Code Definition

C1099 — EPS Motor Malfunction

System: Chassis  |  Type: Manufacturer-Specific  |  Make: Mazda

About C1099

C1099 is a manufacturer-specific chassis diagnostic trouble code recorded for Mazda vehicles. It belongs to the C-prefix family of codes, which covers chassis, braking, steering, suspension, or stability-control faults.

Scanning & clearing: Chassis (C) codes are stored in the ABS, traction control, or stability-control modules. An enhanced or OEM-level scan tool is usually required to read and clear them.

C1099 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The Electric Power Steering (EPS) control module continuously monitors the EPS motor operation by evaluating motor current draw, rotational response, and feedback signals during steering assist operation. DTC C1099 is set when the EPS control module detects an abnormal condition in the EPS motor, such as excessive or insufficient current, lack of expected motor response, or internal motor performance outside calibrated limits. This indicates the EPS motor cannot provide correct steering assist and the system may enter a fail-safe or reduced assist mode.

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