While your explanation seems to be valid, That is not the entire case. You can change ignition switches without issue, but if you change the key cylinder you get a vehicle that won't start. That is until you run through a reprogramming for the new key cylinder. Found this out when I replaced a bad steering column without putting in original key cylinder from vehicle. Somewhere in there, something is tied to the key/cylinder assembly. Not saying you are wrong, just explaining my experiences.
Back to my issues, the blazer will start right up and idle smooth, give it just a little gas and it chokes , sputters, stumbles, just won't take any fuel. With scanner hooked up, looking at live data, everything seems to be within specs, fuel trims show 1-2% rich, o2 voltages show less that a volt and are moderately steady, MAF shows 5.26 g/s. MAP reads a fairly steady 23-25. Fuel pressure is 59 psi KOEO drops to 54 psi after sitting for ten minutes.
I can clear codes, CEL goes out, P0300 will set as pending as soon as truck goes closed loop, then after driving for 10 minutes ,sets CEL. Read codes again and I get some form of the list posted earlier. As a test , I cleared codes, shut off key and come back an hour later, read codes again, key on engine off, and I get some form of the list of codes, I also noticed that it seems to be failing or at least showing some sensors are not passing the initial test cycle. This leads me to believe there may be a module causing data corruption on the class 2 line. Without having a scan tool that can see data waveforms or test separate modules like a tech2, I'm at a loss as to how to check that part of the system.

 

Les responded: "Funny thing is that Passlock is not paired with the key on a 2001. Sensor internal in ignition switch pairs with BCM and if OK ..." As he said the key is not involved and I'm sure he meant the ignition assembly. Point is swapping the key or the cylinder does not effect the security system.

There are multiple security systems on GM's: Passlock 1 & 2, Passkey 1,2, & 3, and VATs. Some use a chip on the key, some use a transponder and the system on your truck (passlock) uses a hall effect sensor with a specific integrated resistor value programmed to match in the BCM. The key is not involved, the key cylinder is not involved except that it contains the generic magnet to energize the hall effect sensor when rotated, the ignition switch is not involved. The hall effect sensor and its resistor along with its wiring harness connector are mounted to the lock housing which bolts to the column. So you can change the key, cylinder and ignition switch without issue. If you change the hall effect sensor and resistor or those components (incl wiring) are damaged then the BCM will puke and defeat the fuel injectors about two seconds after starting when it does not read the voltage resulting from that specific resistor value.. Some of the other systems defeat the starter but not this one.

Les is one of the best resources on this forum, you would be wise to work with him to fix your vehicle. Besides we have an unwritten rule here that out of respect, once one of the members starts helping someone the rest of us let the OP and responding member finish the project together unless the member asks for an assist.


George

 

I can't help him. Maybe you can? Apparently refusing to check cam sensor retard and wants to argue about Passlock. Maybe his equipment in not capable of reading cam sensor retard. Not sure why he is here asking for help if he knows so much.

To the OP....... FWIW the lock cylinder assembly contains the lock cylinder AND the Passlock sensor. You can replace the lock cylinder by itself, or replace the entire lock assembly. If you replace the lock cylinder then Passlock is not affected. If you replace the lock assembly, the be BCM needs reprogrammed to recognize and send correct start signals. If you switch the PCM, it needs to be programmed to your vehicle so the BCM can recognize it or the start signal will never be sent.

 

@GeorgeLG I have not disrespected anyone, I have passed on information that has worked for me. From your explanation, it makes a little more technical sense to me. Thank you.
@LesMyer Cam retard is - 2.2 degrees.

 

I was trying to help you. Les asked you to check cam retard (a common and reasonable first diagnosis step) early on and then you didn't answer. Then you said that the PCM is tied to the passlock and key which is wrong on two counts. Key is irrelevant, and its a hall effect sensor and resistor behind the cylinder tied to the BCM. Les stuck with you and tried to explain how all this works. Then you switched to key cylinder and wont start which are both wrong again. I'm leaving out the whole thing about sensor lines shorted to ground.. And that got us here.

We are a large community of knowledgeable Blazer owners, many of us technical and experienced. If you need help that's what we are here for but it isn't going to work if you ask for help and then try to get help without having to acknowledge gaps in knowledge and the actual need for help.

It sounds like Les is over this thread and that's a shame because he would have been a good resource for you. If you want help I'll give it a shot but your going to have to lay off the tutorials on how passlock etc works and follow the guidance given. If you ask Ill be glad to explain how any of it works but beware, depending on the subject I might need to call on Les for an assist. We are tight like that.

If you want to move forward, what type of scanners do you have and what's the status of the PCM(s), their sources and any code erasing and re reading?


George

 

-2.2 is fine.
report MAF sensor reading and RPM at full throttle 1-2 shift

 

MAF reading at idle in park 5.29g/s @650 rpm. Currently vehicle will not run past about 800 rpm in gear. I can get it to about 3000 rpm in park by very slowly feathering the gas, MAF goes to 7.69g/s.

 

Snap-on scanner was used by a friend to get cam retard. Innova 5160rs is what I am currently using for live data.

 

I shall take my leave and let you two get this truck fixed.

George

 

Ok - this 7.69 @ 3000 rpm is a problem. Pull the pre-cat o2 sensors out for a test. Does MAF reading increase? Does it run better? Im suspecting plugged converters/exhaust. It may have another problem that caused a misfire and plugged converters but we start here.