SES light still

2000 Saturn SC2. I've been plagued by SES lights for some time now. Let me go back to the beginning. When it first happened several months ago I brought the thing to a guy I know who claimed to be a mechanic. He checked the codes and P0440 and, if I can remember, the other was either P0037 or P0137. I remember the 37. He claimed to fix the (37) problem (replaced the Ox sensor after the cat converter) but could not the 440. So I drove it for a while until I got sick of the light (that promptly came back by the way). I then brought it to a reputable service garage and they found both P0037 and P0440. They tested the circuit and sensor that caused the P0037 and found them to be ok but found the emissions 10 amp fuse blown. Replace the fuse and retested it and it would not bring back P0037. For the P0440 they said I should bring it to Saturn because it was something a Saturn dealer should look at. I drove it for about 3 days then the light came back on So I went to visit Saturn. They found a P0133 and replaced a $92. ox sensor. They did not find the P0440 code and seemed puzzled by the other garages finding. So I paid the bill and went on my merry way. Drove it for over 300 miles including to Chicago and back no SES light. I then filled the tank to see if I still get nearly 40 mpg on the highway and the stupid fuel pump did not shut off like it should and gas spilled all over the place. After starting the engine to leave the gas station the SES light went on again. I was fit to be tied. Called Saturn and they said over filling the tank can cause the light to come on. It should turn off eventually. In the mean time I bought a code scanner so I could start diagnosing this stuff myself. The reader came today and it gave me 2 codes both P0037 and one said pending. I checked the emissions fuse and it was blown. Replaced the fuse and erased the codes. Ran it and the fuse blew again. Before I waste another dollar on the so called experts is there anyone that can shed some light on my situation? Thanks in advance.

put a bigger fuse in. if you have a 10 amp.. replace it with a 15amp.. that will keep it from blowing.. if it blows again then it sounds like you have a short somewhere in the wiring.

put a bigger fuse in. if you have a 10 amp.. replace it with a 15amp.. that will keep it from blowing.. if it blows again then it sounds like you have a short somewhere in the wiring.

NO, NO, NO, NO, NONO!!!!! Do NOT FOLLOW THIS ADVICE!

Fuses protect components of a circuit. If a circuit has a 10 amp fuse that means there are one or more components in that circuit that will be damaged if the current exceeds 10 amps. By putting in a higher rated fuse, you are allowing higher current to damage a component. Do not EVER put in a higher rated fuse than what is supposed to be there.

There is no P0037 code so it must have been a p0137 code, "O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)" This is the o2 sensor after the catalytic converter. This o2 sensor does not effect how anything is running or performing, it is simply a check on the catalytic converter to confirm it is operating properly. Probably a bad o2 sensor but this could indicate a bad catalytic convertor.

A P0440 code is "Evaporative Emission Control System Malfunction" This could be caused by a number of things including a bad or loose gas cap or overfilling the fuel tank among other things.

A P0133 is "O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)" This is the first o2 sensor, before the catalytic converter. What this means is that the o2 sensor is not responding quickly enough for the PCM to be happy (aka lazy o2 sensor).
Usually replacing the sensor is called for here.

i wold consider climbing under the car to check the intigrity of the wires to the rear O2 sensor, make sure there isn't an exposed wire making contact to sheetmetal or the exhaust.

I never planned to put in a bigger fuse. Been working with electricity and electronics since 3rd grade. I haven't had a chance to work on this yet but my first step is to get under the car and look at the wires going to the aft ox sensor. When I was under there changing the oil recently I noticed the first wannabe mechanic left the wires going to the sensor hang and were actually hitting the right drive axle. I secured them up at the time but didn't assume that's where the SES light was coming from. I don't think either of the sensors are bad, they've both been replaced. I keep you all updated, and thanks for the replies.

Oh, one more thing there is a P0037. I just confirmed it on my scanner. According to the Saturn manual it's "Shorted condition in downstream oxygen sensor heater control feedback sensing circuit". All the more reason to look at the wiring.

Hmmm, I couldn't find a reference to a p0037. Maybe I didn't look hard enough. :grinyes:

I guess it takes someone with no auto mechanics training to buy his own code reader and do it himself. Turns out the 2 wires coming off the purge solenoid were pinched between a large stiff wire cluster and the starter. One of the wires was showing copper. Taped it up, protected it with some plastic conduit and rerouted it slightly so it couldn't get pinched again. Replaced the fuse and cleared the codes. All fixed. I am so happy.

So the bigger question. Could this short circuit have caused the first codes? Like P0440. Could the short have made it appear the ox sensors that were replaced look bad? I spent over $300 on diagnostics and sensors only to spend less than $1 on electrical tape and conduit to finally bring it to an end. Oh and I spent $72 on Amazon.com for a code scanner on closeout. It already paid for itself.

Thanks to all replies for the help.

Let's have some fun.

Your SES light comes on:

- First mechanic diagnoses and replaces an ox sensor, $81.
Light comes back on the next day.
- Second mechanic diagnoses and replaces a fuse, $73.
Light comes back on 3 days later.
- Go to Saturn, they diagnose and replace the other ox sensor, $175.(ouch)
Light comes back on 12 days later.
- Buy your own code scanner and fix it yourself... PRICELESS.