Weird question but, I see on parts sites and AllData that we have Ambient temp sensors. I cannot find it for the life of me. I wouldnt think these trucks would have that sensor but ive been wrong before. It says its supposed to be behind the grill but i see nothing.
Greetings twebuh,
I scanned the '99 FSM .pdf file, and first found the removal and replacement guidance for this sensor:
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Elsewhere, I discovered in the wiring diagrams that this temp signal is handled by electrical circuit #735.
Rescanning for all instances of '735' I subsequently discovered that this signal is sent to the top
of the line 'Auto Day/Night' rearview mirror:
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So the answer is A) Yes it exists, but B) Only in the fully optioned luxo versions.
You are in good company, for no doubt the chore truck won't have any traces of this behind the radiator grill either. :0)
FWIW --