O2 Sensor Help!

D

DiscoMook

Member
Feb 3, 2008
7
0
NC
Hey, all...long-time lurker here, would appreciate any help you can give.
I have an '02 D2 that just passed 150k miles, have been maintaining it meticulously since I bought it with 100k about 10 years ago. It recently started throwing a P1174, so I pulled and replaced all four O2 sensors (never been changed to my knowledge), and cleaned the MAF and air filter. Now it is giving the following codes:
P0141/P0161 (bank 1 and 2 rear heater circuit)
P0130/P0150 (bank 1 and 2 front sensor)
The exhaust has a creosote smell now...not efficient.

What I have done:
1. Checked that all four sensors are indeed connected; hoping I did no loom damage in trying to contort myself to pull the connectors yet again.
2. Checked as much of the vac system as I could, and found no leaks.
3. Checked the under hood fuse box for condition of #2 EMS fuse.

The sensors were bought on-line, but I believe they are in good condition. The plugs were exact matches--I didn't do the splicing myself.

I was hoping to milk one more oil change interval in before trying to tackle the head gaskets/water pump/oil pump/timing chain later this summer. It is losing a small amount of coolant (about a cup every 500 miles) and the back side of both heads show signs of leaking oil, so the heads are due. The plugs/wires have only about 20k on them.

Could the heads be the culprit? Anything I'm missing? Thanks again for the help!
 
D

discostew

Well-known member
Sep 14, 2010
7,745
1,026
Northern Illinois
Your o2 sensor heater faults should be simple. Your going to have battery voltage coming in and a good ground. The heater itself will measure a little bit of resistance. Your probably either going to find the heater itself open, or a wire pulled out of the plastic connector body. This happens a lot on those disco2 o2 sensor connectors.

Your other faults in the front sensors are listed as a circuit fault and its picking on the sensor not the heater. One thing I have found a bunch of times is the red/black wire looses its ground internally in the pcm. Its easy enough to test. Key on engine off you should measure a good ground path on those wires. If memory serves me you are going to see about 500 mv (1/2 a volt) on the other wire working the sensor.

If you did in fact loose the ground on those red/black wires I have fixed the problem cheap by just cutting the wires before they go into the pcm and grounding them to the brackets behind the glove box. It gets a ground thru the pcm but that is the extent of what the pcm is doing with that ground. It's been my experience that a ground is a ground and it will fix that.
 
D

DiscoMook

Member
Feb 3, 2008
7
0
NC
Thanks, Stew! I'm considering putting the old ones back on, possibly 2 at a time (both front or both rear) and see if the codes go away or change. Before then, I'll do what you stated and see if I can isolate it further. I did get the sensors off eBay, so maybe they are somewhat suspect? If I keep the same codes with the old sensors back on, then I'm likely guilty of being a bit rough with the wires on the car side of the plug. Thanks again for the reply and I'll report back with what I find!
 
rovercanus

rovercanus

Well-known member
Apr 24, 2004
9,651
246
What sensors did you buy? I tried cheap sensor and the damn things simply did not work. Stick with Bosch.
Who did you get the sensors from on ebay? If it's the same place I got them from they know they don't work. They were very good about refunding my money though.
 
D

DiscoMook

Member
Feb 3, 2008
7
0
NC
So, I put the old sensors back on, but just the front. Now I'm just throwing p141, p161, but the p1171/p1174 are back. I think I'm going to try and sell my firstborn to afford four new non-eBay Bosch sensors and live with the 1171/1174 if present until I get the heads done. Thanks again for all the help and suggestions!
 
rovercanus

rovercanus

Well-known member
Apr 24, 2004
9,651
246
You can get sensors cheaper if you are willing to splice and solder your old connector to your new sensor.
I think I paid $60 per front sensor doing this for my 04 from Federated Auto Parts.
 
adriatic04

adriatic04

Well-known member
Mar 22, 2007
2,506
2
cleveland, oh
DiscoMook said:
So, I put the old sensors back on, but just the front. Now I'm just throwing p141, p161, but the p1171/p1174 are back. I think I'm going to try and sell my firstborn to afford four new non-eBay Bosch sensors and live with the 1171/1174 if present until I get the heads done. Thanks again for all the help and suggestions!
Click to expand...

get the bosch o2's from amazon, they ship free and are 45-55 a piece, half the price at local retailers. Just did this in March and it finally cured my bullshit from this ever slowly dying turd.

rears (http://www.amazon.com/Bosch-15630-O...&redirect=true&ref_=oh_aui_detailpage_o00_s00)

fronts (http://www.amazon.com/Bosch-15175-O..._UL160_SR160,160_&refRID=19HWAM3Q716QQZPTT3F9)

edit: links, hopefully they work?
 
WaltNYC

WaltNYC

Well-known member
Mar 3, 2010
714
142
NYC
Plug in directly. They are the proper O2 sensor for AEL trucks (which was included on the Discovery I from mid-1997 onward)
 
D

DiscoMook

Member
Feb 3, 2008
7
0
NC
Thanks for the help, everyone. Bosch from Amazon was the way to go. I got a bad front sensor from Amazon initially, but the replacements they sent did the trick. I'm now just left with a P1174 and a head gasket repair I hope to tackle later this summer. Thanks again!
 
You must log in or register to reply here.
Top Bottom