How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask Dave Nova Your Own Question

Dave Nova
Dave Nova, GMC Technician
Category: GM
Satisfied Customers: 18865
Experience:  ASE Master Certification. GM World Class Certification
11042942
Type Your GM Question Here...
Dave Nova is online now
A new question is answered every 9 seconds

GMC GMC Envoy 2004 GMC Envoy Service engine soon light on Light

Customer Question

2004 GMC Envoy: Service engine soon light on

Light came on solid a few days ago. Owners manual said to check the gas cap and make sure it was tight. Did that, and the light remains on.

Today, I went out, and the light was off. Went driving for about a half hour, and it came back on, with reduced engine power.

What could be causing this?
Submitted: 3 years ago.
Category: GM
Expert:  Dave Nova replied 3 years ago.
Hello and thank you for using JustAnswer. My name is David and I will do my best to help you with your GMC problem.

Usually the check engine light coming on in conjunction with the reduced engine power message is due to a fault in the electronic throttle controls. This could be a problem in the accelerator pedal position sensor, or in the throttle position sensors within the throttle body. Having the codes scanned will give you a better idea of the cause of the failure.
Customer: replied 3 years ago.
Sorry....I guess I should have stated the reduced engine power light didn't come on, just that it was driving that way. I could only get up to about 40 for a while. I pulled over for a few minutes, started driving again, and then got up to 55, but after driving for about 10 minutes, it just started slowing down.

If the problem is what you stated in your answer, any idea how much it would cost to fix? Do dealerships charge to have a code scanned? How about auto part stores?

Thanks.

Dave
Expert:  Dave Nova replied 3 years ago.
The auto parts stores will scan your codes for free, dealerships will charge you a diagnostic fee (usually $50-100). If you want to have the codes scanned at the auto parts store and let me know the code numbers, I will be glad to help you figure out more what the problem is. Low engine power can be the result of low fuel pressure, electrical problems with a sensor or wiring, or could be a restricted catalytic converter. Having the codes will help us to narrow it down.
Customer: replied 3 years ago.
Hi. I just went to Advance Auto Parts, and they did a scan. Here's what came up:

P0171: System too lean...Bank 1

P0172: System too rich...Bank 1

The guy was confused on this one, as he said it should be one or the other.

P0016: Cranshaft position

Camshaft Position

Correlation Bank 1

Sensor A
Expert:  Dave Nova replied 3 years ago.
Normally you would only have either P0171 or P0172, not both. Does your Envoy have the 6 cylinder or V8?
Customer: replied 3 years ago.
6 cylinder
Expert:  Dave Nova replied 3 years ago.
It would be best to clear the codes, (the auto parts store can do this with the scan tool) then drive the vehicle until the light comes back on and have the codes checked again. You will hopefully only have one code reset and this will isolate the problem further.

If the P0171 lean code comes back, the problem will likely be a failing fuel pump. Low fuel pressure will cause this code and will reduce the engine power.

If the P0016 code comes back then the problem will be in the camshaft actuator controls. Most likely a camshaft position actuator solenoid. This is located in the passenger side of the cylinder head.

JustAnswer in the News:

 
 
 
Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.
 
 
 

What Customers are Saying:

 
 
 
  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
< Last | Next >
  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
  • Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
  • I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
  • Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
  • Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland
 
 
 

Meet The Experts:

 
 
 
  • Gary

    GMC Technician

    Satisfied Customers:

    903
    15 years gm master tech/15 years ASE master tech
< Last | Next >
  • http://ww2.justanswer.com/uploads/ggrote1/2009-06-27_031011_me.jpg Gary's Avatar

    Gary

    GMC Technician

    Satisfied Customers:

    903
    15 years gm master tech/15 years ASE master tech
  • http://ww2.justanswer.com/uploads/CA/caprio23/2011-12-13_155550_20111213105344.64x64.jpg Anthony's Avatar

    Anthony

    ASE Certified Technician

    Satisfied Customers:

    476
    ASE Master Automobile Technician with over 20 years exp.
  • http://ww2.justanswer.com/uploads/Rocket2005/2009-09-13_133703_jack.jpg car tech's Avatar

    car tech

    ASE Certified Technician

    Satisfied Customers:

    448
    25 year master tech and shop owner
  • http://ww2.justanswer.com/uploads/2P/2paulm/2012-4-4_183431_justabswer.64x64.jpg Paul M ASE Master's Avatar

    Paul M ASE Master

    ASE Master Tech

    Satisfied Customers:

    187
    ASE Master Tech 20+ Years
  • http://ww2.justanswer.com/uploads/MU/muddyford/2012-6-13_1204_1.64x64.png Chris (aka- Moose)'s Avatar

    Chris (aka- Moose)

    GMC Technician

    Satisfied Customers:

    89
    16 years of experience
  • http://ww2.justanswer.com/uploads/AM/amedee/2013-10-24_23656_Amedee1.64x64.jpg Amedee's Avatar

    Amedee

    GMC Technician

    Satisfied Customers:

    360
    ASE Master Technician advanced level specialist
  • http://ww2.justanswer.com/uploads/DT/dt69nova/2012-6-15_234154_pic1.64x64.jpg Dave Nova's Avatar

    Dave Nova

    GMC Technician

    Satisfied Customers:

    2262
    ASE Master Certification. GM World Class Certification