Faulty pressure control solenoid (electrical failure) (35% likelihood): The pressure control solenoid's internal coil may be open, shorted, or have resistance outside specifications, preventing proper line pressure regulation. Damaged wiring or connector (25% likelihood): Corroded, broken, or chafed wiring in the pressure control solenoid circuit can cause abnormal voltage readings that trigger this electrical code. Contaminated transmission fluid (20% likelihood): Metal particles or debris in the ATF can interfere with the solenoid's electromagnetic operation and damage its internal components. Poor electrical ground (12% likelihood): A loose or corroded transmission ground connection can cause erratic solenoid behavior and trigger electrical fault codes. TCM/PCM driver circuit failure (8% likelihood): The solenoid driver circuit within the control module may be damaged, preventing proper voltage or current control to the solenoid.

How much does it cost to fix P0748?

DIY repair typically costs $30–$150 for parts. Professional repair runs $200–$600 including parts and labor.

P0748

Powertrain

Moderate

Pressure Control Solenoid 'A' Electrical

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P0748 indicates an electrical fault in the Pressure Control Solenoid 'A' circuit. The pressure control solenoid is one of the most critical components in an automatic transmission — it regulates the hydraulic line pressure that controls shift firmness and engagement of all gears. When the PCM detects an electrical problem with this solenoid (abnormal voltage, current, or resistance), this code is set.

Because line pressure affects every gear and every shift, a pressure control solenoid electrical failure can cause widespread transmission problems. You may experience harsh shifts, soft or slipping shifts, delayed engagement, or the transmission going into limp mode (locking into a single gear for protection). This code requires prompt attention because incorrect line pressure can damage clutch packs and bands throughout the transmission.

Diagnosis should start with checking the transmission fluid condition and level, then inspecting the wiring and connector at the solenoid. A multimeter can be used to check the solenoid's resistance, which should fall within the manufacturer's specified range. If the wiring is good and the solenoid resistance is out of spec, solenoid replacement is needed. On many vehicles, the solenoid is part of a pack mounted on the valve body, accessible by removing the transmission pan.

Severity

High — Immediate AttentionWithin 24 Hours

Symptoms

•Harsh or erratic shifting between all gears
•Transmission slipping under acceleration
•Check Engine light illuminated
•Vehicle may enter limp mode (stuck in one gear)
•Delayed engagement when shifting from Park to Drive or Reverse

Likely Causes

Faulty pressure control solenoid (electrical failure)35%

The pressure control solenoid's internal coil may be open, shorted, or have resistance outside specifications, preventing proper line pressure regulation.

Damaged wiring or connector25%

Corroded, broken, or chafed wiring in the pressure control solenoid circuit can cause abnormal voltage readings that trigger this electrical code.

Contaminated transmission fluid20%

Metal particles or debris in the ATF can interfere with the solenoid's electromagnetic operation and damage its internal components.

Poor electrical ground12%

A loose or corroded transmission ground connection can cause erratic solenoid behavior and trigger electrical fault codes.

TCM/PCM driver circuit failure8%

The solenoid driver circuit within the control module may be damaged, preventing proper voltage or current control to the solenoid.