O2 sensor. What is its function? - 1990 Geo Storm

Have your O2 sensors checked, with an OBD2 meter, and see if they are functioning, if not replace them. O2 sensor is located in the exhaust pipe between the motor and the catalytic converter. The front O2 sensor runs the engine and the after cat converter monitors the cat converter.

The upstream (ahead of the catalytic converter) O2 sensor heater circuit has failed. Replaced the upstream O2 sensor and all will be well. O2 sensors wil lnot work below 650 degrees F. To get them functioning sooner after a cold start, and during times when the exhaust is not very hot (idling at stop lights), designers placed a filament inside the O2 sensors to keep them hot so they can measure O2 levels int he exhaust stream (which alloows the engine compouter to mete out the right amonut of fuel to keep the engine running efficiently.) The filament fails open after time so it no longer can heat the sensor. The only solution is to replace the O2 sensor, which is not a big deal.

P0134 - O2 Sensor Circuit No Activity Detected Sensor 1 Bank 1
P0135 - O2 Sensor Heater Circuit Malfunction Bank 1 Sensor 1
P0053 - O2 Heater Resistance Bank 1 Sensor 1
P0030 - O2 Heater Control Circuit Bank 1 Sensor 1
You need to replace the O2 Sensor Bank 1 Sensor 1
Carquest can help you get the correct part and help you locate it.

With a defective O2 Bank 1 front sensor you would expect a poor warm engine running operation.

The before catalytic O2 sensor controls the fueling function to the engine. The mixture air/fuel ratio is calculated from the input from this critical sensor.

With a simple scan tool with graphic function the operation of this O2 can be observed, and diagnosed.

Suggest borrow or if car drive-able take to a parts store that will perform a complementary scan of the O2 function.

These are heated sensors and the heated circuit electrical connection could be the problem.. Exhaust leak, blocked catalytic converter, broken wire are all possible causes. By graphing the function and comparing to bank 2 diagnostics are relatively easy.

The reason at cold startup the engine is OK is that until the O2 heats up the engine is running open loop and the O2 is not hot. To be operational the O2 must be hot.


Hope this helps?

It has one O2 sensor the exhaust header (referred to often as the upstream sensor or cylinder bank one sensor) and one Catalytic Converter efficiency monitor (looks like an O2 but performs a different function) this is also called the "downstream sensor"

All 4 wire O2 sensors are compatible in function. The only difference is the plug for the wiring loom.
A B5 A4 and a C4 A6 should have the same plug...

I wouldn't use a second hand O2 sensor though.., always buy new.

there are a couple of things to consider here. That code indicates that the O2 sensor behind the cat is not functioning like the engine computer expects-either the cat itself is not functioning properly or you may have an exhaust leak, or the heater circuit in the O2 sensor is faulty. The cat should get up to 600 degrees and it burns unburned fuel before ti gets to the 2ed O2 sensor-if it cannot do this, the CEL comes on and you have a P0420. Before replacing the cat, clear the code and see if it comes back-if it does, you might try first replacing the O2 sensor. If that doesn't work, get a 'oil fouler' spark plug adapter and install the O2 sensor in it, then install both into the exhaust-this 'shields' the tip of the O2 sensor and slows it down, fooling the engine computer into seeing it switching slowly, as it is supposed to do. Your only other choice is to replace the cat, and an aftermarket cat is much less than an OEM unit.

By the way, if you have burnt valves, a P0420 is the least of your worries.

P1148 - Closed Loop Control Function Bank 1
This mean that the closed loop control function for bank 1 does not operate even when vehicle is driving in the specified condition.

The Powertrain Control Module (PCM) or Electronic Control Module(ECM) monitor the function of the Front Oxygen (O2) sensor or Air/Fuel (A/F) sensor by comparing the signal with the Rear O2 sensor.

Symptoms:
- Engine Light ON (or Service Engine Soon Warning Light)

Possible causes:
- Harness or connectors Front Oxygen (O2) sensor or Air/Fuel (A/F) sensor 1 circuit is open or shorted.
- Front Oxygen (O2) sensor or Air/Fuel (A/F) sensor bank 1
- Front Oxygen (O2) sensor or Air/Fuel (A/F) sensor bank 1 heater

Possible solution:
- Repair harness or connector. If repair is needed
- Replaced Front Oxygen (O2) sensor or Air/Fuel (A/F) sensor bank 1


Then, possible causes are faulty harness or connectors to the air fuel ratio sensor, a faulty air fuel ratio sensor (1) or faulty air fuel ratio sensor (1) heater. Most likely yes it is just faulty sensor. Just replace this devices and reset the stored codes.

Keep us updated.

You said you changed the O2 sensors, which ones? I do believe that sensor 2 is the Catalyst efficiency monitor, it looks like an O2 but it's function is different. This sensor is behind the Catalytic converter, the O2 is in front. Bank one is the bank that # 1 cylinder is on, so the sensor that is defective is the 2nd sensor back on that sides exhaust pipe.

P0141 - Heated Oxygen Sensor (HO2S) Heater Performance Bank 1 Sensor 2

P0138 - Heated Oxygen Sensor (HO2S) Circuit High Voltage Bank 1 Sensor 2

It can be hard to say which it is, because either one will trip the the code, but in this case I'd place my bet on it being the O2 sensor because it says "warm up" - the O2 sensor has to be up to temperature (around 900 degrees) to function. The computer watches for the O2 sensor to heat up in a certain amount of time, and if it doesn't get to temperature soon enough, the computer diagnoses a faulty heater for the O2 sensor and trips the code.

For the record, this would be the secondary O2 sensor, the one after the cat. That's the one that is used to determine cat functionality and efficiency. The primary sensor, before the cat, is used to fine-tune the fuel delivery.