This is the best solution when adding Efans and getting your AC working correctly! I have done it to both of my trucks and it works flawllessly!

 

Need help, here's what I have. I'm hooking up e fans on ls swap. Had tuner enable fans on ecm. Fan 1 works good. However fan 2 only pulses a ground on/off and does not provide a solid a ground. It's pin 33 on the ecm red connector. Any help would be appreciated, thanks

 

The tune isn't setup correctly

 

My attention was recently brought back to this thread. All this rewiring/repining stuff to make the ac compressor cycle is simply because someone does not know what they are doing in the tune to make it work correctly. I have long used the 02 2156 OS with both analog cycling and the newly added pressure transducer. To enable the pressure transducer all I do is set the DTC for the ac pressure sensor to "No Mil" from its factory "No Error Reported" setting. It enables the sensor and it shows up in the data stream allowing the fans to run. The old analog switches still run the compressor using the analog cycling option. Has worked on numerous 99-02 trucks and SUVs as well as 0411 swaps on GMT400s. On the GMT400s I replace the auto-recirculate switch screwed into the 10mm sensor port on the ac manifold (condenser on TBI trucks) with the transducer. It should even have a shrader valve core so no real refrigerant loss. Going the opposite direction using a DBC analog request capable P59 on an older vehicle without the transducer wired in, disable that DTC to No Error Reported or else the compressor will run for a few seconds, it will throw a DTC and the compressor will stop running due to the PCM seeing the lack of pressure as an empty system. Select Analog Cycling on the P59. If for some odd reason an 03-07 P59 Express van shows up with dual fans the pressure transducer needs to be added and enabled the same way as an 0411. Cold Hose in Florida has all kinds of fittings that add the GM 10mm sensor port including a #8 reduced barrier splice that can be crimped right into a typical GM R134a discharge hose on swaps. I use analog request (either analog or analog cycling depending on the setup) and the pressure transducer on all kinds of swaps as well even Vintage/Old Air or the like installations. From memory seems like Pin 55 needs to be grounded for the compressor to run on AC systems that use a 12V ac request signal even using the Analog setting but do not use a ground side cycling switch. If trying to run a +12V ac request without the ground side cycling switch use Analog request, see if it works and if not ground pin 55 at the PCM. I have only done a couple of swaps that needed this style setup.

 

what a great thread..
thanks, following