I have an 03 disco with Bosch engine, and I searched hard to find the answer before posting this.

I am pulling p0141/61 codes.

I am seeing fluctuating voltage on both banks, from .075 - .870. with resting voltage at .045

What is odd is the signal is maxing then mining very quickly. I pinned out all connections and have very little resistance in the harness. Sensors are aftermarket cheapo, but new.

Is this indicative of Cat failure or should I open my wallet and get OE sensors?








graph of down stream voltage

 

I have exactly same issue and also seeking advice - no luck so far.

 

NTK sensors work well. Is there a known good sensor you could try? Bad cats usually cause bad smells of rotten eggs. There could also be a loss of power. If you don't have those issues, I'd try new sensors. Some will say BOSCH sensors have a lot of failures out of the box. Walker or NTK seems to work best. I ruined a sensor on the trail and replaced both with NTK, so far no issues

 

Are you getting the same codes? P0141 and P0161?

 

Thank you for the advice. Both the old sensor that was on the car and new one, which I have just purchased as replacement are identical Bosh units. Both failing in exact same maner - I'm thinking it's not an issue with the sensor.

 

Exact same codes. The cat on the faulty side runs about 80*F cooler than the one on "good" side, but I'm not having any issues with power and no rotten egg smell out of exhaust.

 

Those are heater circuit codes. Your sensors are functioning normally. There are four wires on the sensor, two are for the sensor, two are for the heater. Look at the Rave wiring diagram, you should have 12 v across the heater wires at the plug. Check the sensors, the heater is just a big resistor, you should have around 10 ohm across the heater wires on the sensor. The heater increases the life of the sensor and helps lower emissions during start up.

 

Thank you for the info. The problem is that the sensor is functioning just fine until the engine is fully wramed up, then it suddenly goes lean.