20A ECU-IG fuse fell out - engine still runs

What is the 20A ECU-IG fuse for? I was able to start the engine without it installed.


Am trying to solve some performance issues. See http://act…ge#2736105

for performance issues.

Specific to this fuse Details:

The fuse panel cover fell off the other day, and the 20A fuse for ECU-IG fell out. I tried to put it back but it was VERY loose. So I took it back out and started the truck.

Am wondering if this is critical to the performance problems.

Am also wondering how the heck it got so loose, that it just falls out.

A quick look at a wiring schematic does not show a 20 amp fuse for this. It shows a 15 amp which provides power to the Main EFI relay. From that relay it branches out to an entire herd of parts; the ECU, O2 sensors, Idle Air Valve, MAF sensor, Data Link Connector, etc., etc.

You might take a VOM or test light and with the key in the RUN position, probe the red/white wire at the Idle Air Valve, MAF, etc. There should be 12 volts+ showing on the VOM or the light should be illuminated.

IF power is shown to exist this leads to varied conclusions.
The fuse that fell out is a spare and the fuse block space is being misinterpreted or the connector locks on the back of the fuse block have let go and disassociated themselves from the fuse block.

Or there has been a fuse block connector problem and someone in the past has routed around the fuse block.

If there is no power shown at the red/white wire then you need to check the Main EFI relay as a first step and make sure that power is provided to several terminals with the key on; not just one.
Hope that helps some.

My limited experience has been that correct labeling of fuses is not one of the automotive industries stronger points. The names appearing on circuit boards or fuse diagrams often to not match the names on the wiring diagrams and sometimes really are associated with fuses other than the one they appear to apply to. I’m guessing that your 20 amp fuse probably really belongs to some other subsystem in the car – brake lights, door locks, etc. Maybe it’s a spare.

As for loose? What can be said? If the fuse fell out, it must be loose. But fuses are not normally mechanically stressed. If you can’t see a mechanical reason for the looseness other than a defective socket, then either the vehicle must have shipped with a bad socket or somebody must have damaged the socket (not that easy to do?) at some point?

Normally you have to pry or pull them out with a tool. You wouldn’t be the first person to have a fuse in the wrong slot. Sometimes the words are above the slot, sometimes below. Often, completely empty slots are scattered all over the block. Take a flashlight and look to make sure there are pin sockets in the slot you’re trying to put the fuse into.