Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer is having trouble understanding the information about how much power the engine should be giving to the wheels.
The P1771 code indicates a problem with the communication between the engine control module and the transmission control module regarding torque information.
The P1771 code is triggered when the engine control module (ECM) detects a discrepancy in the torque data being sent over the Controller Area Network (CAN) bus. This data is crucial for coordinating the engine's output with the transmission's requirements. If the data is inconsistent or implausible, the ECM will set this code.
• Check Engine Light is on
• Poor engine performance
• Transmission shifting issues
• Faulty engine control module (ECM)
• Faulty transmission control module (TCM)
• Issues with the CAN bus wiring or connectors
CAN: Controller Area Network, a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other.
ECM: Engine Control Module, the computer responsible for managing the engine's operations.
• Check for any additional codes and address those first.
• Inspect the CAN bus wiring and connectors for damage or corrosion.
• Test the ECM and TCM for proper operation.
• Repair or replace damaged CAN bus wiring or connectors.
• Reprogram or replace the ECM or TCM if necessary.
• Clear the code and test drive the vehicle to ensure the issue is resolved.
• OBD-II scanner
• Multimeter
• CAN bus diagnostic tool
$200 - $1000
Moderate
• BMW 3 Series
• Mercedes-Benz C-Class
• Audi A4
• Regular maintenance checks on the vehicle's electrical systems.
• Ensure all software updates for the vehicle's modules are installed.
• Inspect wiring and connectors for wear and tear.
Communication Issue
• If the check engine light comes on, have the vehicle inspected by a professional.
• Avoid driving the vehicle in harsh conditions if this code is present.
• Regularly check for software updates from the manufacturer.
Warranty coverage may vary based on the vehicle's age and mileage. Check with the manufacturer or dealer.
The P1771 code has been more common in vehicles with complex electronic communication systems, particularly those with advanced transmission technologies.
Moderate – While the vehicle may still be drivable, it is important to address this issue to prevent potential transmission damage.
Ignoring this code can lead to further mechanical issues and may compromise vehicle safety.
• Vehicle at operating temperature
• Test drive under normal conditions
The CAN bus wiring and connectors are typically located throughout the vehicle, connecting various control modules.
Q: Can I drive with the P1771 code?
A: While the vehicle may still operate, it's best to have it checked to avoid potential transmission damage.
Q: How do I clear the P1771 code?
A: After repairs, use an OBD-II scanner to clear the code, but ensure the issue is fixed first.
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