Montague

In short, I have a 2003 Accord EXL 2.4L that won't stop showing the check engine light, with a code of P0135. This is the timeline of work I've done in an attempt to fix it:

1. Replaced the upstream O2 sensor with a universal sensor from Autozone. Should have done my research, of course this one wouldn't work.
2. Replaced it with a DENSO sensor (this one). Still no luck.
3. Took it to a shop that kept it for a week, drained my battery, and did diddly squat to actually fix it.
4. Took it to another shop that scratched their head, told me "something weird is going on with your battery," and said good luck, we can't help you.
5. Convinced that the battery wasn't the problem, I relented and took it to a honda dealership for a full diagnostic. They recommended I replace BOTH O2 sensors even though I'm only getting the code for the upstream one closer to the front of the car, as well as replace the fuse box relay because I was "getting high voltages." For the bargain price of $900.
7. Bought a fuse box relay from a junkyard for $90 and replaced it myself - didn't fix or change anything.
8. My battery died while I was in the supermarket, guess it is time to replace it. Did.

I've tried resetting the codes, both soft (via an OBD2 reader) and hard (leaving the battery unhooked for several hours). When I reset the codes the CEL turns off, but comes back on after ~5 seconds of the engine being on. I should also say at the start of this fiasco it was also giving me a code for the downstream O2 sensor, which I replaced and the code went away. I've been driving this car with a failed inspection sticker for close to 6 months now. Here in Massachusetts I can't keep doing this much longer. Back in CO where I moved from, I could cover the light and as long as emissions were fine I was good to go. Out here they check the codes. I've already dumped ~$600 into this "problem" (the car runs fine otherwise and passes emissions fine).

This is what I'm thinking for my next steps:

1. Replace the DENSO O2 sensor with an OEM sensor.
2. Buy a multimeter and spend a Saturday afternoon testing everything I can for bad connections.
3. Sell the car in another state.

I like this car. #3 seems absolutely ridiculous given that it's operating extremely well and the car is in excellent cosmetic shape. Any advice you all may have would be greatly appreciated!!

lazlong

#2. There's only 3 possible causes- a bad sensor right out of the box, a bad wire/connection or a bad ECU. Find a service manual and do the diagnostic tree for the heater circuit (P0135).

You can get a paper copy here for about $50: Service Manuals, Owner Manuals, Wiring Diagrams, Service Bulletins - Helm Incorporated Or you can get it on disc or download from eBay for a couple of dollars.

You can get a multimeter For $7 @ Harbor Freight or find a coupon for a free one when you buy something.

EDIT: To test the sensor, measure ohms across the heater circuit terminals of the sensor connector. You should have 10-40 ohms.

Montague

Awesome, thanks for taking the time to read all that and pointing me in the right direction. I've got a multimeter on the way, I'll get my hands on the diagnostic tree and hopefully I can get to the bottom of this.

Thanks!!

DaddyMack2698

I need to replace bank 2 sensor 2 in my 2003 accord can someone help please? Where is it at? A diagram would be great if possible..

lazlong

Bank 2 is the front bank (closest to the bumper). Sensor 2 is the downstream sensor (behind the catalytic converter).

DaddyMack2698

Thanks! Do u have a diagram? I found two with two different spotstyles for bank 2 sensor 2

lazlong

Sorry, don't have a diagram. And I don't know what a spotstyle is.

Your cat should be in the exhaust manifold. Look at the manifold, it should have a sensor sticking out the top and a sensor sticking out the bottom. Sensor 2 is the bottom one.

DaddyMack2698

Is the diagram right? The bank 2 sensor 2 is located in the front, bottom near the front bumper?

Jlmejia316

^^^ That is the V-6 model. The bank 1 sensor 1 HO2S sensor should be located in the intermediate pipe between the exhaust manifold (header) and catalytic converter. With the DTCs that are present, it appears you may have a circuit or ECM/PCM problem. Make sure your getting 12V at the power to the HO2S heater with the KOEO. Make sure when your checking continuity, that the connectors on both sides of the circuit are unplugged. Anything that exceeds 5 Ohms is excessive and the circuit should be overlaid.

DaddyMack2698

Yes I do have the v6 model. So as pictured, bank 2 sensor 2 is in bottom front by bumper? I just wanted to know before changing. Thanks

lazlong

Yes, front bottom.

DaddyMack2698

Thanks very much I'll let u guys know how it works out!