U0243 Lost Communication With Parking Aid Control Module B
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U0243 Lost Communication With Parking Aid Control Module B
OBD-II DTC Datasheet
Lost Communication With Parking Aid Control Module B
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 parking assist control module B (PACM-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.
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 PACM-B is usually located in the trunk of a car. 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 display information to the driver about the rear of the vehicle and what is in the immediate vicinity.
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 low to moderate due to safety issues that arise from the PACM-B's ability to mislead vehicle obstacles.
Symptoms of a U0243 code may include:
- Parking aid control module B does not display information / blank screen / no warnings
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 PACM-B 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 U0243 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 U0243, try accessing PACM-B. If you can access codes from PACM-B, then code U0243 is either intermittent or memory code. If the PACM-B cannot be accessed, then code U0243 set by other modules is active and the problem already exists.
The most common failure is a loss of power or ground to the PACM-B.
Check all fuses supplying the PACM-B on this vehicle. Check all grounds for PACM-B. 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 U0243 returns or you can contact the PACM-B. If no code is returned or communication is restored, the problem is most likely a fuse / connection issue.
If the code returns, locate the CAN bus communication connections on your vehicle, primarily the PACM-B connector, which is usually found in the trunk of your vehicle. Disconnect the negative battery cable before disconnecting the connector on the PACM-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 dielectric silicone grease where the terminals touch.
Perform these few voltage checks before reconnecting the connectors to the PACM-B. You will need access to a digital volt-ohmmeter (DVOM). Make sure the PACM-B has power and ground. Access the wiring diagram and determine where the main power and ground supplies enter the PACM-B. Connect the battery before proceeding with the PACM-B still disconnected. Connect the red wire of your voltmeter to each B + (battery voltage) power source going into the PACM-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 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 U0243, the only thing to do is to seek help from a trained automotive diagnostician, as this will indicate a PACM-B failure. . Most of these PACM-Bs must be programmed or calibrated in order to properly install the vehicle.
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