Hi, new owner here. 1999 996 with 63k. After a PPI I had a reputable indy shop in Portland, OR do some work on the car before taking it home to Washington. Work included fluids, spark plugs and resealing the valve cover gaskets on both sides. On the drive home the CEL came on. I’ve since reset it and it’s thrown the same codes:

P0134 Oxygen Sensor Ahead of Catalytic Converter (Cylinders 1 - 3) - Interruption of Signal
P0154 Oxygen Sensor Ahead of Catalytic Converter (Cylinders 4 - 6) - Interruption of Signal
P1115 Oxygen Sensor Heating 1 After Catalytic Converter - Above Upper Limit
P1119 Oxygen Sensor Heating 2 Ahead of Catalytic Converter - Below Lower Limit

I cleaned the MAF. Unplugging the MAF while the car is running will cause the engine to stumble and then adjust therefore the MAF is likely not completely shot.

I tested crankcase vacuum by removing the oil cap while the car is idling. The engine runs ruff with the cap off and returns to normal with the cap on.

I have not tested for an intake manifold leak yet. I'm not sure what hose to open to test this.

The car has an intermittent rattle in the driver’s side exhaust that I believe is from a loose internal muffler baffle. Not sure if this could be linked to the CEL issues?

Any thoughts would be great. Thanks!

 

^^^^
That rattle could be the Catalytic Converter and quite possibly, the source of your CEL. Personally, I'd inspect the Cats...

I had a Catalytic Converter on one of my RX7's internally break apart and pieces made their way all the way through the muffler and to the tailpipe.

And...hopefully the experts will respond with some additional information and help.

Mike

 

Check if they have forgotten to plug in your O2 sensors. The connections are on the left and right side of the intake airbox (may need to remove the airbox to check the right side if memory serves).

 

That is a very good advice.

 

I agree. That is the first place to check.

 

Thanks so much for the tips. I'll check all the sensor connections in the engine bay and clean them tonight.

 

I checked all 4 connectors and they are good. Gray to gray and black to black. Upon further inspection of the 02 sensors I noticed a small gash in the driver's side pre-cat sensor that looked like it might have been recent. Perhaps the shop mangled the sensor when removing the exhaust for the valve cover job? Would this wreck the sensor and cause error codes on both banks??

 

Yikes. It may generate the codes for one bank but not the other (unless the precat O2 sensor on the other bank looks like this as well).

Do you have Durametric?

 

You should also verify the resistance of both pre-cat sensors (all of your codes are for the pre-cat sensors)

https://www.renntech.org/topic/51759...comment=292721

 

I don't have a Durametric. I just picked up the car and have a simple code reader. I can check if it has 02 readings when the car is running.
Thanks for the tips Ahsai!

 

Wow, they butchered that sensor. I would think this would have been noted had it been like that before. What shop did the work? I'd send them a picture and ask.

 

I have a new sensor on the way to replace this one. I already sent the shop a note. I've give them a chance to reply before naming them.
Using my code reader I can see that two of the four sensors do not change voltage at all, even after the car warms up. I believe that these are both banks, pre-cat.

 

I installed pre-cat Bosch 02 sensors on both banks.
After installing the Bank 2 (smashed) sensor the following codes were cleared: P0154, P1115, P1119. The remaining code was: P0134 Oxygen Sensor Ahead of Catalytic Converter (Cylinders 1 - 3) - Interruption of Signal.
After installing the Bank 1 sensor I cleared the remaining P0134 code and went for a 30 min drive. The car ran great idle was smooth and NO CEL cam on.

This morning I drove the car again and the CEL light came back with a new code: P0131 O2 Sensor circuit low voltage bank 1 sensor 1. Looking at the live data I see that there is ZERO voltage going to 02B1S1.
Why would I all of a sudden have zero voltage in the 02 sensor? Zero at idle, warm and running.

 

few ideas....
1. Wiring was not secured and melted to the exhaust?
2. Defective sensor
3. Another new issue. Some cars have built in programming so when the code sets the DME stops watching the known bad sensor and substitutes it for know good data. Reset the code and see if it responds shortly after.

 

One suggestion - don't just clear the codes, reset the ECU/DME entirely. Disconnect the battery negative lead for about an hour. You really need to do this after replacing O2 sensors. It will return all ECU/DME settings to default. Then go for a drive so the ECU/DME can re-learn all the O2 sensor values feedback and can adjust to new 02 sensors.