Hello everyone,
Thre days ago bought a 1999 blazer with 52k miles after a day or so the service engine soon came on. Looking for any help on what may be the cause so will give all that we have done since buying the blazer.
Codes are PO171 and PO174 lean bank 1 and 2. To give complete service history here is what we have done since getting and before the ses light came on.

1. Got gas in way home from buying the blazer, filled it up was about a 1/4 tank.

2 When we drive noticed no heat or ac the engine temp never much over 100 deg. Figure was stuck stat, when replacing the stat found that someone had removed all but the gasket and top. Did check the block and saw no sign of old stat parts. While installing stat noticed coolant brownish and looked mostly like water. so drained radiator and flushed out radiator, and filled with new coolant.
on test drive is when the ses came on.
engine running great, good oil pressure and temp running right a round 200 deg.

2. While flushing radiator did drop cap under battery tray, so had to remove battery and tray to get the radiator cap.
I trying to figure if anything we did caused the ses light. The blazer is for my son he loves it, with such low miles and a very clean with no leaks or indication thinking something simple.
did read something about delco system and locking it before disconnecting battery.
From the car fax looks like only about 10k miles were put on the last 3-4 years.

Also having little issue with shifting into 4wd. It does go into 4 hi and low but no lights on the dash and at time transfer case shifts hard into 4wd.
plan on draining and putting new fluids in everything.
know this is long but hoping answers most questions of what we done. Looking forward to being part of the group.
thanks

 

Good luck w/ the new Blazer, very low mileage. You can look up the individual codes here but the best starting place is probably the DTC sticky in Tech (DIY) under the Mechanical and Maintenance forum.

One problem that seems to be nearly universal is deteriorated and broken vacuum lines in the engine compartment. Unless someone changed them out already you can start by looking for broken hoses right by the master cylinder. Engine vacuum controls the HVAC system, splits off to control the 4x4 diaphragm found under the battery and the AIR smog/air pump emissions system.

Depending on which 4x4 system you have the control varies a bit. The 3 button uses a vacuum switch on the transfer case and the 4 button (2WD, 4Hi, 4Lo and AWD) uses a vacuum switch on the firewall.

@christine_208 did a very nice write up that helped me quite a bit. Look for her Vacuum line thread as a starting point.

 

Thank you toxyco,
Will start with your suggestions, have already been thinking about replacing the vaccum line.
we do have the 4 button 4wd option. Son wants to start diving his new car aftrtvwe get the heat fixed, should have new actuator in today old one does have a cracked gear.
does any see any issues with him driving with the po171 code till we get it figured out. He may drive 20-50 miles a day right now.
again thanks for the reply and help already reading the suggested threads.

 

Thank you toxyco,
Will start with your suggestions, have already been thinking about replacing the vaccum line.
we do have the 4 button 4wd option. Son wants to start diving his new car aftrtvwe get the heat fixed, should have new actuator in today old one does have a cracked gear.
does any see any issues with him driving with the po171 code till we get it figured out. He may drive 20-50 miles a day right now.
again thanks for the reply and help already reading the suggested threads.

 

That is low mileage, welcome to the forum.

There are multiple potential causes for lean trouble codes but one is in fact a vacuum leak so the suggestions about vacuum lines is a good one. This can also affect your 4wd and HVAC controls. If your scanner has live data capability then look at fuel trims (ST and LT, both banks). They should be high and positive at idle and they should go down at 2500 rpm. They should also go down it you pinch off the vacuum lines at the source. This would confirm a vacuum leak. Any other codes?

Lastly, again if you have live data - after the truck warms up are the b1s1 and b2s1 O2 sensors switching?


George