Having a hard time diagnosing this one. Could really use some guidance and insight.

2000 Civic EX - Automatic, 228k miles


Owned the car for two months. Most of which - no problems. Ignition switch it “sloppy” you can pull the key out in ON position, but - car started and ran. Noticed that is seemed to be consuming a lot more fuel that I expected, but never verified.

Car started giving issues a week back. Engine would die upon braking or die at idle, but would always start back up. Noticed it seemed to start happening after I changed the oil - I used a synthetic 5w 40 royal purple 🤷‍♂️.


Car did the same thing one last time before needing a tow home. Car cranks, but won’t fire. No oil leaks, small trace coolant leaks under the car. But had literally only driven 500 feet from starting point after I left work to dying point in a parking lot. No history of over heating. Checked the overflow…FILTHY. Oil and grime in the overflow. (Starting to think head gasket)

Prior to towing home connected to scan tool. Got the code for Vtech unit or possible low oil pressure. Can’t recall the exact code . Checked vtech solenoid and connection points, no visible damage. Un/Plugged them back in, cranked the car….she starts! Seconds later….she dies. Back to the OBD scan….can’t connect. Tried 3 different scanners. Can’t connect.


Now chasing three potential problems. Vtech Solenoid + oil pressure switch AND/OR head gasket AND/OR ECU/Relays/Fuses/Electrical.

Talked to previous owner; coolant was fresh, recent flush performed. Drained coolant, not contaminated, no discoloration, doesn’t smell burnt. Previous owner confirms he has replaced head gasket, water pump, timing and pulley’s. Ruled out head gasket.

Drain oil (that is less than a week old) Replace oil pressure switch and filter. Oil is pitch black. Very dirty for a week old. No strong smell of gas.

Replace V-Tech unit + solenoids.

No changes. Cranks but won’t turn. Can’t get a read on scan tool.

Check fuses, AC adapter fuse blown. Replaced. Nothing changes. Re-Check fuse - didn’t blow. Still no read on scan tool.

Teat Main Relay. Appears to be bad. Test for voltage at fuel pump, no voltage. Replace main relay. Now getting voltage at main relay. Check fuel pump. Max voltage reading in 6.5v Measured it while Turing to on position and while cranking. 6.5v. Still can’t get OBDII scan tool to connect.

Contact previous owner. Brand new fuel pump. He replaced it because the float was broken and the fuel gauge on dash is inaccurate. Pull the pump. Clean. Screens are clean. Hardwire pump directly to battery. Pump goes into what I assume is a normal cycle. Rule out fuel pump.

Pull the fuel line right after the fuel filter and before fuel rail. Lines are pressurized. Rule out fuel filter.

Pull the plugs. No spark. Plugs and wires are brand new. No visual damage.

So - I’m no fuel (6.5v), I’m no spark? And no OBDII scan tool connect.

My thoughts:
Bad ECU.
short circuit to fuel pump
timing? Distributor cap?
Maybe the new main relay is a bad one (Autozone)
safe mode or anti theft mode activated. I didn’t think 2000 Civics had that…anybody confirm.

After a terribly long write up (sorry) could this be or is this all characteristic of a bad ECU? Anything I’m missing?

A million thank you’s in advance!

 

Is everything original in the car? Have you done any mods or engine swaps?