New member here - been browsing and searching the site and have a conundrum. I have a 1999 Subaru Legacy that has been producing some error codes along with a very rough idle. Here's the breakdown:
1. Initial code was P0170 (fuel trim malfunction, bank 1), which I cleared out. I took it for a diagnostic to a mechanic who said the O2 sensor was dead.
2. Replaced the O2 sensor on my own (Bosch OEM). The rough idling continued regardless and a new error code of P0130 (O2 sensor circuit malfunction, upstream) popped up.
3. The code went away on its own, while rough idle continued.
4. Took the car to my father who has a diagnostic tool and we discovered that the car was stuck in open loop and wasn't reading the O2 sensor….showed 0.00 V for the sensor. Thinking we got a bum sensor, we bought another one - same result. Dang. We checked the electrical connections going to the O2 sensor on B18, B20 and E1 - the sensor seems to be receiving the proper voltages…the ground does seem to be sending a tiny (negligible?) voltage of .06 V. We re-seated a bunch of the the connectors as well just to see if there was a faulty connection anywhere...no dice.
Here are a few other readings from the scan:
Coolant Temp: 86 C
Intake Manifold Pressure: 36 kPa
Airflow Rate: 2.87 grams/second
O2 sensor 1 (upstream): 0.00 V
O2 sensor 2 (downstream): .5 V
Anybody have any thoughts on this, or experienced anything like it? Thank you much for your input!
-Nic
