Chrysler Pacifica Luxury meets versatility in this mid-sized sport utility vehicle

O2 Heated Sensor (four wire) question

Old 04-11-2018, 10:19 AM
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Default O2 Heated Sensor (four wire) question

I have purchased aft and fore four-wire heated O2 sensors from the Dealership. They come with four wires: Blue, White, Black and Black. From what I can tell one Black wire goes to ground and the other Black wire goes to the PCM Heater control. I "believe" the Blue wire goes to PCM Signal and the White wire goes to PCM Return.

Is this correct?

The reason I ask: Prior to doing any work my Pacifica was throwing 132 and 138, and the Live Data Graph on my hand-held ODBII reader show both sensors falt-lining at 1.270 VDC (zero variance). I replaced the O2 sensors and the problem was not resolved. I "toned" the O2 sensor wires in the harness (unplugged on both ends) and Ohm'ed the ground and all seemed good. So I purchased a re-manufactured PCM. After swapping the PCMs I tested again...and still received the 132 138 check codes.

At this point I was convinced I was dealing with a wiring issue. I bypassed the aft and fore O2 sensor wiring and ran my own wires. At first I was able to see some voltage variance on the aft O2 Live Data Feed (nothing on the fore O2 sensor). Now they are both flat-lined at 1.270 vdc. To me, this sounds like a ground issue given both O2 sensors are reading the same. But, all grounds seem good. So now I have to make certain these sensors are wired correctly (hense my question).

Many thanks for any insight.
Old 04-16-2018, 07:51 AM
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This weekend I bypassed the stock wiring from the PCM to the pair of brand new Mopar O2 sensors. My reader live data is showing zero variation in O2 sensor readings (both still flat lined at 1.270v). So, at this point, I have replaced the PCM, O2 sensors and wiring. I triple checked the wiring and everything is good.

Now, I can run the Pacifica for 30 minutes with no check code. Then turn off the engine and restart. After which I receive P0132 and P0138 within 30 seconds. I can clear the codes and repeat these results.
All I can think now is I am having an O2 sensor heater issue. Maybe some undocumented voltage feed specifically for the PCM that drives the heaters. Other than that...I am at a total loss now.
Old 04-16-2018, 01:50 PM
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Old 04-16-2018, 03:25 PM
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2005 Chrysler Pacifica 2WD 3.5L 120k miles
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