C4: "SYS" now appears on instrument cluster
04-10-2011, 11:04 AM
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C4: "SYS" now appears on instrument cluster
All,
A new display, "SYS", now appears on my instrument cluster (not on the idiot panel above the console).
It appears for about 5 seconds (flashes twice), then resumes whatever was previously on the display (Fuel or Gauges info, etc) for 15 seconds; the process then repeats.
I just had a reputable and trusted shop install a manual on/off switch for one of my radiator fans. My C4 runs very cool (170-173 highway, fans remain off), until town where the heat cycles from 170 (when fans turn off) to 181 (fans come on). The manual override for a single fan keeps city temps at a near constant 175, as intended.
The SYS status appears with the manual fan switch on or off. With the switch off, the computer turns on both fan's at 181, just like always. And when the temps drop to 170, the computer turns both fans off, just like always, unless I have the switch ON of course.
We studied the available wiring schematics closely to ensure there "should be" no inadvertent feedback to the computer, yada yada, before installing. Everything seems to be OK in spite of the SYS thing, but if anyone has any info on why it might appear and what the affects might be, we -- mechanic and I -- would appreciate your feedback. We're baffled.
Corvettes... gotta luv 'em.
A new display, "SYS", now appears on my instrument cluster (not on the idiot panel above the console).
It appears for about 5 seconds (flashes twice), then resumes whatever was previously on the display (Fuel or Gauges info, etc) for 15 seconds; the process then repeats.
I just had a reputable and trusted shop install a manual on/off switch for one of my radiator fans. My C4 runs very cool (170-173 highway, fans remain off), until town where the heat cycles from 170 (when fans turn off) to 181 (fans come on). The manual override for a single fan keeps city temps at a near constant 175, as intended.
The SYS status appears with the manual fan switch on or off. With the switch off, the computer turns on both fan's at 181, just like always. And when the temps drop to 170, the computer turns both fans off, just like always, unless I have the switch ON of course.
We studied the available wiring schematics closely to ensure there "should be" no inadvertent feedback to the computer, yada yada, before installing. Everything seems to be OK in spite of the SYS thing, but if anyone has any info on why it might appear and what the affects might be, we -- mechanic and I -- would appreciate your feedback. We're baffled.
Corvettes... gotta luv 'em.
04-10-2011, 11:20 AM
#2
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I had the same issue a while back and it turned out to be my battery. I would load test your battery and also check your alternator output, chance are you will find your problem lies within one of them.
Also make sure all of your battery connections are clean and making good contact.
Also make sure all of your battery connections are clean and making good contact.
04-10-2011, 12:06 PM
#3
Burning Brakes
Your '96 was designed to run both fans at the same time--both at either low or high speed. I don't see how you could wire in a toggle switch to one fan and still have the PCM comtrolling them and not set a light. I would think there would have to be some sort of feed back to the PCM when you manually turn on one fan--the PCM "knows" it has not requested the fans "on" and would set a light. JMO but you'd be much better off to have the PCM programmed for lower temp. fan operation or buy a hand held programmer and do it your self. Have you scanned it for any codes?
Last edited by TWISTERUP; 04-10-2011 at 12:09 PM.
04-10-2011, 12:34 PM
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more instrument cluster SYS information
Your '96 was designed to run both fans at the same time--both at either low or high speed. I don't see how you could wire in a toggle switch to one fan and still have the PCM comtrolling them and not set a light. I would think there would have to be some sort of feed back to the PCM when you manually turn on one fan--the PCM "knows" it has not requested the fans "on" and would set a light. JMO but you'd be much better off to have the PCM programmed for lower temp. fan operation or buy a hand held programmer and do it your self. Have you scanned it for any codes?
I agree, mostly. My CCM is already reprogrammed for fans On at 181, OFF at 170. That's why we studied the schematics to see if if was feasible to insert a manual On/Off switch, and if so to install it. (Why?, well, 'cause, I like near steady-state temps, cooler is better. Call me a temperature snob if that helps.) Searched the 'net I found this gem at CorvetteCentral.com that notes, among other things, that changes to MAF and MAP sensors can be flagged as a SYS "diagnostic" by the CCM. MAP and MAF sensors work was also done by this shop while the car was being spring-tuned.
So, it appears there are other root causes. If that's found to be the case, yahoo. If not, then I will back out the manual On/Off fan switch and chalk it up to experience. Nothing ventured, nothing gained.
Link describing many, many causes for the SYS display:
http://tech.corvettecentral.com/2011...trouble-codes/
04-10-2011, 01:22 PM
#6
Racer
What are the codes the SYS is reporting? There are lots of articles here and through Google on how to pull codes, start there. Don't spend money until you see what it says is wrong!!
04-10-2011, 01:27 PM
#7
Race Director
Troubleshoot, don't guess.
04-10-2011, 01:33 PM
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I have a battery in my Vette.
04-11-2011, 12:27 PM
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That sys is for ccm diagnostic not pcm heck it could be a blown fuse for the air bags. get the code and go from there. FSM tells you how to get codes using the buttons on the dash. you will also need a jump wire on the pdl. not hard to do at all.
04-11-2011, 02:40 PM
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Just had this happen last Friday. Ran fine the whole time and I had the battery tested at Sears....it was fine. I reattached the tender when I got home and haven't had a problem since.
04-11-2011, 08:13 PM
#13
Le Mans Master
How to tell spring has sprung...by the number of flashing "SYS" post.
How old is the battery? Also if the battery was low on power this might happen for awhile until the battery gets back to a normal charged state.
How old is the battery? Also if the battery was low on power this might happen for awhile until the battery gets back to a normal charged state.
