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View Full Version : black smoke and code P0131 oxygen sensor


maxzoom
09-15-2008, 02:02 AM
Just recently my 2005 Sprinter with 99,900 miles on it has been spewing black smoke out the tail pipe on acceleration and up hills. The check engine light has come on too. According to my scan gauge it is code P0131 "Oxygen Sensor shorted to ground" This problem went away for about a week but today it started again.


Has any one had any experience with this? Does one need to buy a new Oxygen Sensor? Or the code "shorted to ground" just means to check the wiring?

Is the O2 sensor easy to remove and replace? According to the service manual it is a 4 step process;

1. Disconnect the negative battery cable
2. Remove the exhaust heat shield
3. Disconnect the O2 sensor harness connector
4. Remove the O2 sensor.

Sounds easy enough but are there any tricks to it or stuff to watch out for? And how does one "remove the O2 sensor"? Does it just pull out or screw out?

autostaretx
09-15-2008, 05:26 AM
I'd certainly check the wiring first... since "shorted to ground" could be a sharp piece of metal anywhere along the harness having sliced through the wires' insulation.
At least unplug the sensor harness connector and see if the error changes.

When it can't trust the O2 sensor, the engine control unit will richen the mixture to avoid over-lean operation. That would perhaps explain the black smoke.

good luck
--dick

rlent
09-17-2008, 08:56 AM
Having had my (upper) heat shield off repeatedly ... and for some duration (it's been off for the last two weeks) ...... I thought that the oxygen sensor seemed to come awfully close to the lower heat shield with high potential for rubbing ..... don't recall the attachment exactly .... but I wouldn't be surprised if it screwed in, with jam nut to hold it.

maxzoom
09-17-2008, 03:57 PM
Thanks for the advice. Here is what I tried so far... I examined the wiring from harness to sensor which appears in excellent condition except there is a sharp bend in the wiring where it has been plastic tied to other wiring by the air filter. Then I simply unscrewed the Oxygen Sensor with a crescent wrench. (I think it is 22mm size which I don't have). The sensor was heavily sooted so I sprayed it and soaked it in brake cleaner. After replacing it and driving a few miles a got the same black smoke and code P0131.

So I tried what Autostaretx suggested... I unpluged the Oxygen Sensor at the wiring harness connector and drove a few miles. This time I got code " P0030 Oxygen Sensor malfunction".

So I guess the problem is like it says, "Oxygen Sensor shorted to ground" It looks very difficult to trace the wires completely. So I'm thinking of any easy fix. How about splice into the O2 ground wire and ground it to the nearest body part?

AircooledJohn
09-17-2008, 04:28 PM
just curious, how much is a new sensor?

John

rlent
09-17-2008, 04:55 PM
At EuroParts, $218 ......

Since it should be covered under the 100K Engine/Emission Warranty (?) ...... I think I'd be calling the dealer pronto .........

maxzoom
09-18-2008, 01:08 AM
I didn't see oxygen sensor listed in the 100,000 parts warranty so it propably isn't covered.

maxzoom
09-23-2008, 03:53 PM
Well I spliced into and grounded what the electrical manual called the "virtual ground" oxygen sensor wire. This didn't help and I got two error codes. What is the difference between a ground and "virtual ground"?

The black smoke problem has almost gone away however. This is maybe because I patched a big hole in the muffler. The black exhaust problem seemed to gradually get better after that. The muffler is however very plugged with black soot and I need to replace as soon as possible... I'm saving up my money to buy a new muffler... about $1,400 :(

autostaretx
09-23-2008, 05:09 PM
If you disconnect, or short-out, or otherwise pester the oxygen sensors, the ECU will switch to "open loop" and inject -more- fuel (thus guaranteeing a rich mixture to avoid burning your valves and pistons from too lean a mixture). That can dump more unburned fuel into your catalytic converter, and sludge/coke it up. (in the Sprinter, they also increase Exhaust Gas Recirculation to up to 35% of intake air volume).

I think i'd assume that a "virtual ground" is a feed directly from the ECU from which the oxygen sensor's output (the O2 sensor -generates- a voltage) is referenced. It may be -near- the vehicle's ground, but it's probably (trying to be) a fully isolated "signal" (thus avoiding voltage fluctuations caused by other currents running through the frame).
Oxygen sensors care about the narrow voltage range between 0.4v and 0.8v, so any picked-up-from-ground "signals" could swamp (or nudge) the real signal.

good luck
--dick

maxzoom
09-28-2008, 04:01 PM
I had a mechanic who has worked on a few Sprinter come by the other day. He said do not worry about the O2 sensor too much. It is only for emissions and does not effect performance (we do not have emmissions test out here either).

He showed me a quick way to clean out the exhaust system too... Spray about 2-3 seconds of brake cleaner into the EGR intake manifold. Wait about 20 minutes and then start the engine. The engine will not start easy... you need to hold the pedal to the metal about 10-20 seconds while cranking. Once started a tremendous cloud of blake smoke and huge puddle of carbon came out the tail pipe. (make sure no one is standing back there)!

talkinghorse43
09-29-2008, 01:31 AM
I had a mechanic who has worked on a few Sprinter come by the other day. He said do not worry about the O2 sensor too much. It is only for emissions and does not effect performance (we do not have emmissions test out here either).

He showed me a quick way to clean out the exhaust system too... Spray about 2-3 seconds of brake cleaner into the EGR intake manifold. Wait about 20 minutes and then start the engine. The engine will not start easy... you need to hold the pedal to the metal about 10-20 seconds while cranking. Once started a tremendous cloud of blake smoke and huge puddle of carbon came out the tail pipe. (make sure no one is standing back there)!

That's a mechanic I hope I never run into. Did you actually let him do that to your engine?

maxzoom
09-29-2008, 04:44 AM
Hey it's running alot better now.