'97 Plymouth Voyager O2 Code PO140

Voyager97

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Got a '97 Plymouth Grand Voyager with intermittent O2 codes. Pulled two, "Heater Circuit Low Voltage", within about 2 months. Got a P0140, "O2 Circuit No Activity Detected", just the other day. CEL stayed on for about an hour of driving, hasn't come back on since. Turned itself off while driving. Fuel econ. seemed curiously poor while code light was on and for about a day after code turned off. May be that I was just paying closer attention to fuel gauge.. Both codes were for downstream sensor on cat.

Wiring/connector looks great on both the sensors.

Now, since the codes are coming and going, I would assume that the downstream sensor is starting to get tired. Not dead yet, but getting there. I have a nice OBDII scanner, I want to check the voltages. What range should they be reading at? I also think replacing them would be a good idea just as a, "tune up", repair, van has 127k with original O2's.

Anything else I should look at before replacing? I see that both sensors should be replaced at the same time, and I'd like to replace both, but the upstream could be a real to get a wrench on without a lift.. I can see it, but kind of out of arms reach, looks like the only way to get to it is from underneath, or by removing intake manifold. If it's worth just replacing the downstream sensor, as that's the one with the problem, I will just do that. Van's valve cover gaskets are weeping some, will need replacement in the future. I'd have to pull intake manifold and fuel rail to do that anyways, I'd tackle the upstream then...

Thoughts?
 
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Got a '97 Plymouth Grand Voyager with intermittent O2 codes. Pulled two, "Heater Circuit Low Voltage", within about 2 months. Got a P0140, "O2 Circuit No Activity Detected", just the other day. CEL stayed on for about an hour of driving, hasn't come back on since. Turned itself off while driving. Fuel econ. seemed curiously poor while code light was on and for about a day after code turned off. May be that I was just paying closer attention to fuel gauge.. Both codes were for downstream sensor on cat.

Wiring/connector looks great on both the sensors.

Now, since the codes are coming and going, I would assume that the downstream sensor is starting to get tired. Not dead yet, but getting there. I have a nice OBDII scanner, I want to check the voltages. What range should they be reading at? I also think replacing them would be a good idea just as a, "tune up", repair, van has 127k with original O2's.

Anything else I should look at before replacing? I see that both sensors should be replaced at the same time, and I'd like to replace both, but the upstream could be a real bit*h to get a wrench on without a lift.. I can see it, but kind of out of arms reach, looks like the only way to get to it is from underneath, or by removing intake manifold. If it's worth just replacing the downstream sensor, as that's the one with the problem, I will just do that. Van's valve cover gaskets are weeping some, will need replacement in the future. I'd have to pull intake manifold and fuel rail to do that anyways, I'd tackle the upstream then...

Thoughts?
I replaced the upstream sensor on our 2007 Grand Caravan with the 3.3.

I would guess your '97 is similar.

Once I pulled the cowl it was not too bad - the hardest part was pulling the wiper arms first.
 
I replaced the upstream sensor on our 2007 Grand Caravan with the 3.3.

I would guess your '97 is similar.

Once I pulled the cowl it was not too bad - the hardest part was pulling the wiper arms first.
The '07 (4th gen) is not the same as my '97 (3rd gen). My upstream sensor is right underneath the intake manifold. Only way to really get it mine, is from underneath car, or remove intake manifold.

Much easier on 4th Gen's..
 
The '07 (4th gen) is not the same as my '97 (3rd gen). My upstream sensor is right underneath the intake manifold. Only way to really get it mine, is from underneath car, or remove intake manifold.

Much easier on 4th Gen's..
Thanks, good to know - I haven't worked on a 3rd-gen.

1. What were they were thinking?

2. Glad they improved the design going forward.
 
Sometimes its just worth paying a shop, that’s my thought. If nothing else, have them crack it loose for you.
Yeah, a shop is likely going to charge me for an hour of labor even if it only takes 20 minutes. They're not going to put the car on the lift and charge me $30 bucks.. Lol. If I decide I can't get the upstream, I'll have them do both O2's for me.
 
