I just put a 10K mile engine in my friends 06 HHR with the 2.2. Car fired right up and rand perfect, everything worked, ice cold AC, and put right at 50 miles. Called and told my buddy he could pick up the next day. He didn't have a remote, so I locked the car up using the inside lock button and called it a night. Went to get in the car for another quick road test before he was to come and pick up and grabbed the door handle, forgetting that I had locked it up, and the horn starts honking. I went ahead and opened with the key and put key in ignition which instantly killed the horn. I fired it up and started heading down my 1/4 mile long driveway when I noticed the AC wasn't blowing cold. I looked up at the dash and the temp gauge was on zero as well.
Since then, I scanned with my modis scanner and got a PO118 Engine temp below -40. I also noticed that the radiator cooling fan starts up when you turn the key on with ac in off position. I have checked the fan relay, not stuck, checked the 5.0 volts to the temp sensor, removed codes and disconnected battery to make sure for approx 20 minutes. When I turn ignition on, the code immediately comes back after 3 seconds. In the first 3 seconds, the temp sensor starts rising like it is going to work, and then code comes back and bums me out. I have checked all wiring, all grounds, removed fuse box and cleaned an relubricated all the pins before putting back together. Still, when I clear codes with scanner, 3 seconds or less, code comes back. Any help would sure be appreciated.

 

The real description of P0118 is "Engine Coolant Temperature Sensor Circuit High Voltage". Which means that either the sensor is bad or the low ref (digital ground) is disconnected, since you say 5 volt is good.

NEVER bother reading the description any scanner gives for any given code. They don't mean what a human thinks it says.

 

The code indicates a bad temperature sending sensor, is it a new one? Do you have the one from the original engine to sway and see if that resolves the code? Is there air in the coolant system? Did you burp the coolant?
What thermostat did you install? AC Delco 131-158? 180 degrees F thermostat?

double check the connector at the temp sensor, they could be loose.

 

Wow!
Never been on this site before and had no idea of where to post. Sorry if I made a mistake.

 

No mistake, I will fix it.


There, done.

 

The sensor was the one that came with the 10k mile engine. Yes, I did burp the system several times to make sure. I did use the old sensor to test by clamping it to the side of the engine for ground and plugging it in with the same outcome. No, I do not have a AC Delco 131-158 180 thermostat in it. Sensor does feel tight. Are you thinking vapor lock of some kind?

 

It could be, I’d change the sensor and install the correct thermostat

 

Neither Oreillys, autozone, or napa have that 131-158 in stock, but I am working on finding one and will do so as soon as I can put my hands on one. It is a hard code that resets within 3 seconds. When I clear it with my scanner, the needle of the temp gauge immediately starts rising and then, like you flipped a switch, and with an audible click under the hood which is the throttle body, it drops back down to zero and sets the same P0118 code.

 

Confirms the temperature sensor is toast, swap it with the original one!
and the thermostat is available at RockAuto, do a part number search and don’t forget the discount code

 

Old Blue, you were right, the connector was making poor connection. I found an 07 plug on another car and it was obviously updated and solved that problem. Gauge works, AC iced cold, but now computer spit out a lost communication with transmission code. I have a 131-158 coming monday or tuesday. I will start attacking this code next. U0101