Blows OBD fuse after a few cycles?

Tiny
TTOKAR
  • MEMBER
  • 2004 PONTIAC VIBE
  • 1.8L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 213,000 MILES
Blows OBD fuse after a few cycles -- new cat and both 02's are new. I have a Haynes buy it does not
cover emission wiring schematic.
Thursday, January 8th, 2026 AT 12:33 PM

6 Replies

Tiny
KEN L
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  • 54,494 POSTS
So to confirm the OBD fuse 7.5 amp located at the fuse panel at the left side of the dash correct? If so, this fuse only feeds the OBD2 connector there is nothing else on this circuit. So, it must be the wiring to the connector or there is heavy corrosion on the connector. Please inspect the wire color (red/blk) to make sure no one has tapped into the wire for an aftermarket accessory. Please check it out and let me know what you find.
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Friday, January 9th, 2026 AT 9:37 AM
Tiny
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Ken, thank you -- yes -- 7.5 in fuse under the dash. You and I both know that wires (especially hot wires) begin and finalize somewhere. The DAC is on the left side under the afore mentioned fuse panel -- I'm assuming (because I do not have a schematic) that the other DAC wires go to various places including the ECM which is on the right side behind the glove box. Replacing the 7.5 amp fuse allows a code reader to power up, check for DCT's and eliminate the check engine light for several start stop cycles but eventually pops the fuse again. Something is causing it -- a color coded schematic would sure help.
Thanks again.
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Friday, January 9th, 2026 AT 12:19 PM
Tiny
KEN L
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How is the engine running? I have seen a shorted fuel injector or ignition coil cause this problem. Also, can you plug the scanner into another car to see if it blows the fuse? It can be the scanner itself. Here are the wiring diagrams for the OBD2 connector as requested. Please let us know what you find. Check out the images (below).
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Saturday, January 10th, 2026 AT 9:07 AM
Tiny
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Thanks Ken -- much better schematic than Haynes -- Yes, I have a Foxwell scanner that works on other cars and a wireless OBD2 Car pro -- no where can I find wire schematic (there is vacuum line schematics) to the much confused vent valve (under hood) and vent solenoid (charcoal canister) behind drivers tire. Both have two wires going to them.
Also, your site will only allow one picture up loaded -- I wanted to follow the red/blk
wire on picture one but again, only one hot wire to the DLC I guess I can run a jumper and by-pass any harness problems. The car runs and idles fine -- it seems slightly better when the CEL lite is out -- not really limp mode but noticeable. I've only pot 3000 miles of the 213,000 on it -- fuel injectors couldn't hurt but the have their own power and relay -- coils should show a miss fire but they get replaced at my first tune up. I've owned Toyota's
since the early 70's and many Corolla's, Matrix and this my fourth Vibe --- tis a mystery.
Yes, I will share if and when I figure this out.
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Saturday, January 10th, 2026 AT 12:14 PM
Tiny
KEN L
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That would be great if you could tell us why the fuse blows, also please start new questions of each of the other problems you are having, I don't know why the site only let you upload one image, we have not had that problem before, it might have been a glitch. I like the idea for running a new wire that should take care of the problem, please let me know, Ken
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Sunday, January 11th, 2026 AT 9:45 AM
Tiny
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Ken sure will if I fix it -- here is the second picture but it does not show the origin of the red-black wire before the fuse. It's going to be more parts cannon I guess -- I'll change a few relays because they're cheap -- the car is 24 years old -- could have moisture I'm not familiar with but everything seems to work.
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Sunday, January 11th, 2026 AT 11:01 AM

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