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Always Curious

No Power To Diagnostic Port, Check Engine Light, Etc

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Hey there! This is a long story so I'll try to make it short, but probably leave out important details so please bare with me. (bear? bare? lol)

Friend's car. 2001. Just had used motor with 50k miles put in. Sounds and runs great.

Problem 1: Took it to smog station. Everything passed EXCEPT the check engine light got caught on the test.

Problem 2: Shop that did the work was across the parking lot so we took it over there to see if they'd help find out what was wrong. Wasn't the motor or emissions, cuz that part passed. When they got the machine to do a diagnostic, they discovered no power to the port. Mechanic checked fuses, and anything else that would apply. Nothing there...and the lighter worked.

Question: Would electrical problems with radio cause check engine light? Radio might be wired wrong.

Question: Without buying a book and figuring out what could be wrong, how do restore power to the diagnostic port? It wasn't a fuse.This could take years without a pro with past experience with this particular issue.

Question: What is the 10 amp fuse for the Engine' for? We did discover a 7.5 in that slot....but this was later after giving up on trying the smog/mechanic/retesting/DMV/yadayadayada.

I don't have all the year/make/model info except what I posted here. I do know the car is a 2001 but they used a 2000 motor. The check engine light did come on indescriminantly prior to the motor swap, never staying on for long or turn the car off and on and it would stay gone for days.

Let me add, the smog station said to drive it for a few days so it resets itself. Problem with that is, the car's tags are expired...long overdue so DMV won't give temp permit for window. not an issue to resolve...just want some info on bigger problem.

Thanks to everyone for even considering the dilemma! Any questions or advice is great appreciated!

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KL-G4 Automatic Transmission DLC

The diagnostic link connector (DLC) port gets power from the 40A BTN fuse under the hood, then to the 15A ROOM fuse in the joint box (located by the drivers foot). It receives 12V through those fuses. It is probably going to be a yellow wire with red stripe going into what visually would be pin #1 on the DLC terminal side. Probe the wire not the pin. My guess is something else is going on because if your BTN or ROOM fuses were blown you would get a whole host of ungodly issues like the car wouldn't even start or none of the interior electronics would work. It would be pretty obvious. My guess is your issue is a bad harness connection, missing pin in the DLC, or a short farther on down the line. It's possible the CPU (not ECU) isn't recognizing the scanner or vice versa but you would need another one to check it out. That should put you on the right track.

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Thanks so much for your response! I don't have any feedback yet but will let you know the results. It's great to have a place to start.

I'm not sure when the last time the port worked so this info might trigger something for the person who drives it most, in case he did something else and didn't know this would happen. Owner of the car is not the primary driver and doesn't have anything additional to pinpoint the possible reason.

If anyone else has some input regarding the smog hiccup in California, it would be great to hear thoughts or personal experience. What they're hoping for is, the computer resets itself. The check engine light still hasn't come on so maybe it'll be a Pass tomorrow when it's retested. What a pain in the butt!

Since my friend bought this car, she had to get a new tranny, catalytic converter, and now a motor. This is all within a few years.

What else is going to fall apart next?


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California cars I believe require the pre-catalytic converter (warm-up catalyst) to pass the stricter emissions. It also has an additional O2 sensor. You're not going to get far in guessing on what the CEL is for until you figure out why the check engine light is coming on in the first place. You need to ability to pull the codes. The radio is wired to the RADIO fuse not ROOM fuse. I have heard of instances of the ILLUM fuse being knocked out by a bad radio installation but never anything about the DLC. A 2000 engine will swap into 2001 without any issues. I wouldn't worry about any of your issues other than getting your diagnostic system working. That should be priority #1 for you. After that everything else will fall into place. You can attempt to reset the ECU yes but there's no guarantee that it's not going to immediately trip another code. Continous memory codes are only set after 10-20 times driving the car from A to B. You can bypass allowing a continuous memory code to fail your emissions testing by resetting the ECU prior to emissions testing. If it's a hard fault code then no amount of resetting the ECU is going to help.

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