U0143: Lost Communication With Body Control Module "C"

What Does The U0143 Code Mean?

The body control module (BCM) is an electronic module that is part of the vehicle’s entire electrical system and it controls functions including but not limited to the tire pressure monitor, remote keyless entry, door locks, the anti-theft alarm, heated mirrors, the rear window defroster, front and rear washers and wipers and the horn.

It also receives switch inputs from the seat belts, ignition, the chime telling you the door is ajar, the parking brake, cruise control, the engine oil level, the cruise control and the window washer and wiper. Battery rundown protection, the temperature sensor and the low power mode function may all be affected by a bad BCM, loose connection to the BCM or an open/short in the BCM’s harness.

Code U0143 pertains to the BCM “C” or the wiring to the BCM from the engine control module (ECM). The code, depending on the year, make and model of the vehicle, may mean that the BCM is bad, that the BCM is not receiving or sending a signal, the BCM harness has an open or short, or that the BCM is not communicating with the ECM via the controller area network – the CAN communication line.

The code may be detected when the ECM has not received an emission-related CAN signal from the BCM for at least two seconds.

Note: This DTC is basically identical to U0140, U0141, U0142, U0144, and U0145.

What Are The Symptoms Of The U0143 Code?

Not only will the MIL – malfunction indicator light (a.k.a. check engine light) come on, thus notifying you that the ECM set a code, but you may notice certain body control functions not working properly. Depending on the type of problem – wiring, the BCM itself or a short – some or all of the systems that are controlled by the body control module may not work properly or at all.

Other symptoms of a U0143 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

What Are The Potential Causes Of The U0143 Code?

Several incidences may cause the BCM or it’s wiring to fail. If the BCM is shocked in an accident – that is, if it is jarred hard enough from impact – it could fail completely, the wiring harness could be knocked loose or one or more wires in the harness may be exposed or cut completely through. If a wire is exposed and it touches another wire or metal part of the vehicle, this will cause a short.

Excessive heat from the vehicle’s engine or from a fire mishap may damage the BCM or melt the insulation on the wiring harness. At the other end of the spectrum, if the BCM becomes water logged, it will most likely fail. Furthermore if the sensors become water logged or otherwise damaged, the BCM cannot do what you are instructing it to do, i.e., open the door locks remotely; nor can it forward that signal to the ECM.

Excessive vibration can lead to wear and tear of the BCM, such as that from unbalanced tires or other damages parts that may cause your vehicle to vibrate. And, just simple wear and tear will eventually lead to the failure of the BCM.

How Can You Fix The U0143 Code?

Before you attempt to diagnose the BCM, check the technical service bulletins for the BCM on your vehicle. If a problem is known and covered under warranty, you’ll save yourself the diagnostic time. Locate the BCM on your vehicle by using the appropriate repair guide for your vehicle as the BCM may not be in the same place for different models.

You can help determine if the BCM or its wiring is the problem by noting which things are not working on the vehicle such as the door locks, the remote start and other things that the BCM controls. Of course, you should always check the fuses first – check fuses and relays (if applicable) to the non-working functions and for the BCM.

If you believe the BCM or the wiring is bad, the easiest thing to do is to check the connections. Gently wiggle the connector to ensure that it is not loose. If not, remove the connector and check to see that there is no corrosion on both sides of the connector. Check to ensure that none of the individual pins are loose.

If the connector looks fine, then you’ll need to check for power at each terminal. Use a diagnostic code reader for body control modules to help you determine which pin or pins have an issue. If any of the terminals are not getting power, then the problem is most likely in the wiring harness. If the terminals are getting power, then the problem is in the BCM itself.

Recommended Parts

Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:

>>> Twippo 372Pcs Waterproof Wire Connectors Kit
>>> INNOVA 5210

Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!

Reference Sources

U0143 Lost Communication With Body Control Module “C”, OBD-Codes.