P1170 front pre-cat O2 sensor

[kruiser]

I had a P1170 for about a month (HO2S Bank 1 Sensor 1 Circuit Fixed ), and occasionally also P0134 - O2 Sensor Circuit No Activity Detected Bank 1 Sensor 1 and P0140 - O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2. I hoped that the P0140 is also related to the first O2 sensor. So I replaced the pre-cat O2 sensor yesterday with a Bosch 13362. I clear the codes and went for a 1/2 hour drive. The codes didn't come back. But this morning the P1170 came back again! As far as I know the P1170 indicates a front O2 sensor circuit fault, so why is it still there after a new one was put in?

By the way the car is 96 with 1.5L.

[loganss]

Was there another post here before? Seemed like someone had a few answers to my questions of the haynes manual not having enough information.
Semi-related thread

My pro is also forced to running in open loop due to my O2 sensor error code.

My pro also takes a while for the codes to come back on. I erased the codes in northern nj drove to dc/md area (~230+ miles), and drove an additional 15+ miles before the code came back on.

[kruiser]

I have been monitoring my first (front) O2 sensor voltage for a few days during driving, with a laptop scan tool. Most of the time the voltage is on the order of 0.01V. During idle and cruising at constant speeds, the voltage is 0.000V, only during hard acceleration does it go up above 0.5V. Correct me if I'm wrong - the front O2 sensor is supposed to range from 0.1 to 0.9 volts, and most of the time it should fluctuate around 0.5V (0.45 or 0.5V being the 14.7:1 fuel/air stoichiometric ratio). My brand new Bosch sensor with OEM connector is not producing any voltage most of the time, which explains why I still have the P1170 code after changing the sensor (P1170 means the first O2 sensor is not switching). Is it safe to say that the P1170 is not caused by the sensor but some other related circuitry? What could cause an O2 sensor to stick?

Also, during stop and go driving, the code would go away but it would come back when I start cruising on the highway. I know that the ECM relies on the first O2 sensor for fuel/air adjustment in closed loop. So this could be why the MIL with P1170 comes on when I start cruising.

Another problem is that the long term fuel trim is always 0. I have no idea if this is related to the O2 sensor not switching. Only the short term fuel trim changes - it goes up to 25% but never negative. According to TSB 3870 in the FAQ section, the long term fuel trim must change at different RPMs in order for my I/M monitors to set, this explains why I have 4 monitors in the Not Ready state - which seems to be a common problem for 96 Proteges. As stated in the TSB, I'm going to recheck my idle RPM and timing.

So these are the problems I have observed, but I don't have any solutions or where to start looking. Any help or ideas would be greatly appreciated.

[loganss]

Oh ok so you have a laptop connected to the OBD terminal that gives you more indepth read outs. If you don't mind me asking can you post how you set up the laptop (i.e. software, cables, etc). I've just been using a simple actron scan tool.

I'm not sure what you mean by fuel trim. Is this an OBD read out?

Did you check to make sure there is nothing wrong with the O2 sensor wiring (exposed wires, dirty terminals)?

Maybe you could turn the car on and have it running for 2+ mins w/ your laptop scan tool plugged in and use the method I used in the other thread for checking the O2 sensor. Could help to determine if it's a wiring problem.

[goldstar]

I don't know how helpful this will be since this info comes from the '02 FSM but I'll relate to you what it states since it's all OBD II.

Possible Causes for P0134 (Front) circuit no activity detected:
Front O2 sensor deterioration or heater malfunction
Leakage from exhaust system
Open or short to ground circuit between front O2 terminal A and PCM terminal 60
Insufficient compression
Engine malfunction

Possible Causes for P0140 (Rear) circuit no activity detected:
Rear O2 sensor deterioration or heater malfunction
Leakage from exhaust system
Open or short to ground circuit between rear O2 terminal A and PCM terminal 35
Insufficient compression
Engine malfunction

Also according to FSM, reasons for front O2 sensor to exhibit low voltage stick (voltage from sensor remains below .45 V):
Sensor malfunction
Fuel injector malfuntion
Pressure regulator malfunction
Fuel pump malfunction
Fuel delivery hose leakage
Air suction or leakage
PCV valve malfunction
Purge solenoid valve malfunction or hoses hooked up incorrectly
Ignition coil malfunction
Insufficient compression
Engine malfunction

Finally, fuel trim problems short or long term, can be caused by inoperative or malfunctioning front O2 sensor as well as by some of the same causes for O2 sensor low voltage stick.

I hope at least some of this will be useful to you. Good luck in finding the problem.