I know that there are similar posts to this, but I am wondering if my DTC's are all inter-related. I took my 1995 Blazer LT into the tranny shop for fluid change, and a problem with a hard 1-2 shift. They ran and found the following DTCs, P0133, P0134, P0137, P0141, P1406 and P1133. My question is if I replace the O2 sensor(s) and clean or replace the EGR, will this clear up the codes? and also, where do I find all of the o2 sensors, and the EGR. I have reviewed the other posts, but did not find where the EGR is on my 1995 blazer. I have 4.3L (W) vin code motor, with a manufacture date of 02/95. I appreciate all of the help, and wonder if this will also clear up the hard 1-2 shift. My tranny guy says it is OK to shift hard, but I wonder why this is happening now, and before I did not have this problem, then changed the fluid and cleaned the valve body and still no change. By the way, the tranny has all the latest updates to the valve body. Thanks again, and this is a great forum!!!

 

Your EGR valve is located in the same position as it is in the newer engines; front/center of the engine below the throttle body.

You may fix the problem by replacing the sensors, but you really should diagnose the problems. The O2 sensor codes could all be caused by a loose ground or, worse, a faulty PCM.

I doubt that these codes are causing your harsh shift.

 

Thanks for the quick response, and for quick reference, do you have a link to your previous post on troubleshooting the O2 sensors. If it is the PCM, what is the cost on replacing, and where is that located.

Also, do you have any way to troubleshoot the harsh 1-2 shift?
Thanks again.

 

Check out the Tech Article (DIY) section for further information in both regards (links in my sig).

 

When checking the o2 sensor, clear the codes unhook the proper bank and sensor go for a quick run come back and see if you get the same pending code to make sure its the right o2 sensor. You should have three sensors, one on the drivers side manifold, one on the passenger side manifold, and one right after the cat (unless you have true dual for some reason)

 

There are actually two different setups in '95. In either case, there is only one upstream sensor and this is directly behind the 'y' in the y-pipe.

Here is a schematic showing the OBD1.5 & OBD2 setups used in '95:


For the true OBD1 setup used in '95, there is no post cat O2 sensor.

 

I only found 2 O2 sensors as Swartlkk mentioned one before the "Y" pipe and then post cat. I will clear codes and troubleshoot each sensor as described. I will post the results after the weekend, since I am also going to clean the EGR as this was one of the codes as well P1406 EGR ... Does anyone recommend the Seafoam? Thanks again for all the response. FYI. just took a long highway trip and am getting 18.5 MPG and around 13.8 MPG city. Hopefully when I get this trimmed out, it should give me a nother 1 MPG.

 

Search for "Seafoam" and decide for yourself! LOL I use it quite frequently!

 

Update - I did the troubleshooting and found the B1S1 O2 Sensor was bad, so I replaced with NGK, then cleared codes, and now I only see P1406, the only problem is my EGR is the InLine type, so can't really clean it effectively, but tried and then ran it again, but still threw a DTC P1406. I really do not want to replace this since it is about $115, but I do not want to have any performance or emissions problems. Also added a pint of Seafoam, and from all the posts I have read Kyle, it seems like this stuff is every bit worth the $10.00 I spent for the pint. The only issue I am having now is a leaking water pump, which will be replaced next weekend, and my Cruise Control just went out. Also having some issues with Volt Meter surge, not sure of the source, I did test the Alt. and it passed with flying colors, so could be a regulator within the Alt, that is starting to go. Any Suggestions?? Thanks everyone, Erik