|Trouble Code||Fault Location||Probable Cause|
|U0481||Invalid Data Received From Automatic Lighting Control Module|
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What Does Code U0481 Mean?
OBD II fault code U0481 is a generic trouble code that is defined as, U0481 – “Invalid Data Received from Automatic Lighting Control Module”, and is set when the PCM (Powertrain Control Module) or other control module detects implausible, inaccurate, invalid, or implausible input data from the Automatic Lighting Control Module.
All vehicles made after 2003 are fitted with a variety of serial bus communications systems whose function it is to link the high number of control modules in a vehicle together without the need to include a so-called “host computer” to manage communications between different classes of control module.
We need not delve into the complexities of serial communication systems here, beyond saying that all modern vehicles are now also fitted with a dedicated control module to control all the lighting functions on the vehicle. These functions include headlight control, automatic headlight leveling, automatic switching between high and low beams, and automatic headlight activation of the headlights in poor visibility conditions. Other functions include control and management of the indicator lights (turn signals), brake/tail lights, interior courtesy lights, reverse lights, and even vanity lights in the sunshades. In some applications, the lighting control module also controls the hazard lights and the “Lights On” warning chime.
To make all of the listed functions work, the automatic lighting control module obtains input data from a host of input devices. These include light sensors, seat occupancy sensors, proximity warning sensors, and humidity sensors that produce the trigger signals the lighting control module uses to activate or deactivate some lighting functions. However, since the automatic lighting sensor is a part of at least one CAN bus communications system, it shares input data and information with several other control modules.
In practice though, each control module in a communications system is programmed to both identify itself to other modules during data transmissions, and to acknowledge receipt of information transmitted by all other linked control modules. However, this is where things often go wrong, because data transmissions are constructed in a certain way to make them recognizable to control modules that are intended to receive them.
For instance, if a fault, defect, or malfunction in the automatic lighting control module causes the module to activate the brake lights, but the brake control module does not sense a brake application, the brake control module will recognize the brake light activation as invalid, and it will set code U0481 – “Invalid Data Received from Automatic Lighting Control Module”. Similarly, if the lighting control module commands the headlights on, but the ambient light sensor registers bring sunlight one or more other control modules will recognize the invalid command, and one or more of them might also set code U0481 as a result.
There are many other possible examples, but the fact is that the automatic lighting control modules on many vehicles are notoriously unreliable and prone to faults, meaning that code U0481 is arguably among the most common generic communication fault codes across a wide range of vehicle makes and models.
Where is the U0481 sensor located?
This image shows the panel that needs to be removed on an E60 5-Series BMW model to gain access to the automatic lighting control module.
Note though that on other applications, the module could be located under the dashboard close to the steering column, in the center console, or behind a kick panel in the footwell on the driver’s side. Note that these locations may also contain a variety of other, unrelated control modules, so be sure to consult reliable service information for the affected vehicle to locate and identify the lighting control module correctly.
What are the common causes of code U0481?
Common causes of code U0481 could include one or more of the following-
- Damaged, burnt, shorted, disconnected, and/or corroded wiring or connectors anywhere in any circuit that is associated with the automatic lighting control module
- The failure of any switch, sensor, or monitoring device that is associated with the automatic lighting control module
- Blown or damaged fuses and/or fusible links in any circuit that is associated with the automatic lighting control module
- Abnormally high or low system voltages
- Failure of the lighting control module, which is a fairly common occurrence
What are the symptoms of code U0481?
Common symptoms of code U0481 are much the same across all applications, and typically include the following-
- Stored trouble code and possibly one or more illuminated warning lights
- Headlights won’t activate, or won’t switch off, or won’t switch between high and low beams automatically
- Brake/tail lights won’t activate, or won’t switch off
- Some lights may only work intermittently or erratically
- Turn signals may blink too fast, or too slow
- Interior courtesy lights may not turn off
- If one or more types of lighting do not deactivate fully the vehicle may never enter sleep mode, which can cause a severe parasitic battery drain