[malangon]

Had the following codes pop up with the "Service Engine Soon" light on a 2002 Discovery 2: P0134, P0135, P0155.

Replaced both front O2 sensors on the advice of some of the board members.

Immediately had the codes pop up again. Reset the codes thinking I had to run through a few cycles. After about 30 miles and 3 resets, they keep coming up.

Can somebody recommend a next course of action?

Thanks!

 

[redtruck12]

I'm an auto mechanic. O2 lean codes such as 134 and 135 are commonly caused by air intake leaks or vacuum leaks. First things I would check are vacuum lines and air intake duct connections between the air flow sensor on air filter box and the engine air intake. It is common for people to jump to the conclusion of a bad o2 sensor when in fact it is something like a loos air intake clamp. Vacuum leaks and ir intake leaks can usually be heard as an abnormal sucking sound if they are substantial.
P.m. Me if you need more help.

 

[malangon]

Wiring

While double-checking the work that the mechanics did, I noticed that the wire that connects the harness and runs into the unknown somewhere (I assume to the ecm) has the outside covering disintegrated a bit from where it was touching the main part of the engine. I'm wondering if the wiring could be bad, but I'm not sure where to find the end of this wire.

I did a quick look in Rave, but it didn't pop out at me. Can anybody suggest where to get some more info on checking the wiring? I'm assuming that's the next step in troubleshooting. It wouldn't make sens however that both front would throw a simultaneous code unless both wires went which is unlikely.

 

[Disco Mike]

Not to correct Red's information on the codes, but he is wrong, these codes are indicating the 02's are dead and as such they are not caused by any sort of leak. If that were the case, there would be either lean or rich codes for both banks.
Need to check more into the wiring.

 

[malangon]

Follow-Up

That's what I was thinking Disco Mike, bu two follow-on questions:

1) What's your best recommendation on getting some idea of where the wiring goes? It's very tight behind the engine block to trace this. I'd rather find the beginning and end and use an ohm meter to see if it's cut somewhere.

2) Another member posted in a previous message that no matter what I do, I will always get codes unless I change each side in pairs (front and rear). I only changed the front. Is there anything to this claim?

Thanks in advance

 

[redtruck12]

My apologies I was thinking 140 codes ( high voltage ) sory to mislead anyone

 

[Disco Mike]

No problem Red.
As for changing the 02's you do them in pairs be it front front pairs or rear pairs.

 

[malangon]

Wiring

I had the front pair of O2 sensors changed and immediately got the same codes. When I looked under the hood (bonnet), I found wiring from behind the engine block that terminates in a red harness. The mechanic connect the gray, white, and black wires from that red harness a few inches down to another black harness, and then a down to the sensor. It appears as if there are 2 harnesses in line here and I can't figure out why. If the codes are thrown because of a wiring problem, it seems poor practice to introduce multiple points of failure.

Has anybody seen this before?

 

[Disco Mike]

Have you searched out info on the Rave CD, have you used a real time scanner to verify if the 02's are working or not?