P21B3

P21B3-CLOSED LOOP NOX ABSORBER CONTROL AT LIMIT - TOO HIGH

For a complete wiring diagram, refer to the Wiring Information.

- When Monitored:
Must be in DeNOx mode and must have initiated closed loop control fueling for three seconds.

- Set Condition:
If the time duration after an active soot regeneration is requested exceeds a calibrated threshold and the Diesel Oxidation Catalyst inlet temperature has not reached the light off temperature threshold to begin closed loop control.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1.

NOTE: If there are any DTCs present for the MAF Sensor, EGR Valve, EGR Airflow Control Valve, or EGR Cooler Bypass Valve, repair those DTCs before proceeding.
CHECK THE MAF SENSOR
1. Ignition on, engine not running.
2. With the scan tool in Sensors, read the Mass Air Flow sensor.

Does the Mass Air Flow sensor read 0 +/- 2lb/min?

Yes

- Go To 2

No

- Replace the Mass Air Flow Sensor.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

2. CHECK THE EGR AIR FLOW CONTROL VALVE
1. Verify operation of the EGR Air Flow Control Valve.

NOTE: Repair any EGR Air Flow Control Valve DTCs that are present before continuing.

Does the EGR Air Flow Control Valve operate normally?

Yes

- Go To 3

No

- Perform the appropriate repair.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

3. CHECK THE THERMOSTAT OUTLET
1. Remove the EGR Outlet Temperature Sensor from the thermostat outlet.

Is the outlet free of debris?

Yes

- Go To 4

No

- Remove debris from outlet.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. CHECK FOR EGR CROSSOVER TUBE RESTRICTION
1. Remove EGR Crossover tube from EGR Cooler and EGR Valve.
2. Inspect tube for restriction.

Is the EGR crossover tube restricted?

Yes

- If possible, clean the tube. If not, replace the tube.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 5

5. CHECK THE EGR VALVE
1. Check the EGR Valve for binding or excessive soot build up.

Were any problems found?

Yes

- Clean or replace the EGR Valve.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 6

6. CHECK THE EGR COOLER BYPASS CONTROL VALVE
1. Verify operation of the EGR Cooler Bypass Control Valve.

NOTE: Repair any EGR Cooler Bypass Control Valve DTCs that are present before continuing.

Does the EGR Cooler Bypass Control Valve operate normally?

Yes

- Go To 7

No

- Perform the appropriate repair.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

7. CHECK THE FUEL DELIVERY SYSTEM
1. Perform the CHECKING THE FUEL DELIVERY SYSTEM diagnostic procedure. Checking The Fuel Delivery System

Were any problems found with the fuel system?

Yes

- Perform the appropriate repair.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 8

8. CHECK FOR EGR COOLER FOULING
1. Remove and inspect the EGR Cooler for excessive soot fouling.

Was the EGR Cooler found to be fouled?

Yes

- Clean the EGR Cooler with approved Mopar EGR System cleaner. Determine the root cause of the excessive soot build up.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 9

9. CHECK THE INJECTOR RETURN FLOW
1. Injector Return Flow Test

Does the injector drainage meet the test specification?

Yes

- Replace the NOx Absorbing Catalyst.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Repair cause of high Fuel Injector leakage.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.