[b][/b]I've been chasing a P0134 code for "no signal bank 1 upstream O2 sensor" on our 2001 Chrysler T&C with the 3.8 V6 for a while now. In another thread I explained how a groundhog or rodent chewed the wires of both upstream and the downstream O2 sensors (and two ignition cables) so I had to replace them. After I did I still get the the code P0134 so I replaced the upstream O2 sensor with another new one (Denso, listed as O.E) and still get the error code P0134. Doing more internet searching I find a story of how an owner of a 2005 was told there were two different versions for the upstream 3.3/3.8 V6 and the only way to tell that you get the correct replacement is by a code/stamping on the original? Along with that his Mopar dealer told him that you can only get the correct version through Mopar??? I called our Chrysler dealer's parts department and he said there is no such information that he has heard of or sees in the parts info but he has heard of problems with aftermarket O2 sensors from auto parts stores and would only trust an O2 sensor from a Mopar dealership's parts. The O2 sensors from Mopar are Denso and so are the two that I got from the local Advance store at less than 1/2 the price of the $160 Mopar O2 sensor.

The fact that I'm still getting the code P0134 after two Advance Denso O2 sensors and after checking the wiring harness and ECM connections, etc., makes me think that maybe there is some truth to this but......... My good friend said today that of the more than 50+ O2 sensors that he has replaced over the years he can recall 2 sensors that gave him issues like described that they were out of the read parameters of the ECM but......

Anyone ever run across issues with auto parts sourced O2 sensors versus a Mopar sensor?

TIA,

Mike

Not O2 sensors but throttle position sensors: yes. I tried the parts store TPS on my '01 and they simply did not work correctly. As soon as I put a Mopar one in, truck ran perfect.

Like yourself, I found Denso to be the OEM supplier for Chrysler, so, I'm using the correct Denso O2 sensor on one of my 2Gens and am not having any issues.

You might have an ECM issue due to the nature (ha ha ) of the wiring issue you had. There could have been a voltage spike if two of those bare wires touched, or, if one touched metal. Related: I have a steady error code because I was messing around with resistors on the O2 wiring to fool the computer to think my catalytic convertor is still there. I zapped my ECM, because the code immediately switched to powertrain control error, but the truck has been running fine for years like this. It was just the downstream O2 sensor circuit that was cooked so it doesn't affect how the truck runs.

Have you looked at scan data for the o2 sensor? Does it toggle rich/lean? If not...have you tried forcing it rich/lean to see if it reacts? Almost sounds like an open in the 02 signal circuit which would put the signal voltage at roughly 450mv. From Alldata:

SYMPTOM
P0134-1/1 O2 SENSOR STAYS AT CENTER

WHEN MONITORED
Engine running for greater than 121 second. Coolant Temperature greater than 66 °C (150.8 °F). Engine in closed loop fuel control mode.

SET CONDITION
O2 signal voltage is between 0.35 volt and 0.58 volt for a total of 30 seconds and than O2 signal volt is 1.5 volts for 60 seconds. One trip fault.

Just got back from running it over to my best friend's house and he put it on his Snap-on scan tool.........not good news. He thinks the ECM got zapped because at first we had a flat line on the scan tool for the upstream then a spike to 3.9-4.0 VOLTS on both O2's After clearing the code and about another 1.2 miles of road test time we got the same voltage 4 volt spike . The upstream gave the strangest info, while the downstream was perfectly normal. Then the voltage spike to 4.0 volts and the downstream went flat and nothing and the check engine light. Then the downstream came back to a normal graph/signal while the upstream stayed flat......

Dcuda69 thanks for the info and funny thing is my friend rattled off the very same info as the SET CONDITIONs that you posted like he knew it off by heart. And all of the rest of the info you posted was displayed on the Snap-on scan tool too. Thanks again.

And thanks Grizzly for your info too you were pretty much spot on with the voltage spike issue....still happening

Mike

Wow...weird stuff! Might want to check to be sure you don't have a short to voltage from the heater circuit caused by your critter attack. I saw 7 volts on an o2 circuit years ago from a short to heater voltage...strangely enough it was another Chrysler mini-van. Good luck!!!

Any time.

I'd try an ECM from Pick and Pull, and maybe double check every wire again just to make sure one didn't get missed.

What controls the heater voltage?

I did a continuity check of the wiring harness from the connection of the upstream O2 sensor to the wiring harness and to the ECM and everything seemed to be fine. One of the 4-pins was 12v when I grounded it to the battery (-) (with the key on) so I thought that it was for the heater circuit and thought everything was okay or is that my problem?

I just checked with my local Advance store and know all of them for years and they can get me a Cardone remanufactured ECM for -30% or about $160 and they'll take a return but I don't want to fry it if the voltage spike is from the 12v at the one of 4-pins if its not supposed to be 12v there??? The scan tool never showed more than the 4 volts at the O2 sensors so I'm hoping it's the ECM

Thought we'd be clever and unplug the downstream O2 sensor and maybe find out that was the real problem with the voltage spike. First I cleared the P0134 upstream O2 sensor code and dash check engine light. I got under and unplugged the downstream O2 sensor at the connection. Start the engine and expected to see the check engine light but nothing yet so I drive the van and as usual in about the same driving distance/time the check engine light appears. Do the 3x key on off cycle and the P0134 code and only that code appears at the odometer and nothing for the downstream (which I don't at this point know what that would be?). I was hoping to see only the downstream or a new/different code or at the worst both the P0134 and a new code for the downstream O2 sensors but still only one code P0134. It doesn't recognize that I've unplugged the downstream O2 sensor I plugged in my "pocket" INNOVA scanner/code reader and the same results just P0134. What do you guys think, is it ECM time??

