Understanding OBD2 codes can be crucial in diagnosing and repairing your vehicle. Among these codes, Obd2 Code P0073 signals a problem within the Ambient Air Temperature (AAT) sensor circuit. As an expert from obd-de.com, I’m here to guide you through understanding, diagnosing, and potentially resolving this issue. This article provides a comprehensive guide to help you tackle the P0073 code effectively.
Understanding OBD2 Code P0073
What Does P0073 Really Mean?
The obd2 code p0073, technically described as “Ambient Air Temperature Sensor Circuit High,” indicates that your vehicle’s Powertrain Control Module (PCM) has detected an abnormally high voltage reading from the Ambient Air Temperature (AAT) sensor circuit.
The AAT sensor’s role is to measure the outside air temperature and relay this information to the PCM. This data is vital for several vehicle systems, including:
- Air Conditioning (AC) System: The PCM uses AAT readings to optimize AC performance and efficiency.
- Temperature Display: The reading is often displayed on your instrument cluster or overhead console, providing you with the external temperature.
- Engine Management: In some vehicles, the AAT sensor data can subtly influence engine management strategies.
The PCM constantly monitors the AAT sensor’s signal. It compares this reading with other temperature sensor inputs like the Intake Air Temperature (IAT) sensor and Engine Coolant Temperature (ECT) sensor, especially when the engine is cold. A significant discrepancy or an implausibly high voltage from the AAT sensor circuit triggers the P0073 code. This usually points towards electrical faults rather than a sensor malfunction itself.
Symptoms Associated with P0073
When the P0073 code is present, you might notice several symptoms:
- Check Engine Light (Malfunction Indicator Lamp) is illuminated: This is the most common and immediate symptom.
- Air Conditioning Malfunctions: Your AC might not cool as effectively or may not function at all.
- Inaccurate Outside Temperature Readings: The temperature displayed in your car might be incorrect or absent.
- Possible Impact on Fuel Efficiency: In some cases, incorrect AAT readings can indirectly affect engine performance and fuel economy, although this is less common.
An example of an Ambient Air Temperature Sensor location, typically found behind the grille or front bumper.
Pinpointing the Causes of OBD2 Code P0073
Several factors can lead to the P0073 code. Here are the most common culprits:
- Open Circuit in the Signal Wire: A break or disconnection in the wiring leading to the AAT sensor can cause a high resistance and trigger the code. This is a frequent issue due to exposure to harsh environmental conditions and vibrations.
- Short to Voltage in the Signal Wire: If the signal wire is shorting to a voltage source, it will send an incorrect high voltage signal to the PCM. This can happen due to damaged wiring insulation.
- Faulty AAT Sensor: While less common than wiring issues, the AAT sensor itself can fail. Internal sensor malfunctions can lead to incorrect readings.
- Corrosion or Damaged Connectors: Connectors at the sensor or PCM can become corroded or damaged, causing poor electrical contact and leading to a high resistance in the circuit.
- PCM Failure (Unlikely): Although rare, a faulty PCM could misinterpret sensor signals or incorrectly diagnose a P0073 code. This is usually considered a last resort diagnosis after ruling out other possibilities.
Step-by-Step Guide to Diagnosing and Fixing P0073
Before you start, remember to consult your vehicle’s specific repair manual for precise locations and procedures. Safety first – always work on your vehicle when it’s parked on a level surface and the engine is off and cool.
Step 1: Initial Checks and Technical Service Bulletins (TSBs)
Begin with the basics:
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Check for TSBs: Search for Technical Service Bulletins (TSBs) related to P0073 and your specific vehicle make and model. Manufacturers often issue TSBs for known issues and their fixes, which can save you significant time.
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Visual Inspection: Locate the AAT sensor. It’s typically positioned in front of the radiator, behind the grille, or in the front bumper area. Carefully inspect the sensor, its wiring, and connectors for any obvious signs of damage:
- Wiring: Look for frayed, broken, or melted wires. Pay close attention to areas where wiring might rub against metal parts.
- Connectors: Check for corrosion, bent or broken pins, and loose connections.
Inspect connectors for signs of corrosion, which can disrupt electrical signals.
Step 2: Testing the AAT Sensor and Circuit
For this step, you’ll need a Digital Volt-Ohm Meter (DVOM).
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Sensor Resistance Test:
- Disconnect the AAT sensor connector.
- Set your DVOM to measure resistance (Ohms).
- Connect the DVOM leads to the sensor terminals.
- Compare the measured resistance to the expected value at the current ambient temperature. You may need to find a temperature-resistance chart for your specific sensor (often available online or in repair manuals).
- An open circuit (infinite resistance or “OL” reading) or a very low resistance reading usually indicates a faulty sensor.
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Voltage Test:
- Leave the sensor disconnected and turn the ignition key to the “ON” position (engine off).
- Set your DVOM to measure DC voltage.
- Probe the connector terminals on the harness side (the side that connects to the vehicle’s wiring, not the sensor itself). You should typically find a 5-volt reference voltage on one of the terminals.
- If there’s no voltage, or voltage is significantly different from 5V, there’s likely a problem in the wiring leading back to the PCM or the PCM itself.
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Signal Wire Continuity and Short to Ground/Voltage Test:
- Turn the ignition OFF.
- Disconnect the PCM connector (refer to your repair manual for location and procedure).
- Using your DVOM in continuity mode, check the signal wire for continuity from the sensor connector to the PCM connector. No continuity indicates an open circuit.
- Test for shorts to ground and voltage. Using the DVOM in resistance mode, check for resistance between the signal wire and ground (chassis ground) and between the signal wire and a 12V source. Low resistance indicates a short.
Step 3: Component Replacement and Final Checks
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Repair Wiring and Connectors: If you found any wiring issues or corroded connectors, repair or replace them. Use proper wiring repair techniques to ensure a reliable connection. Apply dielectric grease to connectors to prevent future corrosion.
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Replace the AAT Sensor (If Necessary): If the sensor resistance test failed, replace the AAT sensor with a new, quality part.
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Clear the OBD2 Code: Use an OBD2 scanner to clear the P0073 code from the PCM memory.
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Test Drive and Re-scan: Take your vehicle for a test drive to see if the code returns. Re-scan the OBD system to confirm that the P0073 code is gone and no new codes have appeared.
Common Mistakes to Avoid
- Jumping to PCM Replacement: Avoid assuming the PCM is faulty immediately. PCM failures are rare. Thoroughly test the sensor and wiring first.
- Using Generic Sensors: Ensure you use a compatible and quality AAT sensor for your vehicle. Generic or low-quality sensors might not function correctly.
- Neglecting Wiring Inspection: Wiring problems are the most common cause of P0073. Don’t skip thorough wiring checks.
- Forgetting to Clear Codes: After repairs, always clear the OBD2 codes and re-scan to confirm the fix.
Conclusion
Dealing with obd2 code p0073 involves a systematic approach to diagnosis and repair. By understanding the function of the AAT sensor, recognizing the symptoms, and following a step-by-step troubleshooting process, you can effectively address this issue. Remember to prioritize safety, consult your vehicle’s repair manual, and if you’re unsure at any point, seek assistance from a qualified automotive technician. Proper diagnosis and repair will ensure your vehicle’s systems operate correctly and efficiently.
Disclaimer: This information is for informational purposes only and should not be considered professional repair advice. Always consult with a qualified technician for vehicle repairs.
