Limp mode, Key Light is Flashing?

TRIPWIRE

MEMBER
2004 HONDA CIVIC
1.7L
4 CYL
2WD
AUTOMATIC
120,000 MILES

My daughter was driving her car and it went into limp mode. The transmission fluid was low, and we added some but it’s still in limp mode. The key light is flashing, and the check engine light is on. It will drive fine in second, first, and reverse but bogs down in drive. The lights on the gear selector display on the gear shift no longer light up. It is also now idling rough.

We disconnected the battery overnight and that did not reset the ECM. When we hook a scan tool to the port it says no link. We have tried the scan tool in a similar Honda, and it works fine.

Any help would be great.

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,602 POSTS

It sounds like the PCM is not working but we should check the fuses first. I would start with the #9 fuse under the hood because that is what powers the ALDL connector. I have seen the Multiplex control unit go out and cause all kinds of weird problems but let's do step 1 first.

Here is a guide to help with the fuse locations in the images below to help you with the test:

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

Also, if you could upload a short video of the engine cranking over, I can tell if the engine is in good shape. Please let me know what you find.

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Sunday, February 19th, 2023 AT 10:43 AM

TRIPWIRE

MEMBER
2 POSTS

Okay, so, the number 9 fuse is good. Here is a video of it running.

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Sunday, February 19th, 2023 AT 1:00 PM

KEN L

MASTER CERTIFIED MECHANIC
47,602 POSTS

Thanks for the video. The fact that the engine is hard starting is telling me the throttle body and IAC valve needs to be serviced and this will cause the car to go into limp mode. Please check out these two guides and the images below to show you how to service the throttle bore on your car:

https://www.2carpros.com/articles/throttle-actuator-service

and

https://www.2carpros.com/articles/reduced-power-limp-mode

You could have an ECM that is out which is why the scanner will not communicate. Here is the location of the ECM so you can get a rebuilt unit by searching Ebay or Google.

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