Active grille shutters (AGS) are featured in a number of domestic and import brands and models of vehicles, dating back to approximately 2005. In essence, this is simply a shutter (louver) assembly located behind the grille, powered by an electric motor and controlled by the engine temperature signal from the coolant temperature sensor. Sometimes active grille shutters are referred to as radiator airflow shutters, active air shutters, active aero louvres, electronically controlled air shutters and electronically controlled aero shutters.
In simple terms, the active grille shutter assembly features a series of horizontal shutters (louvers) that open and close, much like a set of blinds on a window in your house. Instead of requiring manual operation, a controller motor performs the task based on a programmed set of operating conditions. And instead of adjusting the amount of light that passes through a window, the active grille shutters adjust the amount of airflow that enters through the radiator and into the engine bay.
When the engine is “cold,” upon initial startup, the louvers close in order to help the engine reach operating temperature more quickly, and they open when more airflow is needed. The reason for active shutters is two-fold: to enhance aerodynamics (instead of oncoming air moving into the engine bay, the closed shutters help to divert air over the vehicle) and to increase engine efficiency for improved fuel economy and lower tailpipe emissions by helping the catalytic converter light off sooner after initial startup. At low speeds, depending on engine temperature, the louvers may be closed or open. At freeway speeds, the louvers tend to close to increase aerodynamic efficiency.
It should come as no surprise that potential failure problems can occur if the shutters do not function properly. There may be problems due to jammed louvres (ice/snow buildup, dirt/debris), if the vehicle experienced a front-end collision, or if the engine temperature sensor had an issue.
The most common issue involves the active grille shutters becoming stuck – either open or closed. This may be due to a failed motor or the mechanical linkage between the motor and shutters has failed. Or, the electrical signal at the motor may be faulty. If the shutters are mis-aligned (due to manufacturing defect or the result of a collision, mishandling or other damage), the shutter panels may stick or operate intermittently. Bear in mind that the AGS assembly is made of a “thermoplastic/composite” material. As such, the shutters and frame can be susceptible to damage if mishandled or impacted. Continental (one of the manufacturers of AGS in addition to Dorman and SMP) notes that there are a number of issues that can cause an AGS system to fail or work improperly. Some of the most common causes include physical obstructions, excessive debris or electrical issues such as a failed actuator. An actuator with a short in the actuator harness or a connector that is broken, bent, pushed out, or has significant corrosion can cause problems in AGS function. Finally, collision damage can cause an AGS system to work improperly or stop working altogether. Any of these issues can cause more severe problems with a vehicle, including overheating the engine due to the restriction in airflow. With the ever-growing number of trucks and SUVs that utilize AGS systems, it is crucial that service providers understand some of the common problems associated with them.
An array of sensors/signals work in unison to provide the ECM with the required operation. In addition to the engine coolant temperature sensor and vehicle speed monitoring, air speed sensors may be located in the front of the vehicle to measure airflow volume and direction. If the AGS system detects a problem, the check engine light will illuminate. If the system begins to act erratically (constant opening/closing), or remains stuck in the closed position, this can potentially result in engine hot spots (overheating) due to uneven or insufficient airflow. While AGS in theory is a good idea, as it is intended to speed initial engine warm-up, decrease emissions and reduce parasitic drag, the presence of the shutter system in front of the radiator poses a potential for blocking airflow through the radiator if the shutters become stuck in the closed position. As with many technological advancements, there are pros and cons. AGS is an example of one more variable thrown into the equation. Note that a problem with AGS may or may not illuminate a MIL indication to the driver.
As noted earlier, AGS is featured on a range of vehicle makes/models. Examples include, but are not limited to, 2017 and later Honda CRV and Odyssey, 2013 and later Dodge Ram, 2012 and later Ford Focus, 2016 and later F-150, various GM vehicles from 2012 and later, 2016 and later Toyota Prius, 2022 and later Tundra, 2019 and later RAV4, 2022 and later Titan. Again, this is merely a sampling of makes/models that feature AGS.
Variables by vehicles
Here's a look at how it works in some makes and models.
