Yamae

Regarding the code P1600, it sounds like a failed DC regulator in the ECU to me but without checking the board myself, I can't say enough. Did you carefully check traces and parts damages around the leaked capacitor? I worry about damages caused by the leaked liquid.

ourbudd

Yamae, The leakage was minimal and after removing the old capacitors I didn't see any damage I felt would be an issue. I have more caps and could replace them again and look at it closer, After the 1st couple I started mounting them a little higher so I could see the solder on both sides better. Another option would be to buy a either used or "rebuilt" one and either replace the caps or inspect it. Is there a way I could check for the voltage on the board vs the terminals or something you would recommend looking at better? I took before pics but didn't take any after I started the work. Any Help is appreciated. Thanks, Tim

Yamae

There are two items I need to point out seeing photos.

1, You didn't clean the board well enough. As I see the area near C102, the residue is bridging traces. This causes some leakage current and it often causes problems.

2, Legs (lead wires of capacitor) should be as short as possible in order to minimize the impedance. You mounting method is not the best. I would simply insert the capacitor into holes as much as possible and solder only from the bottom side. These are "through holes" and the solder is absorbed well to the hole. You don't need to solder at the top side or should I say, don't solder as you did. Too much heat may damage capacitors too.

Yamae

One more item I want you to check is the polarity. Are they all correct?

ourbudd

Yamae, These pictures are before, i didn't take any afterwords. I will pull it tomorrow and take some pics and again replace the caps, I did verify the polarity on each one and when done checked all of them again. I didn't use much heat and I used a temp control station for the work. As I said the comments and questions are welcome so thanks and we will give it one more shot.

Thanks, Tim

ourbudd

Well, I pulled it back out today and started replacing the caps again, when I got C102 and looked closely at the area that had the leakage earlier looked suspect, I cleaned more and tested with an ohm meter and found that the strip was damaged, I Ran a small wire between the points and put a new cap in and reinstalled (I only replaced C101 and C102 this time). The P1600 code is gone now and we will see if it stays gone. Thanks to Yamae for the help and hopefully this will be it for that for some time.
Thanks, Tim

KJG92

It is amazing to me that doing this solves a ton of problems. I'm with others that feel many of these cars have been lost to the scrapper because of chasing a problem that they could not fix and then getting intimidated because it is a Lexus.

PlatinumV8

I wish we could upvote comments like you can on reddit. I'd upvote this to the moon. Just walking into a lexus dealer with an older model is intimidating, let alone the idea of dealing with their service department.

A lot of their customers turn in their cars every few years and they dump the ones that are not absolutely perfect one owner cars, onto the auction market.

Car is having issues that cannot be solved with remove and replace components? It gets sold and a new car bought. Good on all of us that stick to their guns and work the problem.

Willflow

As the title says I have all the right value caps but they are the KY series instead of the KZE series. Also I have an ecu for my 94 sc400 that will run the engine fine but the MEL signal does not function. I can power the ignition and if I put 12 volts to the MEL pin it will then stay on until I shut off the ignition but when I turn the key back on again I have no signal here. Can this be repaired possibly? Could it be a cap issue? The tricky thing here is this 1uz isn't in a Lexus any more, its in my 89 land cruiser fj62! I have gotten rid of the abs, traction control and theft functions and of course I have no need for the ac or cruise functions so they aren't connected. I have an ecu from a 93 sc400 running the Cruiser now and that's the ecu I plan on recapping but if I can fix the original ecu for a spar I would do it. Thanks, great site!

Lexinky

Edited: 9/11/2015

Replacing the capacitors in the Ecu SOLVED this problem of mis fire codes that were occurring.

1996 LS400 build date 12/1995 135.xxx miles

ECU number 89661- 50303

The car has had several occurrences of p0306 ( misfire cylinder 6) and random misfires on 2,4,6,8, cylinders. No other issues are none that would relate to the ECU

Replaced with NGK brand : spark plugs and wires.

New Denso distributor rotors and caps when timing belt replaced in October of 2012 with no issues since.

It would be Ok for a period of time and then misfires again.

When misfires occurs and the engine continues to run there is much smoke from the exhaust.

Pulled the ECU to examine and 1 capacitor is leaking a small amount onto 3-4 of the 8 traces next to it. The traces appear to be from the 8 transistors ( see upper right of the picture). the leaking capacitor is the second of two that are just below the transistors.

I cleaned the residue from the traces and so far no more misfires but is has only been a short time since cleaning and re-install.

Questions:

Are the 8 transistors I reference for the injectors?

Would incorrect timing of or missing/insufficent signals to the injectors cause the exhaust smoke too?

Does this make sense as to why the car has misfires before cleaning but none after cleaning so far now?

I am trying to gauge whether I am on the right track here.

I have ordered the new capacitors as LSCowboy has described in page 1 (Thank you LS and Yamae -san !!! and all others who contribute) and will have an old school electronics guy install them. ( I know my limits and soldering is not a skill I have aquired )





Side view of leaking capacitor.

AWilson013

iTrader: (2)

Earlier in this thread there is a method of testing the ECU... Mine was a rather easy diagnosis since it wouldn't read codes and had about every other sign of a bad ECU.

Lexinky

Yes I will do that test prior to replacing the capacitors on the ECU. I have a .47uf film capacitor on order with the others.

Thanks.

Yamae

Yes, those 8 transistors at the right upper corner near the connector are injector drivers.
The smoke is caused by the too much injection resulted by the incorrect operation of the main processor.

I suggest you to replace QAS capacitors ASAP before damages become serious.

Lexinky

Thank you Yamae san and others.

I have attempted the ripple test but it is a 1996 LS400 and nothing at OP1 on diagnostic port.

I connect to ECT sensor as shown in photo. Single wire sensor on the front left of the engine.

Is this OK place to take reading?

I have looked and looked for reference on this forum and cannot find.

I have looked at the link Yamae san showed that was for another member with no OP1 pin to reference and did not find the information.

Quote:
Originally Posted by BCinDC View Post
I was excited to try this tip, but after receiving my capacitor, I discovered that the "OP1" slot on my 96 is empty . There is no OP1 slot on the DLC2 under the dash either.

Any other connection location that will work?
This post will be helping you

EDITED:

Also found this but not sure of 2 wire sensor location.

Quote:
Originally Posted by usoff89 View Post
Well..... My new caps came in from digikey (.47uf). I was attempting to check the AC voltage when I noticed there wasn't even a pin connector in the service port????? For the pin OP1, its not there.....
I understand that some early US models don't have the terminal OP1. In that case try to check the ripple voltage at the coolant temp sensor which has 2 wires. Check the AC voltage between those 2 lines inserting 0.47uF film capacitor in series without worrying the polarity of wires. Anther idea is to measure the ripple at the 5V line at the MAF. In this case, the reading ripple voltage is a bit higher.


I will find the 2 wire sensor and try again.

I have new capacitors now and will install, I think it is good to understand before and after conditions.

Thanks.

Rstipton

I am not comfortable with trying to replace the caps myself. Can someone recommend a legitimate service that can do this? There are several on EBay but I don't know that I trust them. Without a working ECU I basically have a giant paperweight. I plan to take a look at the caps in a day or so to make certain but this would explain my problems (periodic loss of power to half the cylinders, air cond. cutting off, dash lighting up like a Christmas tree). No point on even looking at them though if I can't find a legit repair service. Thanks