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  1. R

    A/C Always On?

    Tae is saying that the compressor clutch is always powered even when key is off. It definitely should not do that. There is a relay that turns on and off the power to the clutch. The relay is controlled by the dash mounted AC controller. Until you get this fixed, install a toggle switch hanging...
  2. R

    Solved: What is this plug - driver footwell area

    Or does that provide connections to the steering wheel mounted controls?
  3. R

    Need to know fuel pressure with engine running. 5.3 Flex fuel Z engine.

    Are you having a problem with the way your truck is running? Obviously you could replace the fuel pump or the regulator and bump up the fuel pressure a little, but if it runs ok under load what would that accomplish?
  4. R

    Rough Idle

    Have you checked fuel pressure? Fuel pump in the tank, fuel pressure regulator on top of engine can be culprits. There is an idle air controller (IAC) that can fail. The PCM reads the crank sensor to determine engine rpm, then adjusts the idle rpm to match the programmed idle number. If I was...
  5. R

    Tracing wiring for EVAP p0449

    Is it possible that the tank pressure sensor is malfunctioning? It is my understanding (which may be wrong) that the vent valve is controlled by that sensor.
  6. R

    How can one tell the difference in ignition Coils?

    That aluminum fin thing is a heat sink. It helps to reduce the internal operating temperature of the coil.
  7. R

    02 Tahoe Heavy Misfire P0300

    I am surprised that temp sensors were not changed- Intake air and coolant temp sensors can affect the fuel mixture and are not real expensive. If the PCM thinks the engine is real cold, the mixture will be extra rich. Have you checked the spark plugs to see if any of them are blackened to see...
  8. R

    2000 Yukon with P0300 error code

    Check the wiring harness connections to the coil packs for any corrosion. How old is your battery. Have your alternator checked for a.c. output. If even one of the diodes in the alternator has failed, strange things can happen (unlikely cause).
  9. R

    Failed Emissions

    Good comment, Ian. Thank you for clarifying about the MIL command. The evap code can be the purge valve starting to not seat correctly. It is found under the hood connected to the intake manifold. If you drive on dusty roads, dust gets sucked into the evap system whenever the purge valve is...
  10. R

    MN8 : 4-speed HD Automatic Transmission- 4L85E Running Temps

    Good job-that high temp is hard on the fluid, and hard on the clutches
  11. R

    Wheel Bearing Brand Recommendations and Shocks

    Dave, good logical analysis. That is exactly what happens. When the wheel bearing wears over time, small bits of steel contaminate the grease, which causes erratic sensor readings confusing the ABS system. The fix you did works for a while until more contaminated grease gets on the sensor. Even...
  12. R

    High idle at start up

    That is a strange symptom. Disconnect the wire connector to make sure there is no damage to the contacts. If it continues, something is amiss. Could you have left something unconnected such as intake air temp sensor?
  13. R

    Neutral safety switch help

    Sure sounds like a cheap replacement from you know where. I suggest a GM oem or other quality unit (Rockauto.com is a good source-They sell a wide variety).
  14. R

    C0455 error after replacing intermediate shaft

    The sensor itself works a lot like a cam or crank sensor. The shaft is monitored for movement from the straight ahead position. The position of the wheel is then compared with data from the yaw sensor which is an accelerometer that tries to figure out if you are going where you want to go. So...
  15. R

    Heater being weird - thoughts?

    In certain modes (defrost) the AC compressor will run even when asking for heat. This will obviously cause the air to be even colder. I don't recall if the snowflake symbol shows up on the display when in that mode. It is possible that your engine coolant thermostat is sticking open as you seem...
  16. R

    Side mirrors

    Sometimes strange vehicle behavior can be fixed by removing either battery cable for 5-10 minutes. Another possibility is a battery that is getting close to replacement time. I have fixed strange symptoms that have no logical cause by installing a new battery. I believe that there can be poor...
  17. R

    Steering whining only when turning right?

    The whining is caused by resistance in steering system, so I think you have something binding. I assume that the fluid level is correct on the dip stick.
  18. R

    Rough Idle

    Smart idea to do the filter and plugs. Basic maintenance is not out of fashion yet!
  19. R

    Failed Emissions

    During emissions testing, the PCM is asked to turn on and then turn off the "check engine light" or "maintenance indicator lamp" by issuing a command. So MIL CMD failure means the test technician (term used loosely) did not see the lamp illuminate when commanded to. It could also indicate a...
  20. R

    What do you consider normal oil pressure?

    My 2005 tahoe has 40psi at idle. Those that have lower pressure could have a broken o-ring on the oil pickup tube. Or less likely, oil pressure regulator with a weak spring, worn oil pump gears or worn main bearings. All oil filters have a bypass valve, so that if the filter gets clogged engine...
  21. R

    EVAP valve P0446

    Thanks for sharing about this--pressure sensors like this are made very cheaply using nonmetallic diaphragms which after years of exposure to either gasoline fumes, vacuum or pressure get brittle and either crack or do not move properly as the pressure changes.
  22. R

    A/C low side pressure erratic

    Over time the compressor seals start to wear. This eventully causes a slow freon leak, giving the varying pressures you are seeing. If the leak is small, you can just add freon periodically. No permanent fix, except new compressor. You could do a leak test around the components, but if it is a...
  23. R

    Battery good, fuel pump primes, turn key NOTHING (no clicks). Solved with out and into drive again?

    I agree-that delayed gear indication is the red flag.
  24. R

    Strange stuff with hydro-boost

    One thought on the hydroboost: an advantage is that the connection between engine vacuum and braking system is gone. Any mod that simplifies the running of an engine (by eliminating the vacuum booster) and troubleshooting is a good one.
  25. R

    No codes, power loss

    Knock sensors and intake manifold gaskets ought to be a maintenance item after a lot of miles. The sensors are in a bad place, especially if the vehicle is in a cold weather state. Slush and salt getting into any electrical connection is a problem. Intakes on these engines are known problem...

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