How to trace an intermittent short circuit in a car wiring harness
Intermittent shorts can happen while a car is just sitting parked, meaning they cannot be diagnosed by tracking down physical bumps or vibrations. Because replacing the sensor and connector often fails to fix the issue, the hidden fault remains trapped inside the harness, leaving owners struggling to narrow down its exact location.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Wiggling the wire harness manually to look for spikes
- 2Backprobing the signal wire at the PCM connector with a jumper wire to a meter while driving
- 3Checking where the harness passes through the firewall for rubbed insulation
- 4isolating the load side from the supply side and checking continuity on each circuit individually
In their words
Unedited, most upvoted first, each linked to the thread it came from.
“I have a intermittent short on a FTP sensor circuit (at least I believe) it comes and goes this is for a 06 mustang I’ll put it in run engine off and it’ll float between 0-50 pa on my code reader other times it’ll be 16000 Pa which is when it’s shorting I believe as google says that’s the max value (5v=16000 pa) I’ve changed the FTP sensor and the connector for it but I believe the issue to now be in the harness somewhere what would be a easy way to narrow this issue down?”source ↗
“That’s the weird thing the car can just be sitting on the driveway and sometimes it’ll spike or hold steady it does not even need to be hitting bumps lol”source ↗
“what we do when i attention to a court circuit in machine like this with mluti button what we do to separtion the probleme of court circuit to never get again in any country i want solutuion worked?”source ↗