History of MembersPage/MarcSwanson/MotronicAirTempMod
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2009-03-30 19:17:50 . . . . MembersPage/MarcellGal [unclamping not needed for MAT pullup change]
2009-03-29 00:14:46 . . . . c-24-61-109-220.hsd1.nh.comcast.net [reassembly notes]
2009-03-29 00:12:16 . . . . c-24-61-109-220.hsd1.nh.comcast.net [removed unnecessary html]
2009-03-29 00:11:28 . . . . c-24-61-109-220.hsd1.nh.comcast.net [notes on 1.8t air temp mod]


Changes by last author:

Added:
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This section is not needed - unless you need to disassemble the device for some other reason (hopefully not). To remove the piggyback resistor it is enough to remove the endplate (already done. One does not need to unclamp the FETs for this simple operation, because the resistor is at the endplate, easily reached.

"Unclamping"

Changed:
With the circuit board removed, locate the surface mount resistor that needs to be removed. There are two resistors, one stacked on top of the other. the top resistor is marked '115'. Remove ONLY the top resistor. The resistor is located near the MAP sensor at the back of the circuit board.

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Locate the surface mount resistor that needs to be removed. There are two resistors, one stacked on top of the other. the top resistor is marked '511' or which means 51 * 10e1 = 510 Ohm (or 5100 which is 510 * 10e0 = 510 Ohm, same).

One end of the resistor is connected to the MAT signal. To verify that you found the correct resistor, verify with DVM: you can measure almost 0 Ohm between MAT signal and one leg of this "internal pullup" resistor. This gently pulls up the MAT signal to +5V, allowing the sensor to pull down voltage somewhat (towards ground, in function of temperature).

Remove ONLY the top resistor. The resistor is located near the MAP sensor at the back of the circuit board.

Added:
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Changed:
Once everything is back together the firmware will need to be re-uploaded with the 1.8t air temp sensor calibration curve which is beyond the scope of this document. Contact the VEMS dealer you purchased your ECU from for assistance.
Once everything is back together the firmware will need to be re-uploaded with the 1.8t air temp sensor ("NTC 2252/256") calibration curve which is beyond the scope of this document. Contact the VEMS dealer you purchased your ECU from for assistance.