P2045 – High Reducer Temperature Sensor Circuit

How Serious Is This DTC?

A stored P2045 code should be considered serious and addressed as soon as possible. The SCR system could be disabled because of this. Catalyst damage could occur if the conditions that contributed to the code being stored are not corrected in a timely manner.

What Are Some of the Symptoms of the Code?

Symptoms of a P2045 trouble code may include:

Reduced fuel efficiency
Excessive black smoke from the vehicle’s exhaust
Decreased engine performance
Other SCR-related codes

What Are Some Common Causes of the Code?

Causes

of this code may include:

Faulty reductant temperature sensor
Open or shorted circuits in the reductant temperature sensor system
Faulty SCR controller/PCM or programming error

What Are the P2045 Troubleshooting Steps?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and vehicle-specific diagnostic information source will be needed to diagnose a P2045 code.

You can use your vehicle information source to locate a technical service bulletin (TSB) that matches the vehicle’s year, make, and model; as well as engine size, stored codes, and presented symptoms. If you find one, it might provide useful diagnostic information.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It’s a good idea to record this information before clearing the codes, then test the vehicle until the PCM enters readiness mode or the code resets.

If the PCM enters readiness mode at that point, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions that contributed to the code being stored may need to worsen before an accurate diagnosis can be made.

If the code immediately resets, the next step in your diagnosis will require you to search your vehicle information source for diagnostic flowcharts, connector pinout diagrams, connector face views, and component testing procedures/specifications.

Step 1

Use the DVOM to test the reductant temperature sensor according to manufacturer specifications. Components that do not test within the allowed parameters should be considered faulty.

Step 2

If the actual reductant temperature is within specifications, the P2045 code persists, and the sensor in question is operational, use the DVOM to test the input and output signal circuits between the temperature sensor and the PCM/SCR controller. Disconnect all controllers before using the DVOM for testing.

Reductant temperature sensor codes are typically attributed to a faulty or disconnected sensor

OBD2 Code P1443 Audi: Complete Diagnostic and Repair Guide

Understanding OBD2 Code P1443 in Audi Vehicles

When your Audi’s check engine light illuminates and diagnostic scanning reveals code P1443, you’re dealing with a specific emissions-related issue that requires immediate attention. This diagnostic trouble code (DTC) indicates a malfunction within the secondary air injection system, specifically related to the pump switching valve circuit. The P1443 code is particularly common in various Audi models, including the A4, A6, and other vehicles within the Volkswagen Group family.

What Does P1443 Code Mean Specifically?

The P1443 diagnostic trouble code specifically points to a malfunction in the secondary air injection system’s pump switching valve control circuit. This system is designed to reduce hydrocarbon and carbon monoxide emissions during cold engine starts by injecting fresh air into the exhaust stream, helping the catalytic converter reach optimal operating temperature more quickly. When this system fails, it can lead to increased emissions and potential damage to other emission control components.

Technical Definition and System Operation

According to SAE standards, P1443 indicates “Secondary Air Injection System Control Circuit/Open (Bank 1).” The system consists of several key components: the secondary air injection pump, combination valve, vacuum solenoid valves, and various vacuum lines. During cold starts (typically below 40°C/104°F coolant temperature), the engine control module (ECM) activates the system for approximately 100 seconds to minimize cold-start emissions.

Audi Models Commonly Affected by P1443

Audi A4 (B6, B7 platforms with 1.8T and 2.0T engines)
Audi A6 (C5, C6 platforms with various engine configurations)
Audi TT with 1.8T and 2.0T FSI engines
Audi Q5 with 2.0T engines
Various Volkswagen and SEAT models sharing similar engine management systems

Comprehensive Diagnostic Procedure for P1443

Proper diagnosis of P1443 requires a systematic approach to identify the root cause rather than simply replacing components. The diagnostic process should begin with visual inspection and progress through electrical testing and functional checks to accurately pinpoint the failure point.

