Question about 2004 GMC Envoy

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Electrical power loss under engine load

I recently installed a used engine and new alternator in my 2004 Envoy XL SLS. All went well, once installed and everything hooked up I started it and it runs great. The issue is that when you put it in gear and start to accelerate its like you turned the key off (all gauges go to minimum, radio turns off, Ac turns off, etc). It also does this just by holding brake (while in drive) and giving it some gas. When you let up on the gas pedal all power returns. In park you can rev the engine and all is well (no electrical power loss). It seems that when engine is under a load then all electrical power is lost?

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  • Corey Miller
    Corey Miller Apr 21, 2014

    REPAIRED! I had a ground wire connected at the Alternator mounting bolts. Removed ground and reconnected to body (I al ready had another connected to the engine block and frame). After this all was well. Now I had to replace some stepper motors for Speedo and Fuel gauges. Then Vehicle is ready for the road!

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  • 11 Answers

It could be a throttle position sensor is the check is light on? There is also a crank position sensor that has to be re learned sometimes with engine swaps as well

Posted on Apr 13, 2014

Testimonial: "So would either one of these cause the loss of all electrical power when engine is under load?"

  • Steven Warren Apr 21, 2014

    Is the CEL on when the vehicle is running?

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