After I replaced the head gaskets on my 98 4.0 disco about a month ago, I started getting the CEL with code 1187 (oxygen sensor heater circuit short upstream) along with lousy gas mileage.

I recently replaced the two upstream (front) o2 sensors, and my mileage went back up to 13-14mpg, but that damn code keeps coming up!! Fawking frustrating! :mad3: Anyone have a clue where to look next?

You pinched the wires in the harness while doing the heads?

Ron

Alex:
What are you using to read the codes?

Some Generic OBDII readers are confused by the Rover data stream. If you have a short circuit in the heater circuit, I would not have expected the improvement in mileage as the sensors would never get hot enough to go into closed loop mode.

I think I'd start by checking to see if I had power to the heater circuit right at the sensor. If the juice is present, something else is happening to make the ECU think the sensors either aren't heating up, or the sensor itself has an internal fault to ground on the heater circuit.Is the fault engine bank specific? If so, swap sensors or wiring.

Worst case, I'm hoping to be in your neck of the woods, perhaps next weekend, I can bring the "Black Box" with me. But, you'll owe me, oh will you owe me!:flipoff2:

Whose idea was it to put the oxygen sensor connectors on the bellhousing?

Pinched the harness? Yikes! I hope its nothing like that. Its impossible to get to those wires. Some little things, like the engine, blocking access to them!

I'm using the scan tool from obd-2.com running on a laptop to grab the codes. As far as I know its pretty reliable. I do have two more new sensors, maybe I'll try taking the installed ones out and putting the new ones in, although I have my doubts it will work, since my fuel mileage has nearly doubled since I installed them.

Yeah tell me about it, the connectors on the bellhousing. Replacing the pass. side one reminded me of a documentary I once saw on a farm veterenarian helping a cow give birth by putting his arm *into* the cow up to his shoulder. Damn limey bastards!!!











So when did you say you were going to be in town Paul??:D :D :D :D

Originally posted by darkstar










So when did you say you were going to be in town Paul??:D :D :D :D

This will be the fourth or fifth attempt at bringing that Rangie home. Between weather, vehicle failures and scheduling conflicts... At least I got the engine yesterday.

I go to look at a car trailer to buy sometime this week yet, then, we hope to be up there on the 7th.

We should get together while you're here, even if I get this thing figured out by then (which doesn't seem likely, since my herniated disc is acting up right now, and that makes it anywhere from painful to downright impossible to work in the garage)...

But JIC, do you know which wires carry the heater circuit? I,m planning on cutting off a dead sensor off the lead so I can plug it in and put a multimeter on it.

In any case, shoot me a pm before you head out, I may just take you up on your offer to bring the magic box out. At least you guys will get a free dinner out of it!

Originally posted by darkstar
But JIC, do you know which wires carry the heater circuit?

In any case, shoot me a pm before you head out, I may just take you up on your offer to bring the magic box out. At least you guys will get a free dinner out of it!

Not off the top of my head, and none handy to even look at. You will likely figure it out by wire colors and size/appearance.

Next weekend doesn't look good, work arriving Friday evening to be done by Monday morning. How'd you like to tow that hulk to Fort Wayne for me? Free Rovacom hookup! You could sleep on the couch, but you're back would never be the same:flipoff2:

YOU WANT ME TO DRIVE TO THE NEXT STATE WITH MY OXYGEN SENSOR HEATER BROKEN???? WHY DON'T I JUST DRIVE MY TRUCK INTO LAKE MICHIGAN INSTEAD?

Some friend you are :flipoff2: :flipoff2: :flipoff2: :flipoff2:

I had to do another reply, I was worried that the sarcasm from the previous post would taint anything else that was tacked on to the end.

THe wires are black-red-white-yelo


I guess I'll have to look through the ETM to see if I can find it, although staring at those diagrams rarely leads to any understanding on my part.

I'm not going to do any hands on testing until my back is either better, or I know exactly which wires to try. Hell, I'm not even typing this from the garage computer!

alex, what part of "beer budget" has "garage computer" written on it?? . . . . . :flipoff2:

Originally posted by darkstar
I had to do another reply, I was worried that the sarcasm from the previous post would taint anything else that was tacked on to the end.

THe wires are black-red-white-yelo


I guess I'll have to look through the ETM to see if I can find it, although staring at those diagrams rarely leads to any understanding on my part.

I'm not going to do any hands on testing until my back is either better, or I know exactly which wires to try. Hell, I'm not even typing this from the garage computer!

Taint? Isn't that the...

I'd expect the black/red to be the heater and the others signal. I bought some Molex-type pins to make a test harness and promptly lost the pins.

Backpain-the thought of dealing with those connnectors back there makes my back hurt.

Just think how I treat my enemies:flipoff2:

Still looking for the sarcasm,
PT

SeaRover alex, what part of "beer budget" has "garage computer" written on it?? . . . . .

It was donated many years ago by a kind member of the D-90 list. And who said that LR owners were latte-sipping-biscotti-eating-look-down-their-nose-at-you-snobs? This dude was nice enough to take on a charity case like myself. :D

edit: time to take two vicodin, a shot of ketel and watch a futurama dvd. I'm going to tackle this annoyance later in the week.

Oxide on the connectors?

My 4.6 HSE wouldn't pass emissions. Overfuelling and terrible CO. Would run OK sometimes, but the fall back to dirty mode.

I wiped some engine oil from the connectors, took them apart, and put them back again. Consistently clean exhaust after that.

I finally got around to looking at this today. It looks like the problem was one of the o2 sensor connectors was falling apart. I pushed the terminals and the weatherpack insulation back in there, and it seems to be fixed. Luckily the problem was on the drivers side connector, which I could get to from the engine compartment.