ECM fuse switch

[justinowen]

84 monte carlo v6

Hi all,
I've got a switch under the steering column that the previous owner said he thought was related to electric fuel pump. But when I looked into it, it actually takes the place of the ECM fuse.
In the switch wire there is an inline fuse though.

Any idea why someone would have done this? The shop manual seems to indicate this fuse is for the check engine light, ignition, and "continuous power for memory" to the ECM.

I think I am going to put a 10 amp fuse back in and remove the switch. Any reason not to?

 

[ELCAM]

Looks like a good way to eliminate those pesky check engine warnings that can fail your emissions check.

Just curious. Do you have smog check of some kind where you are? Is the CCC system all there and functional?

 

[justinowen]

Just curious. Do you have smog check of some kind where you are? Is the CCC system all there and functional?

vehicles this old don't need to pass an emissions test in missouri (only a safety check) but i don't know where this car lived most of its life.
i believe the CCC is all there and functional. i was able to download a fault code (45 rich exhaust) the other day and i got the flashing 12 (which i believe means the ECU is working).

 

[Clone TIE Pilot]

These cars are notorious for having bizarre wiring modifications done by previous owners. Frankly we can only guess viewing this from online. It would take in person inspection for us to figure out what the modification are and how they function or how they are supposed to. Sometimes PO modifications are completely senseless since they don’t always understand what they are doing.

 

[JimmyCamino]

Do you notice it runs any different from a cold start with the switch on or off? I put an on/off switch in the ECM fuse circuit in my '82 Malibu because when it was cold it wouldn't idle well with the ECM on. Can't remember why I thought to do that.

 

[justinowen]

> It would take in person inspection for us to figure out what the modification are and how they function

The switch functioned like an ECM fuse remover.

> Do you notice it runs any different from a cold start with the switch on or off? I put an on/off switch in the ECM fuse circuit in my '82 Malibu because when it was cold it wouldn't idle well with the ECM on.

I never flipped the switch to off since i didn't understand what it did. 😆
But the car was idling rough when warm in park and when in gear and warm it was idling at such a low RPM it felt like it would die.
But I did some troubleshooting and changed some parts (routine maintenance items: pcv value, crankcase filter, air filter & i replaced the evap canister) and it idles better now.

I hope they didn't install the switch before trying routine maintenance items.