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Yet another question about a flooded car (1998 Honda Civic LX, ECM/PCM partially submerged)

I live in Mexico City and it’s the rainy season. Five or six days ago a heavy rain fell and flooded my street for an hour or so. I didn’t think it got too deep, but apparently I was in about the worst spot and when I got into my car the next day I experienced a very damp sensation and noticed small puddles on the floors. I soaked up the water a bit and, thinking the water hadn’t gotten very high, tried to start me car. It turned over but never started. I tried a few times without luck. I let it sit another day to “dry out”. I tried to start it the next day and, again, no luck. I waited another day, did some more drying inside, and tried to start it again–still no luck.

At this point, after having done a bit of research on this discussion board, I realized I was gonna have to do a bit more work to dry my car out and, more importantly, that I may have more dire troubles since my ECM/PCM (i.e. the computer) was partially submerged in the flood. (After pulling the center console out–that wraps around the shifter stick–I verified that the water went as high as about the bottom of the stick which was high enough to put the ECM at least halfway under water.)

Finally, I pulled the ECM box out, praying it wasn’t full of water. After bringing it inside and taking the side plate off, it didn’t appear too bad. Though the plate makes a pretty good seal, dirty water DID leak in through the bottom—where the connectors attach to the circuitboard—and made it about one inch up the circuitboard. One connector had some powdery residue on it, which may have formed when I heard the snap, crackle, and pop (a few times) when I turned the key to ON. I only hope my ECM/PCM is not toast at this point.

Today, with the ECM pulled out, I tried to start my car once again. It didn’t.

So, finally, here are my questions:

  • With everything else in working order, can my car start without the ECM/PCM?
  • If this is the case (that it CAN start without an ECM), what could be likely causes of it not starting? I haven’t done anything with “blowing out the water” or checking for spark, as I don’t have any tools with me (though I can easily get tools to change the plugs).
  • I checked the oil on the dipstick and didn’t see any signs of water, though I’m not sure it’d show up there. Is it absolutely vital to change the oil and filter (and trans. fluid, and fuel filter…) before the car is started?
  • If I do need to replace my ECM, can I install a used one from another 98 Honda Civic LX without needing to install new software or reset it (or whatever) as others on this discussion board have said at times?

Thanks very much in advance! Dean G.


You won’t be able to start the car without the ECM.

If you see no signs of water on the dipstick and can get the car to start then go for it, most likely the water level would need to get quite high before it entered the engine.

Just for kicks you could take the spark plugs out and turn the engine over just to make sure that water didn’t get into the combustion chamber, but if it did and you’ve been turning it over already you’re probably fine (or at least can do no worse).

As long as the part number on the used ECM matches or is compatible with your existing ECM then go for it. Normally resetting the ECM involves unhooking the battery for a few seconds. Since your car is a '98 there should be no special procedures that you need to follow.

Good luck!

I once drove my 1998 Civic through a tropical storm, and managed to screw things up, but after several days of letting the engine dry out, things went back to normal.

I would pull off the plug wires, the plugs, and maybe the distributor cap to let things dry out for a few days and try again.

If muddy water got into the ECM, first thing to do is flush off all the circuit boards with distilled or purified water. If the mud sticks, use a paint brush to remove it. Flush three times, then flush with alcohol and let dry for 24 hours.

The powdery residue on the connector may be some corrosion, brush it off with an acid brush. You can get these at a plumbing supply store. You can also use one instead of a paint brush.

Do all the things in the previous posts. This applies especially to the distributor cap.

When you check the oil, if the oil level is above the full mark, there is water in the bottom of the oil pan. The oil is picked up by the oil pump from the bottom of the pan so you want to get it out of there before you start the engine. Same for the transmission. If you have an automatic transmission, the dipstick was under water.

You do not want to start this engine if the automatic has water in it. Right now, you can drain the transmission and get most of the water out. Once it starts, then getting the water out will be far more difficult.

Thank you all very much–your suggestions make a lot of sense. I’ve taken the distributor cap off and it appears dry in there but can’t hurt to let it “breath” a bit. I took the rear plate off the ECM assembly and have the circuitboard completely detached from its metal case. I now see more dirt and powdery residue on the other side and will definitely give the water/alcohol rinse a go. Carpet and padding are still a mess and may be tossed, but if I come away with a car that still gets me from A to B I’ll be very happy. Thanks again! Dean G.

The ECM is the brains of the system. It turns the fuel pump on when you try to start it and directs when there will be spark for the spark plugs, what the fuel ratio will be and so on. Just can’t do without it. It would be like taking the mother board out of the computer and looking at the screen.

You can certainly get a used ECM. The numbers need to match on the outside. Also (at least on GM) you have to take the prom out of the old one and put it in the new one. Now, there is no certainty that that is the problem though. It could be other components as well such as the crank sensor which would have been low enough to get flooded.