Hi all, my buddy's 1kz 1994 Surf is having some trans issues. It is hesitant to upshift, usually dragging up to 3k rpm before going into 2nd or 3rd, then it wont go into 4th at all. We've swapped the temperature sensor and all 3 shift solenoids and obviously checked the level 1000000 times. Not sure where to go from here and supposed to leave for a 1600km roadtrip with both our rigs in 36 hours. Any tips or things to check would be much appreciated. We are planning to check the throttle body TPS and the speed sensor next, but not optimistic about those. Cheers!
A340H Automatic transmission won't shift to 4th
- Thread starter dawsonmarch
- Start date
-
- Tags
- transmission
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
This is my Surf and we were able to solve the issue. After some more research and asking around, we found out that the electrolytic capacitors in the ECU can leak. The fluid in the caps is corrisive and can degrade the copper traces on the PCB. It seems sometimes the fix can be as simple as replacing these capacitors, but in my case I had to reconnect the traces manually because some had been completely disconnected due to corrosion. I wouldn't recommend doing this for anyone who doesn't have very much experience working with PCB and soldering.
First you need to find the traces that have been corroded in the surrounding areas of the caps. These will look discoloured in comparison to the other healthy traces. Then at the edges of the corrosion, scrape off the solder mask that is protecting the intact trace to expose the copper. The idea here is to add in another wire and short over the corroded part of the trace. Take a small wire, I just used the end of a through hole resistor, and solder it down to the exposed parts of the traces. I found the easiest way to do this was melt some solder onto the traces first, then place the wire and solder one side down at a time. In addition to fixing the traces, also replace the caps just in case.
I did this on two different traces, one appeared to be a power rail, and the other a small signal trace. Be very careful doing this, especially when you scraping off the solder mask. You don't want to accidently cut another small signal trace. It wouldn't also be good to use some extra flux, but I had none on hand. Some solder wick is handy as well.
Here are some photos of the not so pretty job I did.
First you need to find the traces that have been corroded in the surrounding areas of the caps. These will look discoloured in comparison to the other healthy traces. Then at the edges of the corrosion, scrape off the solder mask that is protecting the intact trace to expose the copper. The idea here is to add in another wire and short over the corroded part of the trace. Take a small wire, I just used the end of a through hole resistor, and solder it down to the exposed parts of the traces. I found the easiest way to do this was melt some solder onto the traces first, then place the wire and solder one side down at a time. In addition to fixing the traces, also replace the caps just in case.
I did this on two different traces, one appeared to be a power rail, and the other a small signal trace. Be very careful doing this, especially when you scraping off the solder mask. You don't want to accidently cut another small signal trace. It wouldn't also be good to use some extra flux, but I had none on hand. Some solder wick is handy as well.
Here are some photos of the not so pretty job I did.
