I bought this car about two minths ago.. sence then i installed LT's and a ORY just resently the SES light flashes at high RPM under a load...I cant figure out what is causing it. The SES light has been on sence i bought the car with a 420 code now it has the 2 rear o2's removed so it has 2 more codes but no others.

From my little expierance i always thought a flashing SES light meant a missfire.
but there is no misfire code?

The car idles great and drives fine but at high RPM it bucks pretty bad.

I think its is advancing to much at high RPM. cause when i went to the track i put some octane booster in it and it ran fine. If it is advancing to much what would cause it to and why didnt this happen before? My dad has a hand held scanner and at 5000 RPM it is advancing 40* ?? not sure if that the norm or not??

From what i know the car never got a tune. The only mod to the car was a lid when i bought it.


Please help!!

 

DTC P0420 or P0430

In order to maintain reasonably low emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx), the engine controls system uses a 3-way catalytic converter. The catalyst within the converter promotes a chemical reaction which oxidizestheHC and CO in the exhaust gas. This reaction converts these chemicalsinto harmless water vapor andcarbondioxide. The catalyst alsoreduces NOx, converting the NOx tonitrogen. The powertrain control module (PCM)monitorsthisprocess using Bank 1 HO2S #2. Bank 1HO2S #2, located inthe exhauststream past the 3-way catalytic converter, produces anoutput signal which indicatestheoxygen storage capacity of the catalyst.This determinesthe catalyst's ability to effectively convert theexhaust emissions. If the catalyst is functioning correctly, the Bank 1 HO2S #2 signalwill be far less active than the signal produced by Bank 1HO2S #1. This indicates that the 3-way catalyticconvertersoxygen storage capacity is below an acceptable threshold.

When the Conditions for Running this DTC are met, the following conditions occur:

• The PCM captures the current rear HO2S rich-to-lean status.

• The Air/Fuel ratio transitions from rich to lean, or from lean to rich, depending on the capture rear HO2S rich-to-lean status.

• The Air/Fuel ratio transitions a second time opposite the first Air/Fuel ratio transition.

• The PCM captures the response time of the front and rear heated oxygen sensors when the Air/Fuelratio transitions occurred. The response time is the time during which the HO2S goes from below 300 mV to above 600 mV, and from 600 mV to below 300 mV.

• The PCM measures the time for the rear HO2S voltage to cross a reference rich-to-lean threshold, minus the time for the front HO2S voltage to cross the same rich-to-lean threshold. The time difference from the front and rear HO2S is the oxygen storage capacity of thecatalyst. This DTC setsif the time exceeds a predetermined threshold.

Conditions for Running the DTC
• DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0171, P0172, P0174, P0175, P0200, P0300, P0325, P0327, P0332, P0335, P0336, P0341, P0342, P0343, P0351-P0358, P0410, P0412, P0418, P0440, P0442, P0443, P0446, P0449 , P0500,P0502, P0506, P0507, P0704, P0801, P0803, P1258, P1336, P1415, P1416, and P1441 are not set.

• The engine is operating for more than 450 seconds.

• The ECT is between 75°C (167°F)-120°C (248°F).

• The IAT is between -18°C (64°F)-80°C (176°F).

• Since the end of the last idle test, the engine speed is more than 1,000 RPM for a minimum of 37 seconds for a manual transmission

• Since the end of the last idle test, the engine speed is more than 1,000 RPM for a minimum of 44 seconds for an automatic transmission

• The BARO is more than 74 kPa.

• The fuel system is operating in closed loop.

Conditions for Setting the DTC
The PCM determines that the oxygen storage capability of the catalytic converter has degraded below a calibrated threshold.

Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• Clear the MIL and the DTC with a scan tool.

 

A flashing SES light means that catalyst damage is occurring. This is usually due to misfire.

Does 40 degrees of advance at 4000rpm seem a bit high to anyone? Just asking...

 

I've had a flashing SES light from plugwires not being fully connected on my old car, my little brother has had some issues with his plug wires on his LT1 touching his headers under load and causing a flashing SES.

 

Does anyone know what Flipper is talkin about and how it helps me?? lol..... If it was miss firing wouldn't i get a miss fire code? I'll change my plugs and wires and see if that helps at all.

 

Flipper just cut and pasted some GM info for you. It is useful information to help you understand the code, how it works, and it may help you troubleshoot. This information tells you how the diagnostic test runs and thus will help you understand why the test failed and why your SES light is on.

I still think you may want to check some timing issues. You say it ran find when you ran higher octane right? If you're advancing too much you will have a problem. Is your light still flashing? Does it just flash and go off? Or does it flash and stay on?

Do you have a tech 2 to be able to check your freeze frame data? You may have a misfire code in there so check. I'm miffed that you are not getting a P0300 misfire code. Flashing light does mean catalyst damage which can be caused by misfire conditions. It is the end result of something else happening upstream like a bad injector or incorrect spark issues. Check and let us know.

 

Ok no p0300 code... The light only flashes when i get on it. Then it stays on it has three codes 2 are no rear o2 activity cause they are disconected. and a 0420 code that has been there sence i bought the car. at the track with octane booster it didnt flash at all. could this be the booster or cause it was running colder. It is posable that the car was once tuned and the missfire detedtion was tuned off.

 

You really need to figure out if misfire was turned off. I just can't believe your light is flashing and you don't have a misfire code. In any event, don't beat the thing up until you figure out what's going on since misfire is quite serious as I'm sure I don't need to tell you. The SES light will flash when misfire is detected. The PCM will remember load and RPM parameters where the event happened. Then the light will stop flashing and go off when the misfire goes away. If misfire happens again within a certain range and load of the first failure the light will flash again but this time it will stay on letting you know that misfire has been detected two times within the same limit.

About the 420 code, check out a post just a few threads down.

Definitly see about getting misfire turned on if it is off. And double check your timing. I'm still waiting to see what anyone has to say about timing vs. rpm. Does anyone have a chart or some input on that?

 

For my information, how many miles are on your car?

 

41,000
Im goignto go talk to the previos owner and see if he had a tune done to it.. And im taking off my valve covers today just to make sure every thing is ok under there. not sure what else to do..

Im not to worried about the 420 code accually im not sure if its still there after i put he ORY on. I didn't delete the code at the time so im goingn to have to go do that.

 

You can try to delete the code but i'm not sure it'll go away. Probably come right back.

Check with previous owner and post an update.

 

I went out today with a mechanic friend and tryed to get the light to flash like it was..but now it wont flash lol.... so i really dont get it now... I have a feeling it will come back and haunt me though

Maybe ill just go out and buy a cam and head package and get a tune so i wont have to worry about it

 

Did you get a hold of the previous owner to ask if he had done any tuning?

Head and cam package sounds good to me!