Another o2 sensor thing….First! I have read most every codes thread I could find here and elsewhere, so have pretty good idea what it could be. that said I thought I would post my specifics and see if I can get any closer to a solution. What I have a 04 D2 that intermittently show the CEL for codes P0160/P0161. Can happen everyday or once a week, at idle or at speed, cold or warm. What I have done -

Truck purchased July 2020 175k

• Cooling system overhaul July 2020. All the usual pieces. Runs 195-204.8 deg. 95% of the time. No leaks or pressurization.
• Oil pressure is good. 52 psi @ idle cold and usually over 40 psi @ 2000rpm hot. Has the Rover hot idle tick. I’m in the piston slap camp on this and ignore it - for now.
• Plugs & Wires August 2020- This smoothed out the idle - mostly and overall drivability. Codes still popped up randomly.
• Both rear o2 sensors replaced August 2020. Walkers. Appeared to slow the CEL down but it returned.
• CEL appeared to light more frequently and gas milage seems to be worse. so -
• Cleaned MAF Jan 2021
• Replaced front o2 Sensors Jan 2021 with Walkers. Should have done all 4 last summer. Truck ran smoother then it ever has for three days. Then BOOM! CEL pops back up P0160. idles rough-ish again. To be clear the idle is not that bad but is a bit rough. I think its running rich but exhaust doesn’t smell. Took photos of the UG info below. The number all move in range but the o2 B2S2 does not fluctuate nearly as much as the others, hoovers around .450v but does move. Knowing it can default to .450 but not sure if this is the case for me as it does fluctuate some. Hoping this is evidence to something specific.

So thinking -

If it gets a reading in all 4 sensors, are they all working?

Is the ECU working?

Could there be an intermittent short in the harness which is why the CEL pops up randomly?

Why did it work great for 3 days with the new sensor then back to before? Did it roast the new sensor that fast? why?

New gas cap needed?

Any help appreciated.

 

I have owned 16 of these, still don't have the codes memorized. If you post asking for help, tell us not just the code but what the code reads.

So that code is for downstream sensor, 0160 is no activity, 0161 is bad heater circuit. That combination typically means a wiring issue, on top of that downstream sensors almost never go bad. That said, it is possible the ECU is bad but that is very rare.

To truly diagnose, we need more data. You need to chart all four sensor voltage readings. Use the torque app or a similar scan tool that will chart the voltages. Chart and record them from cold start up. They should go near 1 volt when cold and then start cycling. The 0160 code means they are not cycling, but it also indicates only the rear is not cycling.

If you want, you can check the wiring at the ECU to see if anything is grounded. If it is, you have a wire pinched.

Good luck.

 

Thanks Extinct, Good info. I have a Foxwell that is supposed to chart but I haven't tried it yet but will. Question, how do you test for ground at the ECM? Thanks Again

 

Ok, got the chart info off of the Foxwell. looks like banks 2 rear is flatlined. this is at operating temp +/- 195 deg.

 

Ok, easiest test is to swap rear 02s left and right. If the flat reading stays with the 02, you have a bad sensor, if it stays with the location you have a wiring or ecu problem. My money is on the sensor.

 

Thanks Extinct, I will give that a try when the weather clears here. On my truck had the front driveshaft cut loose at some point in its life as there is evidence of it. Banged up the tranny bellhousing and put a decent dent in the floor. The b2s2 sensor harness looks to be rebuilt as the shaft probability whacked the original away. That said the wires go above the tranny and disappear so I am a bit worried how to get to the wires where I can't see them. Any tricks for this? Is there another connector upstream from the O2 sensor connector or just harness? I have the Rave page 17-2-14 with control voltage listed. Is that the voltage to test for a short? Thanks again.

 

You will need to disconnect the connector plug from the ECU, the one with the 02 sensor wires in it (don't remember which one that is but rave will show it). Check each pin with an ohm meter to ground. If any have continuity to ground you have a problem. Unfortunately wiring in the main harness runs to the back of the engine, down the top of the trans tunnel, so it might be easier to run new wires if you have a problem.

 

Ok thanks. I have the Rave page for the connector. Sorry to be thick on the procedure to test for ground but it's a bit new to me. Would the below be correct?

• Unplug connecter at the o2b2 side
• Unplug connector at the ECU. This would be connector 2 (C635)
• With DMM put setting on ohm setting. Any one will work? 20/200/2000?
• Touch one lead to pin on harness the other to chassis for ground. 0 is the correct number for good wiring. Any other number indicates resistance and a problem?

With my intermittent code appearances it would make sense there is a short due to truck vibration etc. I might have my son shake (gently) the wiring harness for the o2 connector while I test to see if it changes.
Thanks again.
Edit - When looking at the ECU which connector would be C0635 that has the o2 sensor pins? There are 4 I labeled A-D

 

You have it correct, set it to the lowest setting. Don't remember which connector it is but the Rave wiring diagram shows the connector number, then the connector illustrations in the electrical manual will show the connector position and which wires are which 02's.

 

Well...the plot thickens. Had a weather window today and got tired of zoom calls so I decompressed by crawling under the truck. First I unplugged both rear o2's and checked power at the harness. With the key on I got .45v and 12v at the two pins indicated and 0 at the other two. If my sources are correct that's OK as the other two are grounds. See image below. This was the same for both rear o2 connectors. Not messing with the fronts here. Moving on I decided to checkout the wiring as I suspected it had been "molested". Sure enough, I got into the harness side and it looks like it has been rewired on both sides all the way up to the top of the tunnel. The good thing..ish is I was able to snip several zip ties and get the harness loose to inspect off one side of the tranny. The loom disintegrated as it came down so I need to replace that, no big deal. So at this point with daylight leaving, I switched the rear o2 sensors set the harness back with zip ties until I can get new loom, etc. Checked voltage, same as above. Started it up. Cleared the p0160 code and let it warm up. Foxwell shows the same, b2 flatlined on the right, b2 wavy on the left. No code so far. Rats! I was hoping the voltage reading meant the wiring was OK, which it might be. Does this lead to ECU issues? Other than this little debacle the truck is great.