What Does C0291 Mean?
This diagnostic trouble code indicates that the vehicle's network controller or another control module has lost communication with the Body Control Module (BCM). The BCM is responsible for controlling various electrical accessories and systems throughout the vehicle, and other modules communicate with it via the CAN bus or other communication networks. When this communication is interrupted or fails, multiple vehicle systems may become inoperative or function improperly.
Safety Warning
This is a critical issue that may cause loss of multiple vehicle functions including lighting, wipers, security systems, power windows, and potentially engine starting or stability control systems. Vehicle should not be driven until properly diagnosed and repaired as essential safety systems may be compromised.
Common Causes
35%
Damaged, corroded, or loose wiring and connectors in the CAN bus network between the BCM and other modules
30%
Failed or defective Body Control Module requiring replacement or reprogramming
20%
Low battery voltage or poor battery/charging system performance causing communication disruption
10%
Faulty termination resistors or short/open circuit on the CAN bus network
5%
Software or firmware corruption in the BCM requiring reflashing or updates
Diagnostic Steps
1
Step 1: Perform a visual inspection of the BCM and its connector for obvious damage, corrosion, water intrusion, or loose/backed-out pins. Check all ground connections associated with the BCM for tightness and corrosion.
2
Step 2: Using a digital multimeter, verify battery voltage is at least 12.4V with engine off and 13.5-14.5V with engine running. Test voltage at the BCM power and ground pins to confirm adequate power supply.
3
Step 3: With a multimeter set to resistance mode, measure CAN bus termination resistance between CAN High and CAN Low terminals (should read approximately 60 ohms with all modules connected, 120 ohms at each termination resistor). Check for shorts to ground or voltage on CAN lines.
4
Step 4: Inspect all wiring harnesses between the BCM and other modules for damage, pinching, rodent damage, or modifications. Pay special attention to areas where harnesses pass through firewalls or near moving components.
5
Step 5: Using the scan tool's module scan function, attempt to communicate with the BCM directly and check if other modules can also communicate on the network. Document which modules are responding and which are not.
6
Step 6: If all wiring and voltage tests pass but communication remains lost, attempt to reprogram or reflash the BCM with the latest software. If unsuccessful, replace the BCM and program it to the vehicle.
Estimated Repair Cost
$150 - $1,800
Parts + labor, varies by vehicle and location
This diagnostic trouble code indicates that the vehicle's network controller or another control module has lost communication with the Body Control Module (BCM). The BCM is responsible for controlling various electrical accessories and systems throughout the vehicle, and other modules communicate wi...
The most common cause of C0291 (Lost Communications With BCM) is: Damaged, corroded, or loose wiring and connectors in the CAN bus network between the BCM and other modules
Typical repair costs for C0291 range from $150 to $1,800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This is a critical issue that may cause loss of multiple vehicle functions including lighting, wipers, security systems, power windows, and potentially engine starting or stability control systems. Vehicle should not be driven until properly diagnosed and repaired as essential safety systems may be compromised.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C0291 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Chassis
System
Vehicle Communication Network / Body Control Systems
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