Initial Visual Inspection Steps

Begin with a thorough visual examination of the secondary air injection system components. Look for obvious signs of damage, corrosion, or disconnection. Pay particular attention to:

Vacuum lines for cracks, brittleness, or disconnections
Electrical connectors to the air pump and combination valve
Physical damage to the air pump housing or mounting points
Corrosion on electrical terminals and wiring harnesses
Obstructions in the air intake filter for the secondary air system

Electrical Circuit Testing Methodology

Using a digital multimeter, perform comprehensive electrical testing of the secondary air injection system circuit. Test procedures should include:

Checking power supply to the air injection pump (typically 12V during activation)
Verifying ground circuit integrity and resistance
Testing control signals from the engine control module
Measuring circuit resistance and checking for shorts or opens
Inspecting fuse and relay operation in the engine bay fuse panel

Functional Testing and Live Data Monitoring

Advanced diagnosis requires monitoring live data using a professional scan tool. Key parameters to monitor include:

Secondary air injection system status during cold start
Air mass sensor readings before and during system activation
Oxygen sensor response during secondary air operation
Engine coolant temperature correlation with system activation
Commanded versus actual secondary air pump operation

Common Causes and Professional Repair Solutions

The P1443 code can result from various failures within the secondary air injection system. Understanding the most common failure points helps technicians develop efficient repair strategies and prevent unnecessary component replacement.

Primary Failure Components and Replacement Procedures

The secondary air injection pump is the most common failure point in Audi vehicles triggering P1443. Replacement requires:

Disconnecting the battery to prevent electrical shorts
Removing necessary components for access (varies by model)
Replacing the pump assembly with OEM or quality aftermarket parts
Ensuring proper sealing of all connections and mounting points
Performing system functional test after replacement

Vacuum System and Combination Valve Issues

Vacuum leaks and combination valve failures represent significant contributors to P1443 occurrences. Diagnosis should include:

Testing vacuum supply to the combination valve
Checking combination valve diaphragm integrity
Verifying proper valve operation during system activation
Inspecting vacuum reservoir tanks for leaks or damage
Testing vacuum solenoid valves for proper operation

Electrical and Control Circuit Repairs

Wiring issues and control circuit problems require meticulous repair approaches:

Repairing damaged wiring using proper automotive-grade connectors
Addressing corrosion at electrical connectors with contact cleaner
Testing ECM output signals using oscilloscope when necessary
Checking for water intrusion in connector housings
Verifying proper circuit protection device operation

Advanced Technical Considerations and Prevention

Beyond basic repair, understanding the broader implications of P1443 helps prevent recurrence and ensures comprehensive system restoration. Technical professionals should consider these advanced aspects when addressing this diagnostic trouble code.

Impact on Emission Compliance and Vehicle Performance

The secondary air injection system plays a critical role in meeting emission standards. System failure can result in:

Increased hydrocarbon and carbon monoxide emissions
Potential catalytic converter damage from unburned fuel
Reduced engine efficiency during warm-up periods
Failed emission testing in regulated areas
Activation of reduced power or limp modes in some models

Software Updates and Technical Service Bulletins

Audi has released numerous technical service bulletins addressing P1443 and related secondary air system issues. Professional repair should include:

Checking for available ECM software updates
Reviewing manufacturer technical service bulletins
Implementing modified repair procedures when specified
Using updated part numbers when replacements are necessary
Documenting repair procedures for future reference

Preventive Maintenance Recommendations

Preventing P1443 recurrence requires addressing underlying conditions that contribute to system failure:

Regular inspection of secondary air system components
Addressing oil leaks that can contaminate electrical components
Ensuring proper battery and charging system operation
Maintaining clean air filters to reduce pump workload
Periodic inspection of vacuum lines and electrical connections

Successfully diagnosing and repairing P1443 in Audi vehicles requires understanding the interconnected nature of emission control systems. By following systematic diagnostic procedures and addressing both immediate failures and underlying conditions, technicians can restore proper operation and ensure compliance with emission standards. Regular maintenance and prompt attention to check engine lights remain crucial for preventing more serious secondary air system failures.

