2005 Trailblazer EXT LT ambient temp sensor ground issue

[Lee's Automotive]

Hello I have a 05 trailblazer ext with the auto climate control and I have the b0159 code for the ambient air temp sensor I've replaced the sensor and still have the code and 50F on the display I did some digging and found out that I have 5v on the green wire but barely have a ground on the brown wire I used a test light and it barely lights up but I have checked ground on every other temp sensor and everything has a ground and the HVAC module has a perfect ground on the brown wire as well, my question is can I just run a new ground wire to the ambient temp sensor or what do I need to do to fix it?

Also something to mention is i disconnected the C105 connector by the fuse box and and on the male side of the connector I barely have a ground on the brown wire as well I also have a program cluster message when I open the door or start the vehicle

 

[budwich]

Hello I have a 05 trailblazer ext with the auto climate control and I have the b0159 code for the ambient air temp sensor I've replaced the sensor and still have the code and 50F on the display I did some digging and found out that I have 5v on the green wire but barely have a ground on the brown wire I used a test light and it barely lights up but I have checked ground on every other temp sensor and everything has a ground and the HVAC module has a perfect ground on the brown wire as well, my question is can I just run a new ground wire to the ambient temp sensor or what do I need to do to fix it?

Also something to mention is i disconnected the C105 connector by the fuse box and and on the male side of the connector I barely have a ground on the brown wire as well I also have a program cluster message when I open the door or start the vehicle

Sorry for the late response. Hopefully, you found your answer and I don't think its running a new ground... that's because the BN is NOT ground... its a "low ref" which means it is tied to some non-grounded internal circuit in the HVAC control module. IF you grounded that, you might have some "bad things" happening. From your description, it appears that all the other sensors are functional with proper electrical values. All the temperature sensors run to a common splice point (s271). Its possible that the wiring at that splice point has an issue as there are 7 wires spliced at that point. The splice appears to be on under the passenger side dash area towards the center.... based on my "poor read" of the diagrams.... look for the "pile of BN's".