cooling fans not running - pcm failure? - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums

Welcome to LS1LT1.com/LS3forums.com - please click here to register...

LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums
Presented by:

New User? Register
LS1 Forums Register Photo Gallery Tech/FAQ Members List Calendar Auto Loans Search Today's Posts Mark Forums Read Auto EscrowInsurance
Premium Membership Videos Perf Tools Mobile/iPhone Link to Us! Social Groups Follow LS1LT1 on Twitter


Go Back   LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums > General Tech > General Tech

LS1LT1.com is the premier Pontiac Forum on the internet. Registered Users do not see the above ads.
Reply
 
Share LinkBack Thread Tools
Old 04-15-2012, 05:54 PM   #1
Regular Member
 
Join Date: Apr 2012
Posts: 8
catfishlady user's tech expertise is unknown at this point
Unhappy cooling fans not running - pcm failure?

I have a 93 Camaro 3.4l that I put a 96 engine/trans/susp/pcm etc into about 6 years go.
Suddenly my cooling fans stopped working. Fans work when D1 & D4 are jumpered, but not when the coolant temp sensor is unplugged.
I have no ground at A10 and A11 on the PCM with ignition on and coolant temp sensor unplugged, they are both live in fact. I think that means my PCM is bad? Can anyone confirm?

(At first I thought it meant that there was a short between the PCM and relays and so cut the wires and spliced in a couple of new ones but nothing has changed)

The tag on my PCM is 16214399 / 16242261 BWWY, which doesn't appear to match any broadcast codes I can find.

I was hoping to just buy a cheap PCM on ebay and stick it in but it doesn't appear that there are many AT 96 camaro PCMs around...

Which used PCMs can I plug into my AT 96 LT1 Camaro without programming?

Impala/Corvette? perhaps a 97? Any help GRATEFULLY received

(To bypass the VATS/PCM issue previously, I popped the resistor out and stuck it into my old ignition key. heh)
catfishlady is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Sponsored Links
Advertisement
 
Old 04-16-2012, 09:16 AM   #2
Global Moderator
 
cocobolo95's Avatar
 
Join Date: Sep 2008
Location: Fruitland Park,Florida
Posts: 9,506
cocobolo95 Tradesman Level Tech II
Default

There will be no ground on A10 and A11 until the pcm commands the fans on. In fact according to the pcm pinout chart, until the pcm commands the fans on you will see voltage on A10 & 11 as your volt meter supplies the ground to get a reading at that spot, but doesn't ground the 2 pins. Try grounding A10 & A11, 1 at a time of course, and see if fans run then. When you unplugged the temp sensor and the fans didn't run I hope you unpluged the one on the water pump. The other temp sensor is just for the temp gauge. The pcm's on these cars don't fail very often, but if it helps to put your mind at ease, replace it and see. Here's a link to search salvage yards, you can search local, statewide , or whole country as most yards ship.
www.car-part.com

Last edited by cocobolo95; 04-16-2012 at 09:19 AM.
cocobolo95 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 09:20 AM   #3
Regular Member
 
Join Date: Apr 2012
Posts: 8
catfishlady user's tech expertise is unknown at this point
Default

I unplugged the sensor on the front of the waterpump, which should have triggered the PCM to provide ground to the fans, yes?

If not, then when I ran the car to beyond 3/4 on the gauge then I should have gotten a ground from the PCM? My AC is bad so I can't trust that to trigger fans.

The fans do run when I ground A10 or A11 wires from the relays (DCed from the PCM)

I was hoping to avoid a "replace it and see" situation on a $150 used part, but I ordered one with a BCC for a 96 A4 camaro today. Hopefully this resolves it, otherwise I'm fresh out of ideas

Last edited by catfishlady; 04-16-2012 at 09:29 AM.
catfishlady is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 09:25 AM   #4
Global Moderator
 
cocobolo95's Avatar
 
Join Date: Sep 2008
Location: Fruitland Park,Florida
Posts: 9,506
cocobolo95 Tradesman Level Tech II
Default

You might want to go to www.shbox.com and hook up a manual fan switch for now. The beauty of how it hooks up is that when its off the pcm can still command the fans on.
Do you have working a/c , when you turn it on it should run the fans.
Also the factory fan turn on temps are hellishly high.
One thing I haven't asked is since you have a 93 with 96 pcm, do you still have the 2 relay fan setup or did you switch to the newer 3 relay fan set up.
When you grounded A 10 & 11 did you do it at the relay or the pcm end. Asking because if you grounded at the relay end and made the fans run, The wires going from relay to pcm A 10 & 11 could be bad. So grab you ohm meter disconnect wires at both relay end and pcm end to see if you have continuity.

Last edited by cocobolo95; 04-16-2012 at 09:30 AM.
cocobolo95 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 09:34 AM   #5
Global Moderator
 
cocobolo95's Avatar
 
Join Date: Sep 2008
Location: Fruitland Park,Florida
Posts: 9,506
cocobolo95 Tradesman Level Tech II
Default

If A10 & 11 don't have continuity check connector C100, its on the passenger side inner fender and is a large connector. This is where you would splice into to hook up the manual fan switch. Blue and a green wire, make sure c100 is connected well and no burnt pins or wires that have pulled out of pins.
cocobolo95 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 09:42 AM   #6
Regular Member
 
Join Date: Apr 2012
Posts: 8
catfishlady user's tech expertise is unknown at this point
Default

I replaced just about everything on the 93 body with that from the 96, so I have a 3 relay fan system.

