Welcome to Camaro Z28!

Welcome to CamaroZ28.Com, the ultimate Source for Camaro enthusiasts! Here you can join over 90,000 Camaro enthusiasts from around the world discussing all things related to Camaros and more. You are currently viewing as a guest which gives you limited access to view discussions

To gain full access to our forums you must register for a free account. As a registered member you will be able to:
  • Participate in over 40 different forums and search/browse from over 5 million posts.
  • Upload your Camaro details to your Garage
  • Post photos, respond to polls and access other special features
  • Gain access to our free marketplace to buy, sell and trade Camaros, parts and more.
All this and much more is available to you absolutely free when you register for an account, so join our community today today!

If you have any problems with the registration process or your account login, please contact support.


Go Back   CamaroZ28.Com Message Board > 1967-2002 F-Body Technical Discussion > General 1967-2002 F-Body Tech
Sign in using an external account
Register Forgot Password?


Reply Post New Thread
 
 
LinkBack Thread Tools Search this Thread Display Modes
Old 06-19-2013, 02:13 PM   #1
Registered User
 
Join Date: Jun 2013
Posts: 9
Cooling fans not being commanded on

Alright, let me start by saying "Hi," and this will be my first post. Well, I just bought a 96 z28 and am having a few problems. The one that bothers me the most is the cooling fans not working at all. I used my genisys and checked the fans and they both come on when commanded. I checked all the relays and they work fine. I changed out the ect that goes to the pcm and still a no go. I ran down the trouble shooting chart from ondemand5 and they all tell me relay and it's not the relays. I hooked the genisys up and did a live data record and the fan was never commanded on not even when I just let it sit there and run and had it almost to 260. I am at a loss. I was thinking pcm but I was told that it might not be the problem but I don't know what else it could be. The car has had its air compressor removed along with the high and low pressure lines to the compressor. I'm not sure if the genisys is bypassing the pcm to activate the fans or if it is telling the pcm to activate them. Oh and the pcm is reading the accurate temp as the gauge according to the scan tool. Any help would be greatly appreciated.
This ad is not displayed to registered members.
Register your free account today and become a member on CamaroZ28.com!
Mha8649 is offline   Reply With Quote
Old 06-19-2013, 04:44 PM   #2
Registered User
Premium Member
 
GaryDoug's Avatar
 
Join Date: Jul 2010
Location: Florida West Coast
Posts: 417
Garage
Re: Cooling fans not being commanded on

Your scantool is "asking" the PCM to turn on the fans, and it's evidently doing it. Check all the other parameters to see if anything looks way off, like VSS, MAP, IAT, etc. Maybe something is so far off it is blocking the PCM algorithm for the fans. I just tried this on my benchtop 94 PCM and it would not turn on the fans if the "vehicle" was doing 50mph, but then later it did, so not sure what to think about that. I assume there are no trouble codes of any kind.
__________________
1998 Trans Am, LS1, Automatic, stock all the way.
GaryDoug is offline   Reply With Quote
Old 06-20-2013, 12:52 AM   #3
Registered User
 
Join Date: Jun 2013
Posts: 9
Re: Cooling fans not being commanded on

The only trouble code I have is secondary air pump not working. I am going to replace it but I don't think that would have anything to do with the fans. I went back over the live data and everything else was looking great. iat was reading like 120, vss was right on, map was reading within parameters. I am not sure. I went over the wires and they are in good shape. Like I said in the previous post is I think the pcm is just not telling them to come on for some reason but I don't want to replace it and still have the problem plus pay for the pcm to be programmed to my car. Pulling hairs here.
Mha8649 is offline   Reply With Quote
Old 06-20-2013, 05:01 AM   #4
Super Moderator
 
Injuneer's Avatar
 
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 41,320
Garage
Re: Cooling fans not being commanded on

Is your PCM programming stock, or has it been altered?
__________________
Fred

94 Formula A3+1: 381ci all-forged stroker - Callies Stealth, Oliver 5.85 billet rods, BME nitrous pistons / CNC LT4 heads / Comp Cams custom solid roller / TH400 + GearVendors OD / Strange 12-bolt - 4.11's / 300-shot N2O / Spohn suspension / 6-pt roll bar with integrated SFC's / AutoMeter instrumentation / MoTeC M48Pro engine management system / a few other odds 'n ends. 800HP/800LB-FT at the flywheel.
Injuneer is offline   Reply With Quote
Old 06-20-2013, 06:01 PM   #5
Registered User
 
Join Date: Jun 2013
Posts: 9
Re: Cooling fans not being commanded on

I'm not 100% sure. I just bought the car. It has a rebuilt title. The guy put a new engine in it but he never said anything about the pcm. I think I am going to fork out the 200 and get a new pcm and have it flashed to my car and see if that fixes the problem.

