This procedure covers the removal and replacement of the upstream oxygen sensor on the 6.7L Cummins diesel engine, located in the exhaust system before the diesel particulate filter.

Warnings

Tools required

Parts

• Upstream oxygen sensor × 1 — Use OEM Mopar specification for 6.7L Cummins

Preparation

1. Ensure engine and exhaust system are completely cool to the touch
2. Park vehicle on level surface and apply parking brake
3. Place wheel chocks behind rear wheels
4. Raise front of vehicle using jack and support securely on jack stands
5. Locate upstream oxygen sensor in exhaust downpipe before the diesel particulate filter
6. Visually inspect sensor connector and wiring harness for damage

Procedure

1. 1

   Disconnect battery negative terminal
   Disconnect the negative battery terminal to prevent electrical shorts and clear any oxygen sensor codes from the ECM during replacement. Wait 2 minutes for system capacitors to discharge.
2. 2

   Disconnect oxygen sensor electrical connector
   Locate the electrical connector for the upstream O2 sensor. Press the release tab and carefully disconnect the connector. If connector is corroded or stuck, gently wiggle while pulling. Do not pull on the wiring harness itself.
3. 3

   Access the oxygen sensor
   The upstream sensor is mounted in the exhaust downpipe before the DPF on the driver side. You may need to work from underneath the vehicle. Trace the wiring from the connector to locate the sensor body in the exhaust pipe.
4. 4

   Apply penetrating oil if necessary
   If the sensor has been in place for an extended period, spray penetrating oil around the sensor threads where it enters the exhaust pipe. Allow 10-15 minutes for penetration. This step can prevent thread damage during removal.
5. 5

   Remove the old oxygen sensor
   Using the oxygen sensor socket and ratchet with extension, turn the sensor counterclockwise to remove. The sensor may require significant force initially. Once loose, continue unscrewing by hand and carefully feed the wiring through any clips or brackets as you remove the sensor.
6. 6

   Inspect and clean the mounting bung
   Inspect the threaded bung in the exhaust pipe for damage or carbon buildup. Use a wire brush to clean the threads in the exhaust bung. Ensure threads are clean and free of debris before installing the new sensor.
7. 7

   Prepare new oxygen sensor
   Remove new oxygen sensor from packaging. Apply a thin coat of anti-seize compound to the sensor threads only. Do not allow anti-seize to contact the sensor tip or element as this will contaminate the sensor and cause false readings.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
8. 8

   Install new oxygen sensor
   Carefully thread the new oxygen sensor into the exhaust bung by hand, routing the wiring to avoid contact with hot exhaust components or moving parts. Thread in at least 3-4 full turns by hand to ensure proper thread engagement and prevent cross-threading.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
9. 9

   Torque oxygen sensor to specification
   Using the oxygen sensor socket and torque wrench, tighten the sensor to 45 Nm (33 lb-ft). Ensure the wiring is not twisted or kinked during final tightening.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
10. 10

    Route and secure wiring
    Route the sensor wiring away from heat sources and moving components. Secure wiring in original clips and brackets. Ensure adequate slack exists to prevent tension on the sensor or connector.
11. 11

    Reconnect electrical connector
    Connect the electrical connector to the new oxygen sensor. Ensure the connector clicks into place and is fully seated. Verify the connector locking tab is properly engaged.
12. 12

    Reconnect battery and clear codes
    Reconnect the negative battery terminal. If a scan tool is available, clear any stored oxygen sensor diagnostic trouble codes from the ECM. This ensures proper monitoring of the new sensor.

Reassembly

1. Lower vehicle from jack stands and remove wheel chocks
2. Double-check that all electrical connections are secure and wiring is properly routed
3. Verify no tools or parts were left in the engine compartment or under the vehicle

Verification

• Start the engine and allow it to idle for 2-3 minutes, listening for any exhaust leaks at the sensor location
• Check for diagnostic trouble codes using a scan tool - there should be no O2 sensor codes present
• Verify the oxygen sensor is reading properly on scan tool live data (voltage should fluctuate between 0.1-0.9V when engine is at operating temperature)
• Perform a visual inspection under the vehicle to confirm no exhaust leaks and wiring is secure
• Test drive the vehicle and verify no check engine light illumination and normal engine operation

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