P1C54

P1C54-SCR NOx CATALYST MISSING

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

Theory of Operation

The after treatment system is equipped with two Nox Sensors and modules. The upstream NOx Sensor 1/1 is located before the SCR Catalyst and is permanently connected to a corresponding Nox Sensor Module mounted on the right frame rail. The downstream NOx Sensor 1/2 is located at the outlet of the SCR Catalyst and is permanently connected to a corresponding Nox Sensor Module also mounted on the right frame rail. The NOx Sensors and NOx Sensor Modules are calibrated to each other and must be replaced as an assembly. The two NOx Sensor and Module assemblies are not interchangeable. The NOx Sensor Modules are smart devices and communicate with the Powertrain Control Module (PCM) over the J1939 Data Link. The NOx Sensor Modules perform their own internal diagnostics and report malfunctions back to the PCM. The NOx Sensors are used to monitor the efficiency of the SCR Catalyst and dosing system. The Powertrain Control Module compares the values of the NOx Sensors to monitor the efficiency of the SCR Catalyst and dosing system. The PCM will illuminate the MIL lamp immediately after the monitor runs and fails.

- When Monitored:
NOx Sensor data is gathered over varying engine speeds and loads. When enough data has been gathered, the monitor will run, make a pass/fail decision, and begin to gather data again.

- Set Condition:
The PCM determines that the NOx conversion across the SCR Catalyst is below expectations.





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

1. OTHER DEF SYSTEM DTCs PRESENT
1. Ignition on, engine not running.
2. With the scan tool, View DTCs.

Are there any NOx Sensor or DEF System DTCs active?

Yes

- Repair all other DTCs before proceeding with this test procedure.

No

- Go To 2

2. CHECK THE DIESEL EXHAUST FLUID
1. Turn the ignition off.

NOTE: Repair any fuel, emissions, or DEF system component DTCs before continuing with this diagnostic procedure.

2. Remove the DEF Filter cap and collect a sample of diesel exhaust fluid from the system.
3. Visually inspect the fluid for signs of contamination or debris.
4. Test the quality of the fluid using litmus paper (supplied by parts) or by using an SPX DEF/UREA Refractometer 94-F-00K-108-456 or equivalent.

NOTE: The diesel exhaust fluid should register approximately 9 ph with the litmus paper and 32.5 percent using a refractometer.

Is the diesel exhaust fluid quality within specification and free of debris and contamination?

Yes

- Go To 3

No

- Drain the diesel exhaust fluid from the tank and fill the system. If the fluid is contaminated, follow the cleaning procedure. Procedures.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

3. CHECK THE DIESEL EXHAUST FLUID SYSTEM FOR EXTERNAL LEAKS
1. Visually inspect the DEF system for signs of external leaks.

NOTE: Diesel exhaust fluid will form white deposits around leaky fittings.

Were any leaks found?

Yes

- Go To 4

No

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

4. CHECK THE EXHAUST SYSTEM FOR LEAKS
1. Visually inspect the exhaust system between the Turbocharger outlet and the SCR Catalyst outlet for signs of loose or leaking connections or damaged components

Were any leaks or damage found?

Yes

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

No

- Go To 5

5. CHECK THE DECOMPOSITION TUBE FOR DIESEL EXHAUST FLUID DEPOSITS
1. Remove the DEF Injector. Diesel Exhaust Fluid Injector - Removal.
2. Visually inspect the Decomposition Tube for signs of diesel exhaust fluid crystals or deposits.

Were any deposits found?

Yes

- Clean the deposits from the Decomposition Tube.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 6

6. CHECK THE DEF INJECTOR
1. Reconnect the DEF Injector harness connector.
2. Place the DEF Injector in a container to capture the fluid sprayed.
3. Turn the ignition on.
4. With the scan tool, navigate to Systems Tests and actuate the Diesel Exhaust Fluid Doser Pump Override Test.

NOTE: This Test will run for six minutes before timing out. The amount of flow may fluctuate through out the test, therefore the test must be allowed to run completely in order for the results to be accurate. The fluid should spray out as a mist. There should be no dripping from the holes in the DEF Injector at any time during the duration of the test procedure.

5. Measure the amount of fluid sprayed after the test times out.

Does the fluid sprayed measure between 85 ml and 115 ml?

Yes

- Replace the SCR Catalyst. Selective Catalytic Reduction (SCR) Catalyst - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Replace the DEF Injector. Diesel Exhaust Fluid Injector - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.