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Instrument panel problems along with intermittent starting

Discussion in 'Chevy Trailblazer Forum (GMC Envoy)' started by jakez, Dec 26, 2013.

  1. jakez

    jakez New Member

    I have a 2004 Trailblazer, Which in the past year has started, not starting on occasions. It is not a battery problem or a loose cable problem. When the key is turned over there is no sound of relays, or clicking of the starter, but all the dash lights indicate power. If I let the vehicle sit for a period of time it will start fine. It may go for three weeks and happen again without warning. On other ocassions the vehicle starts, runs fine, but the speedometer and the tach. peg out, and none of the other instruments come on. If I start and stop the engine repeatedly the tach and the speedometer work their way back to their correct position incrementally with each restart. The other instruments will also start working properly.
    As I'm sure everyone else is, I am looking for the cheapest fix along with what the problem may be.
    Has anyone else had the same problems.
    Help!!!! Thanks Jake
  2. TRPLXL2

    TRPLXL2 Epic Member 5+ Years 1000 Posts Platinum Contributor

    Welcome to the club!!

    My on;y thought would be the BCM, because it controls both the starting process and the interior controls.
  3. Camaro69car

    Camaro69car Member 1 Year 100 Posts

    If it's anything like the Silverado's, Check all your grounds and clean them up. (If your Speedo reads 80 when your sitting still)
  4. geraldc

    geraldc New Member

    my 1997 chev truck 1500 2 wd 350 new engine 15,000 miles has many electrical problems. At time all rear lights go out then come back on, at will. So I applied a new brake light system, not part of truck system, so have brake lights when needed. Been in shop 3 times for these light problems, fixed 3 times before new brake light system applied. Now truck lights system work except for brake lights, no wires cut either.
    Now oil pressure gauge reading 60# normal drops down, not to zero, just drops, no reading, when brakes are applied then returns to 60# when brakes released. Did this for about 2 weeks, then stopped working at all, stays all the way on right side of gauge, not zero side.
  5. jakez

    jakez New Member

    OK< What's a BCM
  6. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    The BCM is the Body Control Module (sometimes called the Truck Control Module), it looks after the functions related to the body of the truck, like lights, radio, etc. I think @TRPLXL2 was talking about the PCM (Powertrain Control Module). One of it's functions is to look after the starting of the truck.

    Before you run out and buy a new module, try the cheaper things. There is a relay that is used for starting, try swapping it with a relay that is the same.

    It could be the starter,

    You say you know it isn't the battery, or a cable, but before I believe you, you need to tell me how you have reach this conclusion.

    And, the last thing, and one that is a known failure item on the Trailblazers, is the ignition switch. A new one is around $30. A lot of people reach for a new ignition switch first, because it is one of those items the will fail and the new one is cheaper than the cost of diagnosis.


    @geraldc, are you looking for help, or using your problem experience to help the op?
  7. jakez

    jakez New Member

    I reached the conclusion that the battery was not bad when I tested the battery while the truck would not start. It registered a full charge. When the truck did start there was no hesitation that a weak battery would present. I also checked the condition of the connections of the cables, and no evidence of corrosion. I did clean all connections as well. I realize a cable could be bad without seeing any evidence. Should I give cables a continuity check? I will try a new ignition switch as you suggested, but will that account for the instrument panel problem? Are the two related ?
  8. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    Only from the point that ignition switch provides switched power to the dash. I must say, having the needles peg is an unusual product of a bad switch. In an other [MENTION=51590]Pikey[/MENTION] suggested a battery disconnect to reboot a ECM/PCM, this might also help you.

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