Can you explain how this system works?

Michael Technician California Posted   Latest   Edited  
2011 Lexus IS250 2.5L (4GR-FSE) 6-spd (A760H)
No Dtc's

Scoped signals at these actuators for the HVAC system and got some very weird wave forms. Looked like a mixed signal/composite signal but unsure. Has anyone diagnosed the communication from the amplifier to the actuators and understands the protocol or strategy?

Tim Curriculum Developer
Tim Default

You're seeing LIN waveforms - a simple network where all actuators get the same commands, but the connectors are 'smart' and know which messages are for them. All you can do is verify power, ground, and 0-12 Volt LIN traffic at each connector (OK, it's 0-2 Volts minimum to 12-B+ maximum), as shown in the first attachment (from a '17 GM). If present, then Scan Tool PIDs and bi-directional…

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Josh Technician
Josh Default

That is a very good explanation and examples of the wave forms. Thanks for sharing that.

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Billy Mechanic
New Mexico
Billy Default

Excellent explanation Thank you

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Jim Curriculum Developer
Jim Default

Tim, that is a solid description. The only thing I would add to it is that on Toyota vehicles the motors and data tend to be unique to a position. One motor will have a range of (examples) 28-56 for command and position response. On a dual system you will see specs for position be 5-105 for one blend door while the other will be 4-104. The mode door will be unique as well. The sockets where the…

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