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P0134 and P0135 O2 Sensor Error on 2002 Chrysler Town & Country 3.3L Flex Fuel - Fix & Diagnosis Guide

Model: 2002 Chrysler Town & Country Fault Code: P0134 Posted: 2011-03-26 12:32

Hi everyone, I'm new to this forum and found it through Google. I currently own a 2002 Chrysler Town & Country LX with a 3.3L flex-fuel engine and am experiencing recurring O2 sensor error codes P0134 and P0135. The vehicle has approximately 210,000 miles on it and runs smoothly—no hesitation, no stalling, and no noticeable performance issues when driving. I took the van to an emissions testing facility where they reported these two diagnostic trouble codes (DTCs). However, my check engine light never illuminated during any of the tests. This was confusing because I didn’t realize a CEL could be absent even with active fault codes. The mechanic suggested that the issue might be related to the upstream oxygen sensor located before the catalytic converter—specifically Sensor 1 (bank 1), which is positioned on the rear exhaust manifold. I replaced the O2 sensor with a Denso unit, believing it would resolve the problem based on compatibility claims from RockAuto. After installation, I returned the vehicle to emissions and received the same error codes. The mechanic confirmed that the new sensor appeared physically correct and matched in wiring, but he wasn’t certain whether the engine control module (ECM) needed a reset. I attempted to reset the system by disconnecting the battery for several minutes, hoping this would clear the fault memory—but I’m unsure if it actually worked. The vehicle still shows P0134 and P0135 on the scan tool. My question is: Should I replace the sensor again? Or could there be another underlying issue? I’ve recently completed a full tune-up including spark plugs, wires, cap, rotor, and water pump. The engine runs well under load—flooring it doesn’t cause any issues. However, the persistent O2 sensor errors are preventing me from passing emissions. Any insights or troubleshooting steps would be greatly appreciated. Is there a specific factory OEM sensor required for flex-fuel models? Could a blown heater fuse or wiring issue be contributing to this?

Related fault codes

P0134P0135

Comments (7)

Anonymous 2011-03-26 14:55

For a 2002 Chrysler Town & Country with flex fuel capability, it's critical to use the factory OEM oxygen sensor—such as the NTK part from the original equipment. Denso sensors are not factory-installed and may have different heater resistance characteristics, which can cause misdiagnosis or persistent P0134/P0135 errors in flex-fuel systems where fuel-air mixture sensitivity is high. Always verify compatibility with your VIN to ensure proper sensor matching.

Anonymous 2011-03-26 15:05

I purchased a Denso O2 sensor from RockAuto, which advertised it as the original equipment manufacturer (OEM) part for my vehicle. After confirming all specs—year, make, model, engine type—I was told it would be compatible. Unfortunately, I can't return it now—it's already installed and the emissions test failed again. This makes me question whether third-party sensors are reliable in flex-fuel vehicles with strict emissions requirements.

Anonymous 2011-03-26 19:01

When you turn the ignition key to 'ON' without cranking the engine, does the Check Engine or Service Engine Soon light illuminate? Also, confirm that you replaced the correct sensor—Sensor 1 (upstream) on bank 1, located just before the catalytic converter on the rear exhaust manifold. Misidentification of sensor location is a common cause of P0134/P0135 errors.

Anonymous 2011-03-26 19:35

Thanks for the tip—I’ll try turning the key to 'ON' without cranking and check if the service engine soon light comes on. As for sensor location, I only saw two O2 sensors: one directly before the catalytic converter (bank 1) and another just after it on the rear exhaust manifold. The mechanic told me that the one on the manifold is Sensor 1—this seems to be correct based on standard wiring diagrams.

Anonymous 2011-08-19 14:22

Confirmed—the sensor numbering described in my original post is accurate. Bank 1, Sensor 1 (upstream) is located on the rear exhaust manifold just before the catalytic converter. This aligns with factory specifications and should be the correct target for P0134/P0135 diagnosis.

Anonymous 2014-03-12 18:40

Hi everyone, I'm new here and hoping to solve my O2 sensor issue. Like jmartinez1228, I bought a Denso sensor from RockAuto because they listed it as the OEM original equipment part for $40. However, Oreilly Auto sells an NTK sensor for $28—same model but different brand. My scan tool showed no activity in the sensor signal, and my buddy demonstrated that when revved up, the upper number on the display should change—but it didn’t. I’ve also read that a heater fuse might be blown. Does anyone know where the O2 sensor heater fuse is located in a 2002 Chrysler Town & Country? Any help would be much appreciated. —Tim

Anonymous 2014-03-13 08:18

Tim, this thread is quite old—consider starting a new post with your full vehicle details (year, make, model, engine), all relevant DTCs, and specific symptoms. This will help ensure better visibility and more accurate responses from other users or experts.