I suspected (hoped) that the A10 and A11 wires might be shorted or bad somewhere, so I cut them at the PCM and the relays and replaced them with good test wires. Still no ground at the PCM with the temp sensor unplugged.

I'm pretty sure that my fans used to come on at just over half way on the gauge, at least that's where the temp always sat in bad traffic. It shoots right past that now.

And I had considered a manual switch, but the car is occassionally driven by my other half that I don't trust to look at the temp gauge... ever.
catfishlady is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 10:32 AM   #7
Global Moderator
 
cocobolo95's Avatar
 
Join Date: Sep 2008
Location: Fruitland Park,Florida
Posts: 9,506
cocobolo95 Tradesman Level Tech II
Default

When you ground A10 do the fans run at high speed. When A11 is grounded do fans run at slow speed. Also have you checked the vss for proper operation as it is an input for pcm to run fans. If you put your car on a scanner with real time sensor data , you can monitor the vss speed the computer is seeing and compare it to the speedometer displayed speed to see if there is a difference. This is a last ditch effort to help you get the fans up and running. The only other thing to check would be relay # 3 as it is used to control both low speed fans and high speed fans by either connecting both relay # 1 & 2 in series or for high speed it lets both relays work in parallel
cocobolo95 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 10:59 AM   #8
Regular Member
 
Join Date: Apr 2012
Posts: 8
catfishlady user's tech expertise is unknown at this point
Default

Yes, A10 grounded runs fans at high speed, A11 runs fans at low speed.
All 3 relays were tested and also switched with other working relays.

How does the VSS affect fan function? Turns them off if traveling at x speed? So, if the real time scanner shows 0mph from the vss while sitting idling (with the temp sensor unplugged) then fans should be on? Sorry to be dense, I just want to know what I'm looking for.
catfishlady is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 01:58 PM   #9
Regular Member
 
Join Date: Apr 2012
Posts: 8
catfishlady user's tech expertise is unknown at this point
Default

Okay, crazy update. I went out with my laptop to check the VSS real time data.
The water temp sensor is still unplugged and A10 and A11 are still cut and wired direct with my test wires. Turned the engine on, VSS was 0, I noticed that the coolant temp sensor was -40. I assume this is default when unplugged, but out of curiosity I turned the sensor OFF with the scanner (scantool.net), suddenly both fans turned on at what sounded like high speed (though i think i was simply turning off realtime monitoring with the software and not the actual sensor?). I turned the sensor back ON in the software and the fans kept running. I turned the engine off and back on, fans still running!?

This was during my lunchbreak at work. Now that I'm off I've reconnected the temp sensor and am letting the car idle with the scanner connected to watch for it to get to 235F which I believe is the high speed activation temp. Luckily its 94F here today so shouldn't take too long...
catfishlady is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 02:12 PM   #10
Regular Member
 
Join Date: Apr 2012
Posts: 8
catfishlady user's tech expertise is unknown at this point
Default

Well, fans clicked on at 225F it looks like because I couldn't get her over 226F no matter how long I left her idling... It appears she fixed herself as soon as I pulled out the credit card. She always does that
catfishlady is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 02:14 PM   #11
Regular Member
 
Join Date: Apr 2012
Posts: 8
catfishlady user's tech expertise is unknown at this point
Default

fans still arent coming on with ignition though, are they supposed to?
catfishlady is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 03:00 PM   #12
Administrator
 
Transamman25's Avatar
 
Join Date: Dec 2005
Location: Memphis , Tennessee
Posts: 10,230
Transamman25 Tradesman Level Tech I
Default

My question is do they come on with the A/C on ?
__________________
Transamman25 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 03:14 PM   #13
Regular Member
 
Join Date: Apr 2012
Posts: 8
catfishlady user's tech expertise is unknown at this point
Default

The AC is charged to 35psi but blows warm, has done for years, never worried about spending the money to find out why.

But no, the cooling fans don't come on when the AC is on.

Last edited by catfishlady; 04-16-2012 at 03:21 PM.
catfishlady is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Old 04-16-2012, 03:47 PM   #14
Global Moderator
 
cocobolo95's Avatar
 
Join Date: Sep 2008
Location: Fruitland Park,Florida
Posts: 9,506
cocobolo95 Tradesman Level Tech II
Default

If you mean do fans come on when you first turn ignition switch on, the answer is no. They are made to be commanded on at 226 for low speed 235 for high speed, when pcm coolant temp sensor is unplugged, or when functioning a/c is turned on. If charge is low pcm will not command a/c on which in turn will not command fans on. Certin dtc's will also run fans.
You know you can reprogram the fan turn on temps. For your 96 obd2 pcm the program is pricey, but a tuner could do the job for you for a reasonable amount. I have my fans on at 195 low and 205 for the high speed.
cocobolo95 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Sponsored Links
Advertisement
 
Reply

Bookmarks

Thread Tools

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


» Recommended
Find technical articles on a Chevy Corvette, including tips and tricks on a Chevy Camaro and expert advice for Pontiac Firebird, along with reviews on the Cadillac CTS.
» Auto Insurance
» Sponsors
Powered by vBadvanced CMPS v3.2.2

All times are GMT -5. The time now is 01:55 AM.



Powered by vBulletin® Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.5.2
Copyright © 2005 - 2011 by LS1LT1.com

Our Friends:


Illegal Street Racing | Super Cars | LT1 Tech Articles