Check engine light does not turn on

FAIZUL-HASAN

MEMBER
2004 AUDI A4
1.6L
4 CYL
2WD
MANUAL
84,000 MILES

I bought a used car. Unfortunately, I could not remember whether the check engine light worked when I was inspecting the car to buy. I bought an ELM327 scanner and it was not communicating with ECU. Then I bought another scanner tool (KW820) which also responds "link error" and unable to communicate with ECU. When I was searching for this in internet someone asked to check the check engine light, then I found it does not work. Car service center mechanic still can scan my car with the laptop connected to the OBD port via a cable.

1. Why my check engine light does not turn on?
2. Why can I not scan with those scanners?

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,526 POSTS

Hello,

Can you please check fuse # 34 and # 12? Here is a guide to help you and the wiring diagram so you can see how it works:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Please run down these guides and diagrams and report back.

Cheers, Ken

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Saturday, July 14th, 2018 AT 6:18 PM

FAIZUL-HASAN

MEMBER
2 POSTS

Hello,

Thank you very much for your response.

Both fuses are in good condition. Tested visually and using fuse tester. I think Audi required a specific scanner. Because at vehicle mechanical shop my car can be scanned using a costly scanner. Later, I tried with a cheep VS450 (VW/Audi specific scanner) and I can scan my car now. I think now I can eliminate my second question about scanning the car.

Could you please help me to sort out why the CEL does not light up?

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Monday, July 16th, 2018 AT 10:28 PM

KEN L

MASTER CERTIFIED MECHANIC
47,526 POSTS

It could be just the bulb is out but before you go into the cluster to find out here is a guide to help you check for power to the bulb and the engine wiring diagrams so you can see which wire is to be tested also which fuses you should check for power as well:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Check out the diagrams (below). Please run this test and get back to us.

Cheers, Ken

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