94121 Mercury RETAINER, STARTER ROPE

Enclosed Clean Emission Module (CEM)
Illustration 1 g03752556
Typical NOx sensor locations for an enclosed CEM
(1) Engine out NOx sensor
(2) Exhaust tailpipe (typical example)
(3) Tailpipe out NOx sensorThe engine out NOx sensor is located in the Clean Emissions Module (CEM). The tailpipe out NOx sensor is located in the exhaust tail pipe. Refer to Illustration 1.The exhaust system has two NOx sensors that measure O2 and NOx. The engine out NOx sensor is located in the CEM. This sensor monitors the NOx and O2 exiting the DPF. The tailpipe out NOx sensor is located in the exhaust tail pipe after the SCR catalyst and monitors the NOx and O2 exiting the CEM.Open Clean Emission Module (CEM) - Combined DOC and DPF with SCR
Illustration 2 g06464500
Typical NOx sensor locations for an enclosed CEM
(4) Engine out NOx sensor
(5) Exhaust tailpipe (typical example)
(6) Tailpipe out NOx sensorThe engine out NOx sensor is located in the Clean Emissions Module (CEM). The tailpipe out NOx sensor is located in the exhaust tail pipe. Refer to Illustration 1.The exhaust system has two NOx sensors that measure O2 and NOx. The engine out NOx sensor is located in the CEM. This sensor monitors the NOx and O2 exiting the DPF. The tailpipe out NOx sensor is located in the exhaust tail pipe after the SCR catalyst and monitors the NOx and O2 exiting the CEM.Open Clean Emission Module (CEM) - Combined DPF and SCR with DOC
Illustration 3 g06464499
Typical NOx sensor locations for an enclosed CEM
(7) Engine out NOx sensor
(8) Exhaust tailpipe (typical example)
(9) Tailpipe out NOx sensorThe engine out NOx sensor is located in the Clean Emissions Module (CEM). The tailpipe out NOx sensor is located in the exhaust tail pipe. Refer to Illustration 1.The exhaust system has two NOx sensors that measure O2 and NOx. The engine out NOx sensor is located in the CEM. This sensor monitors the NOx and O2 exiting the DPF. The tailpipe out NOx sensor is located in the exhaust tail pipe after the SCR catalyst and monitors the NOx and O2 exiting the CEM.Complete the procedure in the order in which the steps are listed.
Table 2
Troubleshooting Test Steps Values Results
1. Check the Installation of the NOx Sensors
A. Locate the appropriate NOx Sensor.
B. Check if the sensor is installed correctly.
Correctly Installed / Not installed correctly
Result: The sensor is not installed correctly.
Repair: Install the sensor correctly.
Proceed to Test Step 3.
Result: The sensor is installed correctly.
Proceed to Test Step 2.
2. Check for an Exhaust Leak Between the Turbocharger and the Tailpipe
A. Check for disconnected exhaust lines.
B. Check for broken/loose joints.
Leak found
Result: An exhaust leak is found between the turbo and the tail pipe.
Repair: Repair the exhaust leak.
Proceed to Test Step 3.
3. Perform the Aftertreatment System Functional Test
A. Reset all active codes and clear all logged codes.
B. Use the electronic service tool to perform the "Aftertreatment System Functional Test" to verify that the fault is eliminated.
Test passed
Result: The Aftertreatment System Functional Test passed.
The NOx Sensing system is fully functional and the fault has been eliminated.
Return the unit to service.
Result: The Aftertreatment System Functional Test did not pass and the diagnostic code is still present.
Repair: Replace the sensor.
If the fault is still present, contact the Dealer Solutions Network (DSN).