A 2020 Maxus Deliver 3 rolled into a workshop with a U011187 code and an intermittent charging fault, leading most technicians straight to the high-voltage system. The technician working the bay recorded a single, straightforward symptom. They noted that the van "laddar dåligt till och från", meaning it was charging poorly on and off. In any electric vehicle, intermittent charging issues immediately make you look at the on-board charger or the high-voltage traction battery.
The U011187 code specifically indicates lost communication with the Battery Energy Control Module. The subcode 87 means a missing message. The diagnostic platform we build analyzed this code alongside the symptom and pointed the technician toward a strict sequence of tests, starting far away from the high-voltage cables.
The Heavy Load of the 12-Volt System
Our data ranked a defective or discharged 12-volt auxiliary battery as the most likely root cause for this exact fault, assigning it a 40 percent probability with a medium severity rating. It is one of the most common reasons for intermittent U-codes in electric vehicles.
When you plug this van in for AC charging, the vehicle does not immediately use high voltage to run its computers. The Battery Energy Control Module, the Vehicle Control Unit, and the On-Board Charger are all powered by the 12-volt system. Initiating a charge wakes up multiple control units and closes heavy contactors. This places a sudden demand on the 12-volt circuit before the DC/DC converter has stabilized the system voltage.
If the resting voltage or the capacity of the 12-volt battery drops below a critical threshold of around 12.0 to 12.2 volts, the microprocessor inside the Battery Energy Control Module simply shuts down. It drops off the CAN network. Because the on-board charger requires a constant data exchange with the battery module regarding cell voltage and temperature, losing that data breaks the charge immediately. The required test here is a load test of the 12-volt battery, alongside measuring both the resting voltage and the charging voltage coming from the DC/DC converter.
Chasing Micro-Corrosion on the CAN Bus
If the 12-volt battery holds a load, the next most probable fault sits at 30 percent. This is a wiring or connector issue on the CAN bus feeding the battery module.
The battery pack and chassis wiring on the Maxus Deliver 3 sit low to the ground. They are exposed to moisture, road salt, and constant vibration. Micro-corrosion, known as fretting, on the CAN High and CAN Low pins causes intermittent communication dropouts. A loose pin or moisture ingress in the low-voltage connector to the module does exactly the same thing. The slightest physical disconnect interrupts the regular messages from the module, triggering the missing message subcode and stopping the charge.
The diagnostic path here calls for measuring the CAN bus termination resistance to verify 60 Ohms. A technician must also visually inspect the connector pins for fretting, corrosion, and terminal pull-out. This should be followed by a physical wiggle test of the harness under the vehicle while watching live data on the scanner.
Power Supply Relays and Ground Faults
The remaining possibilities focus on how the battery module receives its power and processes data. At a 15 percent probability, we see intermittent power supply or ground faults.
The module relies on a constant 12-volt feed, known as KL30, and an ignition or wake-up signal, known as KL15, which comes via the on-board charger or a relay. Burned relay contacts, oxidized fuse holders, or a chassis ground point with poor contact will cause the supply voltage to drop out intermittently. This often happens during temperature changes or the exact moment charging activates. Proving this requires a voltage drop test across the supply fuse and relay, plus a multimeter check of the ground points under load.
Internal Hardware Failure
Finally, ranked at a 10 percent probability, is an internal hardware failure within the battery module itself. This module lives inside the sealed housing of the main battery pack.
It can suffer from microcracks in the circuit board solder joints or temperature-sensitive component failures, such as a CAN transceiver that overheats. It can also fail due to internal moisture or condensation within the pack. When the power supply, ground, and external CAN lines all verify as good, the U011187 code points to a crashed or locked-up module. The required test is to verify the 12-volt feed, ground, and CAN signals directly at the module pins while the fault is actively occurring, before checking for manufacturer software updates.
Do you see this same pattern of 12-volt failures causing high-voltage charging aborts in your own bays?