Error code U0140 is a specific extension of OBD-II DTC U0. All U codes indicate a malfunction regarding 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 indicates where the vehicle has encountered an error. In this case, the number 1 signifies an issue regarding a vehicle’s fuel and air metering, which in most cases can mean a variety of things.
So, let’s dive a little deeper.
What Does Code U0140 Mean?
U0140 is a generic diagnostic trouble code (DTC) that stands for “Lost Communication With Body Control Module.” This code generally means that the BCM isn’t properly transmitting or receiving signals.
Keep in mind that there are multiple networks on today’s vehicles, and when one or more modules stop talking, a U-series code is stored.
A U0140 code can have a wide variety of indications. It’s usually related to component failure or wiring problems with the BCM.
However, this code may also be triggered by complications with the data network itself. The network serves as a communication line that connects the BCM to the vehicle’s other modules.
If a short or electrical issue causes the network to become faulty, a code U0140 may show up on 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 such 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 essential to 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
Additional diagnostic trouble codes (DTCs) may indicate problems elsewhere that could be affecting BCM operation. For example, DTCs set for multiple modules may indicate a problem with the CAN network. Any additional DTCs should be addressed prior to delving into U0140.
In the case where multiple modules’ DTCs are stored, diagnosis will shift to the CAN bus. The bus can be checked for typical circuit malfunctions, including shorts and opens. This process usually starts at the data link connector.
The data link connector has 16 pins – pins 6 and 14 are CAN high and CAN low. A technician will connect a digital multimeter (DMM) to one or both of these pins for testing. If a problem is indicated, further testing can be performed at other parts of the CAN network.
CAN bus operation can also be checked with a breakout box. This tool hooks up directly to the data link connector. It is used to monitor bus operation and detect problems.
The two CAN bus terminating resistors can be checked with a DMM at the data link connector. This is done with the DMM connected between pins 6 and 14 of the connector. A reading of 60 ohms indicates the resistors are intact.
Check for a faulty control module
If there are no other DTCs stored, the BCM itself should be checked. Typically, the first thing a technician will do is try to communicate with the BCM. This is done using a diagnostic scan tool connected to the vehicle diagnostic port.
Once connected to the vehicle, the scan tool can communicate directly with the vehicle’s modules, including the BCM.
A non-responsive BCM must be diagnosed. Before condemning the BCM, its circuit should be checked with a DMM. Like any other electrical device, the BCM must have proper power and ground.
If the circuit is OK, the BCM is probably the problem. However, before replacing the BCM, its software should be checked. Oftentimes, the BCM can be reprogrammed instead of replaced. If software isn’t the issue, the BCM will need to be replaced. Oftentimes, the BCM will need to be reprogrammed after replacement.
How Much Does It Cost to Fix a U0140 Code?
A U0140 code, which indicates a “lost communication with the Body Control Module (BCM),” typically costs between $300 and $600 to fix.
The primary expense is the replacement of the BCM itself, along with potential labor costs for diagnosis and wiring checks.