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U0101: Lost Communication with TCM on ISF


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U0101 Code: Lost Communication with TCM

Has anyone come across the above fault on an ISF? I tried a couple things as well as having Lexus look at it. They recommend I bring it to an auto electrician.
There are two scenarios: 1. I get three lights (engine/traction/abs) which makes the car go into limp mode or 2. I clear it (sometimes it doesn't) or the third light (abs) goes away and the car drives normal and through all gears etc

I've not worked on the car besides usual maintenance of changing the engine oil. Battery + connections good, only 2-3 years old

Car is a 2011


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Some more info:

  • Battery Voltage with engine off = ~12.7
  • Control module voltage = 13.828V
  • Oxygen Sensor Output voltage (B2-S2)= 0.155V <------is this something to be worried about?
  • Oxygen Sensor Output voltage (B1-S2)= 0.855V
  • Oxygen Sensor voltage (B1-S1)= 3.246V
  • Oxygen Sensor voltage (B2-S1)= 3.241V
  • Oxygen Sensor Current (B1-S1)= -0.02mA
  • Oxygen Sensor Current (B2-S1)= -0.03mA
  • It fault codes seems to only appear for : ECU (#e8) = U0101 Lost Communication with TCM 1/2 & 2/2
  • No faults for ECU 2 (#e9)
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Do you happen to know where i can locate the fuse for the TCM or a wiring diagram TCM-ECU? 

The only fuse box as per the fuse diagram that I can see relates to the transmission is the one below (15) which is located on the right side drivers side (AUS) panel. It's 7.5amps and looks to be good and not broken.




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  • 1 year later...

Hi AUISF33 did you end up fixing your problem? I have almost the same problem. ABS, Power steering & the seat light are all permanently on. Temp gauge doesn’t work, clunky in manual mode and is in limp mode.

Checked all the fuses, battery is getting enough voltage, checked all the OBD wires with multimeter all good. Pulled out the ECU to see if anything was faulty and cleaned all the electrical connectors and still no good. Got an auto electrician to have a look and he said not getting any signal from my ABS module that’s why can’t communicate with ECU. He said he needed wiring diagram for the ECU, ABS & Power steering which I got and sent to him but hasn’t returned my calls. 
Not sure where to go from here, do I get a new ABS module and hopefully fixes my problem? Don’t want to take it to the deal shop cause they will sting me. Would like to fix it myself if I can.

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