Three problems related to check engine light on have been reported for the 2003 GMC Yukon. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2003 GMC Yukon based on all problems reported for the 2003 Yukon.
While sitting idle my vehicle suddenly went into reduced engine power mode. I was able to get over and pull off the road and shut off the car. 5 minutes later the car started like there was no problem. Over the next few days the rep warning would show up and my car would suddenly lose power. I was crossing the road during one incident. However, when I would shut off the car and restart the check engine light would go away as would the rep warning. After a quick review online it is easy to find hundreds of people who have a similar issue. Gm will only diagnose and if the light is off when you get there there is nothing for them to do except take your money and say good luck.
Intermittently at hwy and side road speeds, truck will shut down, check engine light comes on and extremely rough idle and loss of engine power occurs. Have followed all recommended fixes but problem persists. Engine code 1516, throttle position sensor out f range +- . 05 volts. Scary problem, as this occurs without warning and causes immediate loss of speed. Many many complaints posted on the internet of this same problem but no GMC recommended fixes or assistance. Refuse to take this to a dealer and let them poke around at $95 / hour and or to throw parts at truck in hopes of correcting. GMC needs to address this potentially fatal problem.
I was driving approximately 65 mph uphill when my engine and traction light came on. My speed was immediately reduced to about 35 mph even though I tried to accelerate. I drove home about 8 miles at a reduced speed because I had my children in the truck and it was raining. I took the truck to a mechanic the next day and he replaced the throttle body. I picked up the truck that evening and as I was driving home the same thing happened again. I took the truck back to the mechanic, the check engine light and tc light was on again however he said that there was nothing wrong. His thought was to replace the throttle body again. Two replacements later, the problem remains.