The meaning of the C1728 Code C for Chassis Code Problem is controller area network wiring bus and modules. 1 for MFG – Manufacturer Specific. 7 for Auxiliary Emission Controls. 2 for Air Conditioning (A/C) Clutch Feedback Circuit High Voltage and 8 for PCM Stack Overrun. The automobile dictionary meaning of the code is not acceptable for all car engines. Do not use this meaning and this general meaning may make more trouble for your car engine. You will get the general meaning from online for free. Do not use meanings from different car manufacturers. Now take the car for a test drive.