5AT Solenoid Current -- target, derived or actual current?

[Plain om]

In the FSM 5AT diagnosis section, there's a table of parameters that can be monitored/recorded by the Subaru Select Monitor III, Romraider, FreeSSM, BtSsm etc.

 

For each of the transmission solenoids, there's two parameters; one is the "Solenoid Current", and the other is the "Solenoid Target Pressure".

 

The Target Pressure is clearly not the actual pressure being applied to the clutch or brake piston. But the current parameter isn't apparent.

 

It could also be a "target" current, a "presumed" current (based on the duty cycle drive signal to the solenoid and the battery voltage), or, an actual measurement of the current through the solenoid.

 

Which is it?

[utc_pyro]

It's measured current.

 

Feedback for the target pressures is guessed based on when the various pressure switches fire. Presumably during dev they had actual pressure transducers hooked up to each passage, but that was too expensive for production. So there are a bunch of on-off switches that trigger at a particular pressure.

[Plain om]

It's measured current.

 

Feedback for the target pressures is guessed based on when the various pressure switches fire. Presumably during dev they had actual pressure transducers hooked up to each passage, but that was too expensive for production. So there are a bunch of on-off switches that trigger at a particular pressure.

 

Thanks for the reply.

 

I might not have explained clearly . . .

 

I'm aware that in the 5AT transmission valve body, the shift-related solenoids/valves have a pressure switch that indicates whether or not the solenoid is delivering the required pressure. These switches can also be monitored (indicate off or on) using the SSM or Romraider et0c., and are a very valuable tool when troubleshooting possible problems in the valve body.

 

However, the AWD and torque converter lock up solenoids/valves in the valve body do not have these pressure-confirming switches. As for data availability, there's only the solenoid current and solenoid target pressure. In the case I'm working with, despite the data showing the solenoid should be sending line pressure to the TCC clutch (solenoid current is at same level, i.e.,

~ 0.55 Amps, as other solenoids, there's no sign of lock-up based on the engine and turbine rpm data.

 

I understand the "target pressure" is just a presumed value determined from the duty-cycle % of the solenoid drive signal. If the TCM is working properly, the target pressure data will show a proper value for lock-up, despite the lock-up switching valve not moving to the lock-up position and the clutch remaining disengaged.

 

Consequently, I'm looking to confirm whether or not the solenoid current data can be taken as proof that the solenoid is indeed being driven by the TCM, and therefore if lock-up isn't happening, the problem must be mechanical. e.g., the solenoid valve is not responding, there's a blockage in the lines, or the torque converter clutch isn't functioning.

 

Is there any documentation that clearly defines the solenoid current parameter as an actual measurement, or has anyone checked the current in the line between the TCM and the solenoid to verify that the parameter-indicated value is indeed actual current, and not a presumed/calculated value?

[utc_pyro]

I opened one up a long time ago and took a look. It’s now in Russia, and you can get the ROM dump on romraider. There was a shunt off each solenoid drive mosfet, and some signal conditioning electronics.

[Plain om]

I opened one up a long time ago and took a look. It’s now in Russia, and you can get the ROM dump on romraider. There was a shunt off each solenoid drive mosfet, and some signal conditioning electronics.

 

 

Ah!

 

Do you recall if that was for all the solenoid drives, incl. the torque converter lock-up solenoid?

 

"ROM dump"? Can you clarify what that would reveal and how to get it?