2002 Blazer with 4.3L V6 w 140K

CEL a few months ago P0141. Changed sensor since it had never been changed before and was "hoping" it would fix problem. Three months later it recurred. I did a smoke test and I have a vacuum leak behind passenger side lower intake manifold (part # 12550122). I tried to feel around the manifold for a leak and didn't feel a hole but it is quite rusty. Thoughts on way ahead? Thanks!

 

P0141 is the heater circuit/function for that O2 sensor. Anytime you get a code the only thing you know is that circuit/function has a problem. If its a sensor like this is, you don't know yet if its the O2 sensor heater, its wiring/connectors from the ECM, the ECM, power, ground, etc. If you don't test the entire circuit first then you may wind up replacing a sensor/fuel pump/coil/ICM/etc that is not bad and now have an inferior aftermarket replacement part for an AC Delco OEM part that was not bad and the same problem.

If you have a multimeter and would like to find the problem through proper analysis I will be glad to help you. The heater circuit from the ECM needs to be tested to be sure that it is turning on and can supply the rated current for the O2 sensor heater coil.

Let me know if I can help.


George

 

George,

Thanks! I have a cheap multimeter but now have an excuse to upgrade and get smarter. Would love assistance.

Cheers, Kevin

 

Your front O2 sensors take a 0.450v bias voltage and moves it up and down to tell the ECM what is happening with the fuel mixture. When the signal heads towards 0.85v the mixture is rich. When it heads towards 0.15v the mixture is lean. In live data you should see this voltage swing up and down at around 1 hz at idle when running and in closed loop (O2 sensors controlling fuel delivery). The rear sensor monitors the output from the cat and should hover somewhere around 0.5 - 0.7v and not switch when everything is warmed up. There is a heater element in the sensor to get the O2 sensor up to operating temp quickly and to assist during idle so that the sensor can properly control fuel and lower emissions. That heater gets either fused ignition power (this particular sensor) or power from the ECM and has ground side control from the ECM to turn it on and off.

You should have a 4 wire oxygen sensor. Two wires near the same color (usually) on the vehicle harness (O2 sensor heater power and ground) and two other wires both of different colors on the vehicle harness (signal bias voltage and signal ground). That code is for the heater circuit but it is only implied. The ECM did not see the sensor warm up and turn on fast enough and just assumes that the heater is not working but that is only one potential cause. It might not even be the sensor. It can be the sensor heating element sure but it can also be the wiring, power, ECM ground side control, etc.

Lets start simple and check the heater power circuit first. This is for your rear sensor behind the cat so Disconnect the O2 sensor connector and identify the two harness heater wires (brown and pink, not the same color in this case). On a relatively cold engine, Take an incandescent test light , back probe those 2 harness wires, connect the test light and turn on the ignition. If it does not light up you may have to start the truck to energize the heater circuit. Did you get a bright test light?

Do you have a scanner with live data capability?

George

 

I’m also having kinda the same problem I have an 03 Chevy 4.3 blazer and it has the p0141 error code I bought a new o2 sensor and it still didn’t fix it so I checked out the harness the color were white, white, black and grey on of the white ones did receive a positive charge when the key is in the on position but when I tried to probe for a negative charge nothing lit up I also don’t know which wire should be the negative so I looked up Bosch o2 sensor and it said the ground was the grey wire so I wired a quick connect to that grey wire directly to the ground and still the code persists I need to get this done for emissions so any help would be greatly appreciated I do have a snap on scanner with the live data capability but I’m still new at useing it

 

please start your own thread. This one belongs to someone else.

 

The wire colors on the O2 sensor itself can vary and almost never line up with the vehicle harness wire colors. First we need to get situated and then we can find out what your problem is and fix it.

P0141 is the heater circuit on B1S2 which should be the rear O2 sensor behind the cat. The vehicle harness colors should be brown, pink, ppl/wht, tan/wht. Is this what we have in your case?

After the truck warms up what does that sensor look like in a graph with live data?

George

 

Oh ok I didn’t realize that I only looked at the o2 sensor side of the wires let me check the vehicle harness side and get back to you with the colors and as far as the graph goes I wasn’t aware it had that function till I read your post so I’ll also have to check that and get back to you but what should I be seeing.

 

The moderator just posted to start your own thread which is the correct way to do this. I will follow you on the new thread when you post your answer.

George

 

Alright I think I opened my own thread but not to sure here’s the link if you can’t find it thanks again https://blazerforum.com/forum/engine...03/#post745912