U0185 Lost Communication With Antenna Control Module

Introduction:

The U0185 diagnostic trouble code (DTC) indicates a loss of communication with the Antenna Control Module (ACM). This means the vehicle's computer network, specifically the Controller Area Network (CAN) bus, is unable to reliably communicate with the ACM, which is responsible for controlling various antenna-related functions. This lack of communication can lead to issues with radio reception, satellite radio (if equipped), and potentially other features dependent on antenna signals.

Table: U0185 Lost Communication With Antenna Control Module - Causes, Symptoms, and Diagnostics

Detailed Explanations:

Radio Reception Issues: Poor or no AM/FM radio reception is a common symptom of a U0185 code. This is because the ACM often controls the signal amplification and processing for the radio antenna. A faulty ACM can prevent the radio from receiving a clear signal, resulting in static or complete signal loss.

Satellite Radio Problems: If your vehicle is equipped with satellite radio (e.g., SiriusXM), a U0185 code can cause problems with receiving the satellite signal. You might see a "No Signal" message displayed on the radio, even if your subscription is active and the antenna is not physically damaged.

Navigation System Problems (GPS Antenna): Some vehicles use the ACM to manage the GPS antenna for the navigation system. If the ACM is not communicating properly, the GPS signal may be weak or nonexistent, leading to inaccurate location information or a "No GPS Signal" message.

Remote Keyless Entry (RKE) Issues: The ACM can sometimes be involved in the operation of the remote keyless entry system. A U0185 code may result in a reduced range for the key fobs or a complete failure to lock/unlock doors or start the vehicle remotely.

OnStar/Emergency Services Problems (If Equipped): For vehicles equipped with OnStar or similar emergency services, the ACM might play a role in connecting to the service. A loss of communication can prevent you from connecting to OnStar or automatically notifying emergency services in the event of a crash.

DTC Displayed: The most direct indicator is the presence of the U0185 code itself, which is stored in the vehicle's computer system. This code will be accessible via a scan tool.

Faulty Antenna Control Module (ACM): The most straightforward cause is a failed ACM. Internal electronic components within the module can degrade over time or be damaged by voltage spikes or other electrical issues, rendering the module unable to communicate on the CAN bus.

Wiring Issues: The wiring harness that connects the ACM to the vehicle's electrical system is susceptible to damage. Open circuits (broken wires), short circuits (wires touching each other or ground), and corroded connectors can all interrupt communication.

CAN Bus Problems: The Controller Area Network (CAN) bus is the communication network that allows various modules in the vehicle to exchange information. Problems with the CAN bus itself, such as a short circuit or open circuit in the CAN bus wiring, can prevent the ACM from communicating.

Power Supply Issues to ACM: The ACM requires a stable and adequate power supply to function correctly. A blown fuse, a faulty relay, or wiring problems in the power circuit can lead to insufficient voltage or fluctuating voltage, causing the ACM to malfunction.

Grounding Issues to ACM: A poor or missing ground connection can also prevent the ACM from functioning correctly. Ground connections can become corroded or loose over time, interrupting the flow of electricity.

Water Intrusion: Water damage is a common culprit in electrical problems. If the ACM or its wiring harness is exposed to water, it can lead to corrosion and short circuits, disrupting communication.

Software Glitches: Although less common, a software glitch within the ACM itself can sometimes cause it to stop communicating. This is typically resolved by reprogramming the module.

Scan Tool Diagnosis: A scan tool is essential for diagnosing a U0185 code. It can confirm the presence of the code and provide additional information about the system. It can also be used to monitor CAN bus communication signals to identify any disruptions.

Visual Inspection: A thorough visual inspection of the ACM, wiring harness, and connectors is a crucial first step in the diagnostic process. Look for any signs of damage, corrosion, or loose connections. Also, check for signs of water intrusion.

Wiring Diagram and Testing: Consulting the vehicle's wiring diagram is essential for understanding the ACM's power, ground, and CAN bus connections. A multimeter can then be used to test for voltage, continuity, and resistance in the wiring and connectors.

CAN Bus Testing: A CAN bus analyzer is a specialized tool that can monitor the communication signals on the CAN bus and identify any problems. It can also be used to check for proper termination resistance on the CAN bus.

Module Replacement (ACM): If all other possible causes have been ruled out, the ACM may need to be replaced. It's important to ensure that the replacement module is properly programmed and configured to the vehicle.

Ground Point Verification: Locating and verifying the ACM's ground points is crucial. Clean and securely re-tighten any corroded or loose ground connections.

Power Supply Verification: Use a multimeter to confirm the proper voltage supply to the ACM, both when the vehicle is on and off. Investigate any shorts to ground or open circuits in the power supply wiring.

Frequently Asked Questions:

• What does the U0185 code mean? It means the vehicle's computer has lost communication with the Antenna Control Module.

• Can I fix this problem myself? Depending on your mechanical and electrical skills, you might be able to diagnose and fix simple wiring problems. However, more complex issues may require a professional.

• How much does it cost to fix a U0185 code? The cost varies depending on the cause of the problem. Simple repairs, like fixing a loose connection, may be inexpensive. Replacing the ACM can be more costly, typically ranging from $300 to $1000 or more, including labor.

• Will a U0185 code affect my car's performance? It typically won't affect the engine's performance, but it can impact radio reception, satellite radio, navigation, remote keyless entry, and OnStar/emergency services.

• Can I still drive my car with a U0185 code? Yes, you can usually still drive your car, but you may experience issues with the features mentioned above. It's best to get it diagnosed and repaired as soon as possible.

Conclusion:

The U0185 code indicates a communication breakdown with the Antenna Control Module, leading to potential issues with various antenna-dependent features. Thorough diagnosis, starting with visual inspection and progressing to electrical testing, is crucial for identifying the root cause and implementing the appropriate repair, which may range from simple wiring fixes to ACM replacement.