P1D73 – Active Grill Shutter Performance (Chrysler)

By Reinier (Contact Me)
Last Updated 2023-10-02
Automobile Repair Shop Owner

Manufacturer Specific Definitions for P1D73

Table of Contents

1. What Does Code P1D73 Mean?
2. Where is the P1D73 sensor located?
3. What are the common causes of code P1D73?
4. What are the symptoms of code P1D73?
5. Get Help with P1D73

What Does Code P1D73 Mean?

OBD II fault code P1D73 is a manufacturer-specific trouble code that is defined by carmaker Chrysler as P1D73 – “Active Grill Shutter – Performance” and is set when the BCM (Body Control Module) detects an unexpected voltage or position report/reading from the Active Grill Shutter actuator or position sensor. Note that the term “Performance” in this definition could also include issues like the shutters moving at an abnormally high or low speed or not moving through their full range of allowable movement.

Although the primary function of active grill shutters is to improve the aerodynamics of vehicles by deflecting the airflow around a moving vehicle instead of allowing the airflow to enter the engine compartment where it acts as a brake on the vehicle, active grill shutters have other important, albeit secondary functions.

For example, active grill shutters reduce engine warm-up times by preventing air from flowing through the radiator when the shutters are closed. More importantly, though, active grill shutters also greatly reduce aerodynamic lift balance, which is a phenomenon that tends to lift the front of the car at high road speeds. This phenomenon is caused by the air stream that enters the engine compartment where it is somewhat compressed by the vehicle’s high rate of forward motion. Moreover, the trapped air in the engine compartment also causes significant turbulence in the air that flows around a moving vehicle, which acts as a braking mechanism on the vehicle that increases fuel consumption and harmful exhaust emissions.

In terms of operating principles, the BCM collects input data from several engine sensors, such as (among others) the transmission fluid temperature sensor, the engine coolant sensor, the engine speed sensor, and the A/C system pressure to determine suitable and appropriate active grill shutter strategies.

For example, the shutters will typically not open when the engine coolant is below a certain threshold, or close when the engine coolant temperature is above a maximum allowable threshold. Similarly, the shutters will open when the automatic transmission fluid reaches a maximum allowable threshold to allow for improved cooling of the transmission fluid through the radiator. We could list other examples here, but the point is that while the enabling conditions for active grill operation vary between vehicles, all required enabling conditions must be met before the BCM will activate the shutters in any direction.

It is worth pointing out that despite any other functions and benefits active grill shutters might have, efficient engine cooling largely depends on the active grill shutters working as both designed and expected. For instance, if the shutters are locked or stuck in the closed position, it will be impossible for the radiator to shed heat into the atmosphere, and the engine will overheat very quickly.

Thus, if faults or malfunctions occur in the circuits that control or monitor the active grill shutters that cause the shutters to be in an unexpected position given the current operating and environmental conditions, the BCM will recognize that it cannot manage engine cooling and other functions effectively with the active grill shutters. When this happens, the BCM will set code P1D73 and possibly illuminate a warning light upon detecting the shutter’s unexpected position or behavior for the first time.

Where is the P1D73 sensor located?

This image shows the active grill assembly from a circa 2017 Chrysler 200 model. As with other Chrysler models, the grill assembly attaches to the vehicle’s bodywork between the outer grill and the radiator. In this location, the grill assembly can allow air to pass through the radiator when in the open position or divert the air stream through vents to flow around the vehicle when in the closed position to improve the vehicle’s aerodynamics.

What are the common causes of code P1D73?

Common causes of code P1D73 could include one or more of the following-

• Damaged, burnt, shorted, disconnected, or corroded wiring and connectors in the circuits that monitor and control the active grill shutters
• Failure to perform an active grill shutter relearn procedure after replacing or repairing the active grill shutters or their actuator
• Improperly installed replacement grill shutters
• Defective or malfunctioning active grill shutter actuator
• The presence of accumulated debris or snow in the shutters
• One or more defective or malfunctioning engine sensors
• Mechanical damage to the active grill shutters or actuator caused by minor accidents or impacts with road debris

What are the symptoms of code P1D73?

Common symptoms of code P1D73 could include the following-

• Stored trouble code and possibly an illuminated warning light
• Depending on the nature of the problem, multiple additional trouble codes relating to the active grill shutters may be present along with P1D73
• The engine may overheat
• The transmission may overheat
• The A/C system might be deactivated or not available
• The engine warm-up time may increase noticeably
• Fuel consumption may increase noticeably

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