P2046 – Intermittent Reducer Temperature Sensor Circuit

How Serious Is This DTC?

A stored P2046 code should be considered serious and addressed as quickly as possible. The SCR system could be disabled because of this. Catalyst damage could occur if the conditions that contributed to the code being stored are not corrected in a timely manner.

What Are Some Symptoms of the Code?

Symptoms of a P2046 trouble code may include:

Reduced fuel efficiency
Excessive black smoke from the vehicle’s exhaust
Decreased engine performance
Other SCR-related codes

What Are Some Common Causes of the Code?

Causes

of this code may include:

Faulty reductant temperature sensor
Open or shorted circuits in the reductant temperature sensor system
Faulty SCR controller/PCM or programming error

What Are the P2046 Troubleshooting Steps?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and vehicle-specific diagnostic information source will be needed to diagnose a P2046 code.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It’s a good idea to record this information before clearing the codes, then test drive the vehicle until the PCM enters readiness mode or the code resets.

Step 1

Use the DVOM to test the reductant temperature sensor according to manufacturer specifications. Components that test outside the allowable parameters should be considered defective.

Step 2

If the actual reductant temperature is within specifications, the P2046 code persists, and the sensor in question is operational, use the DVOM to test the input and output signal circuits between the temperature sensor and the PCM/SCR controller. Disconnect all controllers before using the DVOM for testing.

Reductant temperature sensor codes are typically attributed to a faulty or disconnected sensor

P2047 – Reductant Injector Valve Circuit / Open Bank 1 Unit 1

Code P2047: Critical SCR System Fault – Urgent Diagnosis

Severity and Risks:
Code P2047 indicates a serious problem within the SCR (Selective Catalytic Reduction) system. Prompt intervention is imperative to avoid:

Complete deactivation of the SCR system.
Permanent damage to the SCR catalyst.
Worsening of engine and exhaust system conditions.
A significant increase in polluting emissions.

Common Symptoms:

Noticeable drop in engine performance (loss of power).
Excessive black smoke from the exhaust.
Decreased fuel efficiency (excessive fuel consumption).
Possible appearance of other fault codes related to the SCR system.

Probable Causes:

Failure of the reductant (DEF/AdBlue) injection valve.
Electrical problems: Open circuits, short circuits, or poor contacts on the valve control line.
Insufficient reductant (DEF/AdBlue) level in the tank.
Failure of the SCR controller or PCM (Powertrain Control Module) programming error.

Diagnostic Procedure:

Tool Preparation:
- High-performance OBD2 diagnostic scanner.
- Digital multimeter (DVOM).
- Vehicle-specific technical documentation (wiring diagrams, procedures, technical bulletins).
Preliminary Visual Inspection:
- Carefully inspect the wiring and connectors associated with the reductant injection valve and the SCR system.
- Look for any signs of damage, corrosion, burning, or looseness. Repair or replace faulty components before proceeding further.
Electronic Diagnosis (Scanner):
- Connect the scanner and retrieve all present fault codes and freeze frame data. Note this information.
- Clear the codes and perform a drive cycle simulation to see if the P2047 fault reappears and if the PCM reaches its readiness monitor conditions. An intermittent fault complicates the diagnosis.
Electrical Circuit Checks:
- Check the power supply and ground for the SCR system/injection valve using the DVOM (fuses, supply voltage, ground integrity).
- Using the scanner (using the “active command” or “actuator test” function), activate the reductant injection valve during measurement.
- Check the control voltage/signal sent to the valve solenoid with the DVOM. An abnormal or absent voltage points to a circuit or controller (PCM or SCR module) problem.
Reductant Injection Valve Test:
- If the electrical circuits are intact, test the valve itself (solenoid resistance with DVOM, response to scanner activation, nozzle condition).
- Compare measured values to manufacturer specifications. A faulty valve (sticking, internal leak, faulty solenoid) is a common cause of P2047. It can then no longer spray the reductant correctly.

