Question about solenoids

A forum for discussing applications and implementations of the MegaShift transmission controller code for the GPIO from B&G. This can control up to 8-speeds and 6 shift solenoids (plus a 16x9 table for controlling a PWM line pressure valve). It has manual and fully automatic modes (16x9 load x speed table), with under and over rev-limit protection, and full data logging of all inputs and outputs (among many other abilities). A TransStim to test your completed board is also available.
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Joined: Mon Oct 14, 2013 7:14 am
Location: Winchester, England

Question about solenoids

Post by Addicted »

My Audi transmission uses 7 Solenoids.

5 Shift solenoids. One for TCC and one for PC.

The Audi Self Study Program identifies these later solenoids (N93 & N91) as Modulation Solenoids (PWM)

I can buy a new set of Solenoids easily enough.. ... 07&vxp=mtr

The two PWM solenoids are identified by having brown connectors.

However, I have a query..

Audi's own troubleshooting guide for this transmissions lists checks for impedance for the 7 solenoids. It shows that all the solenoids should have an impedance of 55ohms.. except for N93 (PC) which should be 4ohms.
When I check my solenoids they're all to spec.

That means N91 (TCC, which has the brown connector and is listed as a PWM solenoid) has an impendance of 55 ohms, whereas the other 'identical' solenoid (N93, PC) has an impedance of only 4ohms (these are values measured at the TCM installed in the car)

Scoping those two solenoids (N91 & N93) I see that:

N93 (PC) has a lovely 440hz square wave signal (59% duty cycle at idle)
N91 (TCC) has nothing

How can two identical solenoids have such different charactistics?
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