2004 Trailblazer LS 4x4; 82K miles; owned from 10K. After reading many posts both here and at TrailVoy regarding my above referenced "problems", I purchased an Actron CP9580A scantool. Only discovery found was low coolant temp, so replaced the thermostat, CTS, radiator hoses and anti-freeze. Mileage has improved as I would expect with higher coolant temps, 195-205 on the Actron. However, I still have experienced the 900 rpm idle and P0171 code. Have replaced the spark plugs, cleaned the TB, replaced the TB gasket, sprayed all around the intake manifold with carb cleaner, all vacuum hoses are sound and properly connected, new air filter, new fuel filter and replaced the upstream O2 sensor awhile back. The other two common denominators with the high idle/P0171 code are use of the cruise control for extended periods and altitude change, Bay Area to Tahoe (100 to 7,000 feet) and return. The '04 TB does not appear to have a barometric pressure PID as I have seen on some other vehicles. And I cannot imagine how using the cruise control could affect these issues. I only mention it because someone else over at TV had shared the same problem. Also, I had my tranny serviced at the dealer recently and asked for any PCM updates. They said mine was current.
So, any ideas or suggestions for further diagnosis?
So, any ideas or suggestions for further diagnosis?