So, that permanent code I get from messing with my downstream is P0601, Internal Control Module Memory Check Sum Error.

I looked up Chrysler specific for your code and got this:

P0134 CHRYSLER Possible Causes

1. Faulty Front Heated Oxygen Sensor Bank 1
2. Front Heated Oxygen Sensor Bank 1 harness is open or shorted
3. Front Heated Oxygen Sensor Bank 1 circuit poor electrical connection
4. Inappropriate fuel pressure
5. Faulty fuel injectors
6. Intake air leaks may be faulty
7. Exhaust gas leaks

Because your code is still specific to the sensor (and not the Internal one I get), I think your problem (hopefully) still lies in #2 or #3 above.

I know it's a PIA, but follow those four wires off your upstream as far up the vehicle as you can. Blow the connection out with compressed air and use a wire brush inside the plug connection too. I know you know what you are doing, but check also where those wires enter the body of the sensor. The body is sharp and it's real easy to break a wire screwing in the sensor and not see what you did.

Hold off with the ECM for the time being unless your parts supplier is real understanding and will let you return it if it doesn't fix the problem.

I'd hate to be in your shoes having to repair Varmint damage.

OBD II has a ton of monitors(tests) it runs when you drive your car. Not every component is tested every time. Many components/systems need to fail on 2 consecutive trips to set codes. Contrary to popular belief, many systems/components take some time to actually set codes. Is there pending codes set??

For example: That downstream 02 is only used to test catalyst efficiency so the ECM doesn't look at that sensor until it's time to run that catalyst monitor(test). If you fail to drive the vehicle under the conditions required to run the catalyst test.... the ECM never looks at the downstream 02.

My dad had a 300C that received rodent damage on the engine harness. My brother and I replaced the harness but it still ran like poo. We dropped it off at a dealer, 06 or 07, stating that it was running rough. They checked it out and found several of the injector drivers in the PCM were shorted. The unit got replaced under warranty since we didn't give them the full run down. So... you may have some issues upstream that are not obvious physical damage.

How did you "replace/fix" the chewed wires? Code is for the ECM/PCM not seeing any change in the return signal. The heater circuit only "heats up" the sensor faster to get it to operating temperature. Even without the heater circuit not working you should see some change in the return signal as it heats up on it's own from the exhaust(using a scanner). When you checked continuity did you move the wires around to see if you still had continuity? If all the above check out you can wire in a potentiometer to the return signal wire then move the pot and see if it shows up on the scanner. This will tell you that the wiring and ECM/PCM is good.

I had to buy a Mopar for the upstream sensor on my '04 Neon R/T because the aftermarket replacements were too long to clear the heat shield.

The last plan of attack was to unplug the downstream O2 sensor and see if it threw a code for both the upstream (code P0134) and the downstream (P0139) or just the one code or..........???? As you may have read above the results only the upstream "no signal" came up. Off to find the best price on a new (re-manufactured) ECM that just so happened to be unique to the 2001 model Dodge and Chrysler 3.8 V6 and 3.3 V6. My friends at my hometown Advance came through with a great price of $199 and a $30 re-flash with VIN and mileage by Cardone they couldn't get around. Considering the best I could do before was $360 or $499 from the local Mopar dealer I was pretty happy, especially because the guys and gal at Advance said they would take it back (refund) no questions if it didn't fix the problem. I get the new ECM the very next day, flashed and ready to go, but should I check anything else before I install it or just plug it in and see???? I clear all of the codes and I install the ECM and take it for the test drive on the route I've been using and get to the point where the check engine light has been coming on (about 1.5-2.0 miles) and NO CODE OR CHECK ENGINE LIGHT! But I'm not breathing yet so I drive it some more, and more and more and now I'm up to about 14 miles and no code. So I think about how the first time I took it to get E-checked and E-check said I didn't have enough time on the ECM to get a stable reading and figure I would drive some more and put maybe double the mileage on it to be sure and..........yep I hit 15 miles and on goes the "bing Check Engine" light. Drive back home and do the 3 time key on and off and on and two codes appear, the P0184 for battery disconnected within the last 50 starts and a new code P0139 YDS .

Check what the YDS is for and find out it's the "YOU DUMB $#!T" YOU FORGOT TO RECONNECT THE DOWNSTREAM O2 SENSOR YOU DISCONNECTED"!!!!

Connected the downstream O2 sensor the next morning (engine too hot), drive to the E-check, passes and the van has been great and the A/C is ice cold and everything it great again. THANK YOU EVERYONE for all of the help and guidance. Yes the ECM was shorted most likely right when I started the van with the chewed through O2 sensor wires.

THANKS AGAIN,

Mike

Congratulations.

I admire your patience.

Thanks for posting in such an honest way.

If you are glutton for punishment go ahead and tear out your ac evaporator coil from behind the dash and give us a blow by blow description.
My Mother’s van has a slow 134a leak as confirmed by carefully threading the long probe of the Harbor Freight $50 Freon leak beeper through the center vents (barely fits).

“Red Angel” allegedly recovery unit safe leak stopper has cut the freon loss per summer in half.

https://gobdp.com/product/ac-stop-leak/

glad you conquered the beast !
as to the blow by blow evaporator replacement, i did that, [on my 2000 "bus"] and i can truthfully say it takes a LOT of blows to accomplish !
however, i don't have any pics. while you are in there, you might consider replacing the heater core as well. [unless 2001 was the change year for removing the heater core "easily" from around the gas pedal assembly]

Anytime, Mike. Glad it worked.

KTM