U0156 Lost communication with information center A

U0156 Lost communication with information center A

OBD-II DTC Datasheet

Lost connection with Call Center A

What does this mean?

This is a generic communication system diagnostic trouble code that applies to most makes and models of vehicles.

This code means that the Information Center "A" (IC-A) 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.

IC-A is usually located behind the dashboard, usually in the center of the vehicle. It accepts input from various sensors, some of which are directly connected to it, and some are sent over a bus communication system. These inputs allow the module to display information centrally for easy viewing.

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 is always serious because of the safety issues that arise from the IC-A being able to obstruct the driver's view.

Symptoms of a U0156 engine code may include:

• Info center A no info / blank screen

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 HUD module
• 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 U0156 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 U0156, try accessing IC-A. If you can access codes from IC-A then code U0156 is either intermittent or memory code. If you cannot access IC-A, then code U0156 that other modules set is active and the problem already exists.

The most common failure is loss of power or ground to IC-A.

Check all fuses supplying the IC-A module on this vehicle. Check all bases for IC-A. Locate ground anchorage 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 U0156 returns or you can contact the IC-A module. 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 connections on your vehicle, especially the IC-A connector, which is usually located behind the dashboard. Disconnect the negative battery cable before disconnecting the connector on the IC-A module. 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 dielectric silicone grease where the terminals touch.

Before reconnecting the connectors to IC-A, perform these few voltage checks. You will need access to a digital volt/ohmmeter (DVOM). Make sure IC-A has power and ground. Access the wiring diagram and determine where the main power and ground supplies enter IC-A. Connect the battery before continuing with IC-A still disabled. Connect the red lead of your voltmeter to each B+ (battery voltage) power supply included in the IC-A 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 you were unable to reset DTC U0156, the only thing to do is to seek help from a trained automotive diagnostician, as this will indicate an IC-A failure. . Most of these IC-As must be programmed or calibrated in order to properly install the vehicle.

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