Possible causes

– Low transmission fluid level
– Dirty transmission fluid
– Faulty Pressure Control Solenoid
– Pressure Control Solenoid harness is open or shorted
– Pressure Control Solenoid circuit poor electrical connection

When is the code detected?

When the Powertrain Control Module (PCM) detects a continuous open or short in the Pressure Control (PC) solenoid valve circuit the P0748 code is set.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Transmission shift shock

P0748 CADILLAC Description

The Pressure Control (PC) solenoid valve is an electronic device that regulates transmission line pressure based on the current flow through its coil winding. The magnetic field produced by the coil moves the solenoid’s internal valve which varies pressure to the pressure regulator valve. The Powertrain Control Module (PCM) controls the PC solenoid valve by applying a varying amount of amperage to the solenoid. The applied amperage can vary from 0.1 to 1.1 amps. Low amperage (0.1 amp) indicates high line pressure. High amperage (1.1 amps) indicates low line pressure. The duty cycle of the PC solenoid valve is expressed as a percentage of energized ON time. Zero percent indicates zero ON time (non-energized) or no current flow. Approximately 60% at idle indicates maximum ON time (energized) or high current flow. The PCM determines the appropriate line pressure for a given load by comparing the throttle position (TP) voltage, the engine speed and other inputs.

CADILLAC Technical Service Bulletins for P0748 code