P0135 driving me NUTS!

[Ironliftr3]

Okay, I've got a 98 civic DX, 145K. The engine light went on a couple weeks ago, P0135 O2 sensor heater circuit bank 1 sensor 1. So, I replace the pre cat O2 sensor with a Denso. Works fine for a couple days, then the light comes back on. Re-checked the error code just to make sure it's not another problem. Same error. Reset the code. Good for a day an a half, the error comes back. Check wiring and connections, reseat and clean the connectors, disconnect negative battery cable. A-okay. For a day and a half. Code comes back. Measured the sensor. The sensor side measures good. Here's the weird part. I've only got 8-9 VDC on the heater side, pin to pin, coming from the car. Doesn't matter if the sensor is plugged in or not, car running or just the ignition turned. Never 12 VDC. Measure from the connector to the chassis ground, and I get 12 VDC. Obviously not a fuse, the hot side is good. I get an open from what I assume would be ground to the chassis. SHOULD the heater be getting a full 12V? Should the ground be a direct ground to frame? I'm about to run a wire FROM the connector direct to the damn frame. That will sure as hell give it 12V, for better of worse! Any other ideas? I'm thinking it's GOT to be a wiring or connection problem on the ground side somewhere.

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[gearbox]

im pretty sure its a wiring issue because it should be getting 12v. if it does not stay "heated" enough, it will throw the engine light even if the sensor is good.

[Ironliftr3]

Double checked the voltage. Now I am getting 12V to the heater. Of course, it's WORKING, with no engine light, at the moment. Damn intermittent problems. None the less, I'm sure you're right Gearbox, gotta be a wiring problem someplace.

[gearbox]

nice. at least it was easy fix

[ScottDR]

That is always nice . If it comes back on, bring back the new o2 sensor and get it replaced under warranty.

[Ironliftr3]

Originally Posted by gearbox

nice. at least it was easy fix

I'm not a total pessimist, but I'm not convinced it's 'fixed'! Still crossing my fingers every time I start my car....lol.

I know the o2 sensors are sensitive to shocks, but do they really get damaged that easily? Especially the heater circuit, that seems like a relatively simple circuit compared to the actual input circuit.

I really doubt a brand new sensor, exhibiting the same EXACT error as the old one, and intermittently on top of it, would indicate a bad sensor. 20 years worth of electro/mechanical work (although NOT automotive related) and a degree in electronics tells me this is a connection problem someplace and not the sensor itself.

[ScottDR]

Good point, it's unlikely but not impossible. Another option is unplug the ECM plugs a couple of times each (with the battery disconnected of course), then the sensor where it plugs into the harness again. There are no other connection points between the sensor plug and the ECM, and this would eliminate the possibility of any slight corrosion present in the connectors.

Keep us posted.

[Ironliftr3]

Good information Scott, good to know there aren't half a dozen interconnections between the two points. It's been working for a day and a quarter now, I'm about due for another error code around noon today....lol.

[gearbox]

o2 sensors are picky, if you spill stuff or get them dirty they wont work right, even the outside. gotta keep it clean and i think the heating element is just a big resistor or something. vibration i havent heard is bad for them, my car has alot of shakes and the sensor lasts for its normal life around 60-80k.

[Ironliftr3]

I was thinking more along the lines of dropping the thing onto concrete before installing it causing it to fail. I KNOW I didn't do anything like that.

I did try to reform some of the pins on the female connector side yesterday. So far, so good.

[gearbox]

oh, well yea if you drop it, its dead lol.

[ScottDR]

The new O2 could have been very easily dropped (on cement in it's box) before you received it as well! Keep that in mind

[Ironliftr3]

True without a doubt, but my thinking is that kind of physical damage wouldn't likely cause 'intermittent' problems. I'd think that a truly 'damaged' sensor would give an error code constantly. And why a heater code. I can't know the engineering design of the sensor for a fact, but more than likely the heater is just some sort of resistance coil that heats quickly when exposed to current flow, not different than a light bulb. How many intermittent light bulbs have you seen?

Not arguing with you Scott, just having a discussion, and expressing my thinking behind it. I hope you don't take me wrong, because I DO appreciate the input, and in the end, you COULD be totally right....UPS has NEVER been known to 'kind' to packages!! Still keeping my fingers crossed as the error has been gone for two days now!

[gearbox]

we used to throw parts around all the time at the auto stores when stocking product. im sure the warehouse did its fair share too. we would get containers with all sorts of stuff jumbled together, sometimes the boxes are so mangled that the stuff inside got squeezed out.

[Ironliftr3]

Caveat emptor!