Question about GMC Yukon XL
Not without you having the engine computer checked for trouble codes. Most auto parts stores will scan the computer for free in hopes of selling you some parts. The codes are a guide as to what to test.
Posted on Feb 14, 2014
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Posted on Jan 02, 2017
SOURCE: Check engine and VSC lights on
I talked to you on the live chat, and I think that you may have missed the end of my typing...
What I went on to say is that more often than not, on the 02 4Runners, the Check and VSC lights in tandem look mainly after the emission system, and, since you stated no issues during the road test, I would guess that it is a fuel issue (too full/loose gas cap). But, if you can get the vehicle scanned, I will be very glad to provide you with more and better info if you provide me with the DTC codes. That would require your guy or an autozone hookup to a scan tool. I hope my clarification helps; and the graciouness of a FIxYa rating for this question would be greatly appreciated
Posted on Nov 06, 2008
So you have a P0421.
A code P0421 may mean that one or more of the following has happened:
As far as running conditions if it performs normally, you most likely need a catalytic converter. The good part of this is there shouldn't be any abnormal running conditions, so it should be fine unless the engine is running very rich for some reason. (it will usually smell badly when this happens) However, on rare occasions the cat can get hot and melt down causing an exhaust restriction..bad gas mileage, low power, and possible fire potential, but most likely this is not the case. (this is generally speaking here and covering all the bases... )
The most common thing with P0421 that the fuel injection computer detects that the cat is not performing to federal specs an need to be replaced. You will need to have it fixed before your vehicle inspection.
Good luck and I hoped this helped you.
Posted on Dec 27, 2008
If it's the indicator that literally says "service engine soon", and not the check-engine light, then you have no worries. That's programmed to come on at set intervals to remind you that routine service may be due soon (oil change, inspection, tire rotation, etc). It's not an indication of failure. Failures will be shown by the check-engine light. That one is nothing to worry about. Your owner's manual should have a procedure to turn it off.
Posted on Dec 16, 2009
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