ENGINE HOT, but temp gauge sitting on the zero peg.

My wife called me to report that the recently acquired 2013 Impala had a Master Caution light and was reporting ENGINE HOT, and that the radiator fan was staying on with the car turned off. She reported that the temp gauge was sitting on the zero peg, there was coolant in the overflow jug, and the engine did not smell hot. “Sensor problem,” I said, but not overheating, and we had the car carried home by AAA.

I have this device which a friend sent me several years ago, and which sat on my desk unused for over a year because I had no idea what it was or how it might be used. I have since learned.

The device is plugged into the OBD (OnBoard Diagnostic) port under the dash.

Along with an Android application called DashCommand, I can use my cell phone to look at pretty much any sensor on the car via Bluetooth, as well as read codes. I can also buy an advanced suite of features and information for my particular car(s) for $10 apiece from DashCommand.


I don’t have a screenshot of it, but the computer returned the code P0128 and a mechanic pal said that if the engine temp was normal, then the problem was likely a faulty thermostat, stuck open, which would send the car’s computer into a panic. I swung by the Chevrolet dealership, who did not sell just a thermostat for that car, but rather a complete housing with thermostat and gasket for $109, and they did not have one in stock.

I happened to be in contact with the fellow who’d sold me the car about another matter, right when this breakdown occurred. He concurred with my mechanic pal’s call on the P0128 code, and thought that the Chevy dealership was crazy. He offered to repair the car for me and would not give me a price. “We’ll figure that out later.”


This is a screenshot of the DashCommand app running on my Nexus 5 smartphone.

So I drove the car to the man’s shop this morning, a six-mile drive through town, and used DashCommand to monitor the engine temperature. How frickin’ cool is that?! The car never got hotter than 160 degrees.

That thermostat only lasted 72,000 miles.

And the thermostat was indeed wasted. Dude spent $57 on a thermostat, a jug of Dex antifreeze and a new air filter. He said he also cleaned the throttle body. Final bill: one Ben Franklin.