Error code U0140 is a specific variant of an OBD-II DTC U0. All U codes point to an issue with a vehicle’s user network (Wiring Bus/UART). The number 0 indicates that this code is generic and applies to all makes and models.
The third numeral in the code sequence (1) always denotes where the vehicle has logged an error. The number one refers to an issue with a vehicle’s fuel and air metering. In most cases, this could mean a number of things.
With that in mind, let’s take a closer look.
What Does Code U0140 Mean?
U0140 – “Lost Communication with Body Control Module” – The BCM is not talking or listening properly. There are multiple networks on modern vehicles, and if one or more modules have stopped communicating, a U-code is set.
This code can vary in indication, but it is generally attributed to component failure and/or wiring to the BCM.
Sometimes it can be tricky to determine exactly what caused the issue here. This code may also be a result of complications with the data network itself. That’s the communication line that joins the BCM with the other modules in the car.
If there’s a network fault caused by a short or electrical issue, you might see a code U0140 in your scanner.
Potential Causes of a U0140 Code
Code U0140 is typically caused by one of the following:
- A dead battery
- A faulty BCM
- A problem with the BCM circuit
- A problem with the CAN bus
What are the Common Symptoms of the U0140 Code?
Symptoms of a U0140 engine code may include.
- Misfiring at high speeds
- Shaking when you increase your speed
- Poor acceleration
- The vehicle may not start
- You may consistently blow fuses
How to diagnose and repair the U0140 Code?
Perform a preliminary inspection
Sometimes U0140 can pop up intermittently, or it can result from a dead battery. This is especially true if the code is historical code and not current. Clear the code and see if it returns. If it does, the next step is to perform a visual inspection.
A trained eye can check for issues with such things as broken wires and loose connections. If a problem is found, the issue should be repaired and the code cleared. If nothing is discovered, check for technical service bulletins (TSBs).
TSBs are recommended diagnostic and repair procedures put out by the vehicle manufacturer. Finding a related TSB can greatly reduce diagnostic time.
Check the battery
Proper battery voltage is important for proper BCM operation. Before proceeding any further, the battery should be checked and recharged/replaced as needed. Then, clear the code and see if it returns.
Check for other DTCs
Other DTCs may point to a problem elsewhere, causing the problem within the BCM; DTCs set for multiple modules may indicate a problem with the CAN network. These should be dealt with before going to U0140.
If storage of DTCs in multiple modules is the case, diagnosis will shift to the CAN bus. It is typically checked for shorts and opens, generally starting at the data link connector.
There are 16 pins in the data link connector; pins 6 and 14 are CAN high and CAN low. A technician will connect one or both to a digital multimeter for testing. If a problem is indicated, testing can be done further back in the CAN network.
Operation of the CAN bus can also be observed with a breakout box that plugs into the data link connector, permitting a watch of the bus while searching for a problem.
The two CAN bus terminating resistors can be continuity-tested with a digital multimeter at the data link connector, with the DMM connected between the 6 and 14 pins. A reading of 60 ohms indicates that the resistors are intact.
Check for a faulty control module
If no other DTCs exist, check the BCM itself. The technician’s first step is usually trying to communicate with it, and that involves connecting to the vehicle’s diagnostic port with a scan tool.
Once connected to the vehicle, the scanner communicates directly with the BCM and all other vehicle modules.
A non-communicating BCM must be diagnosed – not easily done, but the first step is checking the circuit with a DMM. Like other electrical devices, the BCM must have power and ground.
If the circuit is okay, suspect the BCM; but check its software also – often the BCM can be reprogrammed, not replaced. If software isn’t the culprit, a BCM replacement may be necessary – often it will require reprogramming after the new unit is installed.
How Much Does It Cost to Fix a U0140 Code?
Typically, a U0140 code that indicates a “lost communication with the BCM (Body Control Module)” will cost around $300 to $600 to diagnose and fix.
Replacing the BCM, plus possibly diagnosing the problem and checking wiring, are the main costs.