If the coolant sensor on an OBD2 car on the water pump is faulty, would it as a result affect performance? I was reading in Haynes Manual and it stated that if it was faulty, it could be telling the PCM false readings, which in turn the PCM would be calculating inaccurate fuel tables. Is this accurate?
So, I guess my main question is, that if your sensor is bad or going south, would you see that in track times??

 

Yes it could....the PCM would be using the wrong timing and other values...it could run like crap actually....saw it first hand.

Joe

 

If the coolant temp sensor in the water pump fails, it shows infinite resistance, which means minimum temperature, which is the lower limit of minus40degF. That tells the PCM that the coolant is near freezing, and that is needs to operates in open loop, and that it needs to richen the mixture up, just as the choke would do on a carb'd setup.

On a mass-air car, it isn't going to directly affect the air flow measurement, or the amount of fuel the PCM calculates, like it would in a speed-density car. But it indirectly throws the PCM off be telling it the engine is ice cold and needs a different A/F ratio.

If the sensor fails, you should get a code. The sensor is extremely easy to check, using an ohm meter. There is a table of temperature vs. resistance in my ScanMaster writeup.

 

Wow, thanks for the replies guys. I'm a little confused though on Injuneer's post. I understood your first paragraph easily. The second was not the same. On a mass-air car, you stated that its NOT going to directly affect the air flow measurement, or the fuel calculations.

But you said it INdirecly throws the PCM off, and as a result throwing off the air fuel ratio. I'm confused as to what you mean by "indirectly." Isn't this hurting performance if the PCM thinks the engine is freezing cold by enriching the fuel mixture?

I don't have a SES, or any other trouble code, but I haven't metered the sensor either. I've just had a problem with this particular sensor before, and I'm going to the track on friday, and I want my car to be 100%.

 

Any Clarification?

 

My low coolant light came on the other day and I haven't noticed any change in performance at all, and I don't know if I have codes but I have no SES light. Same thing happened a few months back, but the light just went away on its own.

 

They are talking of the actual 'coolant temp sensor'[the PCM one in the water pump housing]
Not the 'low coolant sensor'..