Logger reading -59*C coolant temp

[93jdmlaser]

I got my car running finally and when I put the logger on it I am reading -59*C. My stock coolant guage isnt working but Im hooking that back up. I also went to pull the cel with my logger and it wasnt for the coolant temp sensor. I know something isnt right. How can I fix this temp reading?

 

[steve]

There are multiple coolant sensors. The ones for the gauge and ECU are different. That are both located in the thermostat housing.Sound like both of your are bad.

What code did you pull, since it wasn't the one for the ECT.

Steve

 

[92awddsm]

I just went through this on another car. Check the wiring to the two 2 prong sensors located on the thermostat housing. Im willing to bet that one of the wires on the lower sensor is broken. The single wire sensor is the one that works the factory gauge.

 

[93jdmlaser]

Were did the wire break on yours. It goes into the harness and I dont wanna have to tear it all open.

 

[92awddsm]

It was within 3" of the plug. Im sure if you get to looking, the wires in that area have become brittle from age, oil, heat, etc. I stripped mine back into the harness just to see and inside the harness, the are still pliable. Just the exsposed section seems to get really brittle.

 

[93jdmlaser]

The wrap on the wires is ripped on both right at the plug but when I stripped it back it was ok. I took my volt meter and there are no volts coming throught the wire to the sensor so are there any fuses that can cause this or are the wires just broken somewhere?

 

[steve]

No fuses, you won't see any voltage unless the ECU is on. Here's where everything goes.

http://www.taboospeedshop.com/wiring.htm

Make sure you have continuity back to the ECU.

Steve

 

[93jdmlaser]

Thanks steve for the link, could you tell me what pins I need to check for continuity. Thanks

 

[steve]

I already did. Follow the wires in the diagram. The pins are marked.

Steve

 

[93jdmlaser]

Ok I looked again and it says for the engine coolant temp sensor that its pin 20 and 24. So I am gonna check that for continuity. If that is ok then I will run new wires from there to the sensor because I think the wires are broken somewhere. I will also check the wires for continuity. If you have anyother ways I should test then let me know. Thanks for the help steve.

 

[steve]

You'll note that the wire that goes to 24 is common with several sensors. Also goes to the TPS, MAF and pin 17 on the ECU. It's the sensor ground and should be on pin 1 of the ECT sensor.
Pin 20 only runs to the ECT sensor pin 2.

With the ECU plugged into the harness you should be able to measure 0 ohms between the sensor ground and the chassis at each of the those sensors.

Steve

 

[93jdmlaser]

Ok well my tps is working fine so that ground is probably ok. I think that the power to the sensor wire is bad. I am getting no volts to it. I will check pin on the ecu to see if its sending voltage to the wire and if its ok I will just run my own wire to the sensor. I read that its supposed to be 4 to 4.5 volts. Is that right?

 

[steve]

I read that its supposed to be 4 to 4.5 volts. Is that right?

The ECU has a pullup to 5v on pin 20, so there should be some voltage on it depending on coolant temp.

Steve

 

[93jdmlaser]

Ok steve, I went over and put the meter on continuity to to check the wire. I put the tester to the one end of the harness where the wire goes and the sensor end and I got no continuity so I assume my wire is shorted or broke somewhere. Can I just cut it at the begining of the harness and run my own wire to the sensor. I will check for voltage tomorrow if I cut the line to put my own in. Thanks

 

[steve]

I would check pin 20 at the ECU when it's powered up to see if you have voltage and then check the unplugged sensor connector again for voltage before cutting things.

Steve

 

[93jdmlaser]

This may sound stupid but since the ecu has to be on to check the pin I will need to have the harness plug in but if I have it plugged in I would have no way to check right at the ecu for voltage. Thanks for all the help. I do have a vpc so I could use a splice connector on the wire in the vpc harness instead of hacking my stock one.

 

[steve]

If you pull on the harness a little bit you can hook up the ECU outside of the center console and since the back of the connector is open you can probe the pins easily.

Steve

 

[93jdmlaser]

Ok I will go try that. Thanks again for all the help. I will post my results.

 

[Pro3racer]

We have a similar problem on my mechanics race car. We have tryed 3 Temp sensors, the sensor that tells the ecu how warm the engine is, not the gauge sensor. His logger repeatedly says -40degrees. The wires for the sensor are fine, we tested it. So now the motor thinks its -40 degrees, so the motor runs like crap because of the overly rich condition. We grounded the sensor out though, and it ran a little better, a little better. The battery did die earlier in the day, could that have erased something? While the car was running, we unplugged the injector harness one by one, all were fine. But when we unplugged his MAFT, it didn't affect the car at all? We also got two codes, the coolant temp sensor(or engine temp, can't remember exactly), and mass air volume code. Any help on what is our problem???? Thanks

 

[steve]

The MAF code was from the MAF being unplugged.
It's a good idea to check the other sensor values to make sure nothing else is out of whack. It's not too unusual for the sensor ground on the ECU to be blown. The quick check is to measure the resistance between the sensor ground and chassis ground. If it's > 0 have the ECU checked out. For the problem with the ECT Sensor you need to do the same things 93jdmlaser is doing to make sure that the sensor is good and that the harness isn't damaged.
Once those check out the only thing left is the ECU.

To test the sensor you measure it's resistance. It should be something like 2.6k ohms @ 68F and 300 ohms @176F

Steve

 

[93jdmlaser]

I can see a few inches out of the harness the wire was cut and had a grey wire from the afc run into it and then all 3 were twisted together and crimped. I have pics but I can not post them until morrow nite, I am waiting on the camera cable. I took the tester and put it on that wire there and I got no continuity between there and the end of the wire. I am not sure what the grey wire is but I will look into it more tomorrow when I have time. I will also do the tests you posted above. Thanks I will post more for you when I get the camera.

 

[steve]

I can see a few inches out of the harness the wire was cut and had a grey wire from the afc run into it and then all 3 were twisted together and crimped. I took the tester and put it on that wire there and I got no continuity between there and the end of the wire.

You sure you have the right pin. The grey wire is for the TPS and would go to pin 19 not pin 20. The wire in pin 19 is green w/white stripe, pin 20 is yellow w/green stripe.

Steve

 

[93jdmlaser]

Lol Im sorry steve, your right I looked at the wrong one. Sorry for waisting your time on that one. I will post pics today.

 

[steve]

No problem, we all make mistakes.
I'll be gone most of tomorrow taking my son to college orientation for incoming freshmen.

Steve

 

[Pro3racer]

We solved our problem, we just made our own ground cable out of the plug, and it worked, we don't really know why, but what the hell, it works.