Operation CHARM: Car repair manuals for everyone.
Home >> Dodge or Ram Truck >> 2012 >> RAM 3500 Chassis Cab Truck 2WD L6-6.7L DSL Turbo >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> U Code Charts >> U029E

U029E






U029E-LOST COMMUNICATION WITH NOx SENSOR "B"





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 assembles 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. The PCM will illuminate the MIL lamp immediately after the monitor runs and fails. The PCM will turn off the MIL Lamp after the monitor runs and passes for three consecutive trips.

- When Monitored:
Continuously with the ignition on.

- Set Condition:
The Powertrain Control Module (PCM) does not receive a message from the NOx Sensor 1/2 over the J1939 Data Link.





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

1. ACTIVE DTC
1. Ignition on, engine not running.
2. With the scan tool, read DTCs.

Is DTC U029E Active?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION - 6.7L diagnostic procedure. Intermittent Condition Test

2. OTHER DTCs

NOTE: Repair any Voltage Low DTCs before proceeding with this test procedure.

NOTE: The J1939 Datalink is a BUS circuit which the PCM uses to communicate with the Turbo Actuator, DEF Dosing Control Unit, NOx Sensor 1/1 and Nox Sensor 1/2. If the J1939 Datalink is shorted or one of these components is internally shorted, communication will be lost and DTCs will set against ALL of these components.

Are there lost communication DTCs present against All of the components listed in the note above?

Yes

- Go To 6

No

- Go To 3

3. CHECK SYSTEM VOLTAGE
1. Check the Batteries and charging system for proper system voltage and operation.

Is the system voltage normal?

Yes

- Go To 4

No

- Diagnose and repair the Batteries and charging system before continuing.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. CHECK THE NOx SENSOR 1/2 POWER AND GROUND CIRCUITS
1. Turn the ignition on, engine not running.
2. Disconnect the NOx Sensor Module 1/2 harness connector.
3. Measure the voltage across the (F505) Cluster Ignition Supply circuit and the (Z914) Ground circuit at the NOx Sensor Module 1/2 harness connector.

NOTE: Measure the voltage at key on, engine cranking, and at idle.

Does the voltage read within 1.0 Volt of battery voltage?

Yes

- Go To 5

No

- Repair the (F505) Fused Ignition Switch Output circuit for an open or short to ground, or check the (Z914) Ground circuit for an open.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

5. CHECK THE J1939 DATALINK OPEN
1. Turn the ignition off.
2. Disconnect the DEF NOx Sensor 1/1 harness connector.
3. Disconnect the Turbo Actuator harness connector.
4. Disconnect the PCM C2 harness connector.
5. Disconnect the DEF Dosing Control Unit C2 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

6. Measure the resistance of the J1939 Datalink (+) circuit between the DEF NOx Sensor 1/2 harness connector and the PCM C2 harness connector.
7. Measure the resistance of the J1939 Datalink (-) circuit between the DEF NOx Sensor 1/2 harness connector and the PCM C2 harness connector.

Is the resistance below 5.0 Ohms for both circuits?

Yes

- Replace the NOx Sensor 1/2. Bank 1 Sensor 2
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Repair the J1939 Datalink circuit that measured above 5.0 Ohms for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

6. CHECK THE COMPONENTS ON THE J1939 DATALINK

NOTE: Disconnect only one component at a time during this next step. If the DTCs for the components that are STILL CONNECTED change from active to stored, the component that was disconnected is faulty. If all of the DTCs remain active, then the disconnected component is not the problem. Reconnect each component before going on to the next one so that only one component is disconnected at a time.

1. Turn the ignition off.
2. Disconnect the Turbo Actuator harness connector. Cycle the ignition key on and off three times ending with the ignition on. Leave the ignition in the off position for 75 seconds each time.

NOTE: Monitor the status of the DTCs for the remaining connected components with the scan tool.

3. Turn the ignition off and reconnect the Turbo Actuator harness connector.
4. Disconnect the NOx Sensor Module 1/1 harness connector. Cycle the ignition key on and off three times ending with the ignition on. Leave the ignition in the off position for 75 seconds each time.

NOTE: Monitor the status of the DTCs for the remaining connected components with the scan tool.

5. Turn the ignition off and reconnect the NOx Sensor Module 1/1 harness connector.
6. Disconnect the NOx Sensor Module 1/2 harness connector. Cycle the ignition key on and off three times ending with the ignition on. Leave the ignition in the off position for 75 seconds each time.

NOTE: Monitor the status of the DTCs for the remaining connected components with the scan tool.

7. Turn the ignition off and reconnect the NOx Sensor Module 1/2 harness connector.
8. Disconnect the DEF Dosing Control Unit C2 harness connector. Cycle the ignition key on and off three times ending with the ignition on. Leave the ignition in the off position for 75 seconds each time.

NOTE: Monitor the status of the DTCs for the remaining connected components with the scan tool.

Did the status of the DTCs change to stored for the components STILL CONNECTED when disconnecting any one of the components listed above?

Yes

- Replace the component that caused the DTC change from active to stored.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 7

7. CHECK THE J1939 DATALINK FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the Turbo Actuator, NOx Sensor Modules, DEF Dosing Control Unit, and the PCM C2 harness connectors.
3. Measure the resistance between ground and the J1939 Datalink (+) circuit at the PCM C2 harness connector.
4. Measure the resistance between ground and the J1939 Datalink (-) circuit at the PCM C2 harness connector.

Is the resistance above 10k Ohms for both circuits?

Yes

- Go To 8

No

- Repair the J1939 Datalink circuit that did not measure above 10k Ohms for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

8. CHECK THE J1939 DATALINK FOR A SHORT
1. Measure the resistance between the J1939 Datalink (+) circuit at the PCM C2 harness connector and all other circuits in the PCM C2 harness connector.
2. Measure the resistance between the J1939 Datalink (-) circuit at the PCM C2 harness connector and all other circuits in the PCM C2 harness connector.

NOTE: Disregard any resistance between 50 and 70 Ohms between the J1939 (+) and the J1939 Datalink (-) pins.

Is the resistance above 10k Ohms for both measurements?

Yes

- Go To 9

No

- Repair the J1939 Datalink circuit for a short to the circuit that did not measure above 10k Ohms.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

9. CHECK THE J1939 DATALINK CIRCUITS FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the J1939 Datalink (+) circuit between the NOx Sensor Module 1/2 harness connector and the PCM C2 harness connector.
2. Measure the resistance of the J1939 Datalink (-) circuit between the NOx Sensor Module 1/2 harness connector and the PCM C2 harness connector.

Is the resistance below 5.0 Ohms for both circuits?

Yes

- Replace the Powertrain Control Module. Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Repair the J1939 circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

pro multis · About Operation CHARM