Okay so i got a Blazer for 1000$ and probably another 800$ into it. Im still getting a P1133 code, P0401 and P0401. i have new O2s on the way, changed all the spark plugs, wires, Distributor, EGR, new thermostat, new Radiator, and new spiders, I just did the smoke test tonight and i had 0 leaks on the vacuum system but one small one around the intake to throttle body ontop. also did new gaskets when i changed the spiders for the intake. The Blazer has a battery which i assume is from 2010 as was wondering if that could be causing all my problems. i checked the EGR plug and got 12v and 5v to show up. As for the EGR itself if i turn it upside down i can hear something move / slide inside. could this be a bad EGR out of the gate? i dont have the OEM one as it was never cleaned and really dirty. im not sure 100% how to check the O2 sensors with a meter but it was at 6.7 ohms if i remember right for Bank 1 Sen 1. Bank 1 Sen 3 was at i believe 6.5 ohms. Im totally lost as these are my LAST 2 PROPLEMS! oh and ball joints but i dont want to go there o.0. i have a FOXWELL NT301 OBD2 Scanner but not really sure how to use it fully to test anything. if someone could explain this i will give an update on the reading 4/7/2024 when the battery charges or if i get a new battery.

Thank you to anyone trying to help.

 

Lets start with the O2 sensors. There are two sections to a sensor. First the heater circuit which is a simple resistive element that brings the sensor up to operating temp faster than from exhaust heat at start up so that the truck can go into closed loop faster. Then there is the fuel control from the sensor itself. The engine computer supplies a 0.45v bias voltage and the sensor causes the voltage to switch between approx 0.9 and 0.1v at a rate of about once per second at idle. Does the truck go into closed loop after it warms up?

Can your scanner plot O2 sensor output in a graph in live data?

That code can be the sensor, it’s wiring or the ECM.


George

 

I am waiting on O2s to come in on the 9th to be put in. The truck will run fine and idle fine until it heats up around 160°f. After that I start to get loss of power up hills. If I clear the codes it starts running fine again for about 15mins. I just jumped the battery which has stamped on it J2 and a 10. So assuming second week in January of 2010 which that's old. As for O2s when it warms up I'll go under it and unplug the O2 on bank 1 sensor 1 and check it. I have 4 pins which I know the outside is power then the one next to it is ground. You want me to check the cable going TO the ecm not the O2 correct? Also alternator is putting out 14.6v from alternator hot to battery negative.

 

Those static voltages for O2 sensor output are not of much use. A graph that shows the switching behavior is better. Given that you have new sensors on order I would wait until you put those in and if you still have problems, we can get fancier on the diagnosis.

George

 

still getting .445v on B1S1 with the new O2 installed. I'm going to let it cool down and put another one in. I connected the OLD O2 and let it hang down. The old one heated up but only was reading .445v. the B2S1 was reading .8 when hot it's also old. I'm so lost and still getting the egr failed. Could this be a bad wire? I'll have to let to cool to test those. I tested the egr wires with the blazer running and all wires pulled voltage, it's like their always hot. I'm going to pull the trigger on an expensive egr to hopefully fix that issue...

Old O2 not even in exhaust but is heating up the tip. At idle

B1S1 new at idle in exhaust. Truck at 195°F

B2 s1 at idle

 

If you install the new B1S1 O2 sensor, start the truck, wait for it to warm up and go into closed loop fuel control, all you get is a flat line 0.445v with no voltage changes over time?

George

 

all I get is .445 constantly. I changed to a new O2 just hanging there. No change at all I'll let it idle and see what I got in about 5mins. I need this thing for tomorrow sadly... It's raining so I can't take the motorcycle.

 

So you get a steady 0.45v but the O2 sensor is not installed in the exhaust pipe, its just hanging by the harness in open air?

George

 

Yes sir. All read .445 (took the old one and swapped it around and a new one.) open air. If I plug the ones inside the exhaust B2S1 read .885 closed in exhaust, B1S3 reads .325ish closed, B1S1 in exhaust closed read .445 and does not changed.

Did a test one wires WITH truck running. O2 unplugged I got FROM TRUCK HARNESS 13v 8v and 8v . Used pink wire as main.
Pink black 13v
Pink purple 8
Pink brown 8

Ran idle for 10mins B1S1 did NOT move.

 

There is no value in looking at the O2 sensor voltage if it is not installed in a running warmed up truck. Hopefully you have an incandescent (not led) test light (scope on a rope, old school).

1. First we need to make sure that the heater circuit is getting powered so that the sensor can heat up and become operational. The two wires that supply power to the simple resistive heating element are black and pink in your case. I am referring to the harness colors not the sensor pigtail colors, those colors are whatever the aftermarket sensor guys says they are. Disconnect the sensor and connect your incandescent test light to those two wires in the harness and see if it lights up. If not, turn the key on, if not, start the truck.
2. Keep the sensor unplugged and get your scanner and live data up and running. That sensor should show a steady 0.45v ish volts. Then ground the test light clip, touch the probe end to battery voltage to prove a good probe ground and then touch the ppl/wht wire in the harness and see if the scanner voltage drops to zero ish. That will prove the integrity of the signal wire from the engine computer to the harness connector.

Report back and we can go from there.

George