2020 Toyota RAV4 Hybrid: The swing grille actuator assembly receives signals from the ECM, hybrid vehicle control ECU assembly and air conditioning amplifier assembly via CAN communication. Based on these signals, the swing grille actuator assembly operates the radiator shutter sub-assembly. If a malfunction occurs in the grille shutter system, a warning will be displayed on the multi-information display and grille shutter system operation will be disabled.
The grille shutter closes or opens when certain conditions related to the vehicle speed, engine coolant temperature, inverter coolant temperature, ambient temperature and refrigerant pressure are met. When the ignition switch is shut off, the grille shutter opens to prevent the grille shutter from becoming stuck closed while the vehicle is stopped. Trouble areas may include the swing grille actuator assembly branch wire or connector, the power source circuit of the swing grille actuator assembly, swing grille actuator assembly ground circuit, the swing grille actuator or radiator shutter assembly.
The Toyota system, citing but one example, is designed to open the shutter system when the engine coolant temperature reaches 167 F. At vehicle speed of 37-93 mph, the shutter closes. The shutter opens automatically when air temperature reaches 95 F or higher and/or when engine temperature reaches about 204 F. During cold winter operation of ambient temperature of 41 F or lower, the winter control mode function suspends grille operation in other than fully open or fully closed to prevent grille freeze-up.
Using Toyota RAV4 Hybrid AGS as an example, the following are potential trouble codes relating to active grille shutters:
- B1333: Shutter control state maintenance mode
- P059F-73: Active grille air shutter “A” actuator stuck closed
- P05A0-72: Active grille air shutter “A” actuator stuck open
- P05A0-74: Active grille air shutter “A” actuator slipping
- P05A2-11: Active grille air shutter “A” circuit short to ground
- P05A2-12: Active grille air shutter “A” circuit short to battery
- P05A2-13: Active grille air shutter “A” circuit open
- P05A2-7E: Active grille air shutter “A” actuator stuck on
- P05A2-7F: Active grille air shutter “A” actuator stuck off
- P05B1-12: Active grille air shutter “B” circuit short to battery
- P05B1-14: Active grille air shutter “B” circuit short to ground or open
- P05B1-31: Active grille air shutter “B” no signal
- U1293-87: Lost communication between hybrid powertrain control module and active grille air shutter...missing message
Note that regardless of make/model, P059F is the “generic” code that indicates an AGS problem, usually indicating a stuck-closed shutter issue.
2016 and later Ford F-150: The active grille shutter system is primarily used to maximize fuel economy by reducing aerodynamic drag, and to shorten engine warm-up time. The active grille shutter actuator(s) receive position commands from the PCM. The active shutter system carries out a calibration sequence whenever the engine is started, fully opening and closing the shutters before positioning the louvers in the programmed position as requested by the PCM. If the truck is equipped with a 2.7L or 3.5L GTDI turbo engine, there are two independent shutters. The upper active grille shutter system is controlled in the traditional sense, which is to moderate air flow to the underhood area. The lower active grille shutter system is dedicated to thermal management of the turbocharger CAC (charge air cooler).
As mentioned, the active grille shutter actuator positions the shutters based on commands from the PCM. The shutter moves 90 degrees from fully closed to fully opened, and based on the position commanded by the PCM is set in one or 16 positions (with about 6 degrees between positions). During normal operation, the shutters may be partially to fully open when the engine is off, depending on ambient temperature. Once the engine is started, a self-calibration occurs which takes about 15 to 20 seconds. The active grille shutter system performs the calibration sequence by detecting the open and closed positions, and continues until successful or a fault is detected. If faults are found (shutter blocked or actuator error), a recalibration is initiated. If the problem is not resolved after three or four attempts, a timer starts and sets a DTC when the timer reaches a predetermined limit.
In a system that features both upper and lower shutter assemblies, the upper shutter control is based on various PCM inputs including vehicle speed, coolant temperature, ambient temperature and A/C system pressure). If equipped with turbochargers, the lower shutter assembly control is dedicated to managing charge air temperature into the turbochargers and is based on additional inputs including turbo charge pressure and charge air temperature.
