[vivekiny2k]

experts, my "service engine soon" light was on for 2 days and then went off. a friendly auto shop checked it and founf P0135, o2 sensor heater circuit malfunction.

I found the explanation below.
OBD-II Trouble Code: P0135 Oxygen O2 Sensor Heater Circuit Malfunction (Bank1, Sensor1)

since it's off now, is it safe to wait until it reappears? how severe is it? how costly it would be to replace the sensor?

considering it's my second car, I don't need it fixed immediately.

[doomsday]

Originally Posted by vivekiny2k

experts, my "service engine soon" light was on for 2 days and then went off. a friendly auto shop checked it and founf P0135, o2 sensor heater circuit malfunction.

I found the explanation below.
OBD-II Trouble Code: P0135 Oxygen O2 Sensor Heater Circuit Malfunction (Bank1, Sensor1)

since it's off now, is it safe to wait until it reappears? how severe is it? how costly it would be to replace the sensor?

considering it's my second car, I don't need it fixed immediately.

The code means that your o2 sensor heater circuit has conked. What the heater circuit does is, that it gets your o2 sensor upto operating temperature quickly; much more quickly than the exhaust itself would do (using a heater coil)

The probable reason that it has disappeared is that once the engine heats up, the exhaust heat alone will be enough to get the o2 sensor upto operating temperature. So your o2 sensor will start working once that threshold is reached (if the o2 sensor itself is not conked).

Did you attempt to start the car after the engine has been cold? Did you get the engine check light again?

If the o2 sensor is not working, you may lose some driveability in the city (since the AFR keeps on changing frequently) and hence the ECU is not able to calculate the needed AFR quickly enough since it is not getting any inputs from the o2 sensor. Also you may lose fuel economy in the city (again the same reason) but not on the freeway/constant speed driving.
Also it will result in higher emmisions.

The cost of the o2 sensor depends on the model of the car. You can check with your local dealer. Although it is pretty costly, atleast here in India. For the OHC VTEC the o2 sensor costs close to 16K INR in the Honda showroom. Although, from outside, it is available for close to 4.5 K INR.

It may not be necessary to replace the o2 sensor in your case, since it is the heating circuit that is conked. So if you can find out the reason behind the same, it may possible to fix the problem (not sure, since u are in the States and people don't believe in jugaads)

[vivekiny2k]

Originally Posted by doomsday

The probable reason that it has disappeared is that once the engine heats up, the exhaust heat alone will be enough to get the o2 sensor upto operating temperature. So your o2 sensor will start working once that threshold is reached (if the o2 sensor itself is not conked).

Did you attempt to start the car after the engine has been cold? Did you get the engine check light again?

thank buddy, it was always on for two days. and just when i was going to take it to the mechanic, while driving it went off, and never came back on again (except for the starting check when everything comes up on for a few seconds).

it's a mitsubishi galant, and i do not want to spend money on it since i am planning to sell it off next year (after my wife has learnt driving and taken her license ).

[doomsday]

Originally Posted by vivekiny2k

thank buddy, it was always on for two days. and just when i was going to take it to the mechanic, while driving it went off, and never came back on again (except for the starting check when everything comes up on for a few seconds).

it's a mitsubishi galant, and i do not want to spend money on it since i am planning to sell it off next year (after my wife has learnt driving and taken her license ).

Hmm... Interesting. So as the saying goes: "If it ain't broke, don't fix it". So I guess whatever was shorting the o2 sensor heater circuit (if it was shorting in the first place) has gone back to normal. So I guess you can drive around without any problems. Heck, this is nothing. I have seen people driving around with completely conked o2 sensors, let alone just the heater, with the engine check light always on. So rest assured and just check with the mech in case the light appears again sometime. This will ensure that it is indeed the o2 sensor which is causing trouble and nothing else.

[vivekiny2k]

alright, couldn't take it anymore. didn't want this to mask any other problem in future, since the light was always on, so went ahead and FIYed it (fix it yourself).

O2 sensor - 79.99$
O2 sensor wrench - 9.99$
1/2" rectangular bar - 12.99 $
deep cut on forearm while trying to loosen the sensor - ouch

feeling after seeing the dash clear of all warning lights after starting the car - priceless

[sunswift]

Can anybody tell me where the O2 sensor of Maruti Swift 1.3L Petrol is located?

[ask77]

Originally Posted by sunswift

Can anybody tell me where the O2 sensor of Maruti Swift 1.3L Petrol is located?

Its on the exhaust manifold