This is typically an electrical wiring connection issue, either at the engine controller or at the sensors being monitored by the manufacturer.
It can occur if the wiring to the vehicle speed sensor breaks or the sensor itself has issues.
Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
The cost to diagnose the U1123 code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.
When the Powertrain Control Module (PCM) is unable to communicate with any other controller on the bus network at any time while the ignition switch is in the RUN position.
This is a manufacturer specific fault code and can be used for several different faults, depending upon what the manufacturer wants to use it for. Controllers communicate over the Serial Communication Protocol (SCP) bus network, also known as J1850 bus, or Controller Area Network or CAN Bus. These bus communication systems may or may not be fault tolerant, which means any type of intermittent/loose connection between these controllers could cause communication to stop. When these controllers are unable to communicate with each other at any time while the ignition switch is turned on, code U1123 will set.
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