National Institute for Automotive Service Excellence. Working to improve the quality of vehicle repair and service by testing and certifying automotive professionals. Corporate Partner

Can you explain how this system works?

Michael Technician California Posted   Latest   Edited  
Discussion
Electrical
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?

0
   
Tim Curriculum Developer
California
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…

+11
Default Ð Awarded
 
Josh Technician
Virginia
Josh Default
 

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

+1
Default Ð Awarded
 
Billy Mechanic
New Mexico
Billy Default
 

Excellent explanation Thank you

+1
Default Ð Awarded
   
Jim Curriculum Developer
Maryland
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…

+3
Default Ð Awarded
National Institute for Automotive Service Excellence. Working to improve the quality of vehicle repair and service by testing and certifying automotive professionals. Corporate Partner