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Oh Honey, I Forgot To Tell You! On My Way Home Yesterday

I need another favor from you guys, already!

Wife’s work commuting car:

1999 Dodge Intrepid 2.7L V-6 (not a boat anchor, yet)

135,000 miles

Automatic Transmission

Check engine MIL light on. Using Actron Reader I got PO133. Official $100+ Chrysler Factory Manual says 1/1 O2 Sensor Slow Response (Oxygen sensor response slower than minimum required switching frequency).

This car has 4 identical O2 sensors, one upstream on each bank and one downstream on each bank. The two upstream ones stare right at you from the front of the engine, easy to get to, under the hood, cool! 1/1 should be the upstream sensor on Bank One.

Most FWD engines are tranversely mounted. This one is stuck in there, longitudinally, just like a RWD.


I am getting conflicting information as to which side (passenger, driver, right, left) Bank 1 is on. One site says that it’s easy to know with transverse, up for debate with longitudinal.

Can you tell me where to find out for sure, specifically, which side is Bank One? I’m thrifty and the sensors are $70 a throw. I don’t want to move it around.

Can I unplug an O2 sensor and set a DTC to find out? How long would it take to set?

I still have an AC sensor socket wrench in the toolbox that says it works on Chrysler, too. Do you have any tricks to get out a 10-year, 135,000 miles old sensor, just in case it doesn’t just turn right out? Is Bosch as good as Chrysler or are they the same?


I need to be educated. If you guys can tell me where to read the answer, I would greatly appreciate it!


Might bank #1 go with cylinder #1, which is the one further forward? Just a guess…

Cylider #1 Is The Forward Cylinder On The Passenger Side, Right (Right Bank).

Is that “Bank One”, for sure? The ends of the crankshaft (longitudinal engine) point at the front and rear bumpers, just like the old-fashioned GTO’s and Mustangs (I miss them).

I would look at the O2 sensor waveforms to confirm one is bad. Then change both since the others’ days are probably numbered.

Good Idea.

I have no way of checking waveforms out here in the snow laden boondocks, but I can put in both upstream sensors. I was just trying to be thrifty.

Look at the cylinder heads. The cylinder head that protrudes out furthest in front of the engine is Bank 1.


You are aware of how often we “remind” people to have/get some kind of repair manual. For some things, especially the DYER, the simpler Haynes, or Chilton’s, repair manuals are better. For instance, the factory manual says, “Use factory scan tool and do so and so with it.” It won’t tell you how to do it if you don’t have some particular factory tool.
At go to Specifications, Specifications, Firing Order. After you do, you will come up with this:,23200242/shopping/specsSelect.htm
I wouldn’t do preventative oxygen sensor replacement. I would: a few minuets after the engine ran, exchange the front oxygen sensors. Then, disconnect the battery for 5 minuets to erase the code (On some cars, this won’t work). Drive the car to see if the CEL comes on. If it does, scan to see which position it’s indicating.

Here It Is, Thanks!

Thanks Hello Kit, Texases, Tester, and Circuit Smith. You all agree. It’s the passenger side. That’s what I thought would be Bank 1, the right side. My book has a good diagram showing cylinder numbers and staggered cylinders (cyl. #1 out front on right), but uses Right Bank and Left Bank, not Bank 1 and Bank 2. The confusion came when an oxygen sensor website advised that it is not straightforward on a longitudinally installed engine.


To answer your other question, if you unplug the sensor, the MIL should come on almost instantly.

Thanks And I Am Thinking The Engine Has To Be Up To Full Operating Temp

Thanks Again, Everyone!

The old sensor fought me a little, but gave up and came out clean. I ran an 18mm thread chaser in there (went right in by hand, no wrench needed) and installed a new Bosch sensor. It did come with anti-seize already on the threads. I turned off the MIL.

Next time When I Here, “Oh honey I forgot to tell you …”, I hope it ends with, " … I baked you an apple pie, today!"

Find out for us. Really! The engine computer will (may) give you a code for “Sensor Disconnected” even if the engine is stone cold.
The engine computer won’t go into “closed loop” operation until it gets to a certain temperature (when the ECM begins to “listen” to the O2 sensor); but, that doesn’t mean that it’s “asleep”.

Disconnecting It Added PO134 To The PO133

PO134, according to Chrysler manual says: 1/1 O2 Sensor Stays At Center (Neither Rich Or Lean Condition Is Detected From The Oxygen Sensor Input.)

I had to drive several miles to get it up to temp, I assume. There were no additional codes when first disconnected.

Just go to AutoZone and they can show you the location. They helped me out with two problems re: O2 sensor and small EGR leak. Fixed the problems with their free loaner tools, also. Both probs together fixed for under $100.