necessary to use the “Reset All Faults” command in INSITE™ electronic service tool to clear this fault and extinguish the amber CHECK ENGINE lamp and/or Malfunction Indicator Lamp (MIL).

Shop Talk:
Troubleshoot all other active NOx sensor and SCR dosing system related fault codes before this fault.

Possible Causes:
1) Malfunctioning diesel exhaust fluid dosing system
2) Exhaust system leaks
3) Malfunctioning SCR catalyst
4) Degraded, diluted, or incorrect diesel exhaust fluid
5) Diesel exhaust fluid deposits in the decomposition tube