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Question: SYS message on digital read out panel

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
Hello I got a question ,I just bought a 1992 corvette coupe about a month ago the car rides and looks great, but I did notice that there is a flashing SYS message on the digital readout display by the speedometer, I was told and seen by reading other threads on here that this can be caused by installing an aftermarket stereo in the car,well the car when I bought it has a aftermarket JVC stereo installed in it. Is there any truth that this can be the cause of it? I had the battery checked and even installed a new alternator but the message is still there. I seen postings on here that you need to install 2-1 ohm,1/2watt resistors to the yellow power wire of the car and then attach each other end of the resistor to the two open circuit dimmer switches, has any one out there dealt with this issue and maybe give me some insight on it? thanks:)
 

hcbph

Well-known member
Joined
Aug 30, 2013
Messages
260
Location
Minneapolis, Mn.
Corvette
86 Red Convertible
Sys light

First thing I'd suggest is read the code rather than just throwing parts at your car. There's a way to jumper a couple of pins in the port below the steering wheel and they'll display but I don't know the combo for a 92. Another method is use a scanner to read them. I believe you can get Autozone to read them and possibly others will also. Get yourself a FSM if you haven't already and though many use the jumper method, I think a scanner is a good tool to have also, just make sure whether your car has ODB1 or ODB2 prior to purchasing one.
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
you need to install 2-1 ohm,1/2watt resistors to the yellow power wire of the car and then attach each other end of the resistor to the two open circuit dimmer switches, has any one out there dealt with this issue and maybe give me some insight on it? thanks:)

The resistors are 1K= 1000 ohms and not 1 ohm.

Short pin A to pin G on the diagnostic connector located above drivers right knee.
Turn the ignition On and look at the Speedometer LCD.


images



Module 1 is the CCM . You will probably see a 72 or 74 which is causing the SYS.
Module 4 is the ECM
Module 9 is ABS/ASR
TSBDoc.1.JPG

TSBDoc.2.JPG
 
Last edited:

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
First thing I'd suggest is read the code rather than just throwing parts at your car. There's a way to jumper a couple of pins in the port below the steering wheel and they'll display but I don't know the combo for a 92. Another method is use a scanner to read them. I believe you can get Autozone to read them and possibly others will also. Get yourself a FSM if you haven't already and though many use the jumper method, I think a scanner is a good tool to have also, just make sure whether your car has ODB1 or ODB2 prior to purchasing one.

Thanks hcbph actually I had the alternator tested at advanced auto and it read 10.5 volts they told me it needed to be 14 at least, that why I bought a new one, it still didn't remove the SYS though, I actually bought a code reader as well the car is OBD1 the scan came back with no code at all, but I do agree the scanner is a great tool to have:)
 

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
The resistors are 1K= 1000 ohms and not 1 ohm.

Short pin A to pin G on the diagnostic connector located above drivers right knee.
Turn the ignition On and look at the Speedometer LCD.


images



Module 1 is the CCM . You will probably see a 72 or 74 which is causing the SYS.
Module 4 is the ECM
Module 9 is ABS/ASR

Note: In the schematic below it shows the wiring for a C68 Auto Climate Control.
It has been mentioned the color of the wires where the resistors are attached to
are different colors for a C60 Manual AC car.


TSBDoc.1.JPG

TSBDoc.2.JPG



ecss thanks for the reply. I actually have this schematic already that I found off someone else's posting on here, but thanks so much for this, I was just wondering who has done this and if it worked, I read a thread that said connect both resistors to the lead wire of the car, to clip the yellow lead wire from the cars original wire harness ,connect it to that lead wire then connect the other end of both the resistors to separate open dimmer wires from the same wire harness(which were also clipped from it) and to put a shrink protector on them to make sure they don't touch and short each other out. my question is if you clip the lead wire to the wire harness and splice the resistors to it doesn't that same lead wire power the aftermarket stereo? and if so I can only assume if has to be reattached to the harness to power the stereo as well, or am I wrong. or do they all just get hooked up sealed and tucked away in the back behind the head unit? what's the best way to splice them also solder? thanks again:)
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
Without knowing how the harness for the radio was modified the easiest method to
install the two resistors is to attach them to the connector that plugs into the back of the HVAC control head.

