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Tahoe / Yukon Service Manual

DTC U029D, U029E, U02A1, or U02A3

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5509069 Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. DTC Descriptor DTC U029D Lost Communication with NOX Sensor - Eng DTC U029E Lost Communication with NOX Sensor - Post_Cat DTC U02A1 Lost Communication with Nitrogen Oxides Sensor 3 DTC U02A3 Lost Communication with Exhaust Particulate Matter Sensor Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performanc
Ignition U029D, U029E, U02A1, U02A3 U029D, U029E, U02A1, U02A3 — —
Powertrain High Speed GMLAN Serial Data (+) U0074, U0076 U029D, U029E, U02A1, U02A3 U029D, U029E, U02A1, U02A3, U0074, U18A2, U18D2, U18E2 —
Powertrain High Speed GMLAN Serial Data (−) U029D, U029E, U02A1, U02A3, U0074, U18A2, U18D2, U18E2 U029D, U029E, U02A1, U02A3 U0074, U0076 —
Ground — U029D, U029E, U02A1, U02A3 — —

Circuit/System Description Devices connected to the Powertrain High Speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices. The devices have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver device as an availability indication of the transmitter device. Each message contains the identification number of the transmitter device. A loss of serial data communications DTC does not represent a failure of the devices that contain the stored DTC. Conditions for Running the DTC The system voltage is between 9–16 V. Conditions for Setting the DTC A supervised periodic message that includes the transmitter device availability has not been received. Action Taken When the DTC Sets DTCs U029D, U029E, and U02A1 are Type A DTCs. DTC U02A3 is a Type B DTC. Conditions for Clearing the DTC DTCs U029D, U029E, and U02A1 are Type A DTCs. DTC U02A3 is a Type B DTC. Reference Information Schematic Reference Engine Controls Schematics Data Communication Schematics Control Module References Connector End View Reference Master Electrical Component List Description and Operation Data Link Communications Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

  1. Verify that DTC U0073, U0074, U0078, U1814, U2099, U0106, B1325, B1330, B1370, B1380, B1424, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, or P0562 is not set. ⇒ If any of the DTCs are set Refer to Diagnostic Trouble Code (DTC) List - Vehicle. ⇓ If none of the DTCs are set
  2. Refer to Circuit/System Testing.
  3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. Verify the DTC does not set. ⇒ If the DTC sets Refer to: Circuit/System Testing ⇓ If the DTC does not set
  4. All OK. Circuit/System Testing
  1. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 10 min for all vehicle systems to power down.
  2. Disconnect the appropriate component: B136 Exhaust Particulate Matter Sensor B195A Nitrogen Oxides Sensor 1 B195B Nitrogen Oxides Sensor 2 B195C Nitrogen Oxides Sensor 3
  3. Test for less than 10 Ω between the test points: { B136 Exhaust Particulate Matter Sensor } Ground circuit terminal 1 & Ground { B195A Nitrogen Oxides Sensor 1 } Ground circuit terminal 4 & Ground { B195B Nitrogen Oxides Sensor 2 } Ground circuit terminal 4 & Ground { B195C Nitrogen Oxides Sensor 3 } Ground circuit terminal 4 & Ground ⇒ If 10 Ω or greater 3.1. Ignition/Vehicle OFF. 3.2. Test for less than 2 Ω in the ground circuit end to end. ⇒ If 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω, repair the open/high resistance in the ground connection. ⇓ If less than 10 Ω
  4. Ignition ON/Vehicle In Service Mode.
  5. Verify a test lamp turns On between the test points: { B136 Exhaust Particulate Matter Sensor } Ignition circuit terminal 4 & Ground { B195A Nitrogen Oxides Sensor 1 } Ignition circuit terminal 1 & Ground { B195B Nitrogen Oxides Sensor 2 } Ignition circuit terminal 1 & Ground { B195C Nitrogen Oxides Sensor 3 } Ignition circuit terminal 1 & Ground ⇒ If the test lamp does not illuminate and the circuit fuse is good 5.1. Ignition/Vehicle OFF, remove the test lamp. 5.2. Test for less than 2 Ω in the ignition circuit end to end. ⇒ If 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω, verify the fuse is OK and there is voltage at the fuse. ⇒ If the test lamp does not illuminate and the circuit fuse is open 5.1. Ignition/Vehicle OFF, remove the test lamp. 5.2. Connect the component disconnected in step 2. 5.3. Ignition » On / Vehicle » In Service Mode 5.4. Replace the component: Fuse 5.5. Verify the fuse does not open. ⇒ If the fuse opens and there are components connected to the circuit » Disconnect a component and repeat procedure starting at step 5.4 ⇒ If the fuse opens with all components disconnected from the circuit » Repair the short to ground on the circuit. ⇒ If the fuse does not open after disconnecting a component from the circuit » Replace the component disconnected last. ⇓ If the fuse does not open with all components connected. 5.6. All OK. ⇓ If the test lamp illuminates
  6. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. Disconnect the harness connectors of the device setting the DTC. It may take up to 10 min for all vehicle systems to power down.
  7. Test for less than 2 Ω in each of the Powertrain high speed GMLAN serial data circuits end to end between the appropriate component and the device setting the DTC. ⇒ If 2 Ω or greater Repair the open/high resistance in the serial data circuit between the appropriate component and the device setting the DTC. ⇓ If less than 2 Ω
  8. Reconnect the harness connectors at the device setting the DTC.
  9. Test for 110–130 Ω between each pair of Powertrain high speed GMLAN serial data circuits at the appropriate component. ⇒ If less than 110 Ω Refer to DTC U0076 to test for a short to ground or a short between the serial data circuits. ⇒ If greater than 130 Ω Refer to DTC U0076 to test for an open/high resistance in the serial data circuit. ⇓ If between 110–130 Ω
  10. Replace the appropriate component: B136 Exhaust Particulate Matter Sensor B195A Nitrogen Oxides Sensor 1 B195B Nitrogen Oxides Sensor 2 B195C Nitrogen Oxides Sensor 3 Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Exhaust Particulate Matter Sensor Replacement Nitrogen Oxides Sensor Replacement - Position 1 Nitrogen Oxides Sensor Replacement - Position 2 Nitrogen Oxides Sensor Replacement - Position 3 Control Module References for device replacement, programming and setup