Scanmaster coding number 15


Active Member
Nov 17, 2011

Recently my dummy light came on and I am showing a code 15 which after looking it up its related to my coolant temp sensor low which from what I understand tells the ECM how to adjust to the current temperature in the engine cooling system.

My question is as follows. Would having a code 15 in anyway tell the ECM to compensate is too throw/increase fuel pressure in any way thereby causing detonation? This was how it was explained to me by an engine builder but I wanted to get you feedback to see if there is validity to it.

Prior to replacing the faulty sensor I did notice my engine was idling between 1000-1400 RPM's at idle and i could smell the exhaust was pretty rich. When I'd put the car under boost I could see black puffs of black smoke. Also, on some occasions during startup the engine would flood with fuel.

I replaced the sensor last night and now the car idles between 800-900RPM

Would a faulty coolant temp sensor be the culprit for all the issues mentioned above?

Thanks in advance for your time and input.
It's possible. When you were throwing the code, what temp was the ECM reporting?

If it was thinking the engine was absolute zero, the chip (depending on the chip) might have added a bunch of fuel to compensate.
sensor has to read -34F to set code
thats puts it in high idle for warmup and also adds fuel similar to a choke on a carb
because it never sees oerating temp it also stays at retarded timing
as to detonating it shouldnt because you shouldnt be trying to go wot while you have an ses light on