U0180 Lost Communication With Automatic Lighting Control Module
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U0180 Lost Communication With Automatic Lighting Control Module
OBD-II DTC Datasheet
Lost Communication with Automatic Lighting Control Module
What does this mean?
This is a generic communications system diagnostic trouble code that applies to most makes and models of OBD-II vehicles.
This code means that the Automatic Light Control Module (ALCM) and other control modules on the vehicle are not communicating with each other. The circuitry most commonly used for communication is known as Controller Area Bus communication, or simply the CAN bus.
Without this CAN bus, control modules cannot communicate and your scan tool may not receive information from the vehicle, depending on which circuit is involved.
The automatic lighting control module is usually located behind the dashboard, usually in the center of the vehicle. It accepts input data from various sensors, some of which are directly connected to it, and most are transmitted over a bus communication system. These inputs allow the module to control the operation of the headlight in a wide variety of operating conditions.
Troubleshooting steps may vary depending on the manufacturer, the type of communication system, the number of wires, and the colors of the wires in the communication system.
Code severity and symptoms
The severity in this case will not be an issue due to the module's backup capabilities. If an electrical problem occurs, the module is backed up and by default it will be in the "always on" position as a safety precaution.
Symptoms of a U0180 code may include:
- Headlights do not go out / do not light up when the ignition is turned on
reasons
Usually the reason for installing this code is:
- Open in CAN + bus circuit
- Open in the CAN bus - electrical circuit
- Short circuit to power in any CAN bus circuit
- Short to ground in any CAN bus circuit
- No power or ground to ALCM
- Rarely - the control module is faulty
Diagnostic and repair procedures
A good starting point is always to check the Technical Service Bulletins (TSB) for your particular vehicle. Your problem may be a known issue with a known manufacturer-released fix and could save you time and money while troubleshooting.
First, look for other DTCs. If any of these are bus communication or battery / ignition related, diagnose them first. Misdiagnosis is known to occur if you diagnose the U0180 code before any of the major codes are thoroughly diagnosed and rejected.
If your scan tool can access trouble codes and the only code you are getting from other modules is U0180, try accessing the Automatic Lighting Control Module (ALCM). If you can access codes from ALCM then code U0180 is either intermittent or memory code. If you can't access ALCM, then code U0180 set by other modules is active and the problem already exists.
The most common failure is a circuit failure that results in a loss of power or ground to the auto lighting control module.
Check all fuses supplying the ALCM on this vehicle. Check all grounds for an ALCM. Locate grounding attachment points on the vehicle and make sure these connections are clean and secure. If necessary, remove them, take a small wire bristle brush and baking soda / water solution and clean each one, both the connector and the place where it connects.
If any repairs have been made, clear the DTCs from memory and see if U0180 returns or you can contact the ALCM. If no code is returned or communication is restored, the problem is most likely a fuse / connection issue.
If the code returns, look for the CAN bus communication connections on your vehicle, especially the ALCM connector, which is usually located behind the dashboard. Disconnect the negative battery cable before disconnecting the connector on the ALCM. Once detected, visually inspect the connectors and wiring. Look for scratches, scuffs, exposed wires, burn marks, or molten plastic.
Disconnect the connectors and carefully inspect the terminals (metal parts) inside the connectors. See if they look burnt or have a green tint indicating corrosion. If you need to clean the terminals, use an electrical contact cleaner and a plastic bristle brush. Allow to dry and apply electrical grease where the terminals touch.
Perform these few voltage checks before connecting the connectors back to the ALCM. You will need access to a digital volt/ohmmeter (DVOM). Make sure the ALCM has power and ground. Access the electrical diagram and determine where the main power and ground sources enter the ALCM. Connect the battery before proceeding with ALCM disabled. Connect the red lead of your voltmeter to each B+ (battery voltage) power supply going into the ALCM connector, and the black lead of your voltmeter to a good ground (if unsure, battery negative always works). You should see the battery voltage reading. Make sure you have a good reason. Connect the red lead of the voltmeter to the battery positive (B+) and the black lead to each ground circuit. Once again, you should see the battery voltage every time you connect. If not, repair the power or ground circuit.
Then check the two communication circuits. Locate CAN B+ (or MSCAN + circuit) and CAN B- (or MSCAN - circuit). With the black wire of the voltmeter connected to a good ground, connect the red wire to CAN B+. With the key on and the engine off, you should see a voltage of about 0.5 volts with little fluctuation. Then connect the red lead of a voltmeter to the CAN B circuit. You should see about 4.4 volts with slight fluctuations.
If all tests pass and communication is still not possible, or if you are unable to reset DTC U0180, the only thing to do is to seek help from a trained automotive diagnostician, as this will indicate an ALCM failure. Most of these ALCMs need to be programmed or calibrated for the vehicle to fit properly.
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