Hello friends!
Some of you know that I've been chasing an intermittent shift anomaly on this newly imported KZJ78. I started with the basics, connectors inspection, AT fluid flush, and AT filter/solenoids replacement. Although these measures did help reduce the frequency of the shift weirdness and certainly helped with the overall quality of transmission performance and longevity, they didn't completely eliminate the strange shifting issues.
I knew right then that the ECU was to blame. Knowing how our trucks (and many other 1990s LandCruiser) were victims of the great 90s capacitor plague, I opened my ECU half expecting to see some leaky electrolytic capacitors. Sure enough, all but one had leaked out their corrosive juice all over the PCB.
@GTSSportCoupe rightfully pointed out that I was in for a challenge (since he did have an experience repairing a similar ECU before). I started gathering up supplies to tackle this job.
Why do you ABSOLUTELY NEED to open up your ECU now?
Even if you have no issues, I highly recommend that you open up your ECU for an inspection. All electrolytic capacitors will fail sooner or later, it is just the nature of this component. But a great many of the capacitors manufactured in the 90s and early 2000s were part of the well known capacitor plague (inferior, malformulated, or flat out counterfeit batches of capacitors manufactured in the east), which cased a wave of high rate of global premature capacitor failures.
If your truck is from that era/region and you still don't have any ECU symptoms, then that is the best case scenario, as replacing the caps now before they physically leak is ideal, since it will be a trivial job compared to what I had to do. You will not have to deal with any trace repairs, missing pad, damaged nearby components etc. So do yourself a favor and replace the caps before they burst.
With that being said, recapping old PCBs is not for everyone. And not using the proper techniques and genuine components is arguably worse than leaving these little ticking time bombs in. So you are at your own risk, do your homework, or, send your ECU to a reputable specialist to do the job for you.
Tip: even if you found that your caps are not physically leaking or damaged, they could be (in fact likely are, if you have symptoms) electrically leaky. When capacitors start to go bad, they turn into resistors of sorts, and slowly degrade further and further until they fail catastrophically and damage other precious components. Remember, a KZJ7x ECU is practically unobtainium, and if you do find one it will cost you many, many hundreds or dollars. Other 70 series UCUs are not off the chopping block either.
The replacement caps:
You MUST source the correct caps from a reputable source like Digikey. No eBay or Amazon junk no matter how convenient. The market is literally teeming with counterfeit caps. The authentic caps are actually very cheap to buy from the right source so no reason to buy the shady ones.
The caps MUST have the same capacitance rating in micro farads (uF), low ECR, and the correct series, but you should consider getting higher voltage rating and higher hour/operational temp rating. I went with almost double the voltage and 5000 hour @ 105° centigrade operational temp on all the electrolytics. Japanese made Panasonic originals except for the bipolar cap as I couldn't find it from Panasonic.
Here is a map of the caps on the two boards. Looking at the board with the connectors facing you:
I bought double the number of caps and it was about $20. Look for EEU series caps from Panasonic as they are of very premium quality.
Here are the tools and supplies I used for this job. This picture is not all inclusive:
1. Soldering iron and solder wire (any good 40w and up iron will do, but make sure you have a wedge tip instead of the common conical tip on)
2. Two pairs of sharp tweezers
3. Solder suction and braid
4. High quality no-clean flux (this is perhaps the most important of all the supplies to have)
5. 30awg vanished copper wire
6. A set of magnifying goggles or a soldering microscope (I have good eyesight but I don't think I could have done it without the 3.5x magnification lenses on the goggles)
7. UV-activated trace mask and a UV light source (direct sunlight would work well too)
8. Q-tips and high concentration isopropanol alcohol
9. Wooden toothpicks
10. Sharp scapel blade
11. #2 Pozidriv screwdrivers (not Philips, don't repeat my mistake)
12. Miscellaneous small gauge insulated wire, heat shrink, heat gun
13 long nose pliers, cropping snips or nail clippers
14. 10mm socket, suitable rachet and extension
15. Glue gun, rubber sheet
(Now you probably won't need some of these supplies and tools, especially if you are doing a recap without trace repairs)
First, disconnect both negative terminals from your batteries. Your ECU sits behind the glove compartment. Just remove the compartment itself (not the lid) with the Pozidriv. The ECU is fastened up with a screw and two 10mm bolts. The ECU will have three non-interchangeable connectors attached to it.
On a bench, open the ECU using the proper screwdriver to avoid damaging the screws. I used a Philips first and paid the price and had to drill out one of the screws.
Inspect the PCBs, look for electrolytic leaks around a the electrolytic capacitors. As you can see, mine were in a bad state of disrepair.