Pull the HVAC control head from the dash.
Plugged into the back is a 10 pin connector.

Pin
1) Brown wire (hot in run)
2) Black
3 Dark Green
4) Orange
5 Orange
6) ?
7) Gray/Black (LCD dimmer circuit)
8) Purple/White (LED dimmer circuit
9 )?
10) ?

Take one end of each resistor twist them together and splice them into the Brown wire.
Take one end of one resistor and splice it into the Gray/Black wire.
Take one endo of one resistor and splice it into the Purple/White wire.

Solder and heat shrink or tape the wires so they don't short out.



)
 
Last edited:

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
Without knowing how the harness for the radio was modified the easiest method to
install the two resistors is to attach them to the connector that plugs into the back of
the HVAC control head.

I looked at the schematics and it appears both C68 and C60 have the same wire colors
that you attach the resistors to.

Pull the HVAC control head from the dash.
Plugged into the back is a 10 pin connector.

Pin
1) Brown wire (hot in run)
2) Black
3 Dark Green
4) Orange
5 Orange
6) ?
7) Gray/Black (LCD dimmer circuit)
8) Purple/White (LED dimmer circuit
9 )?
10) ?

Take one end of each resistor twist them together and splice them into the Brown wire.
Take one end of one resistor and splice it into the Gray/Black wire.
Take one endo of one resistor and splice it into the Purple/White wire.

Solder and heat shrink or tape the wires so they don't short out.



)
ecss so if I pull the connector that plugs into the back of
the HVAC control head. am I cutting wires from this plug and attaching them there? I'm sorry I'm confused now lol
so I don't do nothing with the wire harness from the stereo? or are they one in the same? does the head unit to the stereo still have to come out to access this hvac
plug? now I know why us gals shouldn't work on cars lol I'm sorry for the confusion
 

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
does this brown wire still have to be attached to the hvac head unit to power it? The dimer wires don't do anything so they don't need to be attached to nothing but the resister?
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
The procedure below will work for a C68 auto climate control system which I'm assuming you have.

I edited my prior posts because the C60 does not have a Gray/Black LCD wire at its connector.

************* First disconnect the negative battery cable *****************

Attaching the two resistors at the HVAC control head is easy because the 12 volts (hot in run Brown wire Pin 1 on the connector) is on the same connector as the other two signal wires Pin 7 Gray/Black and Pin 8 Purple/white that you need to install the resistors to.

To remove the bezel that covers the radio control head and HVAC control head.

Open the center console lid. At the front corners hidden under the felt liner are two hidden Fasteners you need to remove the bolts.

Remove the front ash tray liner where there is another bolt.

Shift the transmission lever rearward.

Carefully pull backwards on the console bezel to gain clearance so you can remove the front bezel.

Remove the top right dash cluster air vent grill held on by I believe two torx screws. Could be phillip screws.

This will expose a bolt on the top right corner of the bezel that needs to be removed.

Then pull straight back on the bezel.

Remove the bolts holding the HVAC control head and pull it forward.

Unplug the connector on the back of it.

Strip some of the insulation off of the Brown wire, Gray/Black and Purple/White wires. Do not cut the wires. You strip some insulation off the wires and attach/solder the resistors on to the exposed wires. You don't need to cut any wires.

If you have an automatic trans, make sure when you put the console back the orange shifter indicator is in the proper position. It just sits on a pin.
 
Last edited:

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
The procedure below will work for a C68 auto climate control system which I'm assuming you have.

I edited my prior posts because the C60 does not have a Gray/Black LCD wire at its connector.

************* First disconnect the negative battery cable *****************

Attaching the two resistors at the HVAC control head is easy because the 12 volts (hot in run Brown wire Pin 1 on the connector) is on the same connector as the other two signal wires Pin 7 Gray/Black and Pin 8 Purple/white that you need to install the resistors to.

To remove the bezel that covers the radio control head and HVAC control head.

Open the center console lid. At the front corners hidden under the felt liner are two hidden Fasteners you need to remove the bolts.

Remove the front ash tray liner where there is another bolt.

Shift the transmission lever rearward.

Carefully pull backwards on the console bezel to gain clearance so you can remove the front bezel.