Conclusion:
Code P2047 requires precise diagnosis and immediate repair. Ignoring this fault inevitably leads to degradation of the SCR catalyst, deactivation of the anti-pollution system, increased fuel consumption, and excessive emissions. Methodically following the troubleshooting steps is essential to restore engine performance and the vehicle’s environmental compliance.

P2048 – Reductant Injector Valve Circuit, Bank 1, Unit 1

How Serious Is This DTC?

A stored P2048 code should be considered serious and addressed as soon as possible. The SCR system could be disabled because of this. Catalyst damage could occur if the conditions that contributed to the code being stored are not corrected in a timely manner.

What Are Some of the Symptoms of the Code?

Symptoms of a P2048 trouble code may include:

Decreased engine performance
Excessive black smoke from the vehicle’s exhaust
Reduced fuel efficiency
Other SCR-related codes

What Are Some Common Causes of the Code?

Causes of this code may include:

Faulty reductant injector valve
Open or shorted circuits in the reductant injector valve control
Insufficient DEF in the tank
Faulty SCR controller/PCM or programming error

What Are the P2048 Troubleshooting Steps?

You will need access to a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information to diagnose a P2048 code.

If you can find a technical service bulletin (TSB) that matches the vehicle’s year, make, and model; as well as the engine size, stored code(s), and presented symptoms, it could provide helpful diagnostic information.

You’ll want to start your diagnosis with a visual inspection of the reductant heater system harnesses and connectors. Burned or damaged wiring and/or connectors should be repaired or replaced before continuing.

Proceed by connecting the scanner to the vehicle’s diagnostic connector and retrieving all stored codes and relevant freeze frame data. Note this information before clearing the codes and test drive the vehicle until the PCM enters readiness mode or the code resets.

The code is intermittent and may be much more difficult to diagnose (for the time being) if the PCM enters readiness mode. If this is the case, the conditions that contributed to the code being stored may need to worsen before an accurate diagnosis can be made.

If the code resets, consult your vehicle information source for diagnostic flowcharts, connector pinout diagrams, connector face views, as well as component testing procedures and specifications. This information will be needed to complete the next step of your diagnosis.

Use the DVOM to test the SCR control system’s power supply. Test fuses with the circuit loaded to avoid misdiagnosis. If proper power and ground circuits are detected, use the scanner to activate the reductant injector valve (solenoid) and test the output control circuit voltage. If voltage is insufficient, suspect the controller is faulty or has encountered a programming error.

If the voltage output circuit is within parameters, use the DVOM to test the reductant injector valve in question. If the valve does not meet manufacturer specifications, suspect it has failed.

The reductant injector valve is actually a solenoid injector that sprays reductant fluid into the exhaust…

P2049 – High Value of Reductant Injector Valve Circuit, Bank 1, Unit 1

How serious is this DTC?

A stored P2049 code should be considered serious and addressed as soon as possible. The SCR system could be disabled because of this. Catalyst damage could occur if the conditions that contributed to the code being stored are not corrected in a timely manner.

What are some of the symptoms of the code?

Symptoms of a P2049 trouble code may include:

Decreased engine performance
Excessive black smoke from the vehicle’s exhaust
Reduced fuel efficiency
Other SCR-related codes

What are some common causes of the code?

Causes of this code may include:

Faulty reductant injector valve
Open or shorted circuits in the reductant injector valve control
Insufficient DEF in the tank
Faulty SCR controller/PCM or programming error

What are the troubleshooting steps for P2049?

You will need access to a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information to diagnose a P2049 code.

Proceed by hooking up the scanner to the vehicle’s diagnostic connector and retrieving all stored codes and relevant freeze frame data. Note this information before clearing the codes and test drive the vehicle until the PCM enters readiness mode or the code resets.

Use the DVOM to test the SCR control system power supply. Test fuses with the circuit loaded to avoid misdiagnosis. If proper power and ground circuits are detected, use the scanner to activate the reductant injector valve (solenoid) and test the output control circuit voltage. If voltage is insufficient, suspect the controller is faulty or has encountered a programming error.

