2004 Honda CR-V - P0134

Have 2004 Honda CR-V (4 cylinder) with a P0134 "O2 Sensor Circuit No Activity Detected Bank 1 Sensor 1".

I have performed the following tests:

1. Harness side - Checked both signal wires and verified the desired 1.8V on one and 2.1V on the other, so I have the power coming to the sensor

2. Harness side - Connected a test light across the heater circuits and started the car and test light lights so that circuit seems fine

3. Sensor side - Checked continuity of the Heater circuit and it is within spec.

4. Followed the test procedure with the scan tool (SnapOn Modis Ultra)...Turned the check engine light off, ran the vehicle at operating temperature, saw a flat line on all sensor signals. Rev'd it to 3000 RPMs, held it there and the check engine light came on within 1min and 30 seconds. This verified the sensor was dead according to the manual.

My issue is that I put a new sensor in this car a little over a year ago and now it's dead again. I'm wondering if there could be another issue or if I've missed something. Given this is actually an AFR sensor and I'm not as familiar with these as I am O2 sensors, I'm thinking I'm missing something, doing the wrong tests, or not performing a certain test. I've verified I have the proper voltage coming in and that the heater circuit on the harness side has power so I believe it to be the sensor again.

My questions:

1. Are there other tests to perform that I haven't already completed?
2. Is there a known problem with aftermarket sensors (I'm using a replacement from Denso, Part # 234-9005?
3. Am I over thinking this and it's just a dead sensor?

Please let me know if I can provide any other data to help you help me.

Thanks!

I think you're just looking at another failed sensor, honestly. If you've rechecked the signal circuits and the heater since the newest sensor failed, then I think you're good to go. You're doing the exact same tests I'd do. Was there a warranty?

I'd suggest taking a close look at the sensor tip when you get it out. Any evidence of coolant or oil could possibly explain the failure of the new part. High mileage 2.4's like to drink oil...

OK, thank you! I'll take it out and see if there is any residue (that's a good call). I'll put the new sensor in and see what I get as far as live scan data to verify it's working. I'll write back if there are any new issues.

So many counterfeit parts around it is more than possible that that is the issue.

Update - I put the new sensor in and the signal is still dead while viewing the scan data and the code comes back in 2 mins. Not sure what's going on here, but I guess I have to redo the electrical checks because clearly something is causing the interruption of the signal to the PCM. Do I have to check the PCM?

If you have any ideas they would be greatly appreciated.

What the...?

Would you mind rechecking the signal circuit? Voltage on both wires, sensor plugged in this time. We gotta be missing something.

Eyeball the sensor connector, harness side, for spread pins while you're there.

The 2.2V and 1.8V readings you saw the first time around should have verified PCM and wiring integrity. I suppose something could be wrong inside the the PCM, as a lot of the air/fuel ratio sensor magic takes place there, but I've never seen it before.

OK here's what I've gone back and done (just to check my test methods as well)...connected a jumper wire from BAT NEG connected to the negative probe on the DVOM, then DVOM positive connected to harness and sensor back probe T-pins.

1. Sensor unplugged, took voltage reading on the harness side KOEO. I have 1.8V on signal Negative (yellow wire), 2.1V signal Positive (red wire). This is exactly what ShopkeyPRO test procedure says is normal.

2. Sensor plugged into harness, took voltage readings. I have 1.8V on the on the sensor side Negative (yellow harness wire to white sensor wire), 2.1V on the sensor side positive (red harness wire to blue sensor wire).

When I look at scan data as the engine is running and in closed loop it's a flatline for both of the following:

AF Sensor (mA) = -127.5
AF FB AVE (LT Fuel) = 1.00
AF FB CMD (A/F) = 14.56
AF LAMBDA = 2.00

These values are the same when the car is KOEO too.

Not sure where to go from here because everything I test seems to say I have a good signal.

Additional info:
KOEO Heater Circuit Values were...

Harness side sensor unplugged Heater pin #1 (not sure + or -) was 12.3V and the other was 2.7V
Sensor plugged in 12.3V on both black heater wires (via T-pin backprobing)

Thanks for reconfirming those readings! I'd like to see the sensor high signal closer to 2.2V, but that can come down the DMM being used. Not off enough to cause an issue, IMO. Otherwise, those numbers are awesome.

I'd love to hear other members weigh in on anything I've missed, 'cause otherwise I'm going to suggest an OEM sensor. :lol: As in, from the dealer. Or the OEM part number, at least.

The last few directions I had in my mind were:

1. Try an OEM part (a ~$300 trial effort)
2. Test the PCM, although not sure how to do it and what to look for
3. See if a factory reset would fix the issue...if it were computer related. Drain the capacitors and then reconnect to see if the computer still can't read it.
4. Ship it to a dealer to see if they can figure it out.

