P0072, P0073, and P0074: Ambient Air Temperature Sensor Circuit (Low, High and Intermittent)

P0072: Ambient Air Temperature Sensor Circuit Low Input P0073: Ambient Air Temperature Sensor Circuit High Input P0074: Ambient Air Temperature Sensor Circuit Intermittent

These codes mean that there is a problem with the ambient air temperature sensor or its circuit. This sensor measures the temperature of the air outside the vehicle and sends a signal to the engine control module (ECM) or powertrain control module (PCM). The ECM or PCM uses this information to adjust the fuel injection, ignition timing, and air conditioning system. The ambient air temperature sensor also displays the outside temperature on the instrument cluster or overhead console.

What Do These Codes Mean?

These codes indicate that the input from the ambient air temperature sensor does not match the expected range or varies too much from the inputs of other sensors, such as the intake air temperature sensor and the engine coolant temperature sensor. The ECM or PCM sets these codes when it detects an abnormality in the sensor’s voltage, resistance, or signal frequency.

What Causes These Codes?

The codes P0072, P0073, and P0074 can be caused by various factors, such as:

• A faulty ambient air temperature sensor
• A damaged or corroded wiring or connector in the sensor’s circuit
• A short or open circuit in the sensor’s circuit
• A wrong or improper location of the sensor
• A foreign object or debris hitting or blocking the sensor
• A faulty ECM or PCM (rare)

How A Faulty Ambient Air Temperature Sensor Affects Fuel Economy

The ambient air temperature sensor can cause reduced fuel economy and other engine problems because it affects the air-fuel mixture that the engine needs to run efficiently. The air-fuel mixture is the ratio of air and fuel that is burned in the engine’s combustion chamber. The ideal ratio is 14.7 parts of air to 1 part of fuel, which is called the stoichiometric ratio. This ratio ensures that all the fuel is burned completely and produces the maximum amount of power and the minimum amount of emissions.

However, the ambient air temperature sensor can alter this ratio by sending inaccurate data to the engine control module (ECM) or powertrain control module (PCM). The ECM or PCM is the computer that controls the engine’s operation and adjusts the fuel injection, ignition timing, and air conditioning system according to various inputs from sensors. If the ambient air temperature sensor reports a higher temperature than the actual temperature, the ECM or PCM will think that the air is less dense and will reduce the amount of fuel injected into the engine. This will result in a lean mixture, which means there is more air than fuel in the combustion chamber. A lean mixture can cause engine misfiring, rough idling, stalling, knocking, and increased emissions. It can also damage the engine by causing overheating, detonation, and pre-ignition.

On the other hand, if the ambient air temperature sensor reports a lower temperature than the actual temperature, the ECM or PCM will think that the air is more dense and will increase the amount of fuel injected into the engine. This will result in a rich mixture, which means there is more fuel than air in the combustion chamber. A rich mixture can cause engine flooding, poor acceleration, reduced power, and decreased fuel economy. It can also damage the engine by causing carbon deposits, fouled spark plugs, and catalytic converter failure.

Therefore, it is important to have a functioning ambient air temperature sensor that provides accurate data to the ECM or PCM. This will ensure that the engine runs at its optimal performance and efficiency level. You can find more information about this sensor and its location, function, and failure symptoms in these web search results1234. I hope this helps you understand why this code can cause reduced fuel economy and other engine problems. 😊

How to Diagnose These Codes?

To diagnose these codes, you will need a scan tool, a digital multimeter, and a wiring diagram for your vehicle. Follow these steps to troubleshoot these codes:

• Connect the scan tool to the vehicle’s diagnostic port and retrieve the stored codes and freeze frame data. Note down any other codes that may be related to the ambient air temperature sensor, such as P0112, P0113, P0117, P0118, etc.
• Clear the codes and test drive the vehicle to see if any of them return. If they do, proceed to the next step. If they do not, the problem may be intermittent or caused by a loose connection.
• Locate the ambient air temperature sensor on your vehicle. It is usually mounted in front of the radiator, behind the grille or bumper. Visually inspect the sensor and its wiring for any signs of damage, corrosion, or loose connections. Repair or replace any faulty components as needed.
• Disconnect the sensor connector and check for voltage and ground on the wiring harness side using the multimeter and wiring diagram. You should have battery voltage on one wire and a good ground on another wire. If not, trace the wires and repair any open or short circuits as needed.
• Check for resistance across the sensor terminals using the multimeter and wiring diagram. The resistance should vary according to the ambient temperature. Refer to your vehicle’s service manual for the specific resistance values for your sensor. If the resistance is out of range, replace the sensor.
• Reconnect the sensor connector and check for voltage on the signal wire using the multimeter and wiring diagram. The voltage should also vary according to the ambient temperature. Refer to your vehicle’s service manual for the specific voltage values for your sensor. If the voltage is out of range, replace the sensor.
• If all tests are passed, but any of these codes persist, you may have a faulty ECM or PCM. However, this is very rare and should be confirmed by a professional technician before replacing any expensive components.

How to Fix These Codes?

Depending on which code you have and what caused it, you may need to do one or more of the following to fix it:

• Replace the ambient air temperature sensor
• Repair or replace any damaged or corroded wiring or connectors in the sensor’s circuit
• Repair any open or short circuits in the sensor’s circuit
• Relocate or shield the sensor from external influences
• Replace the ECM or PCM (rare)

What are The Symptoms of These Codes?

These codes may not cause any noticeable drivability issues, but they may affect some functions of your vehicle, such as:

• The check engine light may be on
• The dashboard or overhead console may display an incorrect outside temperature
• The air conditioning system may not work properly
• The engine performance may be reduced
• The fuel economy may be decreased

How Serious are These Codes?

These codes are not very serious problems, but they should be addressed as soon as possible to avoid any potential damage to your engine or other components. If you ignore these codes for too long, you may experience poor fuel economy, increased emissions, or reduced performance.

How Common are These Codes?

These codes are not very common codes, but they can occur in any vehicle that has an ambient air temperature sensor. Some of the vehicles that are more prone to these codes are certain models of Audi, BMW, Chrysler, Dodge, Ford, Jeep, Mazda, Mitsubishi, and Volkswagen.

How to Prevent These Codes?

To prevent these codes from occurring in your vehicle, you should:

• Regularly inspect and maintain your ambient air temperature sensor and its wiring
• Avoid driving through deep water or mud that may damage or clog your sensor
• Keep your grille and bumper clean and free of debris that may block your sensor
• Use only quality replacement parts that are compatible with your vehicle

Conclusion

The codes P0072, P0073, and P0074 are generic codes that indicate a problem with the ambient air temperature sensor or its circuit. This sensor measures the outside air temperature and sends a signal to the ECM or PCM, which uses it to adjust the fuel injection, ignition timing, and air conditioning system. The ambient air temperature sensor also displays the outside temperature on the instrument cluster or overhead console. These codes can be caused by various factors, such as a faulty sensor, a damaged wiring or connector, a short or open circuit, a wrong or improper location of the sensor, a foreign object or debris hitting or blocking the sensor, or a faulty ECM or PCM. To diagnose and fix these codes, you will need a scan tool, a multimeter, and a wiring diagram for your vehicle. You may need to replace the sensor, repair or replace any faulty wiring or connectors, repair any open or short circuits, relocate or shield the sensor from external influences, or replace the ECM or PCM. These codes may not affect your drivability, but they may affect your air conditioning system and your outside temperature display. They may also cause poor fuel economy, increased emissions, or reduced performance. Therefore, you should address these codes as soon as possible to avoid any further damage to your engine or other components.

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