U0297 Lost Communication With AC / DC Converter Control Module-B

U0297 Lost Communication With AC / DC Converter Control Module-B

OBD-II DTC Datasheet

Lost Communication With AC-to-DC Converter Control Module-B

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 AC-to-DC-B control module (ACDCCCM-B) 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.

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 AC / DC Converter Control Module-B (ACDCCCM-B) is typically located under the hood at the rear of the engine / hybrid powertrain. It receives input from various sensors, some of which are directly connected to it, and most are sent over a bus communication system from the powertrain control module (PCM). These inputs allow the module to convert alternating current (AC) voltage to direct current (DC) voltage to control the motors that drive the wheels. Refer to the vehicle-specific handbook to determine which module is "B" in your particular case.

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

In this case, the severity is usually very high, depending on what the problem is. The manufacturer could provide a workaround in the event of a bus failure. Vehicle performance is affected by the lack of ACDCCCM-B operation.

Symptoms of a U0297 code may include:

• Fault indicator light is on
• Vehicle operation may be limited to a petrol / diesel engine.

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 ACDCCCM-B module
• 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 U0297 code before any of the underlying codes are thoroughly diagnosed and corrected.

If the only code you get from other modules is U0297, try accessing ACDCCCM-B. If you can access codes from ACDCCCM-B, then code U0297 is either intermittent or memory code. If the ACDCCCM-B cannot be accessed, then code U0297 set by other modules is active and the problem already exists.

The most common fault is a circuit fault that results in a loss of power or ground to the AC/DC-b control module.

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

If the code returns or communication with the module still cannot be established, locate the CAN bus communication connections on your vehicle, most importantly the ACDCCCM-B connector, which is usually found under the hood at the rear of the engine / hybrid powertrain. Disconnect the negative battery cable before disconnecting the connector on the ACDCCCM-B. 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 plugging the connectors back into the ACDCCCM-B. You will need access to a digital volt-ohmmeter (DVOM). Make sure the ACDCCCM-B has power and ground. Access the wiring diagram and determine where the main power and ground supplies go into the ACDCCCM-B. Reconnect the battery before proceeding with the ACDCCCM-B still disconnected. Connect the red wire of your voltmeter to each B + (battery voltage) power source going to the ACDCCCM-B connector, and the black wire of your voltmeter to a good ground (if unsure, the negative pole of the battery always works). You should see the battery voltage reading. Make sure you have a good reason. Connect the red wire from the voltmeter to battery positive (B +) and the black wire to each ground. Once again, you should see the battery voltage every time you plug it in. If not, troubleshoot 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 if you are unable to reset DTC U0297, the only thing you can do is seek help from a trained automotive diagnostician, as this will indicate an ACDCCCM-B failure. . Most of these ACDCCCM-Bs must be programmed or calibrated in order to properly install the vehicle.

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