Fault code P0748 – a step-by-step guide to diagnosing and fixing it

The meaning of error code P0748 – Pressure Control Solenoid Electrical

P0748: Causes, signs and repairs

Error code P0748 is displayed and the check engine light is on - what does this mean?

The OBD system detects an electrical fault in solenoid valve A of the pressure regulator of the automatic transmission control unit. This DTC P0748 indicates problems in the hydraulic pressure control of the transmission, which is responsible for proper gear changes.

What can cause this error code?

Defective pressure regulator solenoid valve A
Damaged wiring to the solenoid valve
Corroded or loose plug connections
Defective transmission control unit (TCM)
Low transmission oil level or contaminated ATF
Clogged transmission oil filter
Internal transmission damage or valve body problems

What symptoms occur in parallel with fault code P0748?

Shifting problems: The transmission shifts jerkily or with a delay between gears
Emergency running program: The vehicle gets stuck in a gear or activates safety mode
Increased fuel consumption: Fuel consumption increases significantly due to inefficient gear changes
Overheating: The transmission can overheat during long journeys
Starting problems: In rare cases, the vehicle cannot be moved out of park

How can the problem with error code P0748 be rectified?

The repair requires systematic diagnosis and precise execution of the appropriate measures.
Inspection and replacement of the defective pressure regulator solenoid valve A in the transmission, including cleaning the connections and checking the electrical values
Complete inspection of the wiring to the solenoid valve with continuity check, repair of damaged cables and replacement of corroded plug connections
Transmission oil change with high-quality ATF in accordance with the manufacturer's specifications, including replacement of the transmission oil filter and flushing of the system
Diagnosis and, if necessary, replacement of the transmission control unit (TCM) after prior checking of the software version and calibration
Disassembly and cleaning or replacement of the valve body in the event of internal hydraulic problems, including inspection of all valves and channels

FAQ - Frequently asked questions about DTC P0748

Can I continue driving with error code P0748?

Driving is possible in the short term, but you should avoid longer journeys. The transmission may switch to emergency mode and overheat. Visit a workshop as soon as possible.

How much does it cost to repair error code P0748?

The costs vary depending on the cause: solenoid valve replacement 150-400€, wiring repair 80-200€, transmission oil change 120-250€, TCM replacement 800-1500€. A precise diagnosis is required to estimate the costs.

How long does it take to repair error code P0748?

The repair time depends on the cause: Simple repairs such as oil changes take 1-2 hours, solenoid valve replacement 2-4 hours, more complex gearbox repairs can take 1-2 days.

Can I repair error code P0748 myself?

Basic checks such as checking the oil level are possible, but most repairs require specialist knowledge and special tools. Transmission repairs should always be carried out by qualified specialists.

What consequential damage can fault code P0748 cause?

If left untreated, the trouble code can lead to serious damage to the transmission: Overheating, wear of the clutches and belts, complete transmission failure. Early repair prevents expensive consequential damage.

How can I avoid error code P0748 in future?

Regular transmission oil changes according to the manufacturer's instructions, a gentle driving style without abrupt acceleration, regular inspection of the transmission components and immediate repair of leaks prevent recurrence.

Vehicles in which error code P0748 occurs most frequently

Fault code P0748 is an EOBD-specific fault code for automatic transmission solenoid valve problems and can occur in various manufacturers, but is most common in the following vehicles:

Ford: Focus, Fiesta, Mondeo, C-Max (2005-2015)
Opel: Astra, Vectra, Insignia, Zafira (2004-2014)
Volkswagen: Golf, Passat, Touran, Jetta (2006-2016)
BMW: 3 Series, 5 Series, X3, X5 (2007-2017)
Mercedes: C-Class, E-Class, A-Class, B-Class (2008-2018)
Audi: A3, A4, A6, Q5 (2009-2019)

If code P0748 occurs in your vehicle, prompt professional diagnosis is recommended. Modern automatic transmissions are complex systems that should be examined at the first sign of problems. Using an OBD scanner can reveal additional fault codes that will help to identify the cause. Do not hesitate to visit a specialist workshop, as transmission problems can quickly worsen.

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