Check Engine Light

My CEL illuminated on my '02 TrailBlazer LTZ after revving the engine slightly to cool it down after a long climb on a hot day. I turned off the A/C compressor and the lamp illuminated. I contacted OnStar and they told me I had trouble code R1481 which related to idle speed control or something like that. I believe it was just related to the circumstances of what I was doing, and nothing is really wrong. The next morning, I noted that the engine fan wouldn't disengage, and my cruise control wouldn't work. After about 20 minutes of freeway driving, the fan disengaged and my cruise started working again. Everything has been running normal now. So, my question is how can I clear the CEL? I don't think I have a problem, but if I do I'm sure it will light again. I have 59,000 miles on my vehicle, so it's not covered by a warranty anymore and I hate to pay for a diagnosis and part replacement if it isn't necessary.

Thanks in advance.

I use a tool called a creader to read and clear the trouble codes in my '02 LT. They are all over ebay for about $40-$50. It will read the "P" trouble codes, and after showing the codes 3 times, it will erase them and turn off the check engine light. I have had to use mine to explain to a dealer that he had not fixed my trouble. If you want I can send you the description of the p1481 code from my gm stuff. It is for the cooling fan speed regulating.

After you start, drive, and turn off the truck 11 times, the light will go off if the trouble no longer exists. Its a factory default. The OBDII will still keep the code though.

The P1481 code is in reference to the cooling fan actual speed being different than the desired speed commanded by the PCM.
99% of the time there is a fault with the fan clutch assembly.
There are also PCM calibration updates for cooling fan concerns.
Clearing the codes does not fix the problem...just hides it.

The CEL only refers to problems experienced with the Emissions Control System. Either poor emissions are detected or possibly a misfire occured. The fan has nothing to do with your CEL coming on. Read the Manual about the CEL, it explains it all.

The CEL only refers to problems experienced with the Emissions Control System. Either poor emissions are detected or possibly a misfire occured. The fan has nothing to do with your CEL coming on. Read the Manual about the CEL, it explains it all.

Before you post mis information, please check your sources....here is the actions taken straight from the diagnostic chart

DTC P1481
Circuit Description
The powertrain control module (PCM) uses the cooling fan speed signal in order to determine the actual fan speed in relation to the desired fan speed. The PCM uses the cooling fan speed signal in order to reduce the cooling fan noise and in order to maintain the powertrain cooling requirements. The PCM supplies power and ground to the clutch hall effect sensor of the cooling fan clutch. The hall effect sensor returns a signal pulse through the speed signal circuit in response to the reluctor track, which is located inside the fan clutch. If during operation, the PCM detects a loss of the cooling fan speed signal, DTC P1481 will set.

Conditions for Running the DTC
The engine is running.
System voltage is greater than 8.5 volts.
Conditions for Setting the DTC
The PCM has detected a loss of cooling fan speed signal.
The above condition is present for at least 11 seconds.
Read this part

Action Taken When the DTC Sets
The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
The PCM will store the condition as Freeze Frame/Failure Records data.
The PCM commands the cooling fan clutch to 100%.

You should take your own advice. The CHECK Engine Light does ONLY refer to emission faults detected. Ther SERVICE engine light apllies to electrical and other codes. Im not arguing that code P1841 refers to the fan...that is not the point. The point is that drdoug said his CEL came on, not SEL. Yes, he may be experiencing other problems (related to engine fan and P code). I was just informing him that the CEL is emissions based, thus do not go on a wild goose chase for a problem from an indication lamp that monitors emissions. Like I said, its all in the manual, you just have to read it.

You should take your own advice. The CHECK Engine Light does ONLY refer to emission faults detected. Ther SERVICE engine light apllies to electrical and other codes. Im not arguing that code P1841 refers to the fan...that is not the point. The point is that drdoug said his CEL came on, not SEL. Yes, he may be experiencing other problems (related to engine fan and P code). I was just informing him that the CEL is emissions based, thus do not go on a wild goose chase for a problem from an indication lamp that monitors emissions. Like I said, its all in the manual, you just have to read it.

I still do not know where you are finding your information.....on GM vehicles there is a MIL Malfunction Indicator Lamp (also known as the Check engine lamp, service engine soon lamp) which is emissions based.
And a Service Vehicle Soon lamp.
The service VEHICLE soon lamp will illuminate when there is a problem with a safety type item such as a inoperative headlamp.
Not all GM vehicles are equipped with the service vehicle soon lamp operation.

And for more clarification, per the 2004 Trailblazer/Envoy owners manual page 3-40/41
Service Engine soon is the indicator lamp for U.S. vehicles
Check Engine soon is the indicator lamp for Canadian vehicles

hi,i have a 2003 trailblazer,it has 19000 k miles and my service engine light keeps coming on .i bought a creader and the codes that showed up are 1221,1271 and 1680.could anyone tell me what htese mean.thanks