O2 sensor/cat converter/stumbling question. 2005 Ram

Truck acting up lately. Hesitation on acceleration.

Has the following code.

P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

Listed as the O2 sensor after the cat converter. I looked up the sensor on RockAuto and they show 2 sensors. Upstream and Downstream positions.

Would I be looking for the downstream sensor, seeing as how it is after the cat converter?

In the past I have had faulty O2 sensors on other vehicles, and driveabilty usually isn't affected. Hopefully it's this simple.

05 Hemi Ram with 130000km.


Thanks
codfish

Oh yeah. And bank one is located where????

codfish

Bank 1 sensor 2 means its the bank where the #1 cylinder is and the 2 is the downstream as you are correct on that. So on a V8 Dodge it would be the downstream sensor on the drivers side. Also check for any bad connection as a high voltage code can be caused by a bad connection in the circuit. Ron

Thanks Ron.

codfish

In my Cherokee, the upstream o2 started causing hesitation problems without throwing a code. It was only a problem when the jeep wasn't fully up to temp. Apparently the heating element in the o2 can fail and not trip a code, and until the sensor is up to temp it won't work properly, causing a hesitation. Make sure you keep your o2 wires routed far away from the exhaust when you replace it!

Good to know.

I replaced the "downstream" sensor and unhooked the battery to clear the code. No more code or light showing and the first short drive seemed fine. So far so good. I got a 7 hour drive tomorrow so we'll see how it goes.

Thanks
codfish

I ended up replacing BOTH downstream O2 sensors on my '04 Hemi Ram. I did the B1/S2 and a couple weeks later...B2/S2 flagged a code. To say I was is an understatement

So.

This morning I let the truck warm up for maybe 5 mins before I left on my 7 hour drive across the province. Worked flawlessly.

Got to my destination, shut it down and went inside. about 3 hours later, started it up, and drove off. Once again, truck started to hesitate heavily while going up a short but somewhat steep hill. Check engine light flashed on and off this time. . I couldn't stop where I was due to traffic, so I drove to the nearest parking lot. (truck drove fine once the check engine light stopped blinking). I turned the truck off, and checked for any codes by turning the key ahead 3 times in 5 seconds. No codes showing . Hmmm.

Started it up, ran a few errands and drove back to the house. Seems to act better once it's up to operating temps. Tomorrow morn I will warm it up good before I drive it to see if it makes a difference.

Any ideas or educated guess?? Wife wants me to trade it in. I don't want to, but.............

codfish

Maybe the catalytic converter is going bad??? That O2 after the cat monitors the cat. Is the converter overheating (glowing red at full heat) or rattling on a cold start?

My 03 with a 4.7 played that game. It was the back sensor or so we thought. Turns out it was the harness upstream from the plug had rubbed thru on the edge of the cat heat shield and shorted = hi voltage code.

Kevin

The upstream 02 measures emissions before the cat as a reference point to compare to the downstream 02 after the cat. This is how the computer knows to lean out or richen the mixture.

A blinking MIL on an OBDII vehicle means cylinder misfire. It may not show a code but a scan tool may see a pending code in memory.2 consecutive trips with a failure will set an MIL/DTC

The thing is the downstream 02 also sets the goal for the upstream 02. High voltage means rich so it could cause the upstream goal to drive lean and have it running lean enough at times to cause a missfire. You need to have someone who knows what they are doing to scan it and moniter the 02 volts and look at all sensors , codes and trip failures. Ron

Thanks guys.

Ron to get it into a reputable shop for a scan honestly takes 4-5 days wait time here. All shops flat out busy. So for now I will try my best to figure it out. I have a hand held code reader at home (seven hours away) lol.

So I warmed the truck up this morning for maybe 4-5 mins and all seemed well again.

But as mentioned above, there does seem to be a "rattle" every now and again when driving before everything is up to operating conditions.

Is there any sure way to tell if a cat converter is on it's way out?

Thanks for the replies guys.

And of course the truck has 2 of everything (upstream and downstream O2 sensors and 2 cat converters.)

So will checking the temps of the converters help with finding out which one is going bad? I do have a digital temp gun.

Just doing alot of reading on the subject and the symptoms of a faulty cat converter sure do match with what I'm experiencing.

codfish

If the substrate inside the cat(s) goes bad - they can break-up or get loose. It's not unusual for the padding around the brick to fail & then the brick gets loose inside - sometimes they can even turn sideways & block exhaust flow. I had a '96 Ram with a bad cat & it rattled like heck on a cold start, but then when things heated up, the rattling stopped - it never threw a code though. Dodge replaced it under warranty - the OE cats are covered for 8 years or 100,000 miles federal law. When the truck is cold, get under it & put a glove on & bang on the cats & see if one of them rattles inside. If it does, the brick is loose & it needs replacing.