Tip: remove the PCB from the metal housing. Some screws hide behind the foam
Holding the ECU in the vertical and using the soldering iron and plenty of flux, heat up the pads of the capacitors one by one on the back side and pull them out with your fingers from the topside. Be gentle and take your time. When all the caps are out, inspect the traces under them, and use q-tips with IPA to clean the areas and remove the gunk and corrosion. The more stubborn bits will need more IPA and a delicate scrub with the toothpick. Take pictures of your progress for reference.
If you encounter corroded or entirely missing traces (like mine) then you will need to use your eyes and a multimeter to very carefully trace each damaged or missing trace and then scrape off some of the OE trace masking near the damage area using the scapel to reveal good copper. Do this on both sides of the damaged trace. Now drown the copper on one side with flux and lightly tin it with solder. Lay your 30awg wire (or bigger guage if you can get away with it) parallel to (on top of) the tinned part and with more flux, fuse it to the tinned trace with the iron. Route your wire to where it needs to go and repeat. When you verify that everything is correct and nothing is shorting go ahead and lay your UV trace mask where needed with a toothpick and cure it with UV light.
Move to other damaged spots methodically so you don't work yourself into a corner (many of the damaged traces were in clusters, and many were as thin as human hair) When everything checks out, cure the repaired traces in with UV mask and prep the capacitor through-holes for cap installation.
Minding the polarity on the polarized caps, install the caps one by one starting with the smaller ones. Crop off the extra length of the caps' legs after you solder them in. Since we are upgrading to higher voltage/temp caps, the larger, upgraded caps will foul the top PCB if not laid to the side. Verify that the boards close down properly without shorting anything. I used rubber sheets and hot glue to secure some of the larger caps and prevent rattling.
Clean the entire board with an ultrasonic cleaner (mine quit working as soon as I turned it on of course) or IPA and q-tips. Double check everything and then reassemble the ECU. Reinstall the ECU, reconnect your batteries and crank up the truck. When you reach op temps, go for a drive and you will find that your transmission is shifting like a swiss watch!
This repair/upgrade instantly solved my AT mis-shifts and improved the speed of the crank-to-start time and really smoothed the idle as a bonus! The truck drives like it has a modern and a healthy drivetrain now.
Hopefully your caps are still intact!
Cheers!
Moe.
Some of you know that I've been chasing an intermittent shift anomaly on this newly imported KZJ78. I started with the basics, connectors inspection, AT fluid flush, and AT filter/solenoids replacement. Although these measures did help reduce the frequency of the shift weirdness and certainly helped with the overall quality of transmission performance and longevity, they didn't completely eliminate the strange shifting issues.
I knew right then that the ECU was to blame. Knowing how our trucks (and many other 1990s LandCruiser) were victims of the great 90s capacitor plague, I opened my ECU half expecting to see some leaky electrolytic capacitors. Sure enough, all but one had leaked out their corrosive juice all over the PCB.
@GTSSportCoupe rightfully pointed out that I was in for a challenge (since he did have an experience repairing a similar ECU before). I started gathering up supplies to tackle this job.
Why do you ABSOLUTELY NEED to open up your ECU now?
Even if you have no issues, I highly recommend that you open up your ECU for an inspection. All electrolytic capacitors will fail sooner or later, it is just the nature of this component. But a great many of the capacitors manufactured in the 90s and early 2000s were part of the well known capacitor plague (inferior, malformulated, or flat out counterfeit batches of capacitors manufactured in the east), which cased a wave of high rate of global premature capacitor failures.
If your truck is from that era/region and you still don't have any ECU symptoms, then that is the best case scenario, as replacing the caps now before they physically leak is ideal, since it will be a trivial job compared to what I had to do. You will not have to deal with any trace repairs, missing pad, damaged nearby components etc. So do yourself a favor and replace the caps before they burst.
With that being said, recapping old PCBs is not for everyone. And not using the proper techniques and genuine components is arguably worse than leaving these little ticking time bombs in. So you are at your own risk, do your homework, or, send your ECU to a reputable specialist to do the job for you.
Tip: even if you found that your caps are not physically leaking or damaged, they could be (in fact likely are, if you have symptoms) electrically leaky. When capacitors start to go bad, they turn into resistors of sorts, and slowly degrade further and further until they fail catastrophically and damage other precious components. Remember, a KZJ7x ECU is practically unobtainium, and if you do find one it will cost you many, many hundreds or dollars. Other 70 series UCUs are not off the chopping block either.
The replacement caps:
You MUST source the correct caps from a reputable source like Digikey. No eBay or Amazon junk no matter how convenient. The market is literally teeming with counterfeit caps. The authentic caps are actually very cheap to buy from the right source so no reason to buy the shady ones.
