P20A1
DTC P20A1
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P20A1
- Reductant Purge Valve Performance
Diagnostic Fault Information
Circuit/System Description
The reductant purge valve controls the flow of diesel exhaust fluid (DEF). In the normally de-energized state, the purge valve directs reductant from the pump to the reductant injector. When the ignition is turned OFF, the engine control module (ECM) energizes both the reductant purge valve and reductant pump for about 30-45 seconds to purge the supply line of reductant. The ECM also commands the DEF injector to 100% to prevent vacuum from forming during the purge process. Purging prevents the reductant from freezing in the pump or supply line to the reductant injector. The ECM will set a DTC when an abnormal voltage condition on the purge valve circuit is detected.
The ECM provides battery voltage on the actuator high control circuit and ground on the actuator low control circuit. Both circuits are controlled through output drivers within the ECM.
Conditions for Running the DTC
* DTCs P1045, P204C, P204D, P208A, P208D, P20A0, P20A2, or P20A3 are not set.
* The battery voltage is greater than 11 V.
* The engine speed is greater than 600 RPM.
* The engine run time is greater than 10 s.
* The initial reductant system pressure is greater than 350 kPa (51 psi).
* The ambient and DEF temperature is warmer than -7°C (19°F).
* The DTCs run continuously when the above conditions are met.
Conditions for Setting the DTC
The ECM detects the pressure difference between the initial pressure value and the current pressure value is less than 50 kPa (7 psi) after the pressure reduction has been attempted for greater than 5 s.
Action Taken When the DTC Sets
DTC P20A1 is a Type A DTC
Conditions for Clearing the DTC
DTC P20A1 is a Type A DTC
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
* Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Level) Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Level)Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Quality) Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Quality)Diesel Exhaust Fluid (DEF) Warning Strategy (Anti-Tampering) Diesel Exhaust Fluid (DEF) Warning Strategy (Anti-Tampering)Diesel Exhaust Fluid (DEF) Warning Strategy (Emission Control) Diesel Exhaust Fluid (DEF) Warning Strategy (Emission Control)
* Exhaust Aftertreatment System Description Emission Control Systems
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Observe the scan tool Reductant Pressure when turning the ignition ON. The reading should be 0 kPa.
2. Ignition ON, command the Reductant Purge Valve ON and OFF with a scan tool. You should hear an audible click.
3. Ignition ON, command the Reductant Purge Valve ON and OFF with a scan tool while observing the Reductant Purge Vlv Ctrl Ckt Status parameter. The parameter should display OK or Not Run.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Verify the following conditions do not exist with the DEF system components:
* Restricted or plugged Q62 reductant purge valve lines
* Restricted or plugged Q62 reductant purge valve -- Stuck closed
• If a condition is found, repair as necessary.
2. Ignition OFF, disconnect the 24-way harness connector at the DEF Tank. Refer to Inline Harness Connector End Views X100 for connector identification.
Note: Testing for steps 2-5 is performed on the ECM side of the harness connector.
3. Ignition ON, test for 2.5-4.5 V between the DEF reverting valve high control circuit terminal A7 and ground.
• If less than the specified range, test the high control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
• If greater than the specified range, test the high control circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
4. Command the Reductant Purge Valve ON and OFF with a scan tool. The DMM should transition from 2.5-4.5 V when commanded OFF to greater than 10 V, when commanded ON.
• If the circuit voltage does not correspond to the specified values, replace the K20 ECM.
5. Test for 2.5-4.5 V between the DEF reverting valve low control circuit terminal B7 and ground.
• If less than the specified range, test the low control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
• If greater than the specified range, test the low control circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
6. Command the Reductant Purge Valve ON and OFF with a scan tool. The DMM should transition from 2.5-4.5 V when commanded OFF to less than 2 V, when commanded ON.
• If the circuit voltage does not correspond to the specified values, replace the K20 ECM.
Note: Testing for this step is performed on the DEF tank side of the harness connector.
7. Remove the DEF tank and test, inspect, and repair the items listed below. If all items test normal, replace the reductant purge valve.
* Poor connection at the 24-way harness connector
* Open or shorted DEF Reverting Valve High Control circuit
* Open or shorted DEF Reverting Valve Low Control circuit
Repair Instructions
* Emission Reduction Fluid Tank Replacement Emission Reduction Fluid Tank Replacement
* Perform the scan tool Reductant System Reset procedure after replacing the emission reduction fluid tank.
* Control Module References Control Module References for engine control module replacement, programming, and setup
Repair Verification
1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes.
Note: The diesel exhaust fluid (DEF) and ambient air temperatures must be greater than -7°C (19°F) before proceeding with this procedure.
5. Ignition ON, command the Reductant System Leak Test ON with a scan tool. Allow the pressure to build for at least 2 minutes. The first 60 s, the system performs a system purge. Observe the scan tool Reductant Pressure sensor parameter. The reading should be between 400-650 kPa (58-94 psi) and there should be no leaks in the system.
6. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes.
7. Engine idling for 30 s.
8. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes.
9. Ignition ON, perform the Reductant System Data Reset with a scan tool in order to clear the DEF lamp.
• If the DEF lamp does not turn OFF, a condition with the system still exists.