If the voltage output circuit is within parameters, use the DVOM to test the reductant injector valve in question. If the valve does not meet manufacturer specifications, suspect it has failed.

The reductant injector valve is actually a solenoid injector that sprays reductant fluid into the exhaust

P204A – Reductant Pressure Sensor Circuit

How severe is this DTC?

A stored P204A code should be considered severe and addressed as soon as possible. The SCR system may be disabled because of this. Catalyst damage could occur if the conditions that contributed to the code being stored are not corrected in a timely manner.

What are some symptoms of the code?

Symptoms of a P204A fault code may include:

Reduced fuel efficiency
Excessive black smoke from vehicle exhaust
Decreased engine performance
Other SCR-related codes

What are some common causes of the code?

Causes

of this code may include:

Faulty reductant pressure sensor
Open or shorted circuits in the reductant pressure sensor system
Faulty SCR controller/PCM or programming error

What are the troubleshooting steps for P204A?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and vehicle-specific diagnostic information source will be needed to diagnose a P204A code.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It’s a good idea to record this information before clearing the codes, then test drive the vehicle until the PCM enters readiness mode or the code resets.

If the PCM enters readiness mode at this point, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions that contributed to the code being stored may need to worsen before an accurate diagnosis can be made.

Step 1

Use the DVOM to test the reductant pressure sensor according to manufacturer specifications. Components that test outside the allowable parameters should be considered faulty.

Step 2

If the actual reductant system pressure is within specifications, the P204A code persists, and the sensor in question is operational, use the DVOM to test the input and output signal circuits between the pressure sensor and the PCM/SCR controller. Disconnect all controllers before using the DVOM for testing.

Reductant pressure sensor codes are typically attributed to a leaking reductant system pump internally but complete your diagnosis

P204B – Range / Performance of the Pressure Sensor Reduction Circuit

How Serious Is Code P204B?

Code P204B is a serious code that should be addressed promptly. If ignored, it can lead to:

Disabling of the SCR system (selective catalytic reduction), which is essential for reducing pollutant emissions.
Catalyst damage if the issue persists, resulting in costly repairs.
Increased pollution with excessive black smoke emissions.

Prompt intervention is therefore necessary to avoid mechanical complications and failures in emissions testing.

Symptoms of Code P204B

Common signs associated with this code include:

🚨 Check engine light on (or SCR warning message).
⛽ Decreased fuel efficiency (increased fuel consumption).
⚡ Reduced engine performance (lack of power, unstable idle).
💨 Excessive black smoke from the exhaust.
🔍 Other SCR system-related codes (such as P20EE, P2047, etc.).

Possible Causes of Code P204B

Several factors can trigger this fault:

Faulty reductant pressure sensor – Incorrect data sent to the PCM.
Electrical issues – Cut wires, short circuits, or corroded connectors in the sensor circuit.
SCR/PCM module failure – Programming error or internal malfunction.
Mechanical problem in the SCR system – Faulty reductant pump, clogged injector, or insufficient AdBlue level.

Diagnostic Procedure for Code P204B

Required tools:

📟 OBD2 scanner (to read codes and real-time data).
🔌 Multimeter (DVOM) (to test circuits and sensors).
📖 Vehicle-specific repair manual (wiring diagrams, reference values).

Troubleshooting steps:

1. Checking codes and real-time data

Connect the scanner and note all stored codes.
Check live data (SCR pressure, sensor performance).
Look for relevant technical service bulletins (TSB) for the model.

2. Testing the reductant pressure sensor

Using the multimeter, check the sensor’s resistance and voltage according to manufacturer specifications.
If values are out of range, replace the sensor.

3. Inspecting electrical circuits

Check connectors and wiring between the sensor and PCM.
Look for broken wires, short circuits, or corrosion.
Test continuity with the multimeter (disconnected from PCM to avoid damage).

4. Checking the SCR system

Verify the level and quality of AdBlue (urea solution).
Inspect the SCR pump and injector for blockages or leaks.
If necessary, perform cleaning or replacement of faulty components.

