The “Lost Communication With Active Grille Air Shutter Module A” message is a common issue for Ford Focus ST owners, particularly those with aftermarket intercoolers. This article explains the cause of this diagnostic trouble code (DTC), its potential impact, and provides simple solutions to address it.
Why You’re Seeing This Code
Ford equips the Focus ST with active grille air shutters (AGS), a system of adjustable flaps located in front of the radiator and intercooler. These shutters improve aerodynamics and engine warm-up times. However, larger aftermarket intercoolers, often necessary for performance upgrades, require the removal of the entire AGS assembly. This removal triggers the “lost communication” code.
Understanding the Impact: Soft Code vs. Hard Code
The AGS DTC is typically a “soft” code, meaning it won’t illuminate the check engine light (CEL). While this might seem minor, some state inspections may flag this code. Additionally, the dangling electrical connector, exposed to the elements under the bumper, is susceptible to corrosion.
Potential Problems from a Dangling Connector
Dirt, moisture, and road salt can corrode the exposed AGS connector. This connector carries a 12V power line, a ground, and a crucial communications wire known as the LIN BUS (Local Interconnect Network). A shorted LIN BUS can disrupt communication with other components sharing the network, such as the alternator. This can lead to misdiagnosis and unnecessary replacement of alternators, batteries, and cables.
Simple Solutions to Address the Issue
The most straightforward solution involves reconnecting the AGS shutter motor. Remove the motor from the discarded assembly and plug it back into the connector. Securely zip-tie the motor out of the way, perhaps under the driver-side headlight. This eliminates the DTC and requires no calibration.
Unfortunately, Ford doesn’t sell the AGS motor separately; the entire assembly must be replaced. However, used motors (part number BM51-8476-AB) are often available online for a reasonable price. Ensure compatibility with the 2013-2018 USDM Focus ST.
Dealing with Disabled AGS Systems
If your tuner has disabled the AGS system software, consider removing the connector entirely. This prevents future corrosion issues. Simply cutting the connector and sealing the wires is a more reliable long-term solution than using tape or bags, which can degrade over time.
Conclusion
The “lost communication with active grille air shutter module A” code is a common consequence of aftermarket intercooler upgrades on the Ford Focus ST. While not a critical fault, addressing the exposed connector is crucial to prevent potential electrical problems and ensure a smooth state inspection. Reconnecting the motor or removing the connector entirely offers simple, effective solutions. Remember to consult with a qualified mechanic for any electrical diagnosis or repair.
