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Ron Z.
Ron Z., - GMC Tech -
Category: GMC
Satisfied Customers: 18550
Experience:  18+yrs experience. State Inspector & GMC Diagnostics/Repair
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Just got my truck from shop and service emission system

Customer Question

just got my truck from shop and service emission system still on I was told to drive it for 40 miles atleast 65mph it should clear. its been 65 miles ago and has not cleared
Submitted: 1 year ago.
Category: GMC
Expert:  Ron Z. replied 1 year ago.

Do you happen to know the "p-code" that was retrieved from the on-board computer?

Customer: replied 1 year ago.
no they said there was no code just got it back from having fuel pump and injectors changed
Expert:  Ron Z. replied 1 year ago.

Ok. If the engine light is on, there has to be codes stored. The light will not set for any other reason. First, as normal shop work flow, after the repair has been made, the light should have been cleared with the use of a scan-tool. It's just normal operating procedure. If the light was not cleared with the use of a scan-tool, then IF there are no problems in the system, the light "should" clear itelf within 50-75 miles of normal city/highway driving. Sometimes closer to 100 miles. SO, I'd suggest some highway miles be put in, making sure to cruise at a steady rate 55-65mph for a few minutes and then some no-brake deceleration. If the light is still on after 100 miles... there is still a problem and the correct repair has not yet been made. At that point, we'll need the Diagnostic Trouble Codes (aka "P-Codes") read from the on-board computer. These p-codes will point in the direction of the part/sensor that has the problem and from there the correct diagnosis and repair can be made. You can have these p-codes read FREE (except in California) at any local "big chain" part store (ie. AutoZone, PepBoys, Advanced, etc). If my answer has helped you, please help me by leaving a rating using the stars at the top of this page or accept the answer so I may be credited for this Q&A. If you cannot rate or do not see the rating stars, please let me know!

Expert:  Ron Z. replied 1 year ago.

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Expert:  Ron Z. replied 1 year ago.

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