Not sure if this is the best forum for this but heres my issue:
Question about g101. Had a fan problem, so we tested some stuff and figured out the fan is fine, it runs with direct power off the battery. fuses and relays good. So yesterday I replaced the engine coolant temp switch and flushed the coolant. Also did spark plugs and wires while I was at it. I'm confident on the repairs. Problem is when I recranked it ran for a minute then idled down and died. Wont recrank unless I rev engine, dies when I let off the gas.
I think it's the thermostat ground wire g101. I loosened it to reposition when I replaced the switch. Never knew it would shut me down but I've read this is exactly what happens. So I've tried cleaning the terminal and the bolt and repositioning a bunch, can't get it to act right. It has a 3 wire configuration, 2 browns on one lead and one black on the other lead. It ran fine prior to moving it, so i thinks its just being sensitive. Any thoughts?

 

its a 99 civic basic. Btw

 

Sounds more like it is flooded. Pull a spark plug and see if it is wet. Are you sure it is the right plugs and that you have the spark plug wires in the correct order?

 

wires and plugs are good. Plug Gap was perfect. Greased ceramic on plugs and all.
Could be flooded I guess. Ill check it today

 

i had a horrible issue with g101 last winter when it was -8 degrees outside. connection at the tstat was good but the wire was frayed in the loom. it would random die and not restart.

run a quick test wire from the g101 pin in the ecu to any exposed metal down there and see if that helps. its cheap and takes 2 seconds. if so then just solder the wire right into the wire going into the ecu and put an eyelet on the other end and bolt it to the chassis down by the ecu either where that bolts in or one of the dashboard supports.

 

where does g101 goes? sg1 and sg2?
thanks

 

Reading up made me think about the order of the plug wires. Went back and looked at the diagrams and rotated our pattern 90deg to the right...perfection!
Thanks guys

 

Yeah, that's what it sounded like to me. Glad I could help.

 

Glad you sorted it out.

For reference - G101 is the ECU's power ground and logic ground termination point. On certain thermostat housings, there is a M6x1.0 thread on both the waterpipe housing and the hose outlet. The correct location for the ground will be to the waterpipe-side of the housing.

 

Actually it grounds a lot more than that, but it can vary depending on what model and transmission you have... gear position switch, PCM, main relay, power steering pressure switch, radiator fan switch, VSS, and more. If you have ever tore Honda harnesses apart you know just how much they split grounds. It's rather excessive.

 

Bra.. Shoot me the credit

 

This is true. Thats why i dont know why having the ground at the thermostat is relevant anyway.

Motor is grounded to chassis, battery is to chassis

I moved all my grounds inside the cabin. No issues

 

i notiecd that some civics has 3 wires and some has 4 wires for t-stat grounds.

 

Google search "ground loops"