Hvac System Error 21

Tyler121 · February 2, 2008

I ran a diagnostic on the hvac system by pressing the auto button and the recirc button at the same time then turning the key to on, i did this and got the number 21, can someone tell me what the 21 means please

wwest · February 2, 2008

Just guessing but if you didn't have a light shining on the sunlight radiation sensor the diagnostic will stop there showing it as a failure. Holding a shop light above it usually gets you past that "fault".

wwest · February 3, 2008

From '92 LS400 shop/repair manual.

Code 21 is the solar light sensor ciruit.

22 is "locked" compressor.

23-30 not used.

31 is open/short in the reheat/remix damper position sensor circuit.

32 is open/short in the air inlet (fresh/recirc.) damper position sensor circuit.

33 [a] open in reheat/remix damper position circuit, or...

33 open/short in reheat/remix damper servomotor circuit, or....

33 [c] Remix/reheat servomotor "locked"/stalled.

34 [a] open in air inlet damper position sensor, or...

34 open/short in air inlet servomotor circuit, or...

34 [c] air inlet servomotor locked/stalled.

Tyler121 · February 3, 2008

well i don't have a shop light but if i do it outside should it bypass 21? or do i need to go up to my neighbors and use his light

wwest · February 3, 2008

well i don't have a shop light but if i do it outside should it bypass 21? or do i need to go up to my neighbors and use his light

BRIGHT sunlight or flashlight....

What is your reason for testing...??

Tyler121 · February 3, 2008

well i tested again and i got 00, i didnt really have a reason for testing, i just was reading the Faq and saw that i could do that and wanted to test it.