Chassis, generic

C066D Service/Park Brake Chamber Pressure Sensor

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C066D covers a fault in the transducer reporting the air pressure inside the service/spring brake chambers of an air-braked vehicle. No maker documents the code, but the diagnosis of real systems is published. Bendix's Intellipark electronic parking brake measures the delivery pressure of every channel with its own transducer and logs J1939 faults for signals shorted high or to ground; if a sensor fails, park status for that unit cannot be shown, rollaway mitigation is lost and the driver is told to chock the wheels. A WABCO (now ZF) patent uses such a sensor to decide whether the spring brakes are applied or released. Knorr-Bremse, which also builds the parking brake into its electronic air control unit, places sensors at the control inlet and the outlet of the relay valve so each reading can serve as a cross-check on the other.

Likely causes

Sensor signal or 5 V supply shorted to ground or voltage
Pressure transducer in the valve module defective
Sensor outputs shorted together or connectors swapped

Symptoms

  • Parking brake indicator flashes, park status unknown
  • Automatic park functions such as rollaway protection unavailable

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,200
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

service park brake chamber pressure sensorsensor wiringpark brake module

Related codes

C066EC066F

References: static.nhtsa.gov, patents.google.com, patents.google.com, truck.knorr-bremse.com.