My service engine light is on. The code is P1481.

P0440 = evaporative emissions system leak...check gas cap , hoses

P0151 = evaporative emissions systems sensors (O2 sensor, usually the O2 sensor between engine and catalytic converter on Cylinder Bank 2 (the side of the engine with the even-numbered cyclinders, usually left side from under hood if engine is mounted axially, rear of engine if it is mounted transversely)

P1481 = cooling fan speed

See attached picture for location of temp. sensor, but that code has nothing to do with temp sensor. The speed of the fan does not agree with the commanded speed, you may have another bad fan clutch.

I have a service engine soon light and the code that appeared when check is 1481, do you know what this means?

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This is almost always the fan clutch. Years 2002-2004 are prone to fan clutch failure. Also a good idea to check out the harness for any frayed wiring.

USUALLY THAT MEANS YOUR OXYGEN SENSORS, BUT I WOULD DOUBLE CHECK I WOUNT LIKE TO SPEND OVER $130 ON THAT, THOSE MEASURE THE EMMISION CONSUMPTION AND ADJUST THE PROPER GAS NEEDED TO OPERATE ENGINES EMMISION PROPERLY. ALSO WHO EVER TOLD YOU THAT THEY ALSO SHOULD OF TOLD YOU ABOUT THE BLIND CODES THAT COME UP BUT ITS ACTUALLY SOMTHING ELSE LIKE A CLOGGED CATALIC CONVERTOR ALSO. NEED TO GET A SURE CODE SCAN OR THE ACTUAL CODE NUMBER. USUALLY ITS LIKE STARTS WITH A LETTER "P" FOLLOWED BY A 4 NUMBERS

TSB#05-06-02-012B: Service Engine Soon (SES) or Check Engine Light On, DTC P0480, P0526/P1481/P1484 Set (Replace Engine Cooling Fan Wiring Harness) - (Oct 19, 2006)
Subject:
Service Engine Soon (SES) or Check Engine Light On, DTC P0480/P0526/P1481/P1484 Set (Replace Engine Cooling Fan Wiring Harness)
Condition
Some customers may comment that the Service Engine Soon (SES) or Check Engine light is illuminated. This condition may be intermittent and upon investigation, the technician may find either DTC P0480, P0526, P1481 or P1484 set.
Cause
This condition may be caused by the cooling fan harness chaffing against the plastic guide it routes through. This contact may damage the insulation of the wires enclosed in that harness.

Correction
Replace the engine cooling fan harness using the procedure listed below.

1. Remove the cooling fan. Refer to the Cooling Fan and Shroud Replacement procedure in the Engine Cooling sub-section of SI.

2. Place the cooling fan assembly on a bench.
Disconnect the harness electrical connector from the cooling fan clutch.

3. Remove the harness from the plastic guide while feeding the wires out of the slot.

4. Before installing the new harness, wrap the affected area on the wires with electrical tape to keep the protective sleeve in place. Be sure to keep the tape approximately 25 mm (1 in) away from the connector so the wires can be fed into the slot.

5. Feed the wires into the slot and install the harness to the plastic guide.

6. Connect the harness electrical connector to the cooling fan clutch.

7. Install the cooling fan. Refer to the Cooling Fan and Shroud Replacement procedure in the Engine Cooling sub-section of SI.

Part Number 89024920

Description
Harness Assembly, Engine Cooling Fan Wiring
Thank you for using fixya.

Hi:
The gas cap is usually a good suspect in this case, but to figure it out, you need to have your code scanned to figure out what is causing the light. Most auto parts stores will scan it for free, so give them a shot

Service Engine Soon (SES) or Check Engine Light On, DTC P0480, P0526/P1481/P1484 Set (Replace Engine Cooling Fan Wiring Harness) #05-06-02-012B - (10/19/2006)

Models:2004-2006 Buick Rainier
2002-2006 Chevrolet TrailBlazer, TrailBlazer EXT
2002-2006 GMC Envoy, Envoy XL, 

Some customers may comment that the Service Engine Soon (SES) or Check Engine light is illuminated. This condition may be intermittent and upon investigation, the technician may find either DTC P0480, P0526, P1481 or P1484 set.

This condition may be caused by the cooling fan harness chaffing against the plastic guide it routes through. This contact may damage the insulation of the wires enclosed in that harness.

Replace the wire harness: 
Part Number 89024920 Description Harness Assembly, Engine Cooling Fan Wiring

Good luck and keep me posed. 

Read this. Fan.

What is the code? Could simply be a loose gas cap setting the light off. If the light goes off after several engine run cycles, it's not a consistent problem. Blends may affect performance but shouldn't hurt the vehicle if you are using the correct octane. Your owner's manual defines the required octane.
Some parts stores scan your vehicle for free in hopes you'll buy parts to correct whatever the code is. Be careful as codes mean more than 1 thing usually. Get the code from the store and post from there.