Sincereagape

Hello. My family and I own a 2000 Jeep Grand 4.0L California Emissions. Engine light game on a few days ago. Codes - 0135, 0141, 0155, 0161. Looks like it is failures with all 4 o2 sensors. I'm going to try and fix it because we are on a very very tight budget. Not sure where to start to be honest. Any help is appreciated. Do I have to replace all four sensors and how much is that going to cost? Thanks.

dave1123

Look at the wiring first. CA sensors are expensive!

TCP64

I would check the ground wire/s serving the 4 sensors. Typically they are all fed from the same ground connection. The chances of all 4 going bad at the same time is not very likely.

BlueRidgeMark

I agree with the others. It's possible all 4 are bad, but...

Better to first attack something that is:

1. Far more likely to be the cause.
2. Cheap to fix.

Your 02 sensors need to be heated. Conveniently, they have a built-in heater. (Sure beats having to lean out the window to hold a propane torch on them while you're driving down the road!) That heater needs some juice (electricity) to operate. The heater circuit which supplies the juice can be a problem.

Coincidentally, all of your codes are for a "Oxygen Sensor Heater Circuit Malfunction". Hey! Cool! We know where to start looking. (Please note, these codes do NOT mean your sensor is bad [but they might be], but that there is a problem with the HEATER CIRCUIT.


The problem can be as simple as a blown fuse, so, check that first. I'm not sure which fuse that is, so get your searching skills out on that one. If it's blown, replace it with one of the same size and you should be good. If you replace it, and it blows again, we know there is a problem with the wiring or one or more sensors. IF that's the case, report back and we'll tackle that. In NO case should you ever use a LARGER size. Never.

If the fuse is good, check the ground. Again, sorry, I don't know where those things ground. (Possibly through the body of the sensors, in which case you won't find a separate ground point to check/clean. If so, move on to the next step.)

The last thing to do is to get a test light and see if you have good voltage at each of the sensors. Please use a TEST LIGHT, not a voltage meter, for this one. (I have a particular reason for that suggestion, which I'll discuss later.) If the light is good, then use a meter to get an actual number. Do this with the test light lit, and without the test light, and tell us what you have.