U0115 Lost Communication with ECM/PCM “B”

U0115 Lost Communication with ECM / PCM "B"

OBD-II DTC Datasheet

Lost Communication With ECM / PCM "B"

What does this mean?

This is a generic network code which means it covers all brands / models from 1996 onwards. However, specific troubleshooting steps may differ from vehicle to vehicle.

Generic OBD Trouble Code U0115 is a serious situation where the signals between the Electronic Control Module (ECM) or Powertrain Control Module (PCM) and a specific module have been lost. There may also be a problem with the CAN bus wiring that is interfering with communication.

The car will simply shut down at any time and will not restart while the connection is interrupted. Almost everything in modern cars is computer controlled. The engine and transmission are completely controlled by the computer network, its modules and actuators.

The U0115 code is generic because it has the same frame of reference for all vehicles. Somewhere on the CAN bus (Controller Area Network), an electrical connector, wiring harness, module has failed, or a computer crashed.

The CAN bus allows microcontrollers and modules, as well as other devices, to exchange data independently of the host computer. The CAN bus was developed specifically for cars.

Note. This is basically identical to the more common DTC U0100. One refers to PCM "A", the other (this code) refers to PCM "B". In fact, you can see both of these DTCs at the same time.

symptoms

Symptoms of DTC U0115 may include.

• The car stalls, won't start, and won't start
• OBD DTC U0115 will set and the check engine light will illuminate.
• A car can start after a period of inactivity, but its operation is risky as it can fail again at the most inopportune moment.

Possible reasons

This is not a common problem. In my experience, the most likely problem is the ECM, PCM, or transmission control module. The car has at least two places for the CAN bus. They may be under the carpet, behind the side panels, under the driver's seat, under the dashboard, or between the A/C housing and the center console. They provide communication for all modules.

Failure of communication between anything on the network will trigger this code. If additional codes are present to localize the problem, the diagnosis is simplified.

The installation of computer chips or performance enhancing devices may not be compatible with ECM or CAN bus wiring, resulting in loss of the communication code.

A bent or extended contact lug in one of the connectors, or poor grounding of the computer will trigger this code. A low battery bounce and an unintentional polarity reversal will momentarily damage the computer.

Diagnostic and repair procedures

Search the Internet for all service bulletins for your vehicle. Check bulletins for references to U0115 and suggested repair procedure. While online, check to see if any reviews have been posted for this code and check the warranty period.

Diagnosing and fixing these kinds of problems is difficult at best with proper diagnostic equipment. If the problem appears to be a faulty ECM or ECM, it is highly likely that programming will be required before starting the vehicle.

Please refer to your service manual for a detailed description of the additional code associated with the faulty module and its location. Look at the wiring diagram and find the CAN bus for this module and its location.

There are at least two places for the CAN bus. Depending on the manufacturer, they can be located anywhere inside the car - under the carpet near the sill, under the seat, behind the dash, in front of the center console (console removal required), or behind the passenger airbag. CAN bus access.

The location of the module depends on what it is working with. The airbag modules will be located inside the door panel or under the carpet towards the center of the vehicle. Rocker modules are usually found under the seat, in the console, or in the trunk. All later car models have 18 or more modules. Each CAN bus provides communication between the ECM and at least 9 modules.

Refer to the service manual and locate the contacts of the corresponding module. Disconnect the connector and check each wire for a short to ground. If a short is present, instead of replacing the entire harness, cut the shorted wire from the circuit about one inch from either connector and run an equivalent sized wire as an overlay.

Disconnect the module and check the associated wires for continuity. If there are no breaks, replace the module.

If there were no additional codes, we are talking about ECM. Install a memory saver device before unplugging anything to save ECM programming. Treat this diagnosis in the same way. If the CAN bus is good, the ECM must be replaced. In most cases, the car must be programmed to accept the key and the program installed in the computer for its operation.

Have the vehicle towed to the dealer if necessary. The least costly way to fix this type of problem is to find an auto shop with an older, experienced ASE automotive technician with the proper diagnostic equipment.

An experienced technician is usually able to quickly identify and fix a problem in less time at a more reasonable cost. The reasoning is based on the fact that the dealer as well as independent parties charge hourly rates.

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