I am still trying to fix my overheating problem. I have troubleshot it down to the fans. The Primary Fan does NOT come on at 190 degrees (that's when it should according to the FAQ on this site), yet it WILL come on with the ALDL jumper and it WILL come on in Default Mode (when the Secondary Fan is engaged because of the A/C).

Note - The Primary Fan will NOT come on, even at 240, unless the A/C is on?!

-Thanks

 

Here's another thought, check the coolant temp sensor on the front of the intake. That is the only input that the ECM gets from the engine to turn on the pri fan, if it's bad and not closing, then the ECM is never told to ground the relay and turn on the fan. I am not sure, however, how to test that sensor, but that is the only input to the ECM for the pri fan. At least you know it cuts on in default, so you're somewhat ok.
You might be able to close the coolant temp sensor by running a jumper accross the harness plug w/o the sensor.

 

yes i second at least looking at or around the coolant temp sensor.

 

I have already replaced the CTS... Could the relay be bad, and the reason it works in diagnostic mode is because the relay is bypassed?

 

Anyone else have any ideas?!?!

 

Update
----------

I just swapped out the relay... still nothing

The Primary Cooling Fan will NOT kick on when the car gets to temperature. It will ONLY kick on with the ALDL jumper (Diagnostic Mode) and when the A/C is on (Default Mode). I checked the fuse in the fuse panel, replaced the CTS, and replaced the relay (actually I tried 2 relays!). BTW, the ECM is new also!

Please, someone help me... I need my fan

-Thanks

 

OK, I just unhooked my CTS sensor and the Primary Fan kicked on... does this tell us anything?

Unhooking the sensor DID set a SES code.

 

SES is normal here.
I think somethig is backwards here. One would think that you would create an open circuit by unplugging the CTS and the fan shoud not cut on, but you have the exact opposite. You said the ECM is new, is it the correct one for the car?? Are all the wires ok and run to the right places?
I'll give this some more thought.

 

Correct ECM - Yes
Wires ran properly - Yes

It worked fine until a few days ago

How could I verify that the CTS operation is backwards?

 

I believe there should be a sensor in the passenger side head almost directly above the starter.It is the Coolant temp. fan switch.When it reaches a set temp it goes to ground grounding a pin on the ECU and then the ECU turns the pri. fan on.I believe this is what controls the primary not the one in the intake on a dual fan setup at least.

 

Yeap, that would most likely be the problem. It is on the passenger head, between #6 & #8 exhaust ports. If this switch isn't working properly or is shorted out, it is most likely the cause.

 

Actually the SES indication is correct. The ECM sends a voltage signal to the CTS and when the temperature is cold, the CTS resistance is high, but when the resistance is low (high temp., open circuit, or disconnected CTS) the ECM sees a high temperature. So the ECM will command the fan to turn on.

Reference: TPI Swappers Guide, Troubleshooting Guide

-Ozzy

 

The primary fan is controlled by the fan switch? I thought only the aux. fan was?!

 

Oops, edited a minute too late.

 

Huh? Okay, I am confused... I thought the PRIMARY fan was controlled by the ECM and the CTS. And the SECONDARY fan was controlled by the fan switch? My secondary fan works fine, I am trying to get my PRIMARY to work. Did I miss something? Why are you suggesting I replace my fan switch?

 

You had it right the first time, my bad, I edited the reply.

Just so I don't get confussed:
Primary fan is on driver side, turned on by AC or ECM.
Secondary fan is on passenger side, turned on by Fan Switch.

If you did disconnect the CTS and the fan came on, then the circuit to the fan including the relay is OK, and the CTS is bad. Even a new sensor could be bad.

Sorry for the mix-up,
-Ozzy

 

I have tried 2 new CTS's. Are you sure it's bad? I am gonna test the ohms with a multimeter in a few minutes.

 

Temperature to Resistance Values (Approx)

Deg. F - Ohms
212 - 177
194 - 241
176 - 332
158 - 467
140 - 667
122 - 973
113 - 1188
104 - 1459
95 - 1802
86 - 2238
77 - 2796

 

If you have the stock chip, the ECM turns on the fan at 226 F. Try to read the temp with a scantool.