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2G Coolant System Issue

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dizily555

Proven Member
112
3
May 30, 2013
North Mankato, Minnesota
Last issue on this rebuild, my engine is not staying cool and I don't understand why. I am checking coolant temp via my OBD2 scan tool. With the car at idle or driving it will heat up to 223 and maybe more if I let it, the fan doesn't turn on at any point and to fix this I tried replacing the coolant temp sensor, coolant temp switch, and replaced relays, all to no solve the problem and lead me to fixing the fan by directly wiring the fans to the battery. I know the thermostat is good because it opens in boiling water, and I can only believe the water pump is good because it is brand new and is a good brand from O'Reilly's where I work. However with this being said it still gets hot, with the cap off I see no coolant moving which gives me a red flag but I don't know why, the thermostat has to be open at 180 or close to it and the water pump must be moving coolant because the system has pressure and with a funnel used to get air bubbles out, they come out. I flushed the heater core and radiator so they aren't clogged and I completely rebuilt the entire motor nothing can be clogged as I would know. Wondering if anyone can point me in a directed of what to try next, cooling fans need to turn on when the car reaches temp and I need to see coolant rushing past the open cap. I don't know what to try next, please help!
 
Finally found some time to keep trouble shooting and this is what I found. I do have 5 volts going to the CTS connector, I spliced in and monitored the voltage while its warming up to find that the CTS is receiving the correct signal even when the ecu is reading the high temp when the fans kick on. For example my scanner is reading 295-311 but at the same time my multi meter is reading .6 volts with my auto meter reading a perfect 180. Looking into it further I checked to see if the sensor was grounding through the chassis and it is. In trying to fix this I found the black with white striped wire coming from the sensor and made sure it was not going through the chassis ground. I then connected only this wire to the sensor ground. Turned the key to auxiliary to see my scanner read a -40 degrees. Why would this happen? With the CTS connected properly it should have read the correct temp. I absolutely confirmed that the positive and negative from the CTS are going to the correct pins. I did not check to see if I still had 5v but if I didn't would that mean the ecu is sending the wrong signal? In other posts I dealt with terrible wiring issues from the previous owner. He decided to connect a lot of the grounds coming from the engine harness to the same point, so sensor and chassis ground are connected together somehow. To fix this I'm wondering what sensors are to be grounded at the sensor ground and which are supposed to go to chassis ground.
Thanks again all help is immensely appreciated!
 
On a 2g, ECU pin 92 goes to the signal grounds of the following engine sensors: manifold diff pressure, engine coolant temp, front O2, rear O2, TPS, volume air flow (MAF), and on the 98 & 99 fuel tank diff pressure. (Note that ECU Pin 92 is grounded inside the ECU but all these sensors signal grounds must NOT be grounded anywhere but through pin 92.)

A typical example where people connect it wrong is at the front O2 sensor where they mistakenly connect the signal ground to the engine/chassis.

A -40* reading is caused by the ECU's internal sensor ground trace being blown. This is due to too much current flowing there because of a short or more often by someone connecting an O2 sensor wrong (eg. connecting the 12v heater ground wire (or power wire) to the sensor ground). Here's how to fix it but make sure you first have all the sensors signal grounds connected properly or you may blow it again: http://www.dsmlink.com/wiki/blownsensorground.

O2 sensor wiring: http://www.dsmtuners.com/threads/oxygen-sensor-wiring.244376/
 
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That was my problem, I'm not sure where in the system chassis ground was connecting to sensor ground but it was. Tracked down each sensor's ground and rewired them to pin 92. Now the car couldn't be running better!

Thank you @luv2rallye for your contribution to this site, I can't even begin to imagine how long it would have taken me to solve that problem.
 
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