[EASY] HOW TO FIND A SHORT-TO-GROUND (NO SWEAT YOU GOT THIS)
In this video I cover how to locate an intermittent short to ground that is causing a fuse to blow, which in turn is causing a OBD/DLC no communication and unable to charge cell phone.
Info: This is a GMC Envoy
Concern/Complaint: Customer is unable to obtain a smog check inspection because of a no communication error. Also unable to use the power outlet to charge his cell phone.
Diagnosis: Verified concern: visually inspected Fuse 13 and was not present, also noticed starter relay cover is missing and should be replaced.
Used a fused jumper wire on fuse 13, with an amp clamp to check current draw at fuse and obtained a measurement of 14.00mV, being the clamp is a 1mV/10mA, the circuit was drawing 140mA. Using a breakout box on the OBDII connector I had 14.3v at pin 16 to pin 5 ground. I was able to use the smog machine to communicate with the car.
With all test equipment installed I tapped on the lower steering column cover, at that moment I lost voltage at pin 16 and my circuit breaker tripped meaning a short circuit had been created.
We removed the lower steering column cover along with the center console cover to access the OBDII port and the cigarette lighter wiring. Behind the center console cover I found 2 bare wires leading to the cigarette lighter, when these two wires contact they short to ground bypassing the load and blowing the fuse.
To verify I did a continuity test between pin16 power to pin 5 ground and normally should read OL (open circuit) but I had a reading of 2 ohms, meaning power circuit is contacting a ground circuit.
Recommendation:
At this point the best solution is to replace the dashboard wiring harness or have the damaged circuits repaired by cutting old bare wire, soldering, heat shrinking and protecting the wire connections and replaced the cigarette lighter female connector. Many other wires near these wires are damaged as well, see pictures below.
This is an instructional video, I don't make any claims verbally or in writing that these steps will help you or repair your particular vehicle. This is not to be substituted for factory vehicle information. I don't own the rights to the wiring diagrams those were provided to me by ShopKeyPro.com a branch of Mitchell OnDemand.
I make these claims of information using my experience as an automotive technician and instructor, I don't claim to be right nor is this the only way to perform these tests. If you feel shortcuts are better, if you feel guessing is better then my all means take that approach.