Hello, I have a 2000 S10 Blazer with a 4.3V6 Automatic trans. Here's the problem: basically I'm waiting on 2 monitors to set (catalyst, sec air), now the reason they are not set is my SES (mil) light came on about a month ago. I plugged my scanner in and it gave a P0440 & P0452. When this happened I noticed when putting gas I could hear pressure release as I would remove the gas cap? Well I replaced the gas cap with a new one. But the SES light did turn off so I thought it was the gas cap, but it would come back on (SES) as soon as I was just under a 1/4 tank of gas. Then I'd fill up and it would turn off after about 2 to 3 starts. Then it just never came back on even with a low tank of gas. So I figured it corrected itself, or whatever.
Then before I was going to take it for the smog, I checked it again and it still had 1 code (P0452) so I thought that would mean it wouldn't pass so I cleared it not knowing that it would also reset the monitors!!! UGGGG
So I've been trying to do the Drive Cycles to the best that I can for my surroundings (LA) and all have set (monitors) except the CATALYST & SEC AIR! And to make things worse the dam SES light came on again with the same codes but went away after I filled the tank???? I took it to a mechanic shop and they just said keep driving and that the catalyst & sec air dont have anything to do with the code that came up (P0452) they said it was the EVAP and that monitor is set.
So I guess I just keep driving it. I've put 800 miles on it so far. Anyone have any other ideas.

 

Here's what it takes before the catalyst readiness test will run. Note that EVAP DTCs are included in the things that will prevent a P0420 catalyst problem from being tested (means no test is run)

After that is what it takes before the A.I.R. system test will run. Note that EVAP DTCs are included in the things that will prevent a P0410 air injection problem from being tested. (means no test is run).

Your EVAP problem is preventing the tests from running, and that even a pending code without SES light would prevent these tests from running.

Shop you went to does not have a clue. Fix the EVAP problem (both P0440 and P0452 are EVAP), and the readiness tests should run (hopefully pass) unless there are other problems that surface once the readiness monitors complete. I suspect you have a problem with the tank pressure sensor for both codes, but don't just replace it - diagnose it.

p.s. if you can fill your tank from empty to full without it shutting off all the time, chances are your EVAP vent valve and carbon cannister are OK.

CONDITIONS FOR RUNNING THE P0420 DTC - catalyst efficiency (& readiness test).

* No active secondary AIR DTCs
* No active CMP sensor DTCs
* No active ECT sensor DTCs
* No active EGR DTCs
* No active Fuel Trim DTCs
* No active IAC DTCs
* No active IAT sensor DTCs
* No active MAF sensor DTCs
* No active MAP sensor DTCs
* No active O2 sensor DTCs
* No active transmission DTCs
* No active EVAP system DTCs
* No active TP sensor DTCs
* No active VS sensor DTCs
* No active misfire DTCs
* The engine speed is 900 RPM or more for more than 35 seconds since the last idle period.
* The engine has been running for more than 346 seconds and the long term fuel trim is stable.
* The predicted catalyst temperature is more than 475°C (887°F) .
* The system is in Closed Loop.
* The BARO is 73 kPa or more.
* The IAT is between -7 to 117°C (20-167°F) .
* The ECT is between 75-117°C (167-243°F) .
* The engine has been idling for less than 60 seconds .
* The actual engine speed is within 100 RPM of the desired idle speed.

CONDITIONS FOR RUNNING THE P0410 DTC secondary air injection (& readiness test)

* No active ECT sensor DTCs
* No active IAC sensor DTCs
* No active HO2S DTCs
* No active misfire DTCs
* No active MAP DTCs
* No active Fuel Trim DTCs
* No active EVAP DTCs
* No active TP sensor DTCs
* No active IAT DTCs
* No active MAF DTCs
* The MAF is less than 25 g/s .
* The commanded air/fuel ratio is 14.7:1.
* The engine load is less than 34 percent .
* Power Enrichment Mode is not active.
* DFCO (Decel Fuel Cutoff Mode) is not active.
* Catalyst overtemp protection is not active.
* The system has been in Closed Loop Mode for more than 20 seconds .
* The Short Term Fuel Trim is between 124-132 counts.
* The engine speed is more than 550 RPM .
* The ECT is between 80-110°C (176-230°F) .
* The system voltage is 11.7 volts or more.

 

Thanks Les
I will try to trouble shoot the EVAP system. Right now the SES light is off but my scan tool reader shows P0452? Once I find the problem will that code go away? Or do I have to clear it even though that will reset all the monitors again.

 

P0452 will go away after 40 warm up cycles with no problem. If your Smog test requires no codes in history, then yes you will probably need to use the scanner to clear the code.

Did you find these yet? Includes factory diagnostic info.
https://blazerforum.com/forum/diagno...plained-35142/

CONDITIONS FOR CLEARING THE MIL OR DTC

* The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed.
* A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle.
* Use a scan tool in order to clear the DTCs.

 

Looks like old photobucket links to images are not working in link. Here are the missing diagnostic charts. A P0452 shouldn't be very difficult to diagnose. If your scanner doesn't do fuel tank pressure / volts, I recommend Car Gauge Pro for Android and the BAFX Bluetooth OBD2 adapter as sold on Amazon - about $35 total. At least it will display fuel tank pressure / volts on my 2001 (as I determined when I was working on my EVAP system).

 

Thank You for all the info much appreciated. My scan tool is just a cheap read only type, ACTRON I believe. A friend of mine said he just picked up one that has the bluetooth and he said he spent $250 on it, so I'll see if it has all the extras to help me fix this. Thanks again I'm going to work on it this weekend.

 

SEC-AIR monitor finally SET!!!!!!!!!!!!!!!!!
I had a feeling about that possibly it wouldn't run (sec air) because I noticed it takes a long time to warm up in the morning, I'm almost already to work before the heater kicks in, and except for summer time the engine runs way below normal operating temp. So I replaced the thermostat yesterday and sure enough the old one wasn't closing all the way!! So $10 fix put a new 195 deg. one yesterday, then later that evening took a trip to the casino plenty of steady driving no where near what a drive cycle calls for and this morning checked it and all the monitors are set!!!!!!!!!!!!!!!!

 

glad to hear of success!!!