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Need help wit code P0430. Car is a 06 base model with M6.Had to change battery so was driving to reset all I/M to get state inspection. So after replacing battery I crossed spark plug wires 2 & 4 so car was misfiring ( probably about 5 minutes before I realized my mistake) car was just idling in my garage. So I fixed my mistake and got ready to take the car out and drove it for about 25 miles. Everything was running great and as I was headed back home, the check engine light came on. Got back to the house and put my scanner on it and that is when, I saw this code. I know this has something to do with the cat on the right side or possibly the oxygen sensors. Do you think that me running it for such a short time with a misfire might have messed the cat up? TIA
I saw you had another issue a few weeks ago with a P0496 (EVAP flow during non purge condition) which tells me your purge valve may have been stuck open drawing those EVAP canister fuel vapors into the engine resulting in a rich condition which will damage your cats…if you have a scan tool and can graph your 4 O2 sensors if the downstream sensors look like the upstreams your cat is shot !!…the other cat is probably not to far behind.
Well still having the same issues. Changed out the purge valve this morning and cleared all the codes. Took the car out for about a 30 miles drive. Was headed home and the CEL came back on. I figured it would because of the converter throwing the P0430 code last week. (Bank 2 converter bad)
I’m still getting the P0496 after replacing the purge valve. Code reader is giving me (6) different things to look at.
(1) Faulty evap canister vent valve
(2) purge valve. (Changed)
(3) Plugged evap canister condition
(4) Faulty evap pressure sensor
(5) Evap canister vent valve harness is opened
(6) Evap canister vent valve circuit poor electrical connection
Before I changed the purge valve I checked to see if it was closed used a vacuum bleeder and it’s closed and holds 12 inches of vacuum for at least 3 hours. The one thing I did notice is the car is sucking up the gas. I used about a 1/4 tank for the 30-35 I just drove it.
With your code reader see if you can look at the “Fuel Tank Pressure Sensor” data PID voltage and also if you have the same PID but is for “inches H20”…these code readers are sometimes useless when trying to diagnose these cars…with the engine NOT running you should see 1.5 volts..this is the voltage for atmospheric pressure in the tank and is applicable to mostly all GM cars…now start the car…if there is vacuum being applied to the fuel tank the inches of H2O value will be a minus value and the voltage will increase from 1.5 up to however much vacuum is in the tank…what sets the code is the ECM see “more than 10 inches of H2O vacuum for 5 seconds during non purge”…if everything looks good leave the scan tool plugged in and clear the code and go for a drive and see if the tank goes into a vacuum..the EVAP test may not run…you can try unplugging the purge valve taking the electrical circuit out of the picture and watch for any tank vacuum…”maybe” the ground wire is shorting out which will open the purge valve…the ECM controls that ground but I’m thinking you would see a P0443 if the wire is shorted…0443 is a “circuit” or wiring code.
Okay, not sure what my reader is tell me but here’s what I found. The reader has purge flow monitoring which it shows four different tests and two of the four show fail. Just not sure what they are referring too. All test are min/max setup
test I.D # C4 has a test valve of 15.0 s ( I’m guessing seconds)
Min. Limit = 60.0 s
Max. Limit = 6553.5 s
status = fail
test ID C5
Limit Type min/max
test valve 14.58 in H20
Min. Limit = 32.12 in H20
Max Limit = 10.04 in H20
status = fail
test ID C6 & C7 both showed passed
C6 values are 0.0 and everything was 0.0 s
c7 values are 0.0 and everything was 0.0L
Notu sure what all this means? I did get the code P0443 but I’m thinking it was when I unplugged the purge valve plug.
Okay, I think the code reader that I have isn’t going to have everything I need. I did get a little information from the Data Stream that it has is limited. Going to see if I can find someone who can check with a better reader.
Engine at idle Engine at 3000 rpm Engine not running , powered up
Looks like your tank is in a vacuum at idle…don’t know why your commanded purge is at 16% at idle ??…should be 0% !!…maybe it’s testing your EVAP system.
This is all with a new purge valve. I watched the video and going to check the new valve in the morning. Is there a relay or something that could be keep the valve open? Okay couldn’t wait after watching the video. Pull the fitting off the purge valve and attached a vacuum gauge and I’m getting 8” of vacuum at idle. Going to recheck it in the morning with the engine cold and see if there’s a difference.
Last edited by miker94; May 9, 2023 at 06:26 PM.
Reason: Added information
The purge solenoid connector has 2 wires…a power and a ground which is controlled by the ECM and is PWM (pulse width modulated)…you can remove the connector and with a LED test light connected to battery positive with the car at idle see if the test light is illuminated when probing the dark green/white wire…the test light should not be on…look at fuel tank pressure sensor voltage…it should read 1.5 volts…as the fuel tank vacuum increases the voltage will increase if there is a vacuum.…if the engine computer is grounding the solenoid when it shouldn’t you will have vacuum in the tank when you shouldn’t…you need a scan tool and not a better reader…the only thing these readers are good for is reading powertrain codes….thats all !!
This is all with a new purge valve. I watched the video and going to check the new valve in the morning. Is there a relay or something that could be keep the valve open? Okay couldn’t wait after watching the video. Pull the fitting off the purge valve and attached a vacuum gauge and I’m getting 8” of vacuum at idle. Going to recheck it in the morning with the engine cold and see if there’s a difference.
