U0250 Lost Communication with the Impact Classification System Module

U0250 Lost Communication with the Impact Classification System Module

OBD-II DTC Datasheet

Lost Communication with Impact Classification System 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 Impact Classification System Module (ICSM) and other control modules on the vehicle do not interact with each other. The circuitry most commonly used for communication is known as Controller Area Bus communication, or simply the CAN bus.

Modules communicate with each other over a network, just like the network you have at home or work. Car manufacturers use several networked systems. Prior to 2004, the most common (non-exhaustive) inter-module communication systems were the serial communication interface, or SCI; SAE J1850 or PCI bus; and Chrysler Collision Detection, or CCD. The most common system used after 2004 is known as Controller Area Network communication, or simply the CAN bus (also used until 2004 on a small segment of vehicles). Without this CAN bus, control modules cannot communicate and your scan tool may or may not receive information from the vehicle, depending on which circuit is affected.

The Impact Classification System (ICSM) module is usually located behind the center of the dashboard. Can also be installed inside the center console. It receives input from a variety of sensors, some of which are directly connected to it, and most are sent over a bus communication system from the powertrain control module (PCM). This input allows the module to determine the type of impact the vehicle has experienced and at what speed the airbags / side air curtains may need to be deployed.

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 may or may not be serious, depending on what the problem is. The manufacturer could manually correct the problem in the event of a bus failure.

Symptoms of a U0250 code may include:

• Airbag indicator is on
• Passenger airbag warning light is on

reasons

Usually the reason for installing this code is:

• Open on CAN bus + or - circuit
• Short to ground or ground in any CAN bus circuit
• No power or ground to ICSM
• Rarely - the control module is faulty

Diagnostic and repair procedures

A good place to start with ALL electrical diagnostics is to check the Technical Service Bulletins (TSB) for your vehicle. The problem you are facing may be known to others in the field. A known fix may have been released by the manufacturer and can save you time and money during diagnostics.

It is assumed that you have access to a code reader at this point, as you may have been able to access the codes up until now. See if there were any other DTCs related to bus communication or battery / ignition. If so, you should diagnose them first, as misdiagnosis is known to occur if you diagnose the U0250 code before any of the underlying codes are thoroughly diagnosed and corrected.

If the only code you get from other modules is U0250, try accessing the ICSM. If you can access codes from ICSM then code U0250 is either intermittent or memory code. If the ICSM cannot be accessed, then code U0250 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 Shock Classification System module.

Check all fuses supplying the ICSM on this vehicle. Check all the grounds for ICSM. 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 any modules that set the code in memory and see if you can now communicate with the ICSM. If communication with the ICSM recovers, the problem is most likely a fuse / connection issue.

If the code returns or communication with the module still fails, look for the CAN bus communication connections on your vehicle, especially the ICSM connector, which is usually located behind the center of the dashboard. can also be installed inside the center console. Disconnect the negative battery cable before disconnecting the connector on the ICSM. 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 ICSM. You will need access to a digital volt/ohmmeter (DVOM). Make sure the ICSM has power and ground. Access the wiring diagram and determine where the main power and grounds enter the ICSM. Reconnect the battery before proceeding with ICSM still disabled. Connect the red lead of the voltmeter to each B+ (battery voltage) power supply included in the ICSM connector, and the black lead of the 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 C+ (or HSCAN+) and CAN C- (or HSCAN - circuit). With the black wire of the voltmeter connected to a good ground, connect the red wire to CAN C+. With the key on and engine off, you should see about 2.6 volts with little fluctuation. Then connect the red wire of the voltmeter to the CAN C- circuit. You should see about 2.4 volts with little fluctuation. Other manufacturers show CAN C- at about 5V and an oscillating key with the engine off. Check your manufacturer's specifications.

If all tests pass and communication is still not possible, or you were unable to reset DTC U0250, the only thing that can be done is to seek help from a trained automotive diagnostician as this will indicate an ICSM failure. Most of these ICSMs must be programmed or calibrated in order to properly install the vehicle.

Related DTC discussions

• There are currently no related topics in our forums. Post a new topic on the forum now.

Need more help with the U0250 code?

If you still need help with DTC U0250, post a question in the comments below this article.

NOTE. This information is provided for informational purposes only. It is not intended to be used as a repair recommendation and we are not responsible for any action you take on any vehicle. All information on this site is protected by copyright.