Why all this extra work? Just change the rear o2 sensor, it's easy and cheap.
Because I'm nuts.. 😅

I read somewhere that both sensors should be changed at the same time. Not sure how true that is, but makes sense to me.

I'm going to attempt to get the upstream, if it proves too difficult, I'll get the downstream done, and replace the upstream when I decide to pull the intake manifold and fuel rail, to do the valve cover gaskets.. That doesn't seem like a difficult job, just a lot of taking apart and putting back together.
 
I don't have much to share as far as your O2 question, but I couldn't help but reminisce over your 3rd Gen van. Being in my early 30's now, I grew up during the "minivan craze". It seemed every family had a van of some kind, at times becoming almost a competition to see who's van had which cool feature.

Of course, after slugging it out through their first child with their 1987 Cavalier hatchback and 1987 Dodge Colt 4 door (years approximate, both horrible) my parents decided to splurge the year my sister was born: They landed on a fire engine red 1993 Plymouth Voyager with matching red interior. Short wheelbase. Options, you ask? Boy was it loaded! My folks really went to town ordering things such as an oil-drinking Mitsubishi V6, air conditioning, power LOCKS (no, not windows), and the one-step-up cassette deck. No tinted glass, no gauge package, absolutely no other options.

Funny story about that van: The transmission grenaded itself the afternoon of my high school freshman orientation, quite literally out front of the school. Ended up selling it to a friend's dad who used Plymouth Sundance parts to convert it to a never factory produced 3.0/5-speed van. I actually drove it, it was fun!

Anywho, now that I've painted a picture of my initial van experience: after the '93 died my folks upgraded to a low-mileage '97 T&C LXi that was LOADED. That dark green over camel leather with the gold pinstripes and gold lace wheels... the one that was in the brochures. This would have been in... '03 and it probably had 60k on it at the time, so still low mileage. That's the van I passed my license test in... good memories.
 
I don't have much to share as far as your O2 question, but I couldn't help but reminisce over your 3rd Gen van. Being in my early 30's now, I grew up during the "minivan craze". It seemed every family had a van of some kind, at times becoming almost a competition to see who's van had which cool feature.

Of course, after slugging it out through their first child with their 1987 Cavalier hatchback and 1987 Dodge Colt 4 door (years approximate, both horrible) my parents decided to splurge the year my sister was born: They landed on a fire engine red 1993 Plymouth Voyager with matching red interior. Short wheelbase. Options, you ask? Boy was it loaded! My folks really went to town ordering things such as an oil-drinking Mitsubishi V6, air conditioning, power LOCKS (no, not windows), and the one-step-up cassette deck. No tinted glass, no gauge package, absolutely no other options.

Funny story about that van: The transmission grenaded itself the afternoon of my high school freshman orientation, quite literally out front of the school. Ended up selling it to a friend's dad who used Plymouth Sundance parts to convert it to a never factory produced 3.0/5-speed van. I actually drove it, it was fun!

Anywho, now that I've painted a picture of my initial van experience: after the '93 died my folks upgraded to a low-mileage '97 T&C LXi that was LOADED. That dark green over camel leather with the gold pinstripes and gold lace wheels... the one that was in the brochures. This would have been in... '03 and it probably had 60k on it at the time, so still low mileage. That's the van I passed my license test in... good memories.
I love the story! I passed my license test in my van too! My father bought it from the family of a deceased lady with 90k. She quite literally drive it to church on Sundays. I needed a car once day, and van became mine!

People really talk smack about these vans, I find most of the time it comes down to poor maintenance. They complain about the transmissions, but still ride around with 30 year old ATF3. People will always find something to bi*ch about.

Every car has it's issues. For some reason the Chrysler minivan is the punching bag. These vans are not '96 Corolla's, but take care of your stuff, and it'll take care of you. I go above and beyond for my van, and she runs better than some of my old Honda's.
 
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