I have been getting a P2000 check engine light on my '05 Honda Civic Hybrid and I have two questions:

I am not sure what the code means. ALL (4) of my scanners (An Auto Xray, CarCode Serial Logger, PLX Kiwi Wireless and DashHawk) all say it means NOx Trap Efficiency Below Threshold. Which directs me to look at the O2 sensor outputs which are alarming...voltage levels on O2 sensors are high for rich, low for lean. Sensor 2 is between the cats, Sensor 3 is aft of the second cat. My second sensor is chronically higher voltage (by 50mv or so) than my forward sensor. When I warm the cats up (spirited driving, etc), it goes way beyond that.

Now the OBDII reports a short term fuel trim capability for both the second and third O2 sensors and the second fluctuates mildly between -2 and 2, probably normal. The third is pegged at 99%.

So I'm guessing due to it registering more rich than the two in front of it, that it has failed and that the failure mode is to do something that the computer will see and flag (like fail rich). The cat isn't rattling or anything so I don't suspect it at this point.

The rub in this while dilemma is that a few places online show a P2000 code as a 'Hybrid Battery System Voltage High' code.

Is anyone here a shop tech who can help me out to either validate my assumption here about the tertiary O2 sensor or verify/deny the P2000 code as a 'Hybrid Battery System Voltage High' issue?

Thanks,

Jason

 

Not a shop tech, but I received info regarding this update; it may be useful in your situation:


http://www.tegger.com/hondafaq/p0420/A07-036.pdf

 

I have your solution.

My car was always showing a p2000 pd (post diagnostic code, meaning it doesn't turn on check engine light). But it also would occasionally flip the CEL on with a p2000 code. It also began throwing a p0134 (front O2 sensor). I too had lost 10 mpg.

Here's the thing:
The O2 sensor will throw the p2000 code, and possibly a p0134 code whenever you breach 10% difference in expected NO levels. Compared to a regular car, the window of allowability is very small for a hybrid.

I was thinking, "catalytic converter, oxygen sensor, $$$".

Turns out it isn't these things. It's your EGR valve that needs cleaned.

The purpose of the EGR valve is to recirculate NO into the engine; hence the name "Exhaust gas recycle" valve. If it becomes clogged, the NO goes straight into your exhaust, tripping your sensors and setting off codes. It is not part of regular service procedures, and yours likely has never been cleaned. Mine wasn't.

It's a simple, do it yourself project. It requires a can of carb cleaner ($2.50) and a 10 or 12 mm socket with extension. You can order a new one for $110, but the most you'll need is the gasket if yours is disintegrated like mine was.

Here is a write up that includes how to do it:
http://www.civicforums.com/forums/11...e-up-mods.html

The write up is for a normal civic, but the procedure doesn't change.

I was frustrated too; but once I cleaned my EGR valve, my gas mileage is back up to 47 mpg and all my trouble codes have cleared! No O2 sensor, no new catalytic converter.

Hope this helps!