P0748 Fault Code in Honda: Causes, Symptoms, and Fixes

Diagnostic Trouble Code (DTC) P0748 indicates that the Transmission Control Module (TCM) has detected an electrical malfunction in the Pressure Control Solenoid “A” circuit. This solenoid helps control hydraulic pressure in the transmission for smooth shifting.

Common Causes:

1. Faulty pressure control solenoid “A”
2. Open or short in solenoid wiring
3. Corroded or loose electrical connectors
4. Faulty Transmission Control Module (TCM)
5. Poor transmission ground connection
6. Burnt or dirty transmission fluid (causing electrical resistance)

Common Symptoms:

1. Harsh, delayed, or erratic shifting
2. Transmission stuck in limp mode
3. Transmission slipping
4. Check Engine Light (CEL) ON

Affected Vehicles:

This is a generic OBD-II code, so it can apply to many vehicles, especially:
1. Nissan
2. Honda/Acura
3. GM/Chevy
4. Ford
5. Toyota/Lexus
6. Hyundai/Kia
Each make might associate it with a different solenoid location or part number.

Diagnosis and Fix:

1. Scan with an advanced scan tool – to monitor solenoid activity.
2. Check solenoid circuit wiring – look for opens, shorts, or damage.
3. Test solenoid resistance – typically 3–10 ohms (check manufacturer spec).
4. Inspect and clean connectors – TCM and solenoid plugs.
5. Replace solenoid “A” if resistance is outside range.
6. Check transmission fluid – burnt or dirty fluid can contribute.
7. Replace or reprogram TCM if all else fails.