Remove the top right dash cluster air vent grill held on by I believe two torx screws. Could be phillip screws.

This will expose a bolt on the top right corner of the bezel that needs to be removed.

Then pull straight back on the bezel.

Remove the bolts holding the HVAC control head and pull it forward.

Unplug the connector on the back of it.

Strip some of the insulation off of the Brown wire, Gray/Black and Purple/White wires. Do not cut the wires. You strip some insulation off the wires and attach/solder the resistors on to the exposed wires. You don't need to cut any wires.

If you have an automatic trans, make sure when you put the console back the orange shifter indicator is in the proper position. It just sits on a pin.


awe!! ok I understand now, wow that does seem kind of easy. Have you had to do this yourself to your car? And this will take the sys away? also if it takes it away will the sys still display if there is a code in the future that I may need to address? and I still do the shrink protector on the resisters also ?
ecss thanks so much you have been great I really appreciate your help I hope this works that SYS drives me crazy lol, may I add you to my friends list?
 

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
I will most likely try this on the weekend due to it getting dark earlier now ughh lol, I get home around 4 and it is dark in an hour from that, I will let you know how it turns out ..thanks again:happyanim:
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
SYS indicates a CCM (electrical problem) error has occurred. In your case if the LCD or LED circuit is the problem you would see an error code of 72 or 74 for module 1.

You can pull the error code by shorting pin A to pin G and turn the ignition On. (don't start the engine). Any codes will be displayed on the LCD.

Installing the resistors should get rid of the SYS and cause no other problems.

If SYS flashes on the LCD, if you pull the codes and there are no codes stored for module 1, that usually indicates a low charged battery.

You can use heat shrink or electrical tape.
Radio Shack has a 5 pack of 1K ohm 1/2 watt 5% resistors for $1.49.
 
Last edited:

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
SYS indicates a CCM (electrical problem) error has occurred. In your case if the LCD or LED circuit is the problem you would see an error code of 72 or 74 for module 1.

You can pull the error code by shorting pin A to pin G and turn the ignition On. (don't start the engine). Any codes will be displayed on the LCD.

Installing the resistors should get rid of the SYS and cause no other problems.

If SYS flashes on the LCD, if you pull the codes and there are no codes stored for module 1, that usually indicates a low charged battery.

You can use heat shrink or electrical tape.
Radio Shack has a 5 pack of 1K ohm 1/2 watt 5% resistors for $1.49.


ok great thanks again for the info ecss I greatly appreciate it, I bought a code scanner last month when all this first started that I can use to pull codes and such and I had already ordered the 1k ohm 1/2 watt 5% carbon film resistors from amazon.com ,I will let you know how it turns out this weekend after I try it..
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,452
Location
CenCoast CA
Corvette
71 04 12 19
A "code scanner" will not work on anything but the engine computer. The "SYS" warning appearing in the IP is coming from the CCM. You need to read CCM codes and you do that by grounding pin G on the diagnostic connector under the dash near your right knee then turning the ign. on but not starting the engine. Codes are displayed by module and the CCM is module 1.1.

If CCM DTC 72 or 74 or both display then the problem is the aftermarket radio. What's happening is the CCM is looking for continuity on the the LCD and LED dimming lines to the radio head, but since the stock radio with those lights has been removed, the CCM diagnostics are seeing an open circuit so it sets those codes.

You have to fool the CCM into "thinking" the dimming is active and you do that by installing the resistors listed in the GM TSB which is shown in an earlier post.

If you get the CCM codes and they are not 72 or 74, please post which codes are set.
 

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
A "code scanner" will not work on anything but the engine computer. The "SYS" warning appearing in the IP is coming from the CCM. You need to read CCM codes and you do that by grounding pin G on the diagnostic connector under the dash near your right knee then turning the ign. on but not starting the engine. Codes are displayed by module and the CCM is module 1.1.

If CCM DTC 72 or 74 or both display then the problem is the aftermarket radio. What's happening is the CCM is looking for continuity on the the LCD and LED dimming lines to the radio head, but since the stock radio with those lights has been removed, the CCM diagnostics are seeing an open circuit so it sets those codes.

You have to fool the CCM into "thinking" the dimming is active and you do that by installing the resistors listed in the GM TSB which is shown in an earlier post.

