There is a little black box wired in between the coolant temp sensor plug that goes to the water pump and the original wiring to the harness. It is connected with crimp conectors.Im thinking that it may be one of those things that you can plug in to trick the computer in to thinking its running cooler. I had thought that this car was unmodified when I bought it, but I may be wrong. I just want to know what it is since im going to be getting tuning done soon. I want to make sure everything is right before I get it done.

Brad

 

You're probably right. It could be a series or parallel resistor with the sensor to change what the PCM sees. What would be worse is that the water pump sensor is not even connected, just the resistance telling the PCM that the engine's at a constant temperature and then your fans would never come on when the engine's too hot. I'd examine that device to see what's it is doing and use a scanner on the PCM to see what it's reading while the engine warms up. If they did bypass the sensor, when you hook it back up make sure the sensor is good.
There's also a small chance that they just cut the wire harness and had to splice in a new connector, although I would have soldered instead crimping.

 

Brad... I am currently testing a modification i did to my car using the coolant temp sensor..

I know exactly where does the PCM turns on and off the fans using a voltage reference points that are influended by the Thermostat. You see as the car gets hoter the resistance in the thermostats drops lower making the voltage between the leads fluctuate and the PCM uses this voltage to trigger the fans...

You are right when you say you can trick the PCM by modifying the sensor reading... but it is a double edged sword. I tested it already and I am working on a "may I call smart" modification to bypass certain drawbacks I encounter when I used a simple method to play with the temps..

I am currently turning my fans on at 180* degrees and turning them back off at about 165*degrees... My first mod worked like a charm yet it gave me problems at start up when cold... so based on what you saying its very probable someone got the idea before I did. (Dam it there goes my chance to Patent the dang thing)

Does your car cranks several times before it fires up when cold?? or does it just starts up like a predator beast after a tender bunny?? (dang I think I just described myself )

Marvin

 

What ever it is, it isn't factory. Changing what the computer reads for temp is a pretty bogus way of trying to get more power, IMO. What year is the car?

 

Not for power Shoebox... for fan cooling. Besides what about Maf translator, Oxygen sensor simulators, etc etc etc... I never claimed I was doing it for power... but power may very well a side effect.


Let me ask you a question... Do you have a 160* thermo in your car?? if you do Why did you put it in there?? I have one and I did it to keep the car cool... of course I enjoy the increased (seat of my pants) performance I have perceived since I installed it.

Of course if you dont have the 160* degree Thermostat than just disregard my question.


Marvin

 

I was in the middle of posting while you were and none of what I said had anything to do with what you posted (I did not see your post).


So you are making the pcm think the engine is colder or hotter?

If you are making it think it is colder, then without other pcm programming, the fans are not going to come on when they are really needed.

If you are making it think it is hotter, so the fans will come on sooner, then the pcm is going to reduce timing because of the higher temp.

I just don't see how tricking the temp sensor really helps. I would want my pcm to know what the real engine temp is and then I can adjust fans or timing with programming.

 

I started taking the harness apart, it looks like I was wrong. It just had a new plug put on it. The little black box that is further up in the harness look like its for the coil or somthing. The new end was put on with crimps should I solder this or will the crimped connections be fine.

Thanks for the help anyways.

Brad

 

Oh no buddy yer not gettin off that easey.... (slap slap slap)

just kidding dude.... I am glad your car hasnt been butchered in that area.

Like I said I am working in a mod that takes into acount only fan turning points... cause in my experience messing that sensor messes with your PCM. It uses a very narrow band at very specific temps to turn the fans on and off and yet it sends the correct data to the computer. Its my hobby though so I enjoy doing things like that.


Marvin

 

I always like soldered connections with heat shrink tubing on them. Remember to slide the tubing on when the wires are apart.

 

Shoebox you are right about the timing.... the PCM does that and I have already tested it beyond that...


The way it works is very similar to the fan mod switch.... the one where you can turn your fans at will.

The difference here is I am using electronics to do it automatically a diff temps... I found out at what points the pcm switches the fans on and then off.... and I designed an electronic circuit to turn the fans on just earlier than the PCM. I employed a Mosfet for the imput and with an input impedance on the 80Megohms range first... I totally did overshoot in the input impedance there...(eager beaver) altough it works just as designed it was also picking up magnetic signals from the ingition... so my second stage I lowered the imput inpedance to 10 kilo Ohms. the added inpedance is so insignificant I cant even read it the voltage load increase on the PCM at all... its in the Micro Amps I guess... the PCM is only using One volt plus at the sensor leads at 195Degrees of temp...

Anyway Its a piggy back design that activates the fan relays independently of the computer.... I am feeding the signal to a voltage comparator, then to a trigger device....it also knows at what temp to turn fans off.... its not just a triger device but a simple logical device.

I am picky so now I am going to ad an outside Potentiometer to adjust the temp manualy too... in other works I am converting it to a gadget.. that perhaps I can sell the idea to all those Import guys .... they like that stuff... the Potentiometer would not be neccesary for out LT1s though..


Tell me what do you think...

Marvin

 

If I understand what you are saying, you are borrowing information from the temperature sensor circuit to activate a separate device that can put a ground out to operate the fan relays (like an automatic fan switch). If so, it is an interesting way to go about it. Probably more electronic design than I am capable of inventing.
If you are not actually changing what the pcm sees, then I don't see any problem with your idea.