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Tahoe / Yukon Service Manual

DTC P048D, P048E, or U0650

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5471208 Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC P048D Exhaust Pressure Regulator Valve Position Sensor Circuit Low — Internal Component Fault DTC P048E Exhaust Pressure Regulator Valve Position Sensor Circuit High — Internal Component Fault DTC U0650 Lost Communication with Exhaust Pressure Regulator Valve Position Sensor Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performanc
5 V Reference P0641* U0650* P0641* —
Serial Data U0650 U0650 U0650 —
Low Reference — U0650* — —
* Additional DTCs may set

Circuit/System Description For an overview of the component/system, refer to: Exhaust Gas Recirculation (EGR) System Description

Circuit Description
5 V Reference Regulated voltage supplied by the control module.
Serial Data Digitally encoded information for communication between devices.
Low Reference Grounded through the control module.
Component Description
M122 Exhaust Pressure Regulator Valve The assembly has several functions: The component is actuated by a bidirectional DC motor. The component contains a contactless inductive position sensor. A fixed transmitter coil excites a movable rotor, which in turn induces a current in a fixed receiver coil. The current varies with the angle of the rotor. Electronics inside the sensor convert the current into digital data which is transmitted via a serial data circuit to the control module.
K20 Engine Control Module The control module contains a microprocessor used to process input data to control outputs. The control module controls a series of actuators to ensure optimal engine performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the engine actuators accordingly.

The control module monitors for the following normal value(s): Valve @ M122 Exhaust Pressure Regulator Valve = 13% or less — Closed Valve @ M122 Exhaust Pressure Regulator Valve = 86% or greater — Open Conditions for Running the DTC { P048D, P048E } DTC U0650 = Not set M64 Starter = Inactive Engine = Running Ignition and Start Signal = Greater than 11 V Frequency the DTC runs = Continuously — After the running conditions are met Conditions for Setting the DTC P048D, P048E Exhaust Pressure Regulator Valve Position = Not within a calibrated range — For greater than 4 s U0650 Serial data message from component: M122 Exhaust Pressure Regulator Valve = Not Received — For greater than 1 s Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type A DTC Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type A DTC Reference Information Schematic Reference Engine Controls Schematics Connector End View Reference Master Electrical Component List Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References Circuit/System Verification

  1. Ignition » On / Vehicle » In Service Mode
  2. Verify DTC P0641 is not set. ⇒ If the DTC is set Refer to: DTC P0641, P0651, P0697, or P06A3 ⇓ If the DTC is not set
  3. Verify DTC P048D, P048E is not set. ⇒ If any of the DTCs are set Replace the component: M122 Exhaust Pressure Regulator Valve ⇓ If none of the DTCs are set
  4. Verify DTC U0650 is not set. ⇒ If the DTC is set Refer to: Circuit/System Testing ⇓ If the DTC is not set
  5. Perform the scan tool control function: Exhaust Pressure Control Valve Motor » Command the component to the minimum position/speed Verify the scan tool parameter: Exhaust Pressure Regulator Valve Position = The parameter value should not change – Perform the action while monitoring the parameter: Wiggle the harness and connector: K20 Engine Control Module Wiggle the harness and connector: M122 Exhaust Pressure Regulator Valve ⇒ If the parameter value changes Repair as necessary » Wiring / Terminal(s) / Electrical Connector(s) ⇓ If the parameter value does not change
  6. 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 is not set
  7. All OK. Circuit/System Testing
  1. Ignition/Vehicle & All vehicle systems » Off
  2. Disconnect the electrical connector: M122 Exhaust Pressure Regulator Valve
  3. Test for less than 10 Ω between the test points: Low Reference circuit terminal 1 & Ground ⇒ If 10 Ω or greater 3.1. Disconnect the electrical connector: X2 @ K20 Engine Control Module 3.2. Test for less than 2 Ω between the test points: Low Reference circuit terminal 1 @ Component harness & The other end of the circuit @ Control module harness ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module ⇓ If less than 10 Ω
  4. Ignition » On / Vehicle » In Service Mode
  5. Test for 4.8 to 5.2 V between the test points: 5 V Reference circuit terminal 3 & Low Reference circuit terminal 1 ⇒ If less than 4.8 V 5.1. Ignition/Vehicle » Off 5.2. Disconnect the electrical connector: X1 @ K20 Engine Control Module 5.3. Test for infinite resistance between the test points: 5 V Reference circuit terminal 3 @ Component harness & Ground ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇓ If infinite resistance 5.4. Test for less than 2 Ω between the test points: 5 V Reference circuit terminal 3 @ Component harness & The other end of the circuit @ Control module harness ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module ⇒ If greater than 5.2 V 5.1. Ignition/Vehicle » Off 5.2. Disconnect the electrical connector: X1 @ K20 Engine Control Module 5.3. Ignition » On / Vehicle » In Service Mode 5.4. Test for less than 1 V between the test points: 5 V Reference circuit terminal 3 @ Component harness & Ground ⇒ If 1 V or greater » Repair the short to voltage on the circuit. ⇒ If less than 1 V » Replace the component: K20 Engine Control Module ⇓ If between 4.8 and 5.2 V
  6. Test for 4.7 to 5.3 V between the test points: Serial Data circuit terminal 2 & Ground ⇒ If less than 4.7 V 6.1. Ignition/Vehicle » Off 6.2. Disconnect the electrical connector: X1 @ K20 Engine Control Module 6.3. Test for infinite resistance between the test points: Serial Data circuit terminal 2 @ Component harness & Ground ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇓ If infinite resistance 6.4. Test for infinite resistance between the test points: Serial Data circuit terminal 2 @ Component harness & Low Reference circuit terminal 1 @ Component harness ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇓ If infinite resistance 6.5. Test for less than 2 Ω between the test points: Serial Data circuit terminal 2 @ Component harness & The other end of the circuit @ Control module harness ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module ⇓ If greater than 5.3 V 6.1. Ignition/Vehicle » Off 6.2. Disconnect the electrical connector: X1 @ K20 Engine Control Module 6.3. Ignition » On / Vehicle » In Service Mode 6.4. Test for less than 1 V between the test points: Serial Data circuit terminal 2 @ Component harness & Ground ⇒ If 1 V or greater » Repair the short to voltage on the circuit. ⇒ If less than 1 V » Replace the component: K20 Engine Control Module ⇓ If between 4.7 and 5.3 V
  7. Test or replace the component: M122 Exhaust Pressure Regulator Valve Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Exhaust Back Pressure Valve Replacement — M122 Exhaust Pressure Regulator Valve For control module replacement, programming, and setup refer to: Control Module References