Engine light

BYRDYSDOG

MEMBER
2002 VOLKSWAGEN JETTA
1.8L
4 CYL
2WD
MANUAL
85,000 MILES

Engine light coming on for years. Air flow.
Oxygen sensors changes multiple times.
Aftermarket catalytic converter in 2013 65,000 miles.
Light starts coming on again.
Oxygen sensors changed multiple times.
One of two mufflers replaced.
Engine light still coming on every 2 months. We just turn it off.
Car runs perfectly.
Mileage for years has been 2000-3000 each year.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,758 POSTS

Hi,

What are the codes that show up? I need to know them to focus on possible causes. Let me know. I suspect they are related to the oxygen sensors based on what you mentioned, but I need to confirm.

If it is a problem related to the O2 sensors, let me know if you have a live data scan tool. I would like to know if you see voltage changes in the sensors and what the short-term fuel trims are.

Take a look through this link. You may find it of interest for testing.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

Joe

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Wednesday, May 26th, 2021 AT 7:09 PM

BYRDYSDOG

MEMBER
2 POSTS

I should have let you know I am a 69 year old woman who has limited understanding of car mechanics. I do know some.

The code has always been P0402. I’ve listened to the mechanics always discussing air flow and have been dealing with the same issue 7-8 years. First, oxygen sensors were replaced, then the catalytic converter. The light stayed off for about a year then started again and we replaced oxygen sensors again. I have kept up with general maintenance ie. Brakes, shocks, water pump, muffler, tune-ups, oil changes. The only other light that ever came on was an EPC light that was apparently related to the car recognizing that the engine was running. That sensor was replaced. That’s all the information I can give you. And, the car runs perfectly. I use premium gas. Thanks for any help.

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Thursday, May 27th, 2021 AT 6:11 AM

JACOBANDNICKOLAS

MECHANIC
109,758 POSTS

Hi,

A P0402 is related to excessive flow through the exhaust gas recirculation (EGR) system. If that is the case, check the EGR where it seats to the engine block to make sure the seal hasn't failed. Also, check the hoses indicated in the pic below for cracks or damage.

In the pic, I circled both the EGR valve and the hose I want you to inspect. You will need to remove the engine cover to actually be able to see these components.

The engine insulator cover is easy to remove. If you look at pic 2, it shows where it is attached. Remove that and inspect the aforementioned things.

Let me know what you find or if you have other questions.

Take care,

Joe

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