Calling All CODE 15s Calling All CODE 15s
 

HI All
I finally got an engine problem code, to be the reason for my cold driving problems.

Code 15

The part is easy enough to obtain (local store has it at fair price, too).
My engine is a 1985 and I know it mus be replaced.

I am correct in that this sensor is located by the Thermostat housing on the intake manifold?

Any tips offered for removing it?

IS IT OK to use Teflon tape on the threads?
I believe I need to to make a leak free seal. And the extra sealant would make the job more secure.

THANKS

Karl, yeah, you can use teflon tape on the threads. It grounds itself thru the engine harness, not thru the engine block. You're right about the sensor location, it'll have a connector with 1 yellow and 1 black wire going to it.

Only "tip" is that the connector on the sensor itself is brittle so it can crack off, but since you're replacing the sensor anyway, it's no concern. It's just a concern if you were going to re-use the sensor. The connector on the wiring harness is pretty durable.

With replacement sensor comes a wire harness, too.
So if I do break the connection....
THANKS TOM

The sensors I have been buying come with a coating on the threads already.

Sensor is on intake, basically right under the throttle body neck. It is a 19mm.

which sensor are we talking about. I'm courious

If your water temp is cold enough the engine does "certain things" to protect itself & produce less emissions.
This sensor is located close by my description the thermostat housing.
It stands upright, verticle, plug goes ontop.
Sucks, wish I knew this sensor goes bad when I did my swap boogie mission several years ago.
This problem been with me for about 3 years.
Don't laugh, ya think it truly gets cold enough in Southern California for this problem/cold engine cycle to happen?

I really enjoy self diagnoising engine problems with the ECM system. A paperclip to tell me the cars troubles. Love it.

i'm getting a code 15 myself

sounds like an easy enough fix, and i'm glad the boards are back up again

WONDERFUL GUY THAT DIRK
HURRAH
WE'RE ALIVE!!!!!!
I'm waiting for alittle bit longer to do this.
Just wrapped up some rear brake work.
This gets attacked shortly, tho.
Price is only $8 for the sensor.

Just so everyone knows why this codes happens and what the sensor does:

The ECT is used for a few things, first off, on cold start, it tells the computer that the engine is obviously cold. This allows the ECm to increase pulse width and make the engine run richer.

Later, the ECT tells the ECM that it's time to go closed loop. For closed loop to begin, 3 things have to happen: ECT above a certain temp, O2 giving signal voltage, and a certain amount of time has to pass since startup.

Now, when you get a code 15...DO NOT ASSUME IT'S THE SENSOR. On something like this it's not a big deal since it's an $8 part and it doesn't hurt to change it.

Here's how it works:

The computer supplies a 5v signal to the sensor and uses the reference wire as the signal wire as well.

The computer has a built in volt meter that basically performs a voltage-drop test across the sensor. As the Temperature of the sensor goes up, it's resistance decreases, and through the magic of voltage-drops, the voltage across the sensor also drops.

If either wire becomes open, either from an catual break or a bad/corroded connection, the signal voltage with peg itself at 5 volts, thelling the ECM that the vehicle is at about -64 F. On the other hand, if the sensor shorts, then the voltage will always read 0v across the sensor and you WILL have either a VERY hard start or NO START on FI vehicles.

Sometimes the code could be caused by another sensor that is bad. On startup, the ECM compares the IAT reading to the ECt reading. If the engine has been sitting for a while(and yes, most computers keep track of it), and the ECT and IAT don't read close together(block at ~ambient temp and IAT reading acutal ambient temp) then you might get a code 15 saying that the ECT is bad, but the IAT might actually be the culprit. This is a long shot on our cars because our computers are fairly stupid, but it COULD happen.

The Image below shows the typical wiring diagram of a 2 wire sensor