Conclusion

Code P204B indicates a critical issue in the SCR system, which can lead to excessive pollution and catalyst damage. An electrical and mechanical inspection is required to identify the source of the problem (sensor, wiring, or SCR module).

🔧 Tip: If diagnosis is complex, consult an SCR system specialist to avoid incorrect repairs.

⚠ Ignoring this code may result in higher repair costs and failure of the emissions control system.

Need help? Share your symptoms in the comments for targeted advice!

P204C – Reductant Pressure Sensor Circuit Low

How Severe Is This DTC?

A stored P204C code should be considered severe and addressed as quickly as possible. The SCR system could be disabled because of this. Catalyst damage may occur if the conditions that contributed to storing the code are not corrected in a timely manner.

What Are Some of the Symptoms of the Code?

Symptoms of a P204C fault code may include:

Reduced fuel efficiency
Excessive black smoke from the vehicle’s exhaust
Decreased engine performance
Other SCR-related codes

What Are Some Common Causes of the Code?

Causes of this code may include:

Faulty reductant pressure sensor
Open or shorted circuits in the reductant pressure sensor system
Faulty SCR controller/PCM or programming error

What Are the P204C Troubleshooting Steps?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information will be needed to diagnose a P204C code.

You can use your vehicle information source to locate a Technical Service Bulletin (TSB) that matches the vehicle’s year, make, and model; as well as engine size, stored codes, and presented symptoms. If you find one, it may provide useful diagnostic information.

If the PCM enters readiness mode at this point, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions that contributed to storing the code may need to worsen before an accurate diagnosis can be made.

Step 1

Use the DVOM to test the reductant pressure sensor according to manufacturer specifications. Components that test outside the allowable parameters should be considered faulty.

Step 2

If the actual reductant system pressure meets specifications, the P204C code persists, and the sensor in question is operational, use the DVOM to test the input and output signal circuits between the pressure sensor and the PCM/SCR controller. Disconnect all controllers before using the DVOM for testing.

Reductant pressure sensor codes are typically attributed to a leaking reductant system pump internally but complete your diagnosis

P204D – High Reducer Pressure Sensor Circuit

How Severe Is This DTC?

A stored P204D code should be considered severe and addressed as quickly as possible. The SCR system could be disabled because of this. Catalyst damage might occur if the conditions that contributed to storing the code are not corrected in a timely manner.

What Are Some of the Symptoms of the Code?

Symptoms of a P204D trouble code may include:

Reduced fuel efficiency
Excessive black smoke from the vehicle’s exhaust
Decreased engine performance
Other SCR-related codes

What Are Some Common Causes of the Code?

Causes of this code may include:

Faulty reductant pressure sensor
Open or shorted circuits in the reductant pressure sensor system
Faulty SCR controller/PCM or programming error

What Are the P204D Troubleshooting Steps?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a vehicle-specific diagnostic information source will be needed to diagnose a P204D code.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It’s a good idea to note this information before clearing the codes, then test the vehicle until the PCM enters readiness mode or the code resets.

If the PCM enters readiness mode at that point, the code is intermittent and may be much harder to diagnose. If that’s the case, the conditions that contributed to storing the code may need to worsen before an accurate diagnosis can be made.

If the code is immediately reset, the next step in your diagnosis will require you to search your vehicle information source for diagnostic flowcharts, connector pinout diagrams, connector face views, and component testing procedures/specifications.

Step 1

Use the DVOM to test the reductant pressure sensor according to the manufacturer’s specifications. Components that do not test within the allowed maximum parameters should be considered faulty.

Step 2

If the actual reductant system pressure is within specifications, the P204D code persists, and the sensor in question is operational, use the DVOM to test the input and output signal circuits between the pressure sensor and the PCM/SCR controller. Disconnect all controllers before using the DVOM for testing.

Reductant pressure sensor codes are often attributed to a leaking reductant system pump internally, but complete your diagnosis.