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FLASHING CEL, returns p0131 (o2 sensor), but no misfire codes?

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Old 01-12-2012, 09:19 PM
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FLASHING CEL, returns p0131 (o2 sensor), but no misfire codes?

Today the mechanic changed the coil and the wires, and effectively cleared my p301 (cylinder 1 misfire) and 1399 (random codes). However, after driving the car for 1/2 hour, the flashing CEL came back, but now the car had noticeable vibration. I took it back to the shop, and they told me the 1399 (random) was still there, and they suggested cleaning the EGR ports. A seemingly logical next step , I told the shop I'd be back tomorrow to get that done, and the made my way out. As I was leaving I noticed , one of the shop-owners whisper into the mechanic's ear. But it was all a bit too suspicious. I decided to immediately make my way into AutoZone, and have the code pulled for myself.....It came up a p0131, with no other misfire codes. The shop lied to me about the 1399 still being there, and obviously to get me back in for a repair (cleaning EGR ports) that is irrelevant to the flashing CEL. But worse, it's clear that somehow they intentionally contributed to the 0P131 (bad primary o2), and made the condition of my vehicle worse. Either they purposefully installed a bad o2 sensor, or they created a short in the circuit, tripping the p0131, all in a plot so that I would come back and spend more and more money in repairs. I have receipts from the shop showing the original codes pulled were p1399 and p301, and I have receipts from Autozone, an hour later, showing the spontaneous p0131. I'm taking them to court.

But anyways, my question is, how could a Flashing CEL, return p0131 (bad o2), but NO ASSOCIATED MISFIRE CODES. I would be expecting a P300 or P1399. Is it plausible the shady mechanic 'rigged' the computer , so somehow it would not return misfire codes? I've heard of something called 'test mode'.............

Last edited by zadeh79; 01-12-2012 at 09:34 PM.
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Old 01-12-2012, 11:25 PM
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Re: FLASHING CEL, returns p0131 (o2 sensor), but no misfire codes?

This is what I found from the the program, All-Data that we use in my shop to diagnose cars. I directly cut and pasted it with no edits.

"Code P1399-Honda does not supply a diagnostic flow chart for this code. P1399 is a random misfire code and Honda/Acura has reported for various models that this could be caused by clogged EGR ports. In addition there is the possibility that the valve clearance specification may be out of range."

This shop you went to prob has this same program, and this is why the most likely why the recommended the EGR port cleaning.

I'm not sure why the O2 sensor code po131:
"The scan tool indicates Diagnostic Trouble Code (DTC) P0131: A low voltage problem in the Primary Heated Oxygen Sensor (HO(2)S) (Sensor 1) circuit."
would come on right after you had a tune up done, except I do know that a misfire could dump too much unburned gas into the cat and cause the cat AND o2 sensor to go bad. And I have never seen a flashing CEL for an O2 sensor before. Most times when it flashes is because of a misfire code. Are you sure auto zone checked the pending and history codes too? Or just the current codes?? It may of had a pending P1399 code not yet stored in current. Some codes take a few trip cycles to actually store the code as current.

The shop may be a sketchy one, But... I highly doubt the shop "booby trapped" your 02 sensor or set you up. You may still have a misfire from something other than the coil or set of wires, like plugs, cap, rotor or injectors, or like alldata and the shop said for random misfire code 1399- dirty EGR ports and make sure your valves have been adjusted properly recently.
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