P0073 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Meaning

The engine control module (ECM) is in continual contact with other modules, such as those that regulate the anti-lock brake system, automatic gearbox, and climate control system, in addition to managing the engine. When it comes to climate control, the ECM has to know when to turn on the air conditioner compressor, which is determined by the climate control module's command (CCM). Similarly, the CCM requires information from the ECM on coolant temperature, ambient air temperatures, and air-conditioning compressor performance.

On cars with automated climate control, the desired cabin temperature (or temperatures, depending on how many zones the system can manage) is simply selected. The CCM is in charge of everything else, including heat or air conditioning application, blend door positions, vent door positions, fan speed, and so on.

The CCM relies on a variety of signals to do these measurements, including outside ambient air temperature, one or more interior air temperature sensors, air-conditioning clutch function, engine coolant temperature, and so on. When one of the signals fails, the CCM stores this diagnostic trouble code (DTC) in memory. 

Causes

The possible causes of DTC P0073 could be 

• Defective powertrain control module (PCM) or engine control module (ECM) 
• A faulty sensor for detecting ambient temperature
• The sensor harness for the ambient air temperature is either broken or shorted
• Air Temperature Sensor Circuit - Bad Electrical Connection

Symptoms

Here is what you’ll notice with a P0073:

• Malfunction Indicator Light (MIL) On 
• Air Conditioning may not perform properly 
• Instrument cluster may not read outside temperature accurately 
• Overhead console may not read outside temperature accurately

Diagnosis

The AAT (ambient air temperature) sensor, connection, and wire harness will need to be inspected due to this DTC. A slow AAT will not set a DTC, but an open or short circuit will. You'll need a DVOM (digital volt-ohm metre), a thermometer, and some free time.

Replace the sensor if the resistance readings are inconsistent or the connection is corroded. If the sensor is working properly then check the wiring.

Use your DVOM to measure the resistance across the AAT sensor's terminals. Check the resistance against the temperature and the repair manual's resistance table. Increase the temperature of the AAT sensor while changing the resistance. Ensure a smooth resistance shift with no dropouts.

Check three-wire sensors when connected and with the key in the “on” position. Check for a 5 V reference, a good ground, and a changing voltage on the signal line. Look up pins and voltages in your repair manual or wiring diagram.

A Check of the Cables; Examine the wire harness for wear. Then inspect the AAT connection for bent or backed-out pins, corrosion, or water intrusion. Assemble the AAT connection.

Check the 5 V reference voltage and the variable signal voltage with the key on. The third wire of three-wire AAT sensors must be grounded. Please refer to your repair manual or electrical wiring diagram for pinout and signal. If there is any problem in AAT sensor, fix it. 

Common Mistakes

It's usual to replace the ambient air temperature sensor without checking the cabling and connection. It is not usually recommended to replace the whole sensor.

How Serious is This?

There is no need to be concerned about the P0073 error code because it has no effect on the vehicle's functionality. This, on the other hand, might make the driver uncomfortable since it could hinder the climate control system (heat and/or air conditioning controls) from operating properly.

What Repairs Can Fix the Code

OBD-II codes have no universal remedy since cars are designed differently by each manufacturer. Special features and extra components can also be customized. So, always follow the manufacturer's repair instructions. Given below is the general way to repair this error code. 

• Broken or Shorted wires should be repaired or replaced
• Remove any corrosion that may have occurred on the electric circuits and connection
• Replace the sensor that measures the temperature of the surrounding air

Related Codes

In most cases, others related codes accompany P0073 such as:

• P0070 “Ambient Air Temperature Sensor Circuit Malfunction”
• P0071 “Ambient Air Temperature Sensor Range/Performance”
• P0072 “Ambient Air Temperature Sensor Circuit Low Input”
• P0074 “Ambient Air Temperature Sensor Circuit Intermittent”

Diagnostic steps for this code are all the same.

Conclusion

DTC- P0073 is not major problem. However, this could lead to serious trouble like failure of PCM or ECM. One may feel intense heat in summer due to this error code. This error can be solved by a little technical knowledge and specific tools.