96 LT4 has had a flashing SYS since I bought the car about 6 months ago. Car runs good and everything seems to work. I have the 6 speed and the one to four lock out has apparently been disabled because although the alert lights up, it doesnt lock me out. Could this be causing the flashing SYS?

 

No, that's not the cause.

Does it have an aftermarket radio? If not, it's probably just a weak battery.

 

 

If the battery checks out ok, the problem could be the one-to-four. I have read that in a '96, if you just unplug the connector from the trans, it will set a code. You could look under the car to see if the connector is unplugged, if so, plug it in and see if the one-to-four kicks in. If it does, you can get a jumper with a resistor in it that plugs into the connector from many aftermarket suppliers that will fool the ccm into thinking the system is operational. Mine is disconnected, as I have said many times, if I wanted help choosing gears, I would drive an automatic.

 

i do have an aftermarket radio. where is the plug for the lock 1/4 lockout?

 

That's your "SYS" issue, not the 1to4. Do a search on aftermarket radios, you'll need to install a resistor.

 

Left side of the transmission.

 

The plug connects to a solenoid on the left side of the trans. On the '92, the two wires in the plug are dark green/white and black.

 

Ok so have checked a couple of things and other threads and it looks like the aftermarket radio is the cause of the SYS and I need to do the resistor mod. The copies of the diagram that Ive seen arent very clear but this is what I've been able to make out. I need to purchase two half watt 1k ohm resistors. What I need help with is what are the colors of the two wires that I need to attach the resistors to? (I assume these two wires are no longer in use and dangling around somewhere behind the head unit). Next, once I locate those two wires do they both have to be splice into the switched power wire, permanent power source, dimmer, what gets spliced with what?

Fashing SYS has me going nuts and I would like it to function when there is actually a real problem.

If you have gone through this and resolved it, your assistance would be greatly appreciated.

 

This link is the only information I have on the resistor for the SYS problem related to the aftermarket radio. The date is pre-96 but still might get you there.

http://www.corvetteforum.net/c4/dave8476/index4.shtml


Good luck

 

Have you run any codes for the ECM or the BCM. this will let you know what the Sys Error is related to. I have my verry own nighmare with a sys light but don't think its related. A open serial bus error is related to many of the "SYS" flashing errors but the only way to know for sure is to pull the codes.

HTH
Bill

 

I tried pulling codes with code reader but found nothing. I read a thread about using a resistor to jump two pins in the OBD port but it was addrssing an older C4, and wasnt sure if it would work on the 96.

I checked out the link provided by another member for the resistor mod and was able to make out that one wire is black and gray, the other one looks like white and red and if I'm reading the schematic correctly i need to splice both wires with one resistor each into the ignition/power wire so I will be trying this soon. I also tried covering the photocell as mentioned in other threads and there is no change to the display which is also a symptom of the aftermarket radio problem.

 

This is how to pull codes from the CCM ( you can not get codes with scanner from CCM. Dash will do the read out. ) the trip/od and fuel buttons will act as the controler for foward and back movement, this way you can flip between the differnt sections.

Enter Diagnostic Mode:
To enter diagnostic mode, ground pin 12 of the Data Link Connector (DLC) and turn the ignition switch "ON".



If the A/C fuse is blown, the CCM will not receive IGN 3 power and will not enter diagnostic mode. This condition should also set code 16.
The CCM will display any diagnostic trouble codes and the module for which they apply in an automatic code display sequence. The CCM is Module 1, the PCM is module 4 and ABS/ASR EBTCM is module 9, and the DERM is module "A". During automatic display sequence, each code is displayed for three seconds, followed by a one second pause before the next code is displayed. There is a 3 second pause between the code display sequence for different modules. The end of the code list for each module is indicated by "---" being displayed in the speedometer. If there is a communications problem between the PCM or EBTCM and the CCM, the speedometer will display "ERR" when the CCM is trying to communicate with the PCM or EBTCM.

CCM Diagnostic Display (Automatic Mode Display)

Specific Module Interrogation:
The particular module being interrogated is indicated on the trip monitor, and the codes are displayed on the speedometer. The speedometer also indicates if the trouble code is a current code or a history code with a "C" or "H", respectively. All PCM and EBTCM codes will be displayed by the CCM as history codes, whether they are current or history.

When all diagnostic trouble codes have been displayed for all modules, the trip monitor will display 1.0 and the speedometer will be blank. This indicates Manual Mode and the CCM is awaiting technician instructions


Clear CCM DTCs

(Diagnostic Mode 1.7)

After all diagnosis and repairs are completed, clear the CCM DTCs as follows (if already in CCM diagnostic mode, begin at Step 3):



With ignition "OFF," ground terminal "12" of DLC connector.
Turn ignition "ON."
Press "TRIP/ODO" button on DIC until "1.7" appears in the trip monitor area of the instrument cluster.
Press "ENG/MET" button on DIC and hold until "---" appears in speedometer area of cluster; this will clear CCM DTCs.
Turn ignition "OFF."
Turn ignition "ON" and verify that no CCM DTCs are present.
Turn ignition "OFF," then remove DLC ground to terminal "12".


I hope this helps.

Bill

 

I agree that using the on board diagnostics should work OK. But the 96 I believe is fully OBD2 and when connecting a OBD2 scanner, it should communicate and work. If he tried the modern day scanner for the local part stores it is probably a OBD2 scanner. He indicated there were no codes and not that it did not communicate which indicates there seems to be no codes.

But I would definitely also try the on board diagnostics to compare those results.


Having said all this, somewhere in the back of my memory and can't find the info right now, when displaying the codes for a 96 it is different then the 95 and earlier. OBD2 codes are different than OBD1. That’s because 95 and earlier is OBD1, (with imbedded OBD2 that is not shown with on board display). Sorry I can't be more accurate at this time.

 

This thread was just eating me up. My previous post is wrong.

Did a search in the Forum for OBD2 for a 96. I have read several threads and all the posts. Bottom line is you can't display the codes on the speedometer on a 96 which are the OBD2 codes

Check this thread last post sums it all up.

http://forums.corvetteforum.com/c4-t...light-lt4.html

I believe this is what I had in mind but just could not remember it all when I wrote my last post.

A scanner is required for a 96 to get the codes.

 

ya you beat me to it

Even with a OEM level scanner you still can not pull CCM codes. I am in alignment that its the raido but I would rather know for sure then guess.

OBD scanners are just that for OBD generic scans and leaves a lot of info and options out of it since its made for general reference.

Its Friday!!
Bill

 

Thanks to all that chimed in. After giving up on trying to pull CCM codes, I went for the Resistor Mod because it was the most apparent suspect.

Initially, all I found was what is likely an after market harness with thick guage wires and color that did not match the TSB. However, I reached back in the hole and down and pulled out two harnesses with thin guage wires and one had the orange, purple with white stripe, and gray with black strip that are detailed in the schematic. I snipped the wires from the harness and connected as outlined in the TSB. Slapped everything back together and that's it, flashing sys finally gone after several months of annoying me. I also tested the LCD photocell by point a flash light at it and the LCD responds by brightening up.

Again, thanks for all the advise. CF rocks!