Hi guys

I changed my ECU recently and when the car stays 2/3 days without engine turned on, check engine light stays on for 20 / 30 seconds. After I listen fuel pump prime, the light turns off and engine can work.

 

If you know the main relay is good (ECU pin A7 ground test), then the ECU is almost surely bad.

 

How can I test it?

 

Check whether the fuel pump always runs during this^ test?

 

I'll test and post here. After the first start, fuel pump starts normal (2 seconds)

 

Sorry, I tried but I don't know how to do the A7 test

 

Civic now stopped and won't start.

Hi, I did the A7 test.
Disconnected A plug
Inserted a jumper wire on A7 plug
Ground this wire on metal under dashboard
Fuel pump didnt prime

Tested main relay wire
Jump wire pin 5 to 7. Fuel pump run
Jump wire pin 1 to 7. Fuel pump run
Jump wire pin 5 and 1 to 7. Fuel pump run and this mode I tried to start engine but it crank and dont start.

 

Have you resoldered the main relay and also cleaned and tightened the G101 ground connection on the thermostat housing?

Main Relay Fix, Troubleshooting (Honda, Acura) and how to solder

https://youtu.be/qMpgmzGhJeE

 

Thank you RonJ.
I have 2 main relay: old mitsuba and a brand new. Mitsuba I redid resoldering and the brand new the points is all ok. I checked this G101 gnd yesterday and it seems ok. Now my civic is on the sidewalk and dont wanna go to the garage :-(

 

Do you have a multimeter? It's likely a simple problem, like a bad wire.

 

yes I have multimeter

 

Good. What is the color of the wire at pin A7 in ECU connector A?

 

A7: green/yellow

 

Great.

Unplug ECU connector A.

Turn key to ON(II).

Measure voltage to body ground at pin A7.

Post the reading.

 

(-) 00.0

Zero

 

The wire at A7 runs to pin 8 (Grn/Yel wire) of the main relay.

With the key in ON(II), what voltage do you measure when back probing the Grn/Yel wire at pin 8? The main relay must remain plugged in for this test.

 

(-) 00.0
Zero

 

Turn key OFF.

Unplug ECU connector A.

Check for continuity to body ground at pins A23 and A24 (black wires) in the ECU connector.

 

Multimeter result: 1 (A23 and A24)

 

1 Ohm or infinite resistance? What does the meter read if you touch the two probes together?

 

Result: 000

 

When you untouch the probes, what does the meter read?

 

1 (or I) stay on left side of the LCD.
Like when done on A23 and A24

 

You found the problem.

The black wires must be grounded at G101 on the thermostat housing. The black wires merge and run as one black wire to a 14P connector on the left side of the engine bay and a 20P connector on the left shock tower. Maybe one of the connectors is not fully seated.

 

G101 gnd cleaned and tightened.
Connectors seated
:-(