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joe, Saturn Technician
Category: Saturn
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Experience:  23+ years in the automotive repair business
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Saturn SL2: I have read the post made here about four years

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I have read the post made here about four years ago, about how to perform an obd2 driving cycle for saturn cars. The one thing that I read here that I hadn't anywhere else, was that the coolant and ambient temperatures need to be above 39˚F for the test to work and system to reset? I took my 2002 sl2 to garage day after thanksgiving for inspection. They said that there were two codes, an intermittent skip and crankshaft position sensor (which they said didn't exist, but meant that there was a bad connection for a certain thing on top of the engine, needed cleaning). The shop owner cleared the codes with his codes scanner and said that I needed to come back in a few days to re-inspect. I have driven the car over 500 miles and five of the sensors have cleared but two (catalyst and evap) still have not cleared. I read elsewhere that you had to do a 'drive cycle' and I did so twice, but it's early winter and it has been below 30˚F the whole time. Am I to assume that I won't get the system cleared until the weather gets above 36˚F and I do the cold start thing? I tried to do exactly the 'drive cycle' instructions found elsewhere, but could not be right next to a highway to do exactly what was instructed without slowing down for curves, or start/stop driving for a mile before doing the load test.


Hello and thank you for using just answer! I am here to help you with your problem, so feel free to ask questions until you are satisfied.


This is a very common problem with Saturn, there is alot of information about this particular problem on the internet, and I have come across this dozens of times in my shop, and here is why:

In order for all the ecm's monitors to ready, the vehicle has to be driven to complete the drive cycle. Two important criteria must be met before this can happen, #2 being the most important especially in a colder climate.


1. The fuel tank must be between 1/4 and 3/4 the whole drive cycle

2. The signal from the coolant temperature sensor is what allows several monitors to run, by telling the vehicles computer that the engine is at operating temperature. If your temp gauge does not reach operating temperature the monitors Will Not reset. The coolant temp sensor is a known failure on these cars (but wont set a trouble code) as is the thermostat (opens too soon to let the engine reach proper operating temperature) If they haven't been replaced I would do so. This will allow the engine to get hot enough to ready all the monitors, and it will pass inspection.

Customer: replied 4 years ago.

Thank you for your reply. I had read somewhere about the gas needing to be in a proper level for the drive cycle to complete; I had filled the gas up twice and actually filled it a few days ago and added some lucas fuel system cleaner (for the skip error) and added new plugs; the old ones were old enough so that the gap was at . 05 instead of .04) and ran it quite a while. The temperature gauge has the first small line, the large middle line, another and then red; normally the indicator goes about 1/2 an inch or more into the first zone and this last week since it's been colder it doesn't quite go quite as far but still is into the first half. Does this sound like it's not warm enough? It's not that far off from where it would be in warm weather and is very consistent in where it reads.


most of the help I have read online hasn't had the gas tank or temperature information; the fact sheet from inspection people that details air pressure, temperature and all (not suggesting the arcane drive cycle where you need a ten mile stretch of empty highway with no traffic or curves, stoplights etc), so that was a surprise and maybe I should point this information to the other 'experts' not on this site? :)



Since the temp gauge is merely a simple indicator of the engines temperature, it isn't accurate to go by it. The engine needs to reach 212 degrees F. before the monitors will run. If it is even a couple degrees below that, the monitors will not run, and a slight difference such as this will not be perceivable by looking at the gauge.

Yes the drive cycle on these saturns is ridiculous, its like jumping through hoops! But if you replace what i said to, keep the fuel tank gauge where it is supposed to be, and i didn't mention earlier but the a/c or defroster cannot be on, it will greatly reduce the length of the drive cycle.

Customer: replied 4 years ago.

Thanks once again. One last thing; I did read somewhere where someone did replace the ambient temp sensor and it sounded like they had to do a complete cycle once again (?). If the car is off when the sensor is changed, (or maybe they unhooked the battery so there weren't any shorts or anything like that) then it should be (to the monitor) that 'everything is the same' except it's now a newer part that works, and it will just finish the whole cycle instead of doing a new one? Could you tell me where the coolant temp sensor is (top, side, bottom of radiator; in front or so of engine where coolant goes into and out of engine) and where the thermostat is on my car? I think the thermostat was changed once, but I know that in general this isn't an expensive part, just wondering if it is difficult to get to both parts.


thanks again,



I have to go out shortly but unfortunately the tank is lower than 1/4 :( so the long drive won't help me after I gas up most of the way

You are exactly right about not having to do a complete drive cycle after replacing the part. There are already some monitors ready, so as long as you don't disconnect the battery or clear the codes, you will not have to do the complete cycle. Both of these items are simple to replace.

The thermostat is on the passengers side lower engine block, at the lower radiator hose. The coolant temp sensor is at the drivers side end of the cylinder head, you need to remove the big air intake tube for the air filter to get to it. It is removed with a 13mm If you can give me a little time I will get you pictures.

Customer: replied 4 years ago.

Thanks! I'll check out the pictures when I get back. Just wanted to say that all of your answers were very helpful and I am very satisfied with the assistance.

Your welcome, please don't forget to rate my answer. I do not receive credit for my work if you don't. The thermostat is in view B, held in with two 10mm bolts.


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