20HW is the Oheat warn box.
Unplug the B connector. you should get a solid BLEED OHEAT light, and a dark ECU OHEAT light that will not test.
unplug 12hw2(?) at #2 engine firewall, should be flashing OHEAT light.
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Please see the attached CMM to test the RP129-02 sensors. I have also attached the FSA 36-00-008-R03-A in regards to the improved RP482-00 or RP482-01 sensors.
Regards,Camron Madsen
Resistances for the temp sensors. you can test these from teh aft compartment without having to remove them.: