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2002 Chrysler Town & Country 3.3L V6: P0134 O2 Sensor No Activity Code After Replacement

Model: 2002 Chrysler Town & Country Fault Code: P0136 Posted: 2014-03-13 19:40

Hi everyone, I'm new here and hoping to get some help with a recurring O2 sensor issue on my 2002 Chrysler Town & Country 3.3L V6 engine. The Check Engine Light came on, and after scanning at Advanced Auto Parts, the diagnosis was a faulty upstream O2 sensor for Bank 1. However, a technician at Napa Auto Center offered a different interpretation — they said the catalytic converter was operating inefficiently and advised not to replace the O2 sensor, citing poor fuel economy as a concern. They reset the code, which lasted about 100 miles before returning with the same P0420 code (Catalyst System Efficiency Below Threshold for Bank 1). I replaced the upstream O2 sensor (Bank 1) with a new Denso unit purchased from Rockauto.com, advertised as 'Original Equipment Manufacturer' at $40. After installation, the vehicle triggered a new P0134 code — 'O2 Sensor No Activity Detected'. My buddy who installed it used his scanner and observed two voltage readings; he noted that the upper set of values should change when revving up, but no change occurred. I've since read that a blown fuse for the O2 sensor heater could cause this behavior. Does anyone know where the heater fuse is located on a 2002 Chrysler Town & Country 3.3L V6? Vehicle details: 2002 Chrysler Town & Country, 3.3L V6, OHV, flex-fuel capable. Note: The P0134 code indicates the engine control module (ECM) is not detecting any signal from the sensor — this could point to wiring issues, a faulty sensor, or an electrical fault such as a blown heater fuse.

Related fault codes

P0136P0137

Comments (6)

Anonymous 2014-03-14 04:58

Hi Tim, try swapping the newly installed Bank 1 upstream O2 sensor with the Bank 2 upstream O2 sensor. Run the vehicle and monitor for any code. If the P0134 code appears on Bank 2, it indicates that the wiring between the ECM and the sensor in Bank 1 is intact — the issue lies with the sensor itself or its circuit. If no code appears on Bank 2, then the problem may be with the sensor or heater circuit. Let me know your results.

Anonymous 2014-03-14 10:07

If you're seeing a P0420 (Catalyst System Efficiency Below Threshold — Bank 1), the PCM compares pre-cat and post-cat O2 sensor readings to determine efficiency. Catalytic converters rarely fail on their own; common causes include oil contamination, misfires, fuel control issues, or exhaust leaks. You replaced a pre-catalyst O2 sensor (Bank 1) when you had a P0420 — this is not recommended. A faulty O2 sensor does not directly cause a P0420 code. The code indicates the system detected an issue in the catalytic converter's performance. Important: Do not 'kill the messenger' when bad news arrives. If you replaced the pre-cat O2 sensor, consider reinstalling the original one to verify whether the problem is with the sensor or elsewhere. On vehicles equipped with Mopar NGC (Next Generation Controller) systems — which combine the transmission and ECU into a 38-pin connector — the O2 sensor circuit design includes voltage bias. The ECM provides a reference of 2.5 volts on the 'signal low' wire, and the sensor's output is added to this reference so that it oscillates between 2.5V and 3.5V (instead of 0–1V). This behavior can be observed with an oscilloscope when measuring between signal high and signal low. If you're replacing O2 sensors on these vehicles, ensure wiring integrity from the ECM to the sensor is confirmed before proceeding. Mopar part number for pre-cat fuel control O2 sensor: 4686938AB.

Anonymous 2014-03-24 09:34

Thanks for the clarification. I replaced the Bank 1 upstream O2 sensor because Advanced Auto Parts initially flagged it as faulty, and Napa suggested a catalytic converter efficiency issue. I assumed replacing one sensor at $45 would be cheaper than a full converter replacement (which could cost up to $300). If the converter does need replacement, I’ll have a new sensor ready for installation. Are there two upstream O2 sensors? I only see one in front of the catalytic converter and another behind it — is that correct?

Anonymous 2017-09-20 12:28

Just to update: I recently fixed my own P0420 issue on a 2005 Dodge Grand Caravan. The fix involved replacing the downstream O2 sensor and adding a check engine light eliminator adapter (~$30 total). For reference, here's a YouTube video showing the process: https://www.youtube.com/watch?v=qkhDeOvvvX0&t=324s

Anonymous 2017-09-20 13:33

You did not fix the root cause — you simply eliminated sensor readings. The system now sees invalid data, which can lead to unsafe driving conditions and potential emissions violations. This is dangerous and not a valid solution. Please ensure any fix addresses actual performance issues rather than masking them.

Anonymous 2017-09-22 08:07

Note: This post is over three years old — while the technical details remain relevant, it's worth considering that some solutions may no longer apply to current vehicle models or software versions.