Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5471207
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 P0476
Exhaust Pressure Regulator Valve Performance
DTC P048A
Exhaust Pressure Regulator Valve Stuck Closed
Diagnostic Fault Information
| Circuit |
Short to Ground |
Open/High Resistance |
Short to Voltage |
Signal Performanc |
| 5 V Reference |
P0641* |
U0650* |
P0641* |
P0476 |
| Serial Data |
U0650 |
U0650 |
U0650 |
P0476 |
| Low Reference |
— |
U0650* |
— |
P0476 |
| * Additional DTCs may set |
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|
|
|
Circuit/System Description
For an overview of the component/system, refer to: Exhaust Gas Recirculation (EGR) System
Description
| Circuit |
Description |
| Control — Terminal 4 |
The output circuit is switched from ground to 12 V to activate the component. |
| Control — Terminal 5 |
The output circuit is switched from ground to 12 V to activate the component. |
|
Component |
Description |
|
|
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 |
|
| Component |
Description |
|
sensors, interprets the data and adjusts the engine actuators accordingly. |
| M122 Exhaust Pressure Control Valve Actuator |
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. |
Conditions for Running the DTC
P0476
DTC P262B, U0650 = Not set
DTCs related to the following system/component = Not Set
– B9 Ambient Air Temperature Sensor
– B34 Engine Coolant Temperature Sensor
– M122 Exhaust Pressure Regulator Valve — Control Circuit & Performance
– Exhaust Pressure Regulator Valve Position Sensor
M64 Starter = Inactive
Ambient Air Temperature Sensor = Warmer than −20°C (−4°F)
Engine = Running
Engine Coolant Temperature Sensor = Warmer than 20°C (68°F)
Ignition and Start Signal = Greater than 11 V
Frequency the DTC runs = Continuously — After the running conditions are met
P048A
DTC P0476 is set.
M122 Exhaust Pressure Regulator Valve = Off — For greater than 2 s
Frequency the DTC runs = Continuously — After the running conditions are met
Frequency the DTC runs = Once — During control module power down
Conditions for Setting the DTC
P0476
M122 Exhaust Pressure Regulator Valve = Mechanically obstructed — For greater than XX s
P048A
M122 Exhaust Pressure Regulator Valve = Mechanically stuck — For greater than XX 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
- Ignition » On / Vehicle » In Service Mode
- Verify there are no DTCs set, except DTC P0476, P048A, P2B97, related to the following
system/component: M122 Exhaust Pressure Regulator Valve
⇒ If a related DTC is set
Refer to: Diagnostic Trouble Code (DTC) List - Vehicle
⇓ If a related DTC is not set
- Ignition/Vehicle » Off — For 30 s
- Ignition » On / Vehicle » In Service Mode
- Verify the following scan tool parameters are within the specified range:
Exhaust Pressure Regulator Valve Learned Closed Position = 6.0 to 14.5%
Exhaust Pressure Regulator Valve Learned Open Position = 73 to 93%
⇒ If not in the specified range
5.1. Ignition/Vehicle » Off
5.2. Remove the component: M122 Exhaust Pressure Regulator Valve
5.3. Verify a condition does not exist with the component: Blade & Bore @ M122 Exhaust
Pressure Regulator Valve — Blocked / Casting Flash / Coking / Debris / Dirty / Visible
Damage
⇒ If a condition exists » Repair or replace as necessary
⇓ If no conditions exist
5.4. Perform the following action: Rotate » Blade @ M122 Exhaust Pressure Regulator Valve
Verify the following conditions do not exist:
Binding or Sticking @ Open / Closed — Position
Open/Close — Without spring pressure
⇒ If a condition exists » Repair or replace as necessary
⇓ If no conditions exist
5.5. Replace the component: M122 Exhaust Pressure Regulator Valve
⇓ If in the specified range
- Perform the scan tool control function: Exhaust Pressure Regulator Valve » Command the
component to the minimum position/speed & Maximum position/speed
Verify the scan tool parameter: Desired Exhaust Pressure Regulator Valve Position = Exhaust
Pressure Regulator Valve Position — Through the entire range
⇒ If not the specified state
6.1. Ignition/Vehicle » Off
6.2. Remove the component: M122 Exhaust Pressure Regulator Valve
6.3. Verify a condition does not exist with the component: Blade & Bore @ M122 Exhaust
Pressure Regulator Valve — Blocked / Casting Flash / Coking / Debris / Dirty / Visible
Damage
⇒ If a condition exists » Repair or replace as necessary
⇓ If no conditions exist
6.4. Perform the following action: Rotate » Blade @ M122 Exhaust Pressure Regulator Valve
Verify the following conditions do not exist:
Binding or Sticking @ Open / Closed — Position
Open/Close — Without spring pressure
⇒ If a condition exists » Repair or replace as necessary
⇓ If no conditions exist
6.5. Replace the component: M122 Exhaust Pressure Regulator Valve
⇓ If the specified state
- 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
Repeat the procedure starting at step 1
⇓ If the DTC does not set
- All OK.
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