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celtic ... 6/7/2019

2003 Honda Civic DX 4 Cyl 1.70L


7 to 10 volts to the G101 ground, 1.7l sohc not 4.2l

I have 7 to 10 volts going to the G101 ground on the thermostat housing? Anyone know a cause for this? I've unwrapped the entire wiring harness and cant find a short anywhere......

1 Answer


Jimm 10/3/2022

Check whether the important G101 ground wire on the thermostat housing is loose or corroded. If so, clean it thoroughly with steel wool and tighten. By the way, if G101 is disconnected or loose, the engine will lack both spark and fuel.
This is a braided cable that runs from the thermostat housing to the body of the car near the radiator.

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.

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.


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