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General Smog Check

Honda Fit Computer Can't Read Smog Codes

I have a 2007 Honda Fit. I need to know why the computer can not read the trouble codes? There are no check engine light on or mechanical issues with car, but when the smog check is done the computer can't read the OBDII trouble codes. The smog technician said the smog machine is not able to communicate with the OBD II connector.


It sounds like your Honda Fit has a problem communicating with the smog machine. The simplest problem that could cause your Honda Fit to be unable to communicate or connect to the smog machine (via the Data Link Connector - OBDII Connector) could be a loose wire within the DLC, or blown DLC communication fuse.

The most complicated fault could be a problem with your Honda Fit's Engine Control Computer (ECU). If you can purchase an inexpensive Trouble Code reader (local auto parts store all have them) go ahead and try connecting to your Honda's ECU via the DLC. If the scanner lights up as it's connected to your vehicle this will indicate there is power at the DLC (data link) and the problem is more then likely with the signal wire between the DLC connector and the ECU.

If the scanner does not light up this might indicate either a loose or disconnected power OR ground wire at the connector. Check your Honda Fit's fuse box for a fuse labeled DLC (Data Link Connector).

Basic Honda Fit DLC Power and Signal Test

A. DLC Terminal 16 should have 12v. Measure voltage between Terminal 16 and known good ground. If no power, check 15amp fuse in the underhood fuse/relay box.

B. DLC Terminal 4 is ground. Measure voltage between Terminal 16 and Terminal 4. If no voltage is measured, check for break in DLC Terminal 4 and ground.

C. DLC Terminal 5 is the ECU signal wire. Check for voltage between Terminal 16 and Terminal 5. If no voltage exists, check for break in Terminal 5 wire between the ECU and DLC.

posted by SmogTips Support 06-27-2015 02:00 PM
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