OBD1 Check Engine Light on – no code – Honda

[Dave]

Hi Forum,
Working on a ’94 Accord (OBD1) with about 130K miles. It starts and runs without any problem but the CEL is illuminated. I checked for a code using the ETCG video for instruction, bridging the leads on the blue diagnostic plug under the passenger side of the dash. Turning the key to the ‘on’ position (not running), the light remains on. There are no diagnostic CEL flashes. Figuring this was a ‘code 0’, I replaced the ECU. That procedure included disconnecting the battery, removing the original ECU, replacing it with another with the same serial number, reconnecting the battery, waiting a few minutes, and checking again. Same problem – no flash/no code but the CEL remains illuminated when the car is running.
Any ideas other than that the replacement ECU has the exact same problem?
Thanks all!

Topic

[Rob]

[quote=”Autophile” post=171451]Hi Forum,
Working on a ’94 Accord (OBD1) with about 130K miles. It starts and runs without any problem but the CEL is illuminated. I checked for a code using the ETCG video for instruction, bridging the leads on the blue diagnostic plug under the passenger side of the dash. Turning the key to the ‘on’ position (not running), the light remains on. There are no diagnostic CEL flashes. Figuring this was a ‘code 0’, I replaced the ECU. That procedure included disconnecting the battery, removing the original ECU, replacing it with another with the same serial number, reconnecting the battery, waiting a few minutes, and checking again. Same problem – no flash/no code but the CEL remains illuminated when the car is running.
Any ideas other than that the replacement ECU has the exact same problem?
Thanks all![/quote]
some cars that methid of getting error code’s will not work…. you might have to get an OBD1 scanner to check it

[Caleb Stovall]

What Rob said.

[Dave]

Thanks to both of you. Any tips as to what brand of scanner will work (I’ve read that some don’t)? Also, any reason this info isn’t out there? Most of what I’ve seen, including Eric’s video, seems to indicate that the paper clip method is all you need.

[Dave]

In case anyone is following this topic or is going through the same problem, I thought I’d provide a little update and information:

I got hold of the factory shop manual for the car and found the full procedure for checking the (OBD1) codes. That procedure includes pulling the backup power fuse for the ECU (7.5 amp) and re-inserting it after 10 seconds. When I gave that a try, I found that the fuse was blown. I replaced it and the CEL started displaying the fault code. On this car, no separate code reader is required and the shop manual does not call for one.

The necessity of resetting the ECU, and also that a blown backup power fuse will prevent the codes from displaying on the CEL have been missed in all of the explanations of this procedure that I’ve seen online. So I thought it worth mentioning here. Btw, at least on a ’94 Accord LX, the clock and radio are both on the same circuit. Neither were working but I was going to address those problems later. Replacing that fuse also fixed them, as it turned out.

[Ole Eggers]

So, what code did you get ?

Glad you found out how to get the codes off it. Too bad you had to fork out a lot of money for a new ECU.

[Dave]

Just a burned out heater in the O2 sensor (code 41).

Thanks. Yeah, no fun buying unneeded parts, but still a lot cheaper than having to take the car to a shop (not to mention being without the car, having to get rides there and back, etc…)!

[Author]

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