P0748 MERCEDES-BENZ code description
The Pressure Control (PC) Solenoid Valve an electronic pressure regulator that controls transmission line pressure based on current flow through its coil windings. As current flow is increased, the magnetic field produced by the coil moves the solenoid’s plunger further away from the exhaust port. Opening the exhaust port decreases the output fluid pressure regulated by the PC solenoid valve, which ultimately decreases line pressure. The line pressure solenoid valve regulates the oil pump discharge pressure to suit the driving condition in response to a signal sent from the Transmission Control Module (TCM).
When is the P0748 MERCEDES-BENZ code detected?
Engine Control Module (ECM) detectes an open or shorted condition on the solenoid circuit
What are P0748 MERCEDES-BENZ code possible symptoms?
Engine Light ON (or Service Engine Soon Warning Light) Transmission shift shock
How do I fix the P0748 MERCEDES-BENZ code?
Car model and year: 2010 Mercedes W212 E350 722.9 Transmission
Symptoms:
Went through flushing and cleaning the solenoids, found some dark matter, used a magnet. Reset everything and bam limp mode and the P0748 code is stubborn. Took it apart, tested the solenoids for the click at 12V, just the blue click, the black makes a different sound, more like a buzz. The resistance is 5.6 plus or minus 0.2 as good.
Mercedes Diagnostic Tool To Use:
Usually the problem with the circuit board is the speed sensors, if you have access to Star (Xentry) then drag codes with it and erase them. Some generic scanners cannot erase TCM codes. I would do this first before going down the rabbit hole. With Xentry you also have the option of performing guided tests together with diagnostic information.
Outfits that fix your original circuit board don’t require coding or customization. If you get a new one from the dealer or outfit that sells virgin (used) then you need someone online with Xentry to unlock and encode the disk. Then make adjustments offline with Xentry.
Take a look at the images below that show I have access to the Laptop Star (xentry) deal:
Suppose you tried to delete and it comes back immediately. Under the first image, click on Tests after clicking on the error in the module. Obviously the solenoid can be bad, chances are the circuit board is bad or damaged in some way. I would probably toss a solenoid valve at it before replacing the circuit board, especially since it is neither a common bug nor multiple bugs.
Since you will not receive any codes for the other solenoid valves, you can temporarily swap the faulty one for a similarly colored solenoid valve (blue vs. black) and scan for codes again. If the code doesn’t change, it’s likely with the circuit board. If any new code shows up, it’s likely the solenoid. Don’t forget to put the solenoids back in their original place.
The 722.9 does not suffer from the same leakage problem as the 722.6. In the .9 variant, the TCM is integrated into the circuit board and the plug is cast in so that nothing can leak into the vehicle wiring harness or plug. Completely different design. The only leak would be past the o-rings on the molded connector and gear body, which would just be a leak that does not affect the electrical connection.
0748 The internal electrical test of component Y3 / 8y2 (solenoid valve K1 clutch actuation (VGS)) has failed. Magnetic filters may need cleaning or replacement.
Does the car have ECO Start / Stop if the only gear pump is not mechanical, e.g. the engine must be running to be ready for operation. If it now has ECO, then there is an electric pump that runs. I am not sure whether it runs with the engine switched off or with the ECO switched off. I suspect it would only work during an ECO stop. Yes, the circuit board usually has a certain flaw. However, there are electrical connections between TCM> PCB> Solenoid, so the PCB may be bad. I think the likelihood is that the solenoid itself is bad or dirty. I would be inclined to swap out and / or replace the solenoid valve first before other parts are thrown at it.
Finally update: I can finally recommend a brand new one. But you can’t buy this part. Only stores licensed by NASTF can purchase this part from dealers here in the US. And even if you could buy, you still need access to the online system for programming and SCN coding. Is also possible offline with Vediamo and DTS Monaco (runs for sdconnect c4 plus DOIP). You just need to find the right CBF and coding.
Abrites can virginize and change the VIN, but it comes at a high price. I very much doubt that the Chinese can log into the online system with your setup. Mercedes blocks unauthorized laptops / PCs. Whether you’re installing a new one or a virgin one, the steps are the same. The flow data of the valve body must be read and transmitted. After that, you need to do programming, SCN coding, personalization, activation and calibration of the distance sensor.