My caddy ECM and I presume all 4.9 ECMs are built to control 2 separate fans. I chose to use the Caddy ECM output for my fan control rather than the old style Fiero fan switch. This proved to be a good choice. The issue was that I could not decide which fan output I wanted. The first fan was set to come on at 201 and the 2nd was set to come on at 221. The 201 is great when using the 180 thermostat during the summer. But in the rather cold days of winter, you really want to run a 195 for that tad bit of extra heat you get. However having the fan come on at 201 and stay on until the engine reached 190 was a royal pain in the butt.
I had been simply pulling the pin from one slot and moving it to the other depending on climate and choice of operating range. I would also change the thermostat accordingly.
Today I decided to get sneaky. I grabbed a 2nd ECM pin and wire and plugged into the 2nd fan slot. Then went to the local auto parts place and got a 3 position switch. I wired the 2 outputs from the ECM to either side of the switch and the fan relay signal wire to the center. I can now at will flip a switch and choose between a low temp fan switch and a high temp fan switch.
I have posted the chip mods below for reference.
the pin out on the ECM for cooling fan relay #1 is A11 on the 24-pin black connector
the pin out on the ECM for cooling fan relay #2 is B8, also on the 24-pin black connector
Below is what the person that did my chip sent me for info. I don't know what the original ECM was set to but I am pretty happy with this chip.
Here are all the changes that are made from stock:
Ip divisor set to 1(00 in hex), so that the Fiero speedometer works properly
RSC set to 4000 pulses to match the Fiero's VSS
VATS removed
Fastchips fuel maps and spark timing curves
Cooling Fan 1 temp set to on at 204 degrees, off at 190 degrees ( Use 180 degree thermostat with this, NOT 160, as 160 is too cool for the computer to enter closed loop )
Cooling Fan 2 temp set to on at 221 degrees, off at 204 degreesbase idle for Park/neutral and drive set to 800 rpm, for your manual tranny.
RPM fuel shutoff raised to 5500 rpm up from stock 5200 rpm, rpm fuel turn on raised to 5400 rpm up from
5100 rpm (the optimum shift points for a stock 4.9L is around 4300 rpm, and if it is modded with a high-
lift cam, about 5100 rpm, so 5500 rpm will allow you to rev high enough for both of them, without damaging
the motor)
MPH shutoff raised to 255 MPH
ALL Cruise control, EGR system fault, auto tranny, purge canister, SMOG, BCM module(A/C is controlled
by BCM), VATS, and Power steering trouble codes have been turned off.
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85GT 5spd ,93 Eldorado 4.9 Dual O2 Custom Chip, Archie Clutch. Custom Exhaust. MSD Everything 245/50/16's Not Your Average 4.9 Capt Fiero Com --- My Over View Cadero Pics Yellow 88GT 5spd Stock.
