2005 Honda Accord Hybrid sedan, 3.0 i-vtec engine. Battery goes dead if it sits a few days. There is a parasitic drain when I turn off the car.

Tools: 1) inductive ammeter. 2) cut-off switch on negative battery terminal. 3) eight-loop wire bypass that bridges the cut-off switch, so battery is always connected, and I can read DC current with inductive ammeter.

Test #1:
- Connect battery and loop.
- Start car, turn off car.
- Close car door. Wait a few minutes.
- Disconnect cut-off switch, leave loop in place.
- Current reads 5 A / 8 at the loop (way too high).
- Wait an hour.
- Current still reads 5 A / 8 at the loop.
- Remove the loop, reattach it.
- Current reads very low at the loop.

Test #2:
- Connect battery and loop.
- Start car, turn off car.
- Close car door. Wait a few minutes.
- Disconnect cut-off switch, leave loop in place.
- Current reads 5 A / 8 at the loop.
- Pull 15A fuse #8 (F1 ECU) at engine compartment.
- Current reads very low at the loop.
- Put fuse back in.
- Current reads very low at the loop.

So disconnecting and reconnecting either the battery or "F1 ECU" stops the parasitic drain. But I don't know what to do next to figure out the cause. No idea what F1 ECU circuit does. Any advice appreciated.

Daniel

 

You need a shop manual w/ a wiring diagram to know everything that is fed by Fuse 8. I looked at 4-cyl manual and there were a number of items fed by fuse 8, however hybrid wiring may be different.

Once you have wiring diagram, you need to sequentially "unload" the circuit by disconnecting items to find the circuit pulling load when keyswitch is OFF.

Shop manual and wiring diagram are essential.

good luck

 

On the Hybrid, under-hood Fuse No. 8 (15A) protects the following components/circuts:

• Data Link Connector (DLC)/ aka OBD-II port
• PGM-FI Main Relay 1.

 

Thanks to both.

Any suggestions about buying a repair manual? I like having a manual. But the ones at the auto parts stores for this car seem pretty generic, with many models included. And the shop manuals seems expensive.

It turned out my local library had a service called chiltonsonline as part of being a library user. I just took a look. It's not great. But it does have electric diagrams.

From Fuse 8 under the hood, it says a WHT/GRN wire runs from "E6" to "D10" under the dash. Then, it goes to "PGM-F1 Main Relay 1", just as you said. Then it exits the little box via "N10" and goes to the DLC (I take it the OBD-II port). I looked around under the dash. I see the fuse box with 3 rows of 11 fuses. I see the ODB-II port under the dash (never saw one before).

Not sure how to test next? Would it help to have the OBD-II port scanned? Do I need to expose the "PGM-F1 Main Relay 1" and do some test? Or maybe replace it? Why would there be a parasitic drain for so long, and then stop when fuse 8 is cycled? It certainly can't be a short, there would still be a short after I put the fuse back in, right?

*** I did another test, this time waiting two hours after shutting the car off. After two hours, it was down to 0.22A / 8 (plenty low), taking into account the 8-wire loop. So after turning off the car, it runs high about 0.7 amps for about 90 minutes, related to fuse 8, then goes down to about 0.03 amps. Any idea why it's doing for so long?

And now I'm puzzled why the battery was drained empty. Sounds it would drain maybe 1 amp-hour (0.7 amp x 1.5 hours), not a huge amount. But it did drain empty, multiple times, and there was never a door ajar or dome light left on.

Any suggestions are appreciated. Thanks again.

Daniel

 

Power from Fuse No. 8 is hot all the time.

• The DLC should not be the source of the excessive parasitic draw unless something was hooked up to it or there was a short in the wiring. Otherwise, the Wht/Grn power wire for the DLC circuit terminates there.
• It would be unusual for the PGM-FI Main Relay 1 to be the source of the excessive parasitic. That relay is normally open. So, unless the PCM sends a ground signal to energize the relay coil and close the relay contacts to allow power from Fuse No. 8 to go through the relay, or if the relay contacts were shorted closed to allow power through; it also may not be the source of the excessive parasitic draw.-- You can pull the PGM-FI Main Relay 1 from the under-dash box and see if things change. (Main Relay 1 is the middle relay in the upper row of three relays.) There is a possibility of the main relay contacts intermittently shorting closed.

You might want to read my other posts in this other thread regarding excessive parasitic draw:

https://www.hondaaccordforum.com/for...y-drain-61105/

 

Thanks for the link to the previous posts. There is nothing hooked up to the DLC / OBD-II. And other than this problem, the car seems to work fine.

It sounds like the DLC and the "PGM-FI Main Relay 1" (I take it "Programmed Fuel Injection") are unlikely causes of a parasitic drain. It also seems the Main Relay is not that easy to get at. Is it tricky to expose?

2003 Honda Accord ECM/PCM Removal and Replacement | Motobild | Auto Repair suggests this activity might be normal behavior. Is that the case? Is it normal for the car to draw some 0.7 amps for about 90 minutes after turning the car off, and then go to sleep? And what might the car be doing for those 90 minutes?

At a minimum, I will have the battery checked again at parts store next chance I have, and scan the ODB-II port. Otherwise, not sure what to do next.

Thanks,
Daniel

 

PGM-FI main relay 1 is the middle relay in the upper row of three relays, above the row of 4 relays. Although unusual, it doesn't rule out the relay.