BLDun

I threw a code - 77- which is cooling fan relay. Problem is I have three of them in the box. Are they in any sequence - i.e. would #1 go out first, etc. or will I have to get them all checked????

shoebox

OBD-I does not differentiate between relay circuits. Test them all by swapping into the foglight relay socket. Easy to do.

BLDun

Good deal! will do! Thanks

BLDun

Shoebox, I did what you said and all three tested out OK, so where else would the code be activated from. My fans are not coming on unless I use my manual switch.

shoebox

What kind of manual switch do you have? There are many ways to wire one. I would be checking your factory wiring from the computer to the relay box.

BLDun

It is a simple flip switch. On or off. No hi speed or low speed. It was already on the car when I bought it. Where does the PCM get its signal to turn on the fans???

Thanks

shoebox

Without knowing how your switch is wired, there is no way to troubleshoot that part any further. The PCM gets it's temp reading from the sensor in the water pump. The PCM, itself, is what turns on the fans.

BLDun

That's odd because my problem began when I replaced the temp sensor. I just checked the plugin wire and it is plugged in tight. Is there any way to test the wire itself and/or the sensor to make sure it is OK. It just seems odd that the changing of the sensor and the fan problem began at the same time. The fans haven't kicked in by themselves since then.

shoebox

http://shbox.com/1/4th_gen_tech2.html#ect