SES light on

[1fastsilverado]

ok i gutted my cats becasue police here are mean and odnt like ppl to have loud vehicles right.......so we did all that and a few days later my SES light came on....normal i knew it was comin. Well now i think somethin wrong. Im gonna need to get a dumby O2 sensor to shut it off. can a SES light ruin performance? a mechanic around here that we have on our pit crew said a SES light puts the computer in lymp mode and it doesnt perform to well becasue it retards the motor. is this true? wil a Dumby O2 sensor bring it back to life? Thanks

[chrisj6]

You will have to get the code cleared after you put the sensor on, but no it wont kill performance at all. That mechanic must be a "shade tree mechanic" who doesnt deal with computer controlled vehicles very much. All the rear o2's are there for is measuring catalytic efficiency, which just tell you mainly when your cats arent functioning properly.

Chris

[1fastsilverado]

o well mine is a 96 silverado and a guy at the local dealership said my pcm is one of the few assheaded ones that do the lymp mode. so i dunno he said all it does is slows shit down. ntiohin to abd.

[chrisj6]

yeah hes full of shit, he just wants you to let him fix it $$$ It just measures catalytic efficiency on all PCMs.

Chris

[1fastsilverado]

uhhh he fixes my stuff free if i buy parts. i dunno.

[TXsilverado]

buy some 02 simulators for your rear 02 sensors. problem fixed. allen could probably fix it for you too but im not sure if he messes with computers of that year??

[JayBo]

Originally posted by 1fastsilverado@Sep 29 2005, 06:28 PM
uhhh he fixes my stuff free if i buy parts. i dunno.

So who are you going to believe?

[Motocycleguy]

Chrisj6 is 100% correct. Im sure your Mechanic is just missinformed.
the maine reason to set the CHECK ENGINE light is for a problem that immediately affects emissions. Removing the oxygen sensor downstream or the catalytic converter will set the MIL, but this sensor has absolutely zero to do with fuel, spark or timing. As far as the ECM is concerned it means your catalytic converter isn't doing its job. Just get some simulators you will be fine even if you dont.

Limp Mode does exist in certain situations and in a good way. These computers are so smart. Pre OBD-II, if your MAF became disconnected the engine would probally stall. On OBD-II cars, a disconnected MAF will cause the computer to keep the engine running using data from RPM, throttle position and other inputs. I was working on a Benz that had the Check Engine on and was Very low on power. One of the cylnders was not firing so the ECM shut off that injector to keep it from dumping raw fuel and heating up the catalytic converter. Some other things that would cause a OBD-II system to go into limp mode are. MAP, IAT, TPS, ECT, CMP and Baro... The computer will just through these inputs out and use predefined ones and or use other setting to keep the vehicle running......LIMP MODE

Ignorance and fear is as American as apple pie. OBD-II has been very good for the automotive industry. cars run cleaner make better power and do it more efficiently. If it was not for SEMA OBD-II regs would be invasive and severe.