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Post by yaemish on May 5, 2020 1:03:22 GMT
My US CC has the indirect TPMS (no sensors on individual wheels). My car does not have a physical button. I changed over to my larger summer rims and would like to reset the system but I am having problems. When I go into "Brakes" > "Coding", you'll see that the "Tire Pressure Monitoring" is installed. When I go into "Basic Settings", it tells me that the monitoring system is "Not Available". I don't see where I can change anything. I also noticed that under "Dashboard" > "Long Coding", it says that it is not installed. I'm not sure what to do next.
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Post by dv52 (Australia) on May 7, 2020 7:14:16 GMT
yeamish; I'm less familiar with the CC rather than MQB platform vehicles like the Golf mk7 - but I'm almost certain that indirect TPMS is the same.
TPMS operates by recording the angular speed of each of the 4 x wheels and then it calculates the difference between wheel speed. The pulses that indicate a revolution of the wheel comes from transducers on the cars ABS system (so the hex03 module). In theory at least, the outer diameter of the wheel will vary sightly with tire pressure - so angular velocity at the rolling surface is a surrogate for tire pressure.
However, it shouldn't matter if you change ALL four tires to another (slightly different) diameter - because it's the difference in rolling surface velocity between wheels that's used to trigger a TPMS alarm.
Again, I'm not sure about the CC, but on MQB platform cars there is a series of software switches on Byte 3, Bits 0-3 on the hex17 module (what OBD11 calls "dashboard") that sets the car's understanding of the wheel circumference. Is this the same on a CC?
Don
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Post by yaemish on May 7, 2020 13:08:36 GMT
The CC has what sounds like the same system. From doing a little research, some VW cars have a physical button in the glove box that tells it to reset. You basically use a gauge to set all four tires the same and then hit the rest. After a drive, the car will use those stored values. However, the CC has no such button. I switched from to 235/45/17 to 235/40/18. The dashboard just triggers the pressure light and when I look at each individual wheel the values are "--". There is an oddity that I noticed and that is that in "Dashboard" > Long Coding", it says that tire pressure monitoring is not installed. I wonder if that means that individual tire pressure sensors are not installed. Before I get carried away, if I check the box and commit... Do I need to turn the care off and back on before going into "Brakes" to try the reset again? Also, thank you for taking the time to respond.
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Post by dv52 (Australia) on May 8, 2020 22:35:58 GMT
yaemish:OK - so on MQB cars with indirect TPMS, if the car doesn't have a physical TPMS switch, the equivalent facility to tell the car that the 4 x wheels have the same starting pressure is via the MENU screen on the dash (i.e. it's a software switch).
But I'm a tad confused by your latest post - you say that "I look at each individual wheel the values are "--"". As you probably are aware from your research, indirect TPMS doesn't actually measure pressure; all of the input data for the system is a surrogate for pressure (i.e. TPMS uses angular velocity, not pressure). Indirect TPMS have NO pressure transducers - so it can't display individual wheel pressures.
Are you sure that your CC has indirect TPMS? This might explain why your pictures say that the software switches on the Brake-module (@ address hex03) for TPMS is switched-off.
Did the caps on the valve stems on the old wheels have pressure transducers? When you scan the car with OBD11- do the results show a tire-pressure module (it's called J502 on MQB cars and the module lives @ address hex65 on the CAN network)?
Don
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Post by yaemish on May 12, 2020 18:17:42 GMT
Thank you for your help. I do not have individual sensors on the wheels, 100% indirect system. I would have assumed that I could reset it via menu in the car, the option doesn't exist though. Google indicates that they put a button in the glove box on some other models, not the CC.
When I say that I looked at each individual wheel, I meant in the dashboard menu on the car. With my summer tires on, it just reads "--" at each wheel. With my stock snow tires on, it reads "30" for each. I'll do a scan later and look for the module.
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