Help please, Scangauge II messed up my engine! (1 Viewer)

[Surfdc]

Just got a scangauge II and the second I hooked it up, my engine started sputtering, idling rough, then stalled. I unplugged it and it ran better, but still idled very rough. I ran with it plugged in for the weekend, and it didn't get any better. I unplugged it Monday and the truck is still running rough, and stalling. I couldnt take it to work this morning.
Also ever since hooking up Scangauge II my alarm goes off every time I hit the unlock button on my keyfob!!
Truck ran perfectly until this.
Something is messed up, any ideas are greatly appreciated and thanks!

Truck:
1997
140,000 mi
no engine mods
electrical mods: Upgraded stereo, Slee light harness

 

[ChiTown]

Sounds like your alarm is tapped into something it should not be.

 

[landcrshr]

Sounds familiar, I think @bicycleagent003 had a similar issue: https://forum.ih8mud.com/threads/replace-ecu-next.809664/

 

[Surfdc]

Thanks guys i will check the alarm wiring, which was installed by the dealer in 1997!
Could plugging in the scangauge damage the ECU? I also have no CEL, or stored codes.

 

[Surfdc]

Just tried it again now and now it won't even start.

 

[ChiTown]

I would uninstall the alarm and try and start it.

 

[TrickyT]

I don't see how a properly functioning SC II could damage your ECU. But it is conceivable to me that the ECU has gotten into some strange logic state. So try this: pull out the 15A EFI fuse for 2 minutes, then plug it back in and see what happens. Pulling the fuse will reset the ECU to factory settings. Your engine will definitely run rough for several trips while the ECU re-learns the particular sensor inputs for your vehicle. In fact, it may be running rough now for that very reason, because the ECU somehow got reset when you plugged in the SC II.

But there's also something else going on with your rig. There is no connection between the ECU and vehicle alarm (at least not the Toyota RS3000 alarm system), so why the alarm function changed is also a mystery. Perhaps the alarm is connected to the same power circuit as the ECU or OBD-II port?

In the future, I suggest you connect the SC II to the OBD-II port with the ignition switch in the off position.

 

[TrickyT]

Just tried it again now and now it won't even start.

"Won't start" as in cranks over but doesn't fire, or starter won't crank the engine?

 

[Surfdc]

Starter cranks ans cranks but engine wont fire.
WIll check on the alarm wiring now...

 

[TrickyT]

The Toyota RS3000 alarm disables the starter, so if your engine cranks it's not the alarm. (Do you have the RS3000, or is it some aftermarket alarm?)

If the engine won't fire, then follow these emergency Troubleshooting Procedures: https://forum.ih8mud.com/threads/em...-item-recommend-keeping-copy-in-truck.115816/

 

[TrickyT]

Another thought: The OBD-II port is attached to the fuse block (or at least very close to it). You may have something funky going on with your fuse block or the wiring to it and the physical force you used to plug in the SC II, even if it was minor, may have disturbed something. You need to carefully check all the fuses in that fuse block and also look at the wiring behind it for any signs of tampering by a previous owner or service technician.

 

[Surfdc]

Will unhooking the battery reset the ECU like pulling the 15A EFI fuse?

 

[Reelitchy]

Will unhooking the battery reset the ECU like pulling the 15A EFI fuse?

Then you might have a problem resetting alarm

 

[Surfdc]

Well pulling that 15A efi fuse for the afternoon worked!!! Still think the alarm is all jacked up but that's for another day. Thanks MUDD members!

 

[Chachie]

 

[Surfdc]

May have spoke too soon...Since resetting the EFI fuse the truck definitely runs better, but it stalled 3 times on the way to work this morning (3 mi through town) and then wont start, have to wait a few minutes then turn the key for a good 10 seconds or so until it fires then i have to pepper the gas to keep it running then if runs fine, then stalls.

 

[Surfdc]

Still stalling and running rough. starts right up in the morning, then 5 minutes later, rough idle, then stalls. Will re-start, run for a while, then stall....

 

[TrickyT]

Lots of possibilities. I doubt your problem is related to plugging in the SC II though. Plug the SC II back in and set one of the gauges to display water temperature. See what it reads with a cold engine and then what it reads 5 minutes later. You may have a bad water temp sensor and the ECU still thinks the engine is cold and thus continues to provide a rich mixture, causing it to stall. Or you've got a vacuum leak and after the engine warms up and the ECU leans out the mixture, the leak causes an overly lean condition and the engine stalls. Like I said, lot of possibilities.

 

[Alleycats]

Correlation does not imply causation.

 

[Surfdc]

Water temp at start up is 85. 5 minutes later it's 195, then it doesn't move according to SG II. Checking the vacuum tonight.
Inspecting the alarm I learned it was installed at the time of purchase by the dealer. Brand is Karr. I trace the alarm wires to the door harness, the ignition, the shifter, there is even a motion sensor. all wires are tapped into existing harnesses. Alarm install definitely looks like it was done by a pro and I couldn't find any wires that tap into or are linked to the fuse box or obd2 connector.
Just so weird that it happened the second I plugged in the SG...