Reasons for "service engine soon" light coming on?

Question

I have a 2003 Chevy Trailblazer and recently, that light comes and goes. It's on for a few days, then off for a few days. Other than that, I don't notice anything strange, like weird sounds or weird performance in the vehicle. I do plan on taking it in even though that will cost me at least $60 just for them to hook it up to the computer and see. I guess better safe than sorry. But, there are people that keep telling me not to take it in and waste my money and that it's this or that.

Does anybody know of any legitimate reasons it would come on and then turn off like that? Maybe I can have my husband try certain things before actually taking it in? Thanks in advance.

Answer 1

If your gas cap is not on tightly, it can cause this.  Check and see if it goes on and off at the times you get gas.

If that isn't it, you can take it to Auto Zone while the light is on and they will scan it for you.  That will at least give you an idea of the problem before you take it to the mechanic.  Or it might be something you can easily fix yourself.

Answer 2

to many to know

when they read it post it here so we can help you with advice about whats wrong

Answer 3

There are ALOT of things that can cause your engine light to come on, there's no point in fixing things that don't need fixing.

Take it into a mechanic and get it scanned before you replace any parts you don't need to replace.

Answer 4

There are a few things that can trigger the "service soon" light to come on. Mileage. worn vacuum lines and just a host of other normal wear and tear conditions.

In any case, there are more reasons to have a qualified tech look at it than to just ignore it. The up side to this is better gas mileage due to maximum engine performance. You could recover that $60.00 in less time than you might guess.

Answer 5

a car is a complicated thing. My philosophy is take it to the manufacturer and have them scope it out, if it is something serious then you'll have nipped it in the bud. If it's something silly like a broken warning light then you might be able to get any charges waived as good will.

Answer 6

Could be any of hundreds of reasons, all legitimate. That's why they make code readers. You could have it read for free at most Auto Parts stores, or buy a code reader for yourself for about $100. Just don't make the mistake that many do, that just because the code says something about the EGR valve for instance, means that just changing that part will fix it. The code only gives you clues, it doesn't tell you exactly what to do.

If you get it read for you, or read it yourself, make sure you get the actual code, not just the description, and post it here, and e-mail it to me to make sure I see it.

If the light is on during reading, you will definitely get a code, but it is possible to get one when the light is off too. Hard to say for sure, but more likely the more it's been on, and the longer it's been on.

If it were a MIL (maintenance indicator lamp), it wouldn't go out unless you reset it.

Answer 7

ill give you the small version of a list that i have compiled.

