Where is Throttle Position Sensor on W211?
10-24-2010, 12:37 AM
#3
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It's a drive by wire car, there are two TPS Pot's on the throttle pedal (clock to run opposite of each other ie when you depress the pedal one pot goes low to high and the other one goes high to low) and then there are two pot's in the throttle body arranged just like the pedal to provide position reporting.
10-24-2010, 12:46 AM
#4
MBWorld Fanatic!
Thread Starter
I want to tap into +5V signal for Data logging. I was hoping I could do it at TPS, however it sounds like I will have to go to ECU... bummer Anyone do this?
10-24-2010, 01:02 AM
#7
MBWorld Fanatic!
ECU reads out two position values. Requested (pedal position) and actual (Throttle blade position) logging for anything more than a rough idea of what were doing with the throttle won't really give you any good data. Mototronic DBW treats the throttle pedal as a request for torque. The ECU looks at several variables before it commands the motor. It looks at how fast you tipped into the throttle, how far, what gear you are in, what load is already on the motor and wheel speed, yaw and acceleration sensors. It takes all that info into consideration then determines the amount of torque you are requesting.
After it figures out the amount of torque you want it then figures out what the best approach to getting that torque is, throttle blade position, supercharger engagement, timing, fueling and transmission variables (gear selection and torque converter lock up)
On a DBW car you might not always see what you expect to see when you log tps
And FWIW some tuners love to rescale the throttle pedal to fool you into thinking that they've done a better job of tuning your car
After it figures out the amount of torque you want it then figures out what the best approach to getting that torque is, throttle blade position, supercharger engagement, timing, fueling and transmission variables (gear selection and torque converter lock up)
On a DBW car you might not always see what you expect to see when you log tps
And FWIW some tuners love to rescale the throttle pedal to fool you into thinking that they've done a better job of tuning your car
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10-24-2010, 01:51 AM
#9
MBWorld Fanatic!
This guy knows his stuff! I am not sure about Mercedes, but for every car I have worked on that you tap into the TPS, it will throw a check engine light if you tap into it. If you tap into the Pedal position sensor (the one for the pedal itself), it will likely NOT throw a CEL. However, it won't be quite as accurate. I have tried Lexus, Toyota (same thing), BMW, Chevrolet, not tried Mercedes. Usually, they will throw an out of range code if you do ... and I think it is usually a second start code (i.e. doesn't happen on first start up). Even when I used high impedance input, it still throws a CEL if I hook into TPS versus pedal position sensor.
As far as one going high vs. low .. again on other vehicles, there are two potentiometers on the TPS, on some both go from low to high and for some they go opposite ways ... this is kind of a crosscheck to make sure there are no issues. The pedal position sensor does the same thing usually. On the E55 I think on the pedal they are just different ranges - 0.2 to 2.25V and 0.4V to 4.5V. The TPS, I don't know
As far as one going high vs. low .. again on other vehicles, there are two potentiometers on the TPS, on some both go from low to high and for some they go opposite ways ... this is kind of a crosscheck to make sure there are no issues. The pedal position sensor does the same thing usually. On the E55 I think on the pedal they are just different ranges - 0.2 to 2.25V and 0.4V to 4.5V. The TPS, I don't know
ECU reads out two position values. Requested (pedal position) and actual (Throttle blade position) logging for anything more than a rough idea of what were doing with the throttle won't really give you any good data. Mototronic DBW treats the throttle pedal as a request for torque. The ECU looks at several variables before it commands the motor. It looks at how fast you tipped into the throttle, how far, what gear you are in, what load is already on the motor and wheel speed, yaw and acceleration sensors. It takes all that info into consideration then determines the amount of torque you are requesting.
After it figures out the amount of torque you want it then figures out what the best approach to getting that torque is, throttle blade position, supercharger engagement, timing, fueling and transmission variables (gear selection and torque converter lock up)
On a DBW car you might not always see what you expect to see when you log tps
And FWIW some tuners love to rescale the throttle pedal to fool you into thinking that they've done a better job of tuning your car
After it figures out the amount of torque you want it then figures out what the best approach to getting that torque is, throttle blade position, supercharger engagement, timing, fueling and transmission variables (gear selection and torque converter lock up)
On a DBW car you might not always see what you expect to see when you log tps
And FWIW some tuners love to rescale the throttle pedal to fool you into thinking that they've done a better job of tuning your car
Last edited by turbo97se; 10-24-2010 at 02:47 AM.
