wastegate Posted February 11, 2022 Report Share Posted February 11, 2022 Hi Guys, Currently have an issue with the Brake switch. At the moment it's configured as per the Altezza base map for DI6 as Brake NC with a Pull Up and set to High. I have this in a IS300 which is identical. It was working fine like this with my G4+ and the G4+ was getting the signal from the brake switch. However with the G4X, it seems to trigger the Brake NC but then doesn't turn off. Latch is not enabled but it's acting like it. I have tried with a pull up, without it, set it to high, set it to low.. Only High with no pull up will sense anything and only the one time. Probing the pin, I get 1.27v and 12.8v with brake depressed. Looking at the wiring diagram for both Altezza and IS300, they are identical with 12v source from battery, to the brake switch then to the ECU to ground. From the diagram, it should be a Normally Open circuit until the pedal is pressed and closes the circuit. However the base map has a Brake NC as DI6 not NO. Seems I'm getting the right voltages to DI6 but for some weird reason, Brake is not triggering correctly. Maphttps://drive.google.com/file/d/1IFgz0CCCq9Erbu2caBoS-G188oSagFRz/view?usp=sharing Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 11, 2022 Report Share Posted February 11, 2022 Brake NC and Brake NO effectively are just opposite logic, in cases where the car only has one brake switch you can use either one and use the active state setting to get it to operate how you like. 11 hours ago, wastegate said: Probing the pin, I get 1.27v and 12.8v with brake depressed. The question here is where is the 1.27V coming from, it should be close to zero. The switching threshold on the DI falling edge is around 1.0V so it needs to fall below that for it to work correctly. If it is not a major job it would be a good test to extract that wire out of the connector to check if the 1.27V is coming out of that wire or out of the ecu. The DI's have a pull down on them so it should be zero V unless the switch or rest of the brake circuit is passing some voltage through. Quote Link to comment Share on other sites More sharing options...
wastegate Posted February 12, 2022 Author Report Share Posted February 12, 2022 Hi Adam, The Toyota shop manual states that STP should be below 1.5V with no brake applied. This is same for Altezza (just in japanese and with the correct pin on the ECU This is the Altezza wiring diagram, I'm unsure where that voltage is coming from. But will pull the pin and check. EDIT: Just pulled the pin from the ECU header and same voltages. 1.27v no brake and 12.4 with brake. I guess there is no way to change the DI falling edge? I noticed also that the STP also goes to the Skid Control/ABS ECU. The IS300 also runs a NC brake switch (ST-) as well. I might see what I did with that wire in the loom... might be a better one to use since it doesn't go to the ABS ECU. EDIT 2: Using ST1- into DI6 instead of STA from the IS300 loom worked 100%. Now have cruise control back working. Cheers Quote Link to comment Share on other sites More sharing options...
essb00 Posted February 12, 2022 Report Share Posted February 12, 2022 How about putting one or two diodes (1N4001 or 1N4007, etc) inline before DI to further drop the voltage? I'm thinking there's a resistor parallel to the stop/brake switch for wire break/fault detection of the stock ECU that's why voltage is not fully dropping down to zero. Quote Link to comment Share on other sites More sharing options...
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