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Hello everybody, just wanted to share the following issue with you and I will appreciate any comments and/ or suggestions. Working on a 2014 KIA Morning (Picanto) 1.0 ltr Engine. A4CF2 Automatic Transmission. Main complain, lack of power when taking off and not shifting gear, actually its stuck in 3th gear and wont shift from there. Obviously if it is taking off in 3rd gear it wont have much power. Scanning report shows P0748 for the VFS solenoid. I have measured the resistance for the VFS at the transmission connector and it measured in specs (2.5 to 4.5 Ohms).. Testing the solenoid using external power supply tested OK by normal clicking sound, Same test can be done with the scan tool and the clicking sound can be heard as well, sometimes the active test using the scan tool might fail and other times it might test OK. Based on my experienced with this same transmission it is very common that the ECU/TCU will go bad and enter Limp home mode after not being able to drive the solenoids properly. I have repaired a lot of these ECUs fixing this kind of issue. So I opened this ECU and found at least 3 leaking Capacitor on the PCB. Cleaned out all the mess and replace all the capacitors. When the car was first started after the ecu repair job it acted like the problem is still there(hard/shaking shifting in reverse and/or drive) and the code P0748 presented. Clearing this code and performed TCU adaptation procedure gave a apparent solution, I drove the car long enough without any issue. Transmission shift ok. It seems like it is a fix but I am not feeling so comfortable with this. The P0748 and the hard in gear shifting when it first started up after ECU work(not test driven at this point) make me feel uncomfortable. I will let the car sit overnight and test drive it again tomorrow starting with a cold engine and see how it goes. I will put an update after this final test. Any comments are welcome, Thank you!
Well done with the PCB repair. No one I know here in the States would have done that for a customer. MAYBE for their own car, IF they're like me and willing to solder components. :silly:
I welcome your updates after your cold test drive, but I think you're fine? :huh: If the code was repeatable before but isn't now, you definitely fixed something. I'd test drive it as much as you need to feel confident before releasing it back to the customer.
Since this is a pressure control solenoid, does actual match desired? As usual, we don't get model in the US, so I don't know how the ECM controls line pressure.
The following user(s) said Thank You: rudolph.palm
Hello, as an update to this case, I would say that the car has been test driven for a long time and it drove fine. It has been released to the customer since Monday morning and it is running fine. So far, this is a fix!! Thanks for following this case.
We currently have a Hyundai i20. Transmission stuck in 3rd gear & shift shock when put into reverse. We however made poor decision to order & replace solenoid without testing first. Replaced VFS/pressure solenoid & still have same problems with P0748 error code.
Checked wiring (visual inspection & continuity test) today & it is okay. Also checked output from ECU, only 43mV but should be around 5V.
We will inspect ECU PCB board tomorrow. Is it easy to visually locate faulty PCB components? OR is electrical testing needed to identify?
Hi, yess!! the problem is most of the time in the ECU/TCU. Whenever I have this kind of problem on these cars I will take some resistance measurements on the transmission connector for all the solenoids on the valve body. If the solenoids read in specs. I will remove and open the ECU/TCU. Most of the time the problem is visible end smelly. 3 capacitors will leak. The problem is that some times they leak badly and leave a mess on the printed board breaking some tracks. You have to clean all the mess up and inspect for broken tracks. If you replace those 3 capacitor, clean all the mess and check all tracks. you will fix the problem.
Yes, you can use any other capacitor. The original ones are surface mount types but you can use the non surface mount types too. As long as you keep the same values, specially the uf values, it will work fine.
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No one I know here in the States would have done that for a customer. MAYBE for their own car, IF they're like me and willing to solder components. :silly: