P214A
P214A-SCR NOx CATALYST INLET TEMPERATURE TOO HIGH
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
Selective Catalytic Reduction (SCR) is a technology that uses a urea based diesel exhaust fluid (DEF) and a catalytic converter to significantly reduce nitrous oxides (NOx) emissions. The system accomplishes this by injecting small quantities of diesel exhaust fluid (DEF) are injected into the exhaust system upstream of the catalyst, where it vaporizes and decomposes to form ammonia and carbon dioxide. The ammonia is the desired product which in conjunction to the SCR Catalyst, converts the NOx to harmless nitrogen and water. The Diesel Exhaust Fluid (DEF) Dosing Control Unit is used to control the operation and monitoring of the Diesel Exhaust Fluid system. The DEF Dosing Control Unit communicates with the Powertrain Control Module over the J1939 Data Link. The SCR system is equipped with two Nox Sensors and modules that are used to monitor the efficiency of the SCR Catalyst and diesel exhaust fluid system. 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 that 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.
- When Monitored:
Continuously with the engine running and active regeneration of the Diesel Particulate Filter is not occurring.
- Set Condition:
The Powertrain Control Module detects that Exhaust Gas Temperature (EGT) Sensor 1/3 is above 650°C (1202°F) for one minute.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
1. CHECK THE OPERATION OF EXHAUST TEMPERATURE SENSORS
NOTE: This fault will go inactive immediately after the SCR outlet temperature drops below the warning limit, and will likely be inactive when the vehicle is in the shop. For these reasons this troubleshooting tree must be used for both active and inactive fault codes.
NOTE: Repair any fuel, emissions, or DEF system component DTCs before continuing with this diagnostic procedure.
1. Start and idle the engine for 10 minutes.
2. With the scan tool, read and compare the Exhaust Gas Temperature (EGT) Sensors.
Do any of the EGT Sensors vary more than 43°F of the others?
Yes
- Go To 3
No
- Go To 2
2. CHECK THE EXHAUST TEMPERATURE SENSOR FOR A SHORT TO ANOTHER CIRCUIT
NOTE: Perform this test on the EGT Sensor that was reading more than 43°F above or below the others.
1. Turn the ignition off.
2. Disconnect the Powertrain Control Module (PCM) C2 harness connector.
3. Measure the resistance between the EGT Sensor Signal circuit and all other circuits in the PCM C2 harness connector.
Was the resistance above 10k Ohms between the EGT Sensor Signal circuit and all other circuits in the PCM C2 harness connector?
Yes
- Replace the Exhaust Gas Temperature Sensor. Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
No
- Repair the short between the Exhaust Gas Temperature Sensor circuit and the circuit that measured below 10k Ohms.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
3. 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 4
4. 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
- If DTC P1451 is present, perform a scan tool initiated regeneration of the after treatment system. If DTC P1451 is not present, replace the DOC/DPF assembly.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.