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Thread: Lexus IS300

  1. #1

    Default Lexus IS300

    Hi guys:
    First of all, my ME2 is doing great on my single Supra. This is the reason why Im surprised that we installed the ME2 on a IS300 (mechanic's car) and a friend of mine installed his ME2 in his IS300, and both of them have the same issues; the cars wont start. Even if they start, they shut off inmediately.
    I wanna ask if we are missing something, like a different setup on the jumpers, maybe a tab not turned on at the configuration menu, maybe an issue with the MAF, I dont know, just brainstorming here.

    Any help is really appreciated.

  2. #2


    You did not mention the model year as there was a change around 2002. The earlier one uses 3 ignition channels with wasted spark coils so you wire 3 channels and configure the MAP-ECU2 to "6 Cylinder Wasted Spark". You also need to set the jumpers the same as a MKIV Supra, i.e. High output drive.

    If it starts and then dies it is usually the air flow signal. The IS300 is very fussy on the MAF signal so make sure you have a good base table configured for the IS300 MAF or use intercept mode and retain the MAF until you get the feel of the MAF charactieristics. The base table is very different to a MKIV Supra.
    MAP-ECU Support

  3. #3


    We changed the jumper setting to High, and now the car starts. However, the car turns off if we follow the ME2 IS300 wiring diagram (MAF signal cut, connected to green and orange cables in 16way harness), but keeps running if the MAF signal is untouched.
    As Im not in the mechanic's place to run some tests changing the MODE, I wanna ask if the MODE needs to be MAF Intercept, instead of MAF Elimination, because of the way the wiring diagram is (just the same as the manual shows, MAF WIRING-Intercept mode). Another way to ask the same is: Why does the IS300 base maps have MAF Elimination in MODE, when the ME2 IS300 wiring diagram shows a MAF Intercept setup?
    Also, what do I put at the MAF Input space? OFF or MAF?

    Thanks in advance for the help.

  4. #4


    The wiring diagram will work for both MAF Eliminate and MAF Intercept. If you load a MAF Eliminate table, it will ignore the MAF signal if the MAF is still plugged in. If you want to run MAF Intercept mode, change the mode and then zero out the fuel table. That will allow the system to run as if the MAF is wired directly to the OEM ECU, i.e. no change. You can then adjust the MAF signal up and down by entering positive and negative numbers in the fuel table. The base IS300 table came from a MAP-ECU tune with 440cc injectors which means you will need to tune it if you have stock injectors.
    MAP-ECU Support

  5. #5


    Thanks for the quick reply, man.
    Any idea as to why the car shuts down after it starts? The IS300 is 2001, injectors are 550cc, wired exactly as the diagram, base map is IS300 440 LB.

    What should I put at the MAF Input space? OFF or MAF?

  6. #6


    Do you get a CEL? Not sure why it would die apart from a wiring issue or the OEM ECU's thinking the MAF signal is not what it expects to see. The IS300 ECU is very fussy.

    If you are running MAF Eliminate mode then "MAF Input" will do nothing.
    MAP-ECU Support

  7. #7


    Well, the car is running now. Everything seems to be working fine. We've done some street tuning and some dyno tuning. The only issue we are having now is that the ecu is creating what it seems to be fuel trims (or so we believe). When it starts to behave improperly (like misfires or bad sparks type of thing), we reset the ecu, the car behaves smoothly, and it will last like 10-15min, then it all starts again.
    You can sometimes get away with fuel trims using piggybacks, when you leave the closed loop section untouched, letting the oem ecu handle that part. With the ME2, Im dealing with a basemap that I dont know what the oem values should be (fuel), contrary to other piggys I've seen, where the starting value is 0 (where 0 means the oem ecu value), and you give or take fuel accordingly.
    This IS300 oem ecu is proving to be a PITA. Im not having any of these issues in my Supra. Any tip or suggestion for this? We've been changing spark plugs just to make sure it wasnt a fouled spark issue. As the car is tuned on the boost section (0psi-up), can I use the AutoLearn option in the "vacuum section" (where the "fuel trim" issue is hitting the car)? Any other way to solve this?
    Last edited by efrainruiz; 20th-April-2009 at 02:53 PM.

  8. #8


    As per our previous posts the IS300 ECU is very fussy and will use the O2 sensors to learn fuel trims more so than the older Supra ECU. That is why we recommended you use MAF Intercept mode so you can zero the closed loop zones and then only adjust the open loop zones. When you zero the fuel table in MAF Intercept mode, the MAF signal is sent to the OEM ECU unmodified.

    The only way to tune closed loop on a more modern ECU like the IS300 is with a scanner that shows closed loop fuel trims so you tune the MAP-ECU2 fuel table for zero fuel trims. This is exactly what the guy's at URD have had to do with the modern Toyota Trucks. Even though it is written for another product, take a look at Gadget's U-Tune guide:

    BTW, if you really want to run different AFR's in closed loop then you need to use O2 Adjust to fool the OEM ECU into thinking the AFR's in closed loop are stock.

    Hope that helps.
    MAP-ECU Support

  9. #9


    I owned a 2001 Turbo IS300 back in 2004. We have noticed that the ECU leans out the piggy back after 30mins of driving. We did two things....

    #1 - wire the ECU to reset itself when you shut off the car.
    #2 - disconnect all O2 sensors and run the car in open loop.

    They worked but were not permanent fixes.

  10. #10


    Hi again,
    Where do I connect the o2adjust cable (yellow), since the IS300 has four o2 sensors?
    I ask because I connected that yellow cable to the Bank1 Sensor1 signal, changed some values in the o2adj table, and nothing happened.

    Thanks in advance.

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