The PCM communicates with the AGS via a LIN. The LIN supports bi-directional communication between the AGS and the PCM, allowing the AGS actuator(s) to communicate position and fault information to the PCM. The PCM sets AGS DTCs when fault information is communicated by the AGS for a predetermined amount of time. Any failures of the LIN for over 10 seconds continuously results in the AGS actuator positioning the grille shutter fully open. There is no indication to the driver when a fault with the AGS is present or an active AGS DTC is set in the PCM.
The AGS actuator is a smart motor which receives position requests from the PCM via the LIN. One of the active grille shutter blinds connects to the AGS shutter actuator using a retainer. The actuator can be serviced separately or as an entire assembly (which includes the active grille shutter, actuator, retainer, housing and jumper harness). The shutter is comprised of shutter “blinds” which are linked together. One of the blindsisi fixed to the actuator. When the actuator moves, it moves the attached shutter blind, which causes the remaining blinds to move.
GM vehicles: A shutter performance issue will always present DTC P059F (active grille air shutter 1 performance) and possibly U0284 (lost communication with actuator 1) for the upper shutters and P05AE (active grille air shutter 2 performance) and U0285 (lost communication with active grille air shutter actuator 2) for the lower shutters. According to GM, shutters should never be replaced if these DTCs are not present.
Check for U0284 and U0285. On light duty trucks, these codes may be paired with DTC U0632 (lost communication with cooling fan motor), U0633 (lost communication with engine cooling fan 2), U0180 (lost communication with battery monitor module) or U1345 (engine control module LIN Bus 1). If any of these codes are set, check the condition of the aero shutter fuse, engine wiring harness, jumper harness to the shutter actuators, X133 connector and other connectors to the aero shutter and J170 splice (light duty trucks only). Even a small amount of movement of the splice may cause an intermittent communication issue.
If DTC P059F and P05AE are set, check for debris in the upper and lower shutters (a louver/vane that may be disengaged from the linkage or a shutter that is binding). Try to remove any debris by hand or by using compressed air before potentially wasting time removing the front fascia and shutter. On light duty trucks, the upper shutter may be binding in the left side air induction plenum. On both light trucks and SUVs, also check for shutter binding on the right side horn or bracket. You should have at least 10mm of clearance between the shutter louver and horn.
Multiple AGS on one vehicle
Some vehicles have more than one Active Grill Shutter that can fail or operate improperly. Vehicles can have an upper, lower, left, and right AGS and if that causes a DTC, it is important for technicians to determine which shutter is the culprit.
It should come as no surprise that, due to the nature of having a series of shutters pivoting up and down as temperatures and vehicle operation change, the shutters must be able to operate freely upon command. While it’s always been important to keep the radiator area clean and free of debris, when a vehicle features AGS, cleanliness becomes even more important. Whenever the vehicle is in your shop for service, try to remember to inspect the AGS and to remove any debris that may cause interference, such as leaves, dirt, insects, etc. If winter conditions result in ice/snow accumulated in the louvres, spray the louvres with warm water or with the careful use of a heat gun to clear any obstructions.
If AGS operation is a concern, inspect the seals/gaskets around the shutter. Damaged seals can allow moisture and dirt to accumulate. If a thorough cleaning is needed, remove the shutter assembly from the vehicle and clean with hot water and soap (such as dishwashing liquid), and then lube the shutter pivot points with a light lube such as WD-40. Reinstall and test the shutter by starting the engine and allowing it to reach operating temperature, noting shutter movement.
Also inspect the shutter assembly to verify that all shutters are straight and parallel with each other. Depending on design, you may be able to correct shutter panel misalignment by loosening the screws that secure the louvers to the frame, aligning and retightening the screws.
Checking an existing AGS or verifying a replacement AGS for operation is easily done with your scan tool by commanding the shutters closed and open. If replacing the AGS, performing commanded tests allow you to verify operation before you go to the trouble of reinstalling the grille and other surround components.