F-body P01/0411 PCM not triggering fans. Fans will work in VCM scanner.

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07-18-2021
Brist

1 Attachment(s)

F-body P01/0411 PCM not triggering fans. Fans will work in VCM scanner.

I've been searching the forums for info on the PCM not triggering the fans per the ECT settings. There are several posts that have a somewhat similar scenario but I'm not finding any resolution. The project is a modified GEN 3 5.3 swap into a 3rd gen Camaro using a 1999 F-body P01 PCM, custom stand alone harness and 98-02 f-body cooling fans using the matching f-body ls1 three relay fan harness. I had just gotten my MAF scaling for the custom CAI and LS7 card MAF dialed in close enough to allow me to warm the engine up to operating temp and start fine tuning the idle when I noticed that the low speed fan had not kicked on. The engine temp was up to 200 degrees according to the scanner and the set points for fan 1 were 190 "on" 185 "off". I was not able to warm the engine to a higher temp as I had also noticed my heater core had developed a leak. Using the VCM scanner both low and high speed seem to be functioning as they should but even by lowering the "on" and "off" temps in the editor to below ambient I am not able to get the fans to trigger on. I'm not sure if this makes any difference but I do have the f-body 3 pin AC pressure switch plugged into the harness. I do not however have the AC compressor plugged in. Still need a couple custom hoses to complete the AC system. What am I missing here? Ill attach the tune but keep in mind it still has a long way to go. Like I said I've just got the MAF and IAT scale close enough for idle tuning. Now I'm working the idle up using another users bulletin for idle tuning with a larger cam.

Attachment 111782
07-18-2021
cadillactech

Quote:

Originally Posted by Brist

I've been searching the forums for info on the PCM not triggering the fans per the ECT settings. There are several posts that have a somewhat similar scenario but I'm not finding any resolution. The project is a modified GEN 3 5.3 swap into a 3rd gen Camaro using a 1999 F-body P01 PCM, custom stand alone harness and 98-02 f-body cooling fans using the matching f-body ls1 three relay fan harness. I had just gotten my MAF scaling for the custom CAI and LS7 card MAF dialed in close enough to allow me to warm the engine up to operating temp and start fine tuning the idle when I noticed that the low speed fan had not kicked on. The engine temp was up to 200 degrees according to the scanner and the set points for fan 1 were 190 "on" 185 "off". I was not able to warm the engine to a higher temp as I had also noticed my heater core had developed a leak. Using the VCM scanner both low and high speed seem to be functioning as they should but even by lowering the "on" and "off" temps in the editor to below ambient I am not able to get the fans to trigger on. I'm not sure if this makes any difference but I do have the f-body 3 pin AC pressure switch plugged into the harness. I do not however have the AC compressor plugged in. Still need a couple custom hoses to complete the AC system. What am I missing here? Ill attach the tune but keep in mind it still has a long way to go. Like I said I've just got the MAF and IAT scale close enough for idle tuning. Now I'm working the idle up using another users bulletin for idle tuning with a larger cam.

Attachment 111782

Does the car have A/C and how is it set up?

Do you have a log of the fans not coming? Make sure to log ECT, VSS, A/C pressures etc.
07-19-2021
Brist

My car does not have a complete AC system. I'll be needing a couple custom hoses to complete the system the way I would like but the harness is built to control the AC using the 3rd gen factory switch to signal the pcm. The pcm will control the AC clutch relay and pressures will be controlled using the 98-02 f-body three wire pressure sensor. Right now that sensor is just plugged into the harness as I'm missing the tube it will screw onto so its not going to read any pressure other than 0. Would I be better off to just set the tune up as if there is no AC for the time being? Unfortunately I did not save the scanner log from warming the engine up to operating temp. The VSS is wired and plugged into the t56 sensor but there wont be any VSS readings as the car is still up on the cribs while I work on the exhaust but I did add it to my channel list along with fan 1&2 "on" and "off". I should have my new heater core tomorrow and I may throw in a new temp sender while I have the coolant drained even though the old one was registering a temp.
07-19-2021
cadillactech

Quote:

Originally Posted by Brist

My car does not have a complete AC system. I'll be needing a couple custom hoses to complete the system the way I would like but the harness is built to control the AC using the 3rd gen factory switch to signal the pcm. The pcm will control the AC clutch relay and pressures will be controlled using the 98-02 f-body three wire pressure sensor. Right now that sensor is just plugged into the harness as I'm missing the tube it will screw onto so its not going to read any pressure other than 0. Would I be better off to just set the tune up as if there is no AC for the time being? Unfortunately I did not save the scanner log from warming the engine up to operating temp. The VSS is wired and plugged into the t56 sensor but there wont be any VSS readings as the car is still up on the cribs while I work on the exhaust but I did add it to my channel list along with fan 1&2 "on" and "off". I should have my new heater core tomorrow and I may throw in a new temp sender while I have the coolant drained even though the old one was registering a temp.

Yes get a log once it is put back together, just want to make sure the AC isn't causing a fan issue.
07-25-2021
Brist

The new heater core is in. I also went ahead and put the new temp sender in making sure it was from the same vehicle the PCM came from even though cross referencing shows the 5.3 and 5.7 ls share the same sender in the year of engine and pcm that I have. A coworker recommended that I bump my "on" temp to 195 because some LS pcm's wont allow the fan to trigger below a 192 set point. This I had never heard of but I figured what do I got to lose and bumped the setpoint up. I started the car up and let her warm up to temp and lo and behold fan 1 kicked on.
07-25-2021
2xLS1

Quote:

Originally Posted by Brist

The new heater core is in. I also went ahead and put the new temp sender in making sure it was from the same vehicle the PCM came from even though cross referencing shows the 5.3 and 5.7 ls share the same sender in the year of engine and pcm that I have. A coworker recommended that I bump my "on" temp to 195 because some LS pcm's wont allow the fan to trigger below a 192 set point. This I had never heard of but I figured what do I got to lose and bumped the setpoint up. I started the car up and let her warm up to temp and lo and behold fan 1 kicked on.

That is gen 4 E38, E67, E78 ECMs.