Matticus289

I've got a 1999 Honda Accord, standard 2.3l (NOT the ULEV). I had a p0135 code (O2 Bank 1 Sensor 1 Heater Circuit) pop up months ago that I'd been putting off and finally decided to fix this week. I had the knee-jerk reaction that I think a lot of people have of just replacing the sensor. I bought a denso 02 sensor from rock auto that didn't solve the problem. It proved to be faulty (was only reading ~.2 ohms across the heater). So, I ran down to autozone and bought a bosch they had in stock. Tested the heater coil and it came in at 15 ohms where it should be. Put it on, fired up the car and voila! Or so I thought. I drove it for about 5 - 10 minutes and the same code came back.

I checked the resistance across the heater and it still came in at ~15ohms. I followed the procedure of checking for power and ground. I have ~12 volts on the black/yellow wire and I've got ground on the black/white wire. So, at this point, I don't know what else would be giving me the code. It appears to be getting what it needs, but the computer doesn't seem to think so. The only thing left that I've seen hinted at is that the computer is bad. I even wired up a 15 ohm resistor to attempt to verify/trick the computer into thinking it had the resistance it needed. No dice. Seems a little odd to me that the CEL went away for a while after first replacing the sensor, but now it comes on immediately after trying to clear the code, but it may be nothing.

Is there anything left to check? A replacement computer is a bit pricey to take a gamble on, so I really hope someone has a magic wand I can wave over this old girl before I do that and find out it isn't the problem either.

99stockcivic

It could be the ECM, which is the only thing I can think of left.

But if you look here:
https://troubleshootmyvehicle.com/ho...0be%20replaced.
It might give you some more troubleshooting first.

Matticus289

Thanks, but that's just a repeat of the steps I've already taken to test for power, ground, etc

Jeremy64

i pcked up a used ecm form my local upull for 20$ and came with a 30 day warranty. May be worth a try.also check www.car-parts.com make sure to use the - between the two words

Matticus289

I'm mostly concerned about dealing with the issues of getting my current keys working with the replacement. The part cost of the replacement computer isn't bad, but I'm seeing talk of a few hundred to get it programmed right.
I see a few videos/articles about modifying the computer to either bypass the key immobilizer altogether or soldering components from the old computer to the new one, but nothing specific to my vehicle. Anyone had any experience with that? I'd prefer just to disable the dang thing so any key will work. I used to have a corvette from the 90's that had a "VATS" (vehicle anti-theft) system. It was a great day when I realized I could just test the resistance across the chip in my keys and then solder in a set of resistors that matched up to the ohms on the lead that went to the computer. Can't find anything like that for Hondas yet...

99stockcivic

I've done both on the keys front.

1 - I bought a reprogrammer - It's called a CK-100+ , they are available from a variety of places, including Walmart
https://www.walmart.com/ip/Car-Key-P...0aAuWAEALw_wcB

It's easy to use, you plug it into the ODB-II port, have your keys to be reprogrammed, and simply hold each one near the device as you add it to the system. Takes 5 minutes to do.

No matter where you go, it's about $100 for the device. It has no limit to amount of keys to be done.

2 - a bypass. This is maybe not as easy, since it requires some soldering of the bypass chip, but it's cheaper because it's only a few bucks for the chip. No need to program keys any longer, they all work if they fit in the lock
https://www.ebay.com/itm/Immo-Emulat...QAAOSwqMxfaEan
$17

3-buy the kit together
Or you can even just buy the whole thing together already done for you, no need to learn anything, just install it.
https://www.ebay.com/itm/1999-HONDA-...4AAOSwPHhfstM1
$99

Matticus289

Excellent! Thanks for finding those options for me!

IndySporty

So what fixed the car? I have a 2000 honda accord with the same problem, known good NEW O2 sensor and I am getting neither power nor ground at harness connector. I checked output at C1 ECU connector (primary O2 sensor heater circuit ground) and it has ground with key off, but with key on only partial ground (something like 5-7v) and I checked fuse 6 is fine getting 12V with key on. Also no code for secondary O2 sensor heater circuit and secondary O2 shows sensible voltage readings in live data. Primary O2 sensor is stuck at 2.65V always in live data.

Is there a known harness damage/short issue similar to 96-2000 civics have underneath intake manifold?

Matticus289

Hrm...if you aren't getting power or ground at the harness, you have a different problem than me. Mine ended up being the computer wasn't reading the 02 sensor, but it was at least getting power. I suppose your issue could still be the computer, though. When I pulled it out, even before I opened it up I could smell burned electrical components. I opened up the computer and found this:




I swapped out the computer and bought a key programmer from walmart. Worked like a charm. If you get a new ECU, DO NOT get the bypass kit. I ruined one ECU trying to get the stupid bypass chip in because it ultimately wouldn't fit right. The soldering pads were spaced too far away.