P1C55

P1C55-NOx SENSOR INTERMITTENT - BANK 1 SENSOR 1




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 PCM will illuminate the MIL lamp immediately after the monitor runs and fails. The PCM will turn off the MIL Lamp immediately after the monitor runs and passes.

- When Monitored:
When the engine is running and the exhaust temperature at NOx Sensor 1/1 is above 150°C (302°F).

- Set Condition:
The PCM has detected that the NOx Sensor 1/1 reading is higher or lower than what is expected for the engine operating conditions.





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

1. OTHER DTCs
1. Ignition on, engine not running.
2. With the scan tool check for active DTCs.

Are any of the P2202, P2209, P220A, U029D DTCs active?

Yes

- Repair the other active DTCs before continuing with this diagnostic procedure.

No

- Go To 2

2. CHECK FOR CYLINDER MISFIRE
1. Start the engine.
2. With the scan tool, navigate to Systems Tests, and perform the injector Kill system test.

Were any cylinders found to be faulty or low?

Yes

- Perform the CHECKING ENGINE MISFIRE / RUNS ROUGH / PERFORMANCE TEST diagnostic procedure. Checking Engine Misfire / Runs Rough / Performance Test
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 3

3. CHECK FOR EXCESSIVE ENGINE OIL BEING INTRODUCED INTO THE AFTERTREATMENT SYSTEM
1. Turn the ignition off.
2. Remove the turbocharger outlet and inspect for signs of oil, fuel or moisture being introduced into the After treatment system from the engine.

Was engine oil, fuel or moisture found in the turbocharger exhaust outlet?

Yes

- Locate the cause of possible diesel fuel or engine oil being carried from the engine into the exhaust system. Inspect the SCR Catalyst for possible damage.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 4

4. CHECK THE EGR SYSTEM FOR LEAKS
1. Visually inspect the entire EGR system for signs soot indicating a leak.

Is there signs of an EGR system leak?

Yes

- Repair the EGR system leak.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Replace the NOx Sensor 1/1. Bank 1 Sensor 1
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.