circuit malfunction

p0101 maf or vaf circuit range performance problem

p0102 maf or vaf circuit low out input

p0103 maf or vaf circuit high output

p0104 mass or volume air flow circuit intermittent

p0105 manifold absolute (map) or barometric (baro) pressure circuit malfunction

p0106 map or baro circuit range performance problem

p0107 map or baro circuit low range

p0108 map or baro circuit high range

p0109 map circuit intermittent

p0110 intake air temperature (iat) circuit malfunction

p0111 iat circuit circuit range performance problem

p0112 iat circuit low input

p0113 iat circuit high input

p0114 iat circuit intermittent

p0115 engine coolant temperature (ect) circuit malfunction

p0116 ect circuit range performance problem  

p0117 ect low input

p0118 ect high input

p0119 ect circuit intermittent

p0120 throttle position (tp) circuit malfunction

p0121 tp circuit range performance problem

p0122 tp circuit low input

p0123 tp circuit high input

p0124 tp circuit intermittent

p0125 excessive time to enter closed loop

p0126 insufficient ect for stable operation

p0128 coolant temperature below thermostat regulating temperature

p0130 oxygen sensor 1, bank 1 circuit malfunction

p0131 oxygen sensor 1, bank 1 low voltage

p0132 oxygen sensor 1, bank 1 high voltage

p0133 oxygen sensor 1, bank 1 slow response

p0134 oxygen sensor 1, bank 1 no activity

p0135 oxygen sensor 1, bank 1 heater malfunction

p0136 oxygen sensor 2, bank 1 circuit malfunction

p0137 oxygen sensor 2, bank 1 low voltage

p0138 oxygen sensor 2, bank 1 high voltage

p0139 oxygen sensor 2, bank 1 slow response

p0140 oxygen sensor 2, bank 1 no activity

p0141 oxygen sensor 2, bank 1 heater malfunction

p0142 oxygen sensor 3, bank 1 circuit malfunction

p0143 oxygen sensor 3, bank 1 low voltage

p0144 oxygen sensor 3, bank 1 high voltage

p0145 oxygen sensor 3, bank 1 slow response

p0146 oxygen sensor 3, bank 1 no activity

p0147 oxygen sensor 3, bank 1 heater malfunction

p0150 oxygen sensor 1, bank 2 circuit malfunction

p0151 oxygen sensor 1, bank 2 low voltage

p0152 oxygen sensor 1, bank 2 high voltage

p0153 oxygen sensor 1, bank 2 slow response

p0154 oxygen sensor 1, bank 2 no activity

p0155 oxygen sensor 1, bank 2 heater malfunction

p0156 oxygen sensor 1, bank 2 circuit malfunction

p0157 oxygen sensor 2, bank 2 low voltage

p0158 oxygen sensor 2, bank 2 high voltage

p0159 oxygen sensor 2, bank 2 slow response

p0160 oxygen sensor 3, bank 2 no activity

p0161 oxygen sensor 3, bank 2 heater malfunction

p0162 oxygen sensor 3, bank 2 circuit malfunction

p0163 oxygen sensor 3, bank 2 low voltage

p0164 oxygen sensor 3, bank 2 high voltage

p0165 oxygen sensor 3, bank 2 slow response

p0166 oxygen sensor 3, bank 2 no activity

p0167 oxygen sensor 3, bank 2 heater malfunction

p0169 fuel composition sensor

p0170 fuel trim (ft) malfunction

p0171 system too lean, bank 1

p0172 system too rich, bank 1

p0173 fuel trim (ft) malfunction, bank 2

p0174 system too lean, bank 2

p0175 system too rich, bank 2

p0176 fuel composition sensor circuit malfunction

p0177 fuel composition sensor range performance

po178 fuel composition sensor low input

p0179 fuel composition sensor high input

p0180 fuel temperature sensor circuit malfunction

p0181 fuel temperature sensor range performance

p0182 fuel temperature sensor low input

p0183 fuel temperature sensor high input

p0184 fuel temperature sensor circuit intermittent

p0185 fuel temperature sensor 2 circuit malfunction

p0186 fuel temperature sensor 2 range performance

p0187 fuel temperature sensor 2 low input

p0188 fuel temperature sensor 2 high input

p0189 fuel temperature sensor 2 circuit intermittent

p0190 fuel rail pressure sensor circuit

p0191 fuel rail pressure sensor circuit performance

p0192 fuel rail pressure sensor circuit low voltage

p0193 fuel rail pressure sensor circuit high voltage

p0194 fuel rail pressure sensor circuit intermittent

p0195 engine oil temperature sensor

p0196 engine oil temperature sensor performance

p0197 engine oil temperature sensor low voltage

p0197 engine oil temperature sensor high voltage

p0198 engine oil temperature sensor intermittent

p02 fuel and air metering

p0200 injector control circuit

p0201 injector circuit malfunction, cylinder 1

p0202 injector circuit malfunction, cylinder 2

p0203 injector circuit malfunction, cylinder 3

p0204 injector circuit malfunction, cylinder 4

p0205 injector circuit malfunction, cylinder 5

p0206 injector circuit malfunction, cylinder 6

p0207 injector circuit malfunction, cylinder 7

p0208 injector circuit malfunction, cylinder 8

p0209 injector circuit malfunction, cylinder 9

p0210 injector circuit malfunction, cylinder 10

p0211 injector circuit malfunction, cylinder 11

p0212 injector circuit malfunction, cylinder 12

p0213 cold start injector 1 malfunction

p0214 cold start inje

Answer 8

The "service enging soon" light is on a timer and comes on at regular intervals to get you to perform regular scheduled maintenance.  Not to be confused with the "check engine" or MIL (malfunction indicator lamp)  which only comes on for an emissions related problem.  You can take it to any parts store to get the codes read for free.