pin 42 c1 fan control

[mickeycarter08]

I'm looking for any ideas concerning this problem. I am working a 99 Chevy S10 with a 6.0 swap. The ECU is from a 2001 K15. It had electric fans that were on a toggle switch and I have wired in some relays to make the ECU control the fans. I have configured the fan parameters for series fans and I am able to turn them on and off using bi-directional controls. I also had to wire the A/C pressure switch in because it was deleted when the swap was done. (the A/C system doesnt work, that part of the swap was never finished). The a/c has no Freon and so the pressure is 0, but I thought the absence of the sensor might turn the fan on. The problem is that the fan #1, running off pin C1 42, runs anytime the engine is running regardless of temp. It doesn't run KOEO but as soon as the engine starts the fan runs. I checked for failure codes and U1255 (body control module)is the only code present. The other fan, running off C2 pin 33 operates as it should if I force the temp high enough. I have attached the tune file. I must be missing something.

[400ss]

Check the diagram i atached. Do a full flash with the tune i atached.

[mickeycarter08]

Thanks for looking at it. I did a full reflash and still have the same issue. The fans are controllable with the DVT section of the scan tool but when that DVT is deactivated the left fan runs all the time. I am aware of the wiring diagram. Looks like the Camaro. when relay 1 is grounded and relay 3 is not the resistance of the fan motors causes the fans to run at a lower speed than when all three relays are grounded. This truck has one fan behind the radiator and two in front. I would not have set it up this way but it should work. The rear fan is running off its own relay controlled by pin 42 and the front fans are on two separate relays controlled by pin 33. The one fan behind the radiator is keeping the car cool enough but if the A/C is fixed the other fans need to work. I could just make all three work of the pin 33. Any other idea would be appreciated.

[joecar]

Look at the STATEnn pids to see if any of those indicate the reason for commanding fans (e.g. AC requested).

[mickeycarter08]

Thanks. It amazes me how much info is available with EFI live. I attached a log file with all the State nn pids. It shows the fan control on. The A/c pids look ok but there is an issue with the way the alternator is wired. The ECU is requesting the alternator light. Could that cause the fan to turn on?

[Brads_rs]

Have you found the problem yet, i have the same issue.

[mickeycarter08]

I never did find out why. I could control the fan with the Bi directional controls but when running on its own the data always showed that fan commanded on. I gave up and wired both relays off the other pin (33). It was on a customer car that has left the shop. It didn't have A/C so it there wasn't a big problem with Controlling the fan for A/C

[Brads_rs]

Looks like i will be doing the same. I went through the pcm several times and cant for the life of me find why the pcm is commanding fan 1 on. I basically the same swap you did, 99 s10 with 5.3. Every thing else worked out great, looks like it was factory installed, customer was thrilled.