Cold air is denser and contains more oxygen than hot air. So, when the air going into the engine is cold, the engine can run at high efficiency. The ambient air temperature sensor is responsible for measuring the temperature of the outside air.
The ambient air temperature sensor causes the check engine light to come on if the air temperature is higher than normal. When the sensor is dirty, faulty, or has loose connections, it, too, sends inaccurate temperature data to the ECU. The ECU then triggers the CEL.
I will discuss the reasons for this problem in detail and provide you with step-by-step solutions to deal with the problem. Let’s get started.
How Does the Ambient Air Temperature Sensor Cause the Check Engine Light?
As I have already said, cold air is more suitable for engines. It ensures the fuel is burnt completely inside the combustion chamber. The engine can produce more power and less emission if the air temperature is lower.
The ambient air temperature or AAT sensor is fitted near the intake manifold. It measures the temperature of the air outside and sends the data to the ECU. Depending on the air temperature, the ECU allows the right amount of fuel into the engine.
When the air-fuel mixture has the right ratio, it burns correctly. So, the engine performance is more efficient and creates less emissions. If the sensor is damaged or malfunctioning, the ECU doesn’t get the ambient air temperature data. That is stored as an error, and the check engine light comes on.
Reasons for Ambient Air Temperature Sensor Causing Check Engine Light
If the check engine light is turned on and you get the P0070-P0073 error code, the problem is related to the ambient air temperature sensor. Let’s see what those problems are and how you can fix them.
1. The Ambient Air Temperature Sensor Is Dirty or Damaged
It is a very common incident for sensors to get dirty. Especially if you drive over dusty or muddy terrains, the sensor can be covered in dirt or mud. This will prevent the sensor from working normally. Sometimes, the sensor can get accidentally damaged during repair.
As a result, the sensor can’t send accurate temperature data to the ECU. This will cause the check engine light to come on. If the check engine light is not working, you can sense the problem by noticing engine misfiring, poor acceleration, low fuel economy, etc.
Step-by-Step Solution
- Locate the ambient air temperature sensor in your car. It should be close to the intake manifold and the front grill.
- Check if the sensor is dirty. If so, you need to clean it. Use compressed air or a soft-bristle brush to clean the sensor.
- If the sensor is damaged, you need to remove the electrical connectors and take the sensor off. Then, install a new sensor. The check engine light should go off now.
You can follow this process to install the AAT sensor:
2. Loose Connections Between the Sensor and the ECU
The electrical connection between the ambient air temperature sensor and the ECU should be tight and error-free. Over time, the wiring can get corroded or damaged. It will result in the system malfunctioning.
As a result, the ECU will not get temperature data from the sensor properly. The check engine light will turn on due to the problem. Sometimes, loosely connected wires can temporarily form a stable connection. If the check engine light came on and then went off, it could be the possible cause.
Step-by-Step Solution
- Open the hood and locate the wiring harness reaching the ambient air temperature sensor.
- Check the wiring harness for signs of damage or corrosion. If the wiring is corroded or damaged, you need to remove the harness and install a new one.
- Make sure the harness has no obstructions. And the harness should be connected tightly to the sensor.
3. Malfunctioning Ambient Air Temperature Sensor
Even though the chances of sensors having internal faults are slim, they can happen. Especially if the car is old, the ambient air temperature sensor can develop faults.
In that case, the sensor can send erratic temperature data to the ECU. It will cause the check engine light to come on.
Step-by-Step Solution
- Use an OBD2 scanner to read the error code. I suggest using the BlueDriver Bluetooth OBDII Scan Tool. If it shows the P0071-P0073 error code, the sensor is malfunctioning. You need to replace the sensor.
- Disconnect the wiring harness by prying the tab on the connector. Then, remove the old sensor from the housing.
- Install a new sensor and connect the wiring harness. Make sure the connector clicks in place.
4. Sudden Temperature Changes
If the ambient temperature sensor is exposed to extreme temperature changes, it can trigger the check engine light. Even though the sensor is working fine, the sudden change in temperature will confuse the ECU. So, the ECU will turn the check engine light on.
Step-by-Step Solution
- You don’t have to do anything as the sensor is working properly. Simply continue driving for some time, and the error will be reset automatically.
5. The ECU Is Malfunctioning
Sometimes, there can be a software glitch in the ECU or electronic control unit. It might not be able to process the temperature data from the sensor correctly. So, the check engine light will come on.
Step-by-Step Solution
You need to reset the ECU. To do this, follow the steps below.
- Turn the car off.
- Open the hood and disconnect the battery terminals. Take the black or negative cable off first. Then, remove the positive cable.
- Press the horn several times so that all the residual charges are drained.
- Connect the positive cable first and then the negative cable to the battery terminals.
- Start the car. The ECU should now be reset, and the check engine light will disappear. If the light is still on, contact an expert technician to reprogram the ECU.
People Also Ask
Check answers to some commonly asked questions about the ambient air temperature sensor and check engine light.
Can an ambient air temperature sensor affect the engine?
Of course. If the sensor doesn’t work properly, the engine will not deliver the desired performance. Besides, the engine can overheat and start misfiring. The fuel economy will also drop.
Can I drive my car with a check engine light caused by the ambient air temperature sensor?
You can, but I suggest not to. Ignoring a faulty ambient air temperature sensor can result in expensive repairs. So, you should diagnose the reason promptly and take steps to solve the problem.
Does the check engine light keep flashing if the ambient air temperature sensor is bad?
No. The check engine light will be steady if the problem is related to the ambient air temperature sensor.
Conclusion
The ambient air temperature sensor is a very small component, but it has a significant effect on engine performance. If the sensor is not working properly, it will cause multiple issues. I mentioned five reasons why the ambient air temperature sensor causes the check engine light.
Knowing these reasons will give you an edge while diagnosing the problem. Then, you can implement the solutions included here to resolve the issue. Once the problem is solved, the engine performance will be restored. The fuel efficiency of the car will also rise, and the check engine light will disappear.