Electrical Fuse E Blowing need help diagnosing

jozsefsz said:

That sucks man, sorry to hear about your problem. It sounds like you've been systematic about troubleshooting. The pain in the rear is that unplugging the sensors and still having a large draw will tell you that the sensor isn't dead-shorted, but unfortunately doesn't tell you if the wiring running to that sensor (or fuel pump) is shorted. Unplugging the PCM will remove power from some of the sensors you list - many receive power through the PCM. So it could still be the wiring running to any of them that's been shorted to ground, so you can't be sure it's the EEC.

I'd personally go hunting for any major areas where you might have a visible wiring problem. Any place where the old harness-sheathing has cracked away, or anything that gets close to the exhaust. O2 sensors wiring is always suspect as it runs right under the headers on the v6, and fuel pump wiring as well since it sits on top of the tank that gets pretty rusty over time. Anything that's been worked on recently - if you had a new fuel pump installed for example, or any area of the car that's had body-damage in the past (a fender for example).

After that, I'd disconnect the harness at the CCRM (the relay module in the engine bay), find a wiring diagram for it, and probe for any leads that are grounded that aren't supposed to be grounded. Best of luck!

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jozsefsz said:

That sucks man, sorry to hear about your problem. It sounds like you've been systematic about troubleshooting. The pain in the rear is that unplugging the sensors and still having a large draw will tell you that the sensor isn't dead-shorted, but unfortunately doesn't tell you if the wiring running to that sensor (or fuel pump) is shorted. Unplugging the PCM will remove power from some of the sensors you list - many receive power through the PCM. So it could still be the wiring running to any of them that's been shorted to ground, so you can't be sure it's the EEC.

I'd personally go hunting for any major areas where you might have a visible wiring problem. Any place where the old harness-sheathing has cracked away, or anything that gets close to the exhaust. O2 sensors wiring is always suspect as it runs right under the headers on the v6, and fuel pump wiring as well since it sits on top of the tank that gets pretty rusty over time. Anything that's been worked on recently - if you had a new fuel pump installed for example, or any area of the car that's had body-damage in the past (a fender for example).

After that, I'd disconnect the harness at the CCRM (the relay module in the engine bay), find a wiring diagram for it, and probe for any leads that are grounded that aren't supposed to be grounded. Best of luck!

Click to expand...

Mike Aggy said:

Hi all,
1994 V6 Mustang, bone stock electronics. I was driving and the car completely shut off. On the side of the road I had a crank no start. After a tow home I see fuse E in the engine bay is blown and has continued to blow as soon as key is switched on.
It controls
- PCM
- Fuel Pump
- O2 sensors
- Canister Purge Solenoid (A/C)
- Ignition Ctl module
- IAC Solenoid
- Fuel injectors
- Transmission
- Camshaft position sensor
- MAF sensor
^ According to service manual ^

I started systematically unplugging sensors to find the one with the high current draw and the only time the fuse would not blow is with the PCM completely unplugged. (Everything listed above still plugged in and ONLY the pcm unplugged.) At this point I am just unsure of how to proceed so any help would be very much appreciated! Thank you

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