Last edited by Mha8649; 06-20-2013 at 07:20 PM.
Mha8649 is offline   Reply With Quote
Old 06-20-2013, 07:47 PM   #6
Registered User
Premium Member
 
GaryDoug's Avatar
 
Join Date: Jul 2010
Location: Florida West Coast
Posts: 417
Garage
Re: Cooling fans not being commanded on

Does your scantool have 3 fan actuators like the Tech II? On my 98 there are three actuators (1, 2 , and both). One of those is never used by the PCM in normal operation. Typically it uses 1 and both. If yours has the three actuators, do they all work?
__________________
1998 Trans Am, LS1, Automatic, stock all the way.
GaryDoug is offline   Reply With Quote
Old 06-22-2013, 01:11 AM   #7
Registered User
 
Join Date: Jun 2013
Posts: 9
Re: Cooling fans not being commanded on

The genisys has 1, 2 and 3, and 1-2-3. when I put on 1 both fans come on low speed. when I put on 2 and 3 the left fan comes on high and the right fan shuts off. when I put on 1 2 and 3 none come on. The genisys never tells the fans to come on it doesn't send the command. I have to pay for a pcm and wait a week and then when it comes in flash it to my car. It's going to be a fun two weeks.
Mha8649 is offline   Reply With Quote
Old 06-22-2013, 08:19 AM   #8
Registered User
Premium Member
 
GaryDoug's Avatar
 
Join Date: Jul 2010
Location: Florida West Coast
Posts: 417
Garage
Re: Cooling fans not being commanded on

So the actuator for relays 1,2, and 3 does NOT work! This seems to indicate an overload issue, since the current is, in that case, doubled for the fan power circuit and is increased by 50% for the fan relay circuit. I would try removing the fan relays one at a time and see if the fan(s) run at any time or temp in normal operation. It is possible that fusible link #C is intermittent and opening under load. The conditions may be different if this is tested with the battery voltage lower than normal (using the scantool in the garage with the engine off maybe?) rather than with the engine running and charging the battery as in normal driving. Another possibility is that one of the relays is drawing excessive current and causing the PCM driver to overload when it is activated, but only when the voltage is normally higher while running.

It just seems so unlikely to be a fault with the PCM's internal circuits.
__________________
1998 Trans Am, LS1, Automatic, stock all the way.
GaryDoug is offline   Reply With Quote
Old 06-24-2013, 01:48 PM   #9
Registered User
 
Join Date: Jun 2013
Posts: 9
Unhappy Re: Cooling fans not being commanded on

I'm sorry, the pcm never sends the command on. The genisys will turn them on when commanded on. I use it while driving to avoid over heating in town. But I don't like to do that because when I goto work I leave the scan tool in the car in the case and will that might be enough of an incentive to break in to my car. While driving and using a live diagnostic the pcm never sends the command to the fans to come on neighter high or low. The pcm is getting the same temp as the gauge. the wires and the relays are good. I ordered the new pcm and will let everyone know if that fixes the problem.
Mha8649 is offline   Reply With Quote
Old 06-29-2013, 12:12 PM   #10
Registered User
 
Join Date: Jun 2013
Posts: 9
Re: Cooling fans not being commanded on

Alright, update. I replaced the pcm and reprogramed it with the tech. The fans kick on now and using actuators 1, 1and2. and 1and2and3 all make the fans come on. But the temp goes up to the white line before the red before the fans kick on and then it drops the temp down to halfway mark. I was told the command on doesn't happen until around 230 for my car. That to me seems a little high. I guess it's better than going up to the red and beyond . I don't know what temp it requires before it turns both fans on high though haven't seen it happen yet.
Mha8649 is offline   Reply With Quote
Old 06-29-2013, 12:20 PM   #11
Super Moderator
 
Injuneer's Avatar
 
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 41,320
Garage
Re: Cooling fans not being commanded on

Stock programming turns the fans on low speed at 226*F and high speed at 235*F. GM designed the engine to run at 210*F. The engine should typically run near the middle of the gauge, unless you are stopped in traffic in hot weather.

The gauge runs off the sensor in the head, the PCM reads the sensor on the water pump housing. I would check both sensors.

http://shbox.com/1/4th_gen_tech2.html#ect
__________________
Fred

94 Formula A3+1: 381ci all-forged stroker - Callies Stealth, Oliver 5.85 billet rods, BME nitrous pistons / CNC LT4 heads / Comp Cams custom solid roller / TH400 + GearVendors OD / Strange 12-bolt - 4.11's / 300-shot N2O / Spohn suspension / 6-pt roll bar with integrated SFC's / AutoMeter instrumentation / MoTeC M48Pro engine management system / a few other odds 'n ends. 800HP/800LB-FT at the flywheel.
Injuneer is offline   Reply With Quote
Old 06-29-2013, 12:20 PM
 
Reply Post New Thread

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 04:42 AM.


Copyright © 1996-2013 CamaroZ28.Com. All rights reserved.

Garage Plus vBulletin Plugins by Drive Thru Online, Inc.