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Check engine light

Can a bad, in need of replacement, muffler on my 99 Toyota 4 Runner cause the check engine light to remain on?

Most auto parts stores will scan for trouble codes free. Go to a parts store, have them check the computer, and find out why the light is on.

Don’t guess. Find out. Then you’ll know for sure and you won’t waste money chasing phantoms.

Yes, but so could many other things. Start by getting the CEL read as mcparadise suggested. That CEL is like the kid in class waving their hand to get the teacher’s attention because they know the answer. Ask the kid that knows (the CEL code).

***Can a bad, in need of replacement, muffler on my 99 Toyota 4 Runner cause the check engine light to remain on? ***

In general, no. The last sensor that the computer talks to is the downstream Oxygen sensor near the catalytic converter a couple of meters forward (upstream) from the muffler. But just maybe a plugged up muffler or some other weird problem is affecting things.

As others have suggested, get the codes read. There’s a fair chance they are telling you about something that you want to know about.

An exhaust leak near or upstream from the O2 sensors can trigger the light.

Like others say, read the code(s).

Muffler set “check engine” light NO. Your car could run without a muffler and not set a “check engine” light.

When these CEL’s began cluttering up dashboards, people routinely removed the bulb or taped over the annoying light. Today, people will pull over and call AAA for a tow truck if the light comes on, certain their car will be destroyed if they drive it another mile…They will spend four figure sums trying to extinguish a light that nags about low EGR flow or evap system purge fault. Amazing, truly amazing…