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Bob, Auto Service Technician
Category: Car
Satisfied Customers: 4087
Experience:  40 year GM Tech. +30 Certified. ASE Master Tech.(expired, retired) Medium Duty, Heavy Line, Retired
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how to reset computer on a 2004 gmc envoy 4.2 eng.

Resolved Question:

i had service done to my vechicle and now service eng. light comes on for 75000 mile service
Submitted: 8 years ago.
Category: Car
Expert:  Bob replied 8 years ago.
Hello, normally the service engine light comes to tell you that the computer has sensed a problem with one of the sensors in the sensor string that monitors the engine or emission system. If the light came on shortly after you had it serviced, it i possible that someone left something unhooked or disturbed a connector when they did the service work. About all you can do is try unhooking the battery for a few seconds and holding the cable ends together to see if it will clear the code or not. Be sure the radio is turned off, before you unhook the battery as you don't want it going into the theft lock mode. If this clears the light and it stays off you are all set. If the light comes back on, then the system is going to have to be scanned with a tool called a TECH 2, this is a special hand held computer that GM dealers use to access and diagnose the on board computers on your car. If it is something caused by the service, they should be happy to take care of it. If you have doubts, take it by any Auto Zone or Pep Boys and they will scan the system for you as a free service and from there you should have an idea of what is needed. If you still have concerns, just post the codes they find here and we can track down the code and problem from here. Thanks
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