You’re seeing vacuum on the side of the purge valve going to the tank ??…there should be none unless the purge is stuck open or electrically open as I explained above…unplug the purge valve connector and see if the vacuum goes away.
Okay, checked for voltage with the LED test light with it connected to the positive side of the battery and probed the ground and there’s no power with the car running. The latest thing that I noticed was both purge valve are doing the same thing. You start the car and both the old and new valves are letting vacuum pass through with or without the electrical plug being installed. The only difference between them is that once you plug them back up they sound like they’re turning off and on ( vacuum is opening and closing) but if you bench test them they are closed until you put 12 volts to them and they open and close properly. I guess I’m going to try and see if I can get someone to do a complete scan for me. I just hope they will give me the information and not want to do the repairs. Need to save some money.
If the purge valve is allowing vacuum from the intake manifold to the tank with it UNPLUGGED the purge valve is defective…is is normally closed !!..if you plug in the connector and you hear a “buzzing” that is the purge valve being PWM (pulse width modulated)…the Engine Computer is opening and closing the ground very quickly…you see it as a percentage on the scan tool…closed is 0% !!…you showed me a number like 16% !!
Well I’m not sure what happened but I decided to flip the hose around on the purge valve. Not sure why this would make a difference but it seems to. I figured the valve is a closed/ open circuit. Now the valve is closed and the command evaporative purge is still reading 16.5 % at idle but as I raise the idle the percentage goes up and then goes to 0.0% when I let off the gas and then returns to 16.5 % plus I’m get movement out of the evap system pressure. Going to try and get some driving in tomorrow morning but it been raining like crazy here.
The hose shouldn’t make a difference…there is no check valve inside of it…and yes it is a 2 wire solenoid and has power going to it with the engine running and the ECM supplies the ground when it dies it’s test to open it up…and like I said it’s PWM so it’s somewhere between 0 and 100%…100% is fully open…watch that fuel tank pressure sensor voltage and voltage will increase as the tank gets drawn into a vacuum…1.5 volts is atmospheric but on a hot day with the car outside as the tank gets hot and the fuel expands and creates pressure the voltage should decrease from 1.5…if you remove the gas cap it should go to 1.5 volts…this may be a bad ECM but take it for a drive and see what happens…I would clear the codes too…if the percentage is 16.5 the EVAP system may be doing its test but it won’t do it for a long time.
That’s what I’m thinking it’s doing a purge test or cycle. The only thing that I could think is that the engine vacuum is pulling down on the solenoid plunger and was opening it up a little and now it’s pulling it against the seat inside the solenoid. See what happens when I put some miles on it.
That’s what I’m thinking it’s doing a purge test or cycle. The only thing that I could think is that the engine vacuum is pulling down on the solenoid plunger and was opening it up a little and now it’s pulling it against the seat inside the solenoid. See what happens when I put some miles on it.
The engine vacuum does not open the purge valve…it’s a solenoid and when grounded it electrically opens depending on the pulse width that the engine computer requests.
Latest update. Looks like the purge valve hoses were installed backwards. Put the hose from the TB/ manifold fitting to the side of the purge valve that’s away from the electrical connection and then the other side goes to the fitting at back by the firewall. Cleared all the codes and drove about 38 miles. So I knew I would probably get the P0430 code( bad cat) but I also got a new code P0443 which I believe is control circuit for the purge valve. So, still thinking that I need to get someone with a good scanner to help me out. I did notice while I was driving is the command evaporator purge was moving all over the place it would go to zero then to go to 50% and sometimes even 100% but then almost automatically dropped back down to zero so I feel like the valve is functioning properly For the most part but now with this other code, I wonder if it’s being intermittent?
Latest update. Looks like the purge valve hoses were installed backwards. Put the hose from the TB/ manifold fitting to the side of the purge valve that’s away from the electrical connection and then the other side goes to the fitting at back by the firewall. Cleared all the codes and drove about 38 miles. So I knew I would probably get the P0430 code( bad cat) but I also got a new code P0443 which I believe is control circuit for the purge valve. So, still thinking that I need to get someone with a good scanner to help me out. I did notice while I was driving is the command evaporator purge was moving all over the place it would go to zero then to go to 50% and sometimes even 100% but then almost automatically dropped back down to zero so I feel like the valve is functioning properly For the most part but now with this other code, I wonder if it’s being intermittent?
The 0443 is a “circuit” code (wiring) so you need to concentrate on wiring and not the purge valve being opened or closed…maybe check for a short to ground on the control wire (dark green/white)…remove the purge valve connector and connect the test light to battery positive or B+ on the alternator…probe the control wire while wiggling the harness as much as you can and see if the test light illuminates…look for “points of contact” where the harness passes near some metal…you can try that !!
With EVAP codes like this, it's just easier to have someone with a scan tool + smoke machine hooked and manually actuate the valves to see if there are any leaks or damage. P0496 is rarely associated with a bad purge valve, usually a leak in the system. There's easy ways to test the purge valve and see if it's leaking internally but since you replaced yours, it's most likely a leak and worse case its the charcoal canister(Theres another valve on the canister + a small leak detection pump that can fail and cause this). Any competent mechanic with a scan tool and smoke machine should be able to diagnose it in a few minutes.
Code P0430
