What P0748 means
Pressure control solenoid A sets line or clutch pressure by current; most are 'normally high', so with no current – as in limp mode – maximum pressure applies. 'A' is usually the line pressure valve, on GM clutch-to-clutch transmissions (6T, 8L, 9T) the pressure valve of clutch 1.
How the engine computer detects it
Ford does not use P0745–P0749 but P0960–P0963. P0748 is the electrical code of this valve, checked by current, duty cycle or terminal voltage: Subaru after 0.14 s with MIL after two trips and limp mode in third, Allison against an 8 Ω current model after 125 ms, GM's diesel 4L80-E for a duty cycle outside 0.5–95 % for 2 s without MIL. The valve is switched off – maximum pressure, harsh shifts, frozen adaption, often a fixed gear (Saab AF40: second and reverse) and reduced torque. Saab's 2010 9-5 uses P0748 for a current deviation instead.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Harsh shifts or engagement (maximum pressure)
- Limp mode in a fixed gear
- Transmission warning or check engine light
- Reduced engine power (torque limit)
Common causes
- Harness or transmission connector (corrosion, oil, chafing) Most likely
- Pressure control solenoid faulty (resistance out of spec) Most likely
- Internal harness, electronic module or mechatronic unit Possible
- System voltage too low Less likely
- Transmission module driver Less likely
How to diagnose P0748
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: pressure control solenoid a, transmission valve body, transmission wiring, transmission control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 7
- Transmission
- 48
- Specific fault
Questions drivers ask
Can I drive with code P0748?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0748?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0748 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.