LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

P1127 - ETCS Actuator Power Source Circuit Malfunction

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Old 01-17-21, 08:51 AM
  #16  
Yamae
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Originally Posted by Einzelherz
And to Yamae's post. I just realized that 0L means Over Limit. After cleaning up some of the flux and mess I'm now getting 190-200 M ohms sometimes, 170 M ohms other times and 140 M ohms other times. I suspect that's not good.
Mine shows 0.7M ohms with my multimeter Fluke 8060A which uses a 9V battery but the reading resistance value depends on the multimeter due to the voltage applied to measure the resistance. I think yours is not fully open.

The code P1127 means that the power supply to the throttle motor is not done. There are two types of no power supply. One is that the line is disconnected due to the open trace or the drive circuit is dead or stopped working. The other is caused by the limp home mode. In this case, something unusual is detected by the processor and the drive circuit is forced to stop by the processor. In order to fix the problem, there needs some more efforts to find out why the motor is not working. If I were there at your garage, I would be able to trace the circuit. It needs some skills to trace the circuit though.

Dealers don't repair ECUs. They just replace it after writing the immobilizer data and charge you some big money. So when you ask them to fix, you need to pay $$$.

You must have done something wrong while replacing capacitors. I am away from you and I can't investigate your ECU board here. At the moment, I only can suggest you to check some more carefully what you have done.


Old 01-17-21, 09:59 AM
  #17  
Einzelherz
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What resistance do you get across the two pins for the throttle clutch? Pins B8 and C12? Mine shows around 3.6M ohms.

There were two capacitors on the list from the ECU thread that I didn't pick the first listed - UHW1H221MPD in place of EEU-FR1H221 and EEU-FC1V331 in place of 35ZLH330MEFC10X12.5.

Technically I also got EKZE500ETC100ME07D instead of EKZE500ELL100ME07D but they just were on tape instead of loose.

I have an idea. If I remove the capacitors one at a time and then recheck the resistance across pins A7 and A8, if that changes significantly, I would think that might give me more information, yes?

Last edited by Einzelherz; 01-17-21 at 10:05 AM.
Old 01-17-21, 06:05 PM
  #18  
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Originally Posted by Einzelherz
What resistance do you get across the two pins for the throttle clutch? Pins B8 and C12? Mine shows around 3.6M ohms.

There were two capacitors on the list from the ECU thread that I didn't pick the first listed - UHW1H221MPD in place of EEU-FR1H221 and EEU-FC1V331 in place of 35ZLH330MEFC10X12.5.

Technically I also got EKZE500ETC100ME07D instead of EKZE500ELL100ME07D but they just were on tape instead of loose.

I have an idea. If I remove the capacitors one at a time and then recheck the resistance across pins A7 and A8, if that changes significantly, I would think that might give me more information, yes?
I think your value 3.6M ohms between Pins B8 and C12 seems fine since it's not ∞. My ECU is now back to the car and I can't measure the resistance quickly.

Regarding capacitors you used, I think they are OK as far as you installed them correctly. There must be something wrong but it is hard for me to pinpoint the exact part without analyzing the board myself using an oscilloscope, a X-ray machine and others.
Old 01-18-21, 08:02 AM
  #19  
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While I'm in the process of repairing the original ECM I'm planning to get a spare from eBay and reprogram it to my car/keys. My original ECM is 89661-50434. There are two barcode variants of this - 175200-3130(mine) and 175200-3131. I'm guessing the 3131 is the California emissions variant? Does this barcode number matter so long as the part number matches?
Old 01-26-21, 10:07 AM
  #20  
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My eventual fix was to get a replacement ebay ECU and swap over my security chip to it. FWIW, it was the 3131 model ECU but so far nothing seems out of the ordinary.
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