1994 LT1, M6: I ordered an OBD1 scanner, should be here Thursday, but in the mean time, figured I'd throw this issue out there and see if anyone else has seen this. After about 15-20 mins of cruising, 70 mph, cruise on, all gauges normal. Temp gauge usually a needle width below half. The SES light comes on. Temp gauge starts dropping. Sometimes goes all the way to 160. Cooling fans are on high. I'm not running the ac or anything. Engine keeps running normally. Shut the car off at work. Start back up after work, everything is normal, no SES light. Drive back home, again about 15-20 mins into the drive, SES light comes on, temp gauge drops to 160. Does this every day. I know I need the code, and hopefully will have it soon. There is a new thermostat, new PCM temperature sensor (the one in the water pump), coolant flush recently done, system bled per procedure. Anyone want to take a guess before my code reader gets here??

 

Depending on which DTC lights the SES lamp, the PCM orders the fans ON to prevent possible engine damage. In other words, some codes cause the fans to go ON while others don't. A full description of the DTC per the Factory Service Manual indicates if the fans will come on.

 

Yeah, I figured that. The mystery will be solved when my code scanner gets here. I'm not driving it any more till I get it figured out.

 

Well, this code reader/scanner did not work. All it did was short the pins together (making the fans come on) and never would connect. This was close to $150. Any more expensive and it will be cheaper to just take it to the dealer. The search continues.....

 

You have OBD-1 . You don't even need a code reader to retrieve the code. Read this :
How to read older GM OBD diagnostic codes for free

 

94 camaro will not flash codes. have you tried it under a different year? even different vehicle? sometimes gm was low on parts when building the camaro in certain years. try 95 and 93, try truck as well. my 93 shows as a 92

 

94 GM, Camaro specifically, will not flash the ses light by shorting the pins. Been there, done that.

 

Hold the fort....craby, I tried again selecting 1992 (thought I tried that) now it says it successfully connected and there are no stored codes. The SES light has come on and gone off on its own multiple times over the past few weeks. I have not disconnected the battery to erase...so there should be something in there if the SES light comes on, right? Or are there certain things that may trigger the light but not set a code?