I did speak to a Honda tech I know and he were baffled as well. He did say it could also be caused by other issues like an exhaust or intake leak since the sensor couldn't set at the right pressures, or a coolant temp issue, but I don't see any sign of that at the surface level.

69Camaro wrote: 1. Try an OEM part (a ~$300 trial effort)

Yeah, that's rough.

2. Test the PCM, although not sure how to do it and what to look for.

I've always used the 1.8/2.2V readings as a confirmation of the PCM, but maybe that isn't accurate. The -127mA reading suggests to me that the PCM is capable of detecting current flow and direction. If you disconnect the sensor, does that value go to zero?

3. See if a factory reset would fix the issue...if it were computer related. Drain the capacitors and then reconnect to see if the computer still can't read it.

I like this. See if you can find the radio code beforehand. radio-navicode.honda.com if you can't.

I did speak to a Honda tech I know and he were baffled as well. He did say it could also be caused by other issues like an exhaust or intake leak since the sensor couldn't set at the right pressures, or a coolant temp issue, but I don't see any sign of that at the surface level.

I hadn't considered this. But, if I remember correctly, -127mA is a FULL lean reading. If the engine were truly that lean, it'd also be running like garbage. There'd be a noticeable idle problem. Lemme look at my old captures and see if I can find a good example for comparison.

Out of shear curiosity, my Mitchell and Alldata show P0134 on this vehicle;

"A/F Sensor (Sensor 1) Signal Stuck Lean"

Did you get the info in your original post from Shopkey?

You may need to perform an ECM reset, and be certain you have no exhaust leak upstream of the A/F, which usually sets a Heat Pump fault, but can set lean.

I'm assuming you've already tried to richen and lean the mixture watching scan data for a response.

I dug up a comparable CR-V on ScanShare.io. The data shows the sensor current reading at zero or very close to it KOEO.

www.scanshare.io/share/Lu2V8lwLqE6LamAHEKTdjg#0,1,2,3,4,5,6

Some others I found in my files. Both 2008 (closest I could find quickly). Both show a very near zero reading KOEO or cold sensor.





Again, I'd be interested to know if that -127mA reading goes away KOEO with the sensor unplugged.

Weycraze's suggestion to lean and richen the mixture is a good one. If all else fails, we can test the signal wires for shorts to ground with an ohm meter. It's a hassle, but I can't think of much else that'd cause this.

Any luck with this one?

I did the factory reset and performed the baseline test (held the engine at 3000 RPM in closed loop). No Check engine light after 5 tests and three road tests. Returned the vehicle to the owner (feeling skeptical that it was solved). Today was notified by the owner that the engine light has returned. I'm due to look at the vehicle again Friday, so I will perform the unplugged tests suggested by "Weycraze" as well as the Rich/Lean tests. I've also been using scan data, I should backprobe and use the lab scope to monitor.

I have been getting all my data/info from my Snap On Modis Ultra and Shopkey. The code shows on the Modis and Shopkey as the "No activity code" mentioned in the original post.

I do these various other things and get back to you this weekend.

Thanks.

Thank you for the update.

So, after the reset, the sensor started operating properly? As in, it came off of -127mA and went back to 0mA? Fuel trims were reasonable?

UPDATE: So the engine light came back on and got all the same readings I've been getting which shows everything being good. I told the customer to take it to a Honda dealer and specifically have them look into the PCM. They just called to tell me that Honda says everything checks out and they want to replace the sensor with a Honda part. I warned them that I didn't think that would be the issue, so we'll see what happens. I'll keep you posted.

Again, many thanks for the update. Can't wait to see how this one turns out.

I've been considering the possibility of an intermittent short to ground, causing the PCM to get 'locked' into this goofy -127mA reading. I've never seen it before, so I'm not sure what a short would do to these circuits.

I need to find someone with one of these vehicles so I can do some testing! :silly:

Customer declined the work there and is bringing it to me so I can swap the sensor for a Honda version (Saves her $200 for me to do it). Doubt that will work but Honda says that's what it needs. However, that means I'll have the car again if you want to let me know what types of tests to perform. I can even upload videos of the testing if it helps. This is such a weird one...but it was nice to here that the Honda tech found all the same results as I did. They just didn't dig further into it as they think it's the sensor.

Yeah, it sure sounds like they saw a non-OE sensor and just stopped there. Maybe it's something they see often, and are confident an OE sensor is the fix?

When are you getting the car back? I'd like to dig around in Mitchell for other A/F sensor codes, and see if any of them cover shorts to ground or shorts between A/F + and -. If there's codes that cover those types of faults, then I'll feel a lot better about doing the OE sensor. I'll be back at work Friday, so I can do some research then.