Radiator Fans

[redrum3g]

okay i dont have no kind of scanner only but the obdII scanner, but my relays working but i have rigged a wire around the smaller fan wire a hooked it up to the battery and a on/off switch both both side of the wire is disconnect will that cause the qdm 1 & 2 failure?

[HotZ28]

Originally Posted by redrum3g

okay i dont have no kind of scanner only but the obdII scanner, but my relays working but i have rigged a wire around the smaller fan wire a hooked it up to the battery and a on/off switch both both side of the wire is disconnect will that cause the qdm 1 & 2 failure?

I am sorry, but I am having a very difficult time interrupting what you just said in the post above. Please use proper sentence structure & grammar, to help us understand.


If you hooked up a jumper to ground on the fan motor, yes the QDM will give a fault. Again, the QDM sends a ground to the relay and in turn will energize the relay, which then sends voltage to the fan. If the PCM detects a break in the ground, it will set a DTC.

[redrum3g]

so you saying the wire i ran from the fan to the switch (that i still have hook up to the fan motor, but off the switch) cause the qdm 1 & 2 failure? If i remove the wire thatz running with that cause the code to resolve itself? Okay what does code p1630 Battery voltage out of range mean? Is the wire causing that code too?

[HotZ28]

Looking at the schematic below, which wire did you cut to install a switch? Give the location and wire color if possible.

[redrum3g]

okay now the left cooling fan motor the line thatz going straight i did that one. and that wire is light blue. I rigged that blue wire with like a power cord you plug in the socket one end of the wire is hooked up to the switch the other end is hooked up to the positive battery and the light blue wire on the motor.

[HotZ28]

“Hot wiring” the fans, is OK to test the fans, but is ABSOLUTELY not a long-term remedy. IF you use a relay with a fused jumper and eliminate the PCM control to the existing relays, you may get by with the jumper for awhile (if you remember to turn it off/on as required). The high-speed fan pulls about 18-20 amps and you could melt the wires and switch which could result in a fire.

You need to do some basic troubleshooting here and see if the PCM is providing a ground to the relay(s) when conditions dictate. Again, without the A/C on, the engine temperature must reach 212 deg before the PCM commands a ground to the low speed fan relay and 220 deg before the high-speed relay is grounded. (Use the schematic above to troubleshoot the wiring circuit). If you find that the PCM is not providing a ground to the fan relays, you can replace the PCM, or you could put your manual switch between an engine/chassis ground and the existing fan relay grounds. Finally, NEVER run a HOT (unfused) 12v jumper without a relay!!

[redrum3g]

how do i test to see if the pcm is providing the relays a ground? If it's not, is it hard to replace the pcm? Where is it located?

[HotZ28]

Originally Posted by redrum3g

how do i test to see if the pcm is providing the relays a ground?

Originally Posted by HotZ28

the engine temperature must reach 212 deg before the PCM commands a ground to the low speed fan relay and 220 deg before the high-speed relay is grounded

When the coolant temp sensor reaches about 180 ohms of resistance, (212 deg) the PCM will detect the voltage feedback of the sensor and the PCM should command a ground to the low-speed fan relay on the Dark Green (DG) wire. You can test (probe) that wire for continuity to ground, if the conditions above are met. The same applies to the high-speed relay ground on the Dark Blue (DBL) wire, if temp reaches 220 deg., or the CTS reaches 145 ohms of resistance. If you do not have a scanner, how were you able to retrieve codes for the “QDM 1 &2 failure” & “code p1630 Battery voltage out of range”?

Originally Posted by redrum3g

If it's not, is it hard to replace the pcm? Where is it located?

The PCM is under the passenger side dash, behind the glove box and somewhat above. You need to remove the hush panel on the bottom of the dash and the glove box to gain access. If you replace the PCM with a rebuilt unit, you will need to change the prom (chip) also. The prom is located under a small cover with two small screws holding the cover in place. Remove the cover and you will see the prom latched to the PC board. Pull back on both latches, then pull up on the prom. Install in reverse in the new PCM. It takes about 45-min to do this if you have removed one before, if not, it could take two hours!

It is essential that you understand how a circuit works before trying to figure out why it doesn't. An electrical schematic shows the electrical current paths when a circuit is operating properly. If you have a hard time understanding basic electrical circuits, it may be best to have someone more familiar with the process do the work for you.

[redrum3g]

I have a obd II scanner. okay so i just can't change out the cts and the fans MIGHT work? I swear i don't wanna go through the process of changing out the pcm.

[BNaylor]

Originally Posted by HotZ28

It is essential that you understand how a circuit works before trying to figure out why it doesn't. An electrical schematic shows the electrical current paths when a circuit is operating properly. If you have a hard time understanding basic electrical circuits, it may be best to have someone more familiar with the process do the work for you.

Good point Bo. To add my two cents worth you need the specific wiring diagram for your specific GM car, preferably the GM FSM. The basic block diagrams you see all over the place have omissions and maybe including the one posted in this thread. They fail to show the diodes aka flywheel diode in the cooling fan circuits. Located between the ECU/PCM/cooling fan relays and each respective cooling fan.

The diodes are used for protection of the circuit. Shorts out the reverse voltage kick commonly seen in inductive motor loads and dc motor circuits.

[redrum3g]

so what exactly is you suggesting i replace to make my fans work? That's the only problem i have with this car and its really upset me because i can't figure out what causing my fans not to work when the engine gets hot.

[BNaylor]

HotZ28 (Bo) pointed out that the engine has to reach a certain operating temperature before the cooling fans will come on with this possible exception. Is your air conditioner working? Do the cooling fans come on with the A/C set to on?

Not sure if this will work in the pre VIN "K" 3.8L engine but what happens when you disconnect the engine coolant temperature sensor (ECT)? In the later years and models the fans will come on as a failsafe when the electrical connector is disconnected at the ECT or if the PCM detects no input signal from the ECT. Just make sure ignition is set to off first before you disconnect it.

[redrum3g]

Yes, my ac works and yes my fans turn on when i turn on the ac, but the code qdm 1 & 2 failure comes up.

I haven't tried to disconnect the ect. Now if my fans turn on when i disconnect the ect does that mean it is bad and needs to be replaced?

[BNaylor]

Won't hurt to try it just for troubleshooting purposes and to rule it. But I'm leaning towards HotZ28's (Bo) suggestion earlier which I believe PCM module due to the quad driver failure DTCs. Of course any sensor the driver's feed can cause the DTC(s) so you need to eliminate them first.

[redrum3g]

ok, also i failed to mention i still have the wire running from the fan to the switch still connected to the manual switch but off the positive battery will that cause the codes to come up?