Hi all,

I'm hoping I can get some direction here. I have an 03 Disco 2 4.6 w/ SAI.

I'm getting a 0130 - B1S1 too-lean code after 15-20 minutes of freeway driving. I'm assuming a vacuum leak is created as the engine gets hot?

History: I did the head gaskets and timing cover gasket in May. The truck was running great for a few months but eventually, I got an 0130 code. I checked the sensor and it was immediately going to zero voltage. Replaced the front sensors with new bosch units and immediately had the same problem - b1s1 cycled then immediately went to zero voltage. Long story short, swapped sensors left and right, and one of the sensors turned out to be DOA. Replace them both again with a different brand and it seems to solve the problem. Voltage readings were normal, with no codes.

Well, that didn't last long, and after a long drive, I had another 0130 code. The voltage was low, but not zero. I left it until the next day and checked again: voltage on all 4 sensors seemed normal, starting at .445, and then cycling between .100 and .800. After around 20 minutes of freeway driving I watched the b1s1 voltage slowing trickle down under .100 and never recover. It was bouncing around .050. Meanwhile, the rear b1s2 had begun to climb above .900. The idle began to get rough after this; not terrible, but slightly off.

So I'm thinking I have a vacuum leak somewhere? I've spent some time spraying the engine down with starter fluid to try and find an obvious leak with no results.

Is this a vacuum leak? It runs perfectly while cold and even at operating temp (194*) for a short time. Could this be an exhaust leak?

Is there anything I'm missing? Will smoke test the engine next.

Thanks!

 

Seems to be bad luck and the b1s1 sensor has failed again. So bank 1 is actually running rich, as indicated by b1s2. That shows the ECM is responding to the b1s1 sensor correctly by adding fuel. If bank 1 was lean, both sensors would show lean (low volts). Maybe swap b1s2 to up front to test. Could you share your source for the O2 sensors? Make sure the b1s1 wires don't rub against the exhaust.

 

Interesting. I thought that could be a possibility because the readings make no sense as you mentioned. But because it works well for awhile I figured I was missing something.

These were denso. I'll swap left and right again and see what happens.

 

I went ahead and swapped the front o2 sensors. The problem seemed to followed the bad o2 sensor. I went ahead and replaced it with a new Walker sensor.

Everything was perfect for 3 days. Then b1s1 eventually dropped to 0.000 and p0130 returned. I checked the vacuum and it seems to be perfect; could not find a drop of smoke anywhere, which makes sense as all gaskets are < one year old.

Long term fuel trim is +25% on b1. All others are hovering from -3% to 3%.

I’m really stumped about what could be causing this. I don’t seem to be losing coolant or burning it. Could a stuck injector be causing this? Maf? Bad wiring? Bad ECU?

Any ideas would be helpful.

 

The good news is you had everything working. Seems like the signal from the B1S1 is shorting to ground (0.000 volts). That could be another bad O2 sensor, or wiring (bare copper touching some other metal), or the ECU (internal short to ground). Did you collect any data (e.g. fuel trims, O2 voltage trends) while everything was working for three days?

The LTFT is calling to add maximum fuel (+25%). Probably if an injector was not allowing fuel to flow, the engine would really shake while driving. It doesn't seem likely that an internal problem with the ECU would come and go, hard to say for sure. Maybe focus on the O2 sensor again and wiring. Frustrating for sure.

 

Unfortunately, I was not watching the LTFT while they were working. I did notice the rear o2 sensors were fluctuating higher than they used to.

Before replacing the B1S1 sensor this time around I did notice that I had a small exhaust leak at the manifold to downpipe connection. I tightened that up and it seemed to seal it.

I did not reset the fuel trim adaptations. Is it possible that after fixing the exhaust leak the overfueling from the LTFT killed the o2 Sensor?

 

The metal body of the O2 sensors is not very strong, so any little ding can cause damage during installation and removal.

High fuel trim values do not cause sensor damage, but dumping a lot of fuel to the cats can cause overheating. Keep after it, you're almost there!