Possible causes

– Faulty Torque Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid
– Torque Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid harness is open or shorted
– Torque Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid circuit poor electrical connection

When is the code detected?

When the PCM detects a continuous open, short to ground or short to power in the TCC PWM solenoid valve circuit, then DTC P1860 sets. DTC P1860 is a type B DTC.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1860 BUICK Description

The Torque Converter Clutch Pulse Width Modulation (TCC PWM) solenoid valve controls the fluid acting on the converter clutch valve. The converter clutch valve controls the TCC application and release. The solenoid attaches to the control valve body within the transmission. The solenoid receives ignition voltage through circuit 239. The Powertrain Control Module (PCM) controls the solenoid by providing a ground path on circuit 418. Current flows through the solenoid coil according to the duty cycle (percentage of ON and OFF time). The TCC PWM solenoid valve provides a smooth engagement of the torque converter clutch by operating during a duty cycle percent of ON time.

BUICK Technical Service Bulletins for P1860 code