My son was working on car and blew ignition coil fuse (15amp) in the left under dash panel. It will turn over but the fuse blows as soon as you turn the key to the ON position. I've check all other fuses and everything is good. For some reason now when I plug up code scanner to data port I get a "NO DATA LINK". The scanner was reading codes fine before the fuse blew. I'm new to the site and have tried everything I know to look for. Can anyone give me some areas to look at.

 

Power is supplied to data link connector (DLC) from Fuse #3 (15A) in underhood fuse box.

Check Pin 16 of DLC for 12V. If missing, there is a problem w/ power supply to DLC. Lower RH side (narrow row) of DLC looking at DLC. Wire connection is wht/grn.

Fuse 3 in underdash box is 7.5A accessory fuse. Fuse 1 is 15A Main Fuel Relay power supply fuse. It could be a wiring fault or defective fuel pump (shorted). Some testing to confirm source of short is indicated.

good luck

 

Circuit D46.docx


Talking further with my son, he applied 12V constant to the blue/yellow wire leaving the EGR valve to keep the CEL from coming on and giving a error code (P0401). Something he read on the net.
I've unplugged all harnesses from each item in the attached D46 circuit and it still blows the #11 15 amp Ignition circuit fuse which leads me to believe there is something else in this circuit that I'm not finding or a frayed/burnt wire causing the short.
I'm I missing something? I've visually inspected all other fuses and they are good. Is there a main ignition relay under the dash that may be somehow connected to this circuit?

 

Fuse 11 (15A) supplies power to the ignition coils and nothing else. It seems more likely that one of the coils has a shorted condition.

Since fuse blows immediately, you may be able to test by disconnecting all coils and sequentially connecting them w/ keyswitch On. When fuse blows, you've just connected the faulty coil.

Your son connected 12V to a voltage reference line from PCM, normally 5V. I don't know if this caused damage or not, but it's possible.

good luck

 

Thanks for the great help. Thats a start and I'll do this coil test and hopefully find the fault. I've got the complete wiring diagram and I've been looking at it from the point of where the 12V was applied to the BL/YL wire at the EGR valve and following the path. It would have traveled through several sensors and ending up at the #11 fuse from what I can see. I will post back with the coil test results.

 

Here's wiring diagram I was using from Honda shop manual.

good luck

 

egr circuit.docx

Thanks for the additional diagram. I've been looking this one over.

 

I did the coil test. 4 blew the fuse, 2 are good. Will install new ones Friday and hope this problem is fixed. I checked the data connector and it still shows, " no link" so that has me worried. Would this short circuit with these coils unplugged give a no link reading on my scanner?

 

Do you have Check Engine Light illuminated?

Check DLC for bent pins.

See attached diagnostic.

good luck

 

The weather here has kept me from installing coils. The CEL light does come on and the green immobilizer key in dash doesnt stay lit but I did start running the DLC Test and at first I had no voltage on the 1st or 2nd test and the AGC 15 A Fuse under the hood was not blown but I wasn't getting 12V on both sides with key on. I pulled the PGM main relay under the dash and then got 12V at the AGC fuse and test 1 and 2 on the DLC did give me voltage. Would you have a test for this main relay? I pulled it apart and visually there is some brown/dark areas on the circuit board.
Thanks for all of your help.