If you get the CCM codes and they are not 72 or 74, please post which codes are set.

ok hib thanks for the info I will try this first, how do you do this? with a paper clip? and is there another pin I use also or just pin G?
 

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
A "code scanner" will not work on anything but the engine computer. The "SYS" warning appearing in the IP is coming from the CCM. You need to read CCM codes and you do that by grounding pin G on the diagnostic connector under the dash near your right knee then turning the ign. on but not starting the engine. Codes are displayed by module and the CCM is module 1.1.

If CCM DTC 72 or 74 or both display then the problem is the aftermarket radio. What's happening is the CCM is looking for continuity on the the LCD and LED dimming lines to the radio head, but since the stock radio with those lights has been removed, the CCM diagnostics are seeing an open circuit so it sets those codes.

You have to fool the CCM into "thinking" the dimming is active and you do that by installing the resistors listed in the GM TSB which is shown in an earlier post.

If you get the CCM codes and they are not 72 or 74, please post which codes are set.

Oh never mind hib I see what pins to use here in an earlier posting, I will let you know what I find this afternoon after I get home from work,thanks
 

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
A "code scanner" will not work on anything but the engine computer. The "SYS" warning appearing in the IP is coming from the CCM. You need to read CCM codes and you do that by grounding pin G on the diagnostic connector under the dash near your right knee then turning the ign. on but not starting the engine. Codes are displayed by module and the CCM is module 1.1.

If CCM DTC 72 or 74 or both display then the problem is the aftermarket radio. What's happening is the CCM is looking for continuity on the the LCD and LED dimming lines to the radio head, but since the stock radio with those lights has been removed, the CCM diagnostics are seeing an open circuit so it sets those codes.

You have to fool the CCM into "thinking" the dimming is active and you do that by installing the resistors listed in the GM TSB which is shown in an earlier post.

If you get the CCM codes and they are not 72 or 74, please post which codes are set.

one question though hib u say module 1.1 is for ccm codes, does it run through all the codes by modules one after another automaticaly? or is there something I need to do to access that particular module to get any codes to display?
 

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
ccm code

hib I did the jumper wire like u said and others on here suggested as well and it showed a small number 1. ,then displayed a bigger bold H72 then displayed a H74 so I guess it is the aftermarket stereo after all, thanks again for the info and help:happyanim:
 

Jessica19699

Well-known member
Joined
Nov 3, 2014
Messages
132
Location
Stephens City Va
Corvette
1992 Bright Red Coupe
The procedure below will work for a C68 auto climate control system which I'm assuming you have.

I edited my prior posts because the C60 does not have a Gray/Black LCD wire at its connector.

************* First disconnect the negative battery cable *****************

Attaching the two resistors at the HVAC control head is easy because the 12 volts (hot in run Brown wire Pin 1 on the connector) is on the same connector as the other two signal wires Pin 7 Gray/Black and Pin 8 Purple/white that you need to install the resistors to.

To remove the bezel that covers the radio control head and HVAC control head.

Open the center console lid. At the front corners hidden under the felt liner are two hidden Fasteners you need to remove the bolts.

Remove the front ash tray liner where there is another bolt.

Shift the transmission lever rearward.

Carefully pull backwards on the console bezel to gain clearance so you can remove the front bezel.

Remove the top right dash cluster air vent grill held on by I believe two torx screws. Could be phillip screws.

This will expose a bolt on the top right corner of the bezel that needs to be removed.

Then pull straight back on the bezel.

Remove the bolts holding the HVAC control head and pull it forward.

Unplug the connector on the back of it.

Strip some of the insulation off of the Brown wire, Gray/Black and Purple/White wires. Do not cut the wires. You strip some insulation off the wires and attach/solder the resistors on to the exposed wires. You don't need to cut any wires.

If you have an automatic trans, make sure when you put the console back the orange shifter indicator is in the proper position. It just sits on a pin.



well ecss me and my boyfriend tried what you said here and I don't know if I did it wrong or not ,im pretty sure I did exactly what you said here and the car ran like crap afterward even more when I turned the ac on so I undid what I did and I will just live with the sys flashing lol,the car runs great again, so anyway thanks again for the help:)
 

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