The caps MUST have the same capacitance rating in micro farads (uF), low ECR, and the correct series, but you should consider getting higher voltage rating and higher hour/operational temp rating. I went with almost double the voltage and 5000 hour @ 105° centigrade operational temp on all the electrolytics. Japanese made Panasonic originals except for the bipolar cap as I couldn't find it from Panasonic.
Here is a map of the caps on the two boards. Looking at the board with the connectors facing you:
I bought double the number of caps and it was about $20. Look for EEU series caps from Panasonic as they are of very premium quality.
Here are the tools and supplies I used for this job. This picture is not all inclusive:
1. Soldering iron and solder wire (any good 40w and up iron will do, but make sure you have a wedge tip instead of the common conical tip on)
2. Two pairs of sharp tweezers
3. Solder suction and braid
4. High quality no-clean flux (this is perhaps the most important of all the supplies to have)
5. 30awg vanished copper wire
6. A set of magnifying goggles or a soldering microscope (I have good eyesight but I don't think I could have done it without the 3.5x magnification lenses on the goggles)
7. UV-activated trace mask and a UV light source (direct sunlight would work well too)
8. Q-tips and high concentration isopropanol alcohol
9. Wooden toothpicks
10. Sharp scapel blade
11. #2 Pozidriv screwdrivers (not Philips, don't repeat my mistake)
12. Miscellaneous small gauge insulated wire, heat shrink, heat gun
13 long nose pliers, cropping snips or nail clippers
14. 10mm socket, suitable rachet and extension
15. Glue gun, rubber sheet
(Now you probably won't need some of these supplies and tools, especially if you are doing a recap without trace repairs)
First, disconnect both negative terminals from your batteries. Your ECU sits behind the glove compartment. Just remove the compartment itself (not the lid) with the Pozidriv. The ECU is fastened up with a screw and two 10mm bolts. The ECU will have three non-interchangeable connectors attached to it.
On a bench, open the ECU using the proper screwdriver to avoid damaging the screws. I used a Philips first and paid the price and had to drill out one of the screws.
Inspect the PCBs, look for electrolytic leaks around a the electrolytic capacitors. As you can see, mine were in a bad state of disrepair.
Tip: remove the PCB from the metal housing. Some screws hide behind the foam
Holding the ECU in the vertical and using the soldering iron and plenty of flux, heat up the pads of the capacitors one by one on the back side and pull them out with your fingers from the topside. Be gentle and take your time. When all the caps are out, inspect the traces under them, and use q-tips with IPA to clean the areas and remove the gunk and corrosion. The more stubborn bits will need more IPA and a delicate scrub with the toothpick. Take pictures of your progress for reference.
If you encounter corroded or entirely missing traces (like mine) then you will need to use your eyes and a multimeter to very carefully trace each damaged or missing trace and then scrape off some of the OE trace masking near the damage area using the scapel to reveal good copper. Do this on both sides of the damaged trace. Now drown the copper on one side with flux and lightly tin it with solder. Lay your 30awg wire (or bigger guage if you can get away with it) parallel to (on top of) the tinned part and with more flux, fuse it to the tinned trace with the iron. Route your wire to where it needs to go and repeat. When you verify that everything is correct and nothing is shorting go ahead and lay your UV trace mask where needed with a toothpick and cure it with UV light.
Move to other damaged spots methodically so you don't work yourself into a corner (many of the damaged traces were in clusters, and many were as thin as human hair) When everything checks out, cure the repaired traces in with UV mask and prep the capacitor through-holes for cap installation.
Minding the polarity on the polarized caps, install the caps one by one starting with the smaller ones. Crop off the extra length of the caps' legs after you solder them in. Since we are upgrading to higher voltage/temp caps, the larger, upgraded caps will foul the top PCB if not laid to the side. Verify that the boards close down properly without shorting anything. I used rubber sheets and hot glue to secure some of the larger caps and prevent rattling.
Clean the entire board with an ultrasonic cleaner (mine quit working as soon as I turned it on of course) or IPA and q-tips. Double check everything and then reassemble the ECU. Reinstall the ECU, reconnect your batteries and crank up the truck. When you reach op temps, go for a drive and you will find that your transmission is shifting like a swiss watch!
This repair/upgrade instantly solved my AT mis-shifts and improved the speed of the crank-to-start time and really smoothed the idle as a bonus! The truck drives like it has a modern and a healthy drivetrain now.
Hopefully your caps are still intact!
Cheers!
Moe.
. I just know that everything is figuroutable if you don't rush things and do your homework lol. 
()
