LingenfelterZ28

Hi guys ive been trying to figure out why my codes keep popping up for Cooling fan 1 & 2 control circut malfunction.. Ive pulled the relays and jumped the fans both operate as should.. Swapped the relays out with the ignition relay to test them and both were good... Wondering if the next step should be to just replace the ect sensor? I know the 98s are the 3 pin and there is a lot of threads on this.. Im assuming (correct me if im wrong please) the third wire is its communication to the pcm? Any more information would be greatly appreciated..

Injuneer

The codes only deal with the signal side of the fan relays, from the PCM to the relay and from the "Cooling Fan" fuse to the relay. The code will not be set by a faulty coolant temp sensor, or failed fans.

First, check the "Cooling Fan" mini fuse (10A) in underhood electrical center 1. If that is OK, verify that you have 12V at the orange wire on each of the three relays in the underhood electrical center. Fan Relay #1 - Pin C3; Fan Relay #2 - Pin B8; Fan Relay #3 - Pin C8.

If you verify all that, the problem is either the relays (odd that all three would die at the same time), or the wiring from the PCM to the three relays (PCM supplies the ground to close the relay). Again, hard to see how all three wires would fail at once.

With regard to the temp sensor, I suspect what they did was combine the coolant temp sensor for the gauge (1-wire sensor), and the coolant temp sensor for the PCM (2-wire sensor) into a single body for economy. You don't need a third wire to feed the signal to the PCM. The PCM connects a 5V power supply to one wire of the 2-wire connector, a ground to the other wire of the 2-wire connector, and reads the voltage, which changes based on the resistance of the sensor element. It's a thermistor, resistance is inversely proportional to the temperature.

GaryDoug

Fred is 100% correct about the ECT sensors

LingenfelterZ28

i checked the fuse before its fine tested for the power its good tested the relays and fans and they are all functioning properly..

GaryDoug

Do these codes happen every time the fans are supposed to start? Try using the a/c to force the fans on. If not, the problem is intermittent and will be difficult to find.

LingenfelterZ28

the codes come up within 30 seconds of the engine start.. im in the process of replacing the ac at this point..something must have gotten into one of the lines during the engine swap

GaryDoug

With the ignition on and engine off, check the voltage at C100 pins J (dark green wires) and H (dark blue wires). Both should be 12vdc. C100 is the most forward of the three larger connectors on the passenger side wheel well. If not 12v, the wires from there to the relay box are suspect. One place to suspect is under the battery.

LingenfelterZ28

10.2 volts.. traced the wires around found a semi bad connection.. replaced and codes went away..