Big Puddin'

Hi, 1994 LT1 4 speed overdrive auto. Removed throttle body coolant flow. installed long tube headers straight to true dual exhaust, egr bypass. Cranks sounds great, I guess from mods or lack of cats, code remains on dash, despite great running. I have no issues except would sorta like to disconnect service engine soon light. Have tried disconnecting battery few times trying to reset, but from reading the lack of cats or maybe EGR bypass ensuring light stays on. Would appreciate your thoughts and thank you for your time.

Injuneer

Easy way to find out - scan the PCM. You could use an old OBD-1 AutoXray scanner, a dual function OBD-1/OBD-2 scanner like the Actron CP9185 (low as $73 online, + extra for the 94 OBD-1 cable), or download free Scan9495 scanning software, from link "stickied" at the top of the "Computer Diagnostics....." forum (cable required).

You can't pull codes in a 94 by shorting the DLC connector pins (so the Actron CP9001 will not work). And some of the Innova and Equus dual function scanners will not work.

In OBD-1 (1993-1995) removing the cat will not set a code, because there is no after-cat O2 sensor. Not sure what an "EGR bypass" is. If you mean you deleted EGR, if you remove the EGR vacuum solenoid, you will get a code, and removing any part of the EGR system may set yet another code for system performance. What did you do with the AIR system when you installed the headers?

Don't delete the SES light. There are ways to eliminate codes with resistors, or they can be "programmed out" of the PCM. Keeping the diagnostic system functional can alert you to problems that can reduce performance or even damage the engine or trans.

Big Puddin'

EGR block off plate. Forgot, yes, removed air injection setup, removed engine oil coolant assy that circulated coolant thru oil filter mounting setup. thank you for reply.