Intermittent problems: Alternator, P0161 and recirculate HVAC - related?

[Martinjmpr]

I'll start off with the basic info: 2004 Suburban LT, 4x4, 5.3, 179,000 miles.

We took a recent 3,000 mile road trip from Denver to the Gulf coast of Texas (Corpus Christi.)

For the 1100 miles down and the 1100 miles back, we were pulling a 3500lb travel trailer (R-Pod 179.) On this trip, 3 separate issues appeared, and I'm wondering if they might somehow be related:

1. The night before we left the truck started throwing a CEL. I have a code reader (Scangauge II) and the code that showed up was P0161, which my internet research shows is an oxygen sensor. I reset the CEL, and it would stay off until I turned off the engine and then turned it back on, and when I did the code would reappear without fail.

2. Once on the way down and twice on the way back up, the alternator light came on and the DIC displayed a "battery not charging" message. This lasted less than 30 seconds and the light went back off. Both times when this happened we were connected to the trailer and towing at highway speeds. The trailer does have a 3 way refrigerator that we run on 12v DC while in motion (once we are stopped we put the fridge on propane if we don't have hookups or 120v AC if we have electric hookups, which we did on this trip.) EDIT: I should note that I replaced the alternator early last year (April 2017) when it failed, so the alternator is a rebuilt unit from an auto store. It is a 145a alternator.

3. When driving through a heavy dust storm, I tried to put the HVAC system onto "recirculate" to keep dust out of the cabin. When I tried this, the light on the "recirculate" button would flash several times and then go off.

Any idea what these issues are and whether they might in some way be related?

 

[Scottydoggs]

recirculate wont work if the defroster setting is being used. it will flash and turn off.

what was the code for the o2? sounds like you need a new one.

no idea on the battery really... other then did the volts drop when the message showed up?

 

[Martinjmpr]

recirculate wont work if the defroster setting is being used. it will flash and turn off.

what was the code for the o2? sounds like you need a new one.

no idea on the battery really... other then did the volts drop when the message showed up?

Hmmm...well the HVAC was set to 'auto' not defrost and it still did exactly what you said - flashed and then went off. I'll try it again on my way home from work today to see if it does the same thing.

As for the battery, the gauge showed the normal ~14v charge. I did flip the Scangauge over to show the voltage but by the time I got it to the VLT display the red alternator light had gone off and it, too, showed 14.5v of charging. It was never on more than a few seconds.

 

[Scottydoggs]

id let the charging message slide for now. might have been the extra draw on the system. you know like when the fridge compressor starts up.

the recalculation button might be a gremlin in there. i dont use the auto, so i never tried to use recalculation button when its on.

 

[Scottydoggs]

i only drive my truck on weekends pretty much, so while warming it up i thought of this thread.

if my cc is set to auto, recirculate dont work, flashes 2 times light goes out.

took a vid, that sound is the wipers, it was raining out.

https://photos.app.goo.gl/Uqk6egFkF2iz3zVn8

 

[Fless]

id let the charging message slide for now. might have been the extra draw on the system. you know like when the fridge compressor starts up.

@Martinjmpr, is the TT new to you, or is there some history of operation with your truck? Previous issues? Not sure if any of this is related to the TT or not.

Is your fridge the absorption style, or does it use a compressor? If it's not a compressor style then there's no excessive startup draw on the truck. Assume you're setting the fridge to only one heat source at a time.

Is the TT battery fully charged when you hook up to go? If it's permitted and works ok, have you tried running the fridge on propane while traveling? Those fridges tend to take a lot of DC draw, and the truck might have trouble keeping up the aux power if power connections (TV or hitch) aren't great.

 

[swathdiver]

I'll start off with the basic info: 2004 Suburban LT, 4x4, 5.3, 179,000 miles.

...code that showed up was P0161

2. Once on the way down and twice on the way back up, the alternator light came on and the DIC displayed a "battery not charging" message. This lasted less than 30 seconds and the light went back off. Both times when this happened we were connected to the trailer and towing at highway speeds. The trailer does have a 3 way refrigerator that we run on 12v DC while in motion (once we are stopped we put the fridge on propane if we don't have hookups or 120v AC if we have electric hookups, which we did on this trip.) EDIT: I should note that I replaced the alternator early last year (April 2017) when it failed, so the alternator is a rebuilt unit from an auto store. It is a 145a alternator.

3. When driving through a heavy dust storm, I tried to put the HVAC system onto "recirculate" to keep dust out of the cabin. When I tried this, the light on the "recirculate" button would flash several times and then go off.

Any idea what these issues are and whether they might in some way be related?

The one thing for sure they have in common is being fifteen years old!

- P0161 is the Bank 2 Sensor 2 and it is for the heating element. Check for a blown fuse, bad wiring. If that checks out, then it is either the ECM or the O2 sensor.

- Did you connect the auxiliary power wire in the 7-pin plug to the truck's fuse block? I would not trust a rebuilt alternator from an auto parts store. Consider 160 amps.

- A Tech2 or other bi-directional scan tool that can read BCM codes can see what's going on with your AC's actuators. No use guessing.

Bill might know about this stuff too. @intheburbs

 

[Martinjmpr]

OK, Update:

First off, the recirculate button "problem" is a non-issue. I dug into the owners manual and found out (to my surprise) that the "recirc" feature does not work if the fan is set to defrost or feet-only (defrost makes sense but I have no idea why it's disabled on feet-only, but it says it in the manual and sure enough, when I put it on feet/dash or dash only the recirculate feature works fine.

WRT the travel trailer: We got the trailer in January and have taken it out 15 times this year, for a total of about 46 nights and around 6500 miles. It does have a 3 way fridge and we do run the fridge on 12vDC when traveling. It is an absorption fridge, not a compressor fridge. The trailer has 2 x 12v Interstate batteries and we keep it plugged in at home to keep them charged. We also run a 2nd fridge in the truck, an Indel-B TB-41 compressor fridge, but that one runs off the "house" battery. The main (starter) battery on the truck is 3 years old and I have run it down to where the truck wouldn't start at least twice since I got it. It's possible, though, that the battery is the culprit. Having said that, the longest it ever showed "not charging" was a few minutes and the problem has not recurred.

Finally, for the P0161 code I'm going to start looking at some troubleshooting guides to see if this is an issue I can work or if I have to farm it out. The truck is due for some other work (front end alignment) so I may just have them look at it then.

 

[intheburbs]

Issue 1) Replace the oxygen sensor. It's a $30 part, and will take you about 10 minutes.

2) I have no experience with absorption fridges. However, doing a little research I found this gem - "Absorption refrigerators tend to be horribly inefficient running on 12-volt power, and will drain the batteries much quicker than a compressor refrigerator." That, plus you have four batteries for the alternator to charge, and it doesn't surprise me that it might have come up a little short a few times. I wouldn't worry about it unless it becomes a regular thing, and in that case I'd look first at the batteries themselves. Then, I'd look at upgrading the alternator. When I needed to replace the alternator in my '01, I bought a 200-amp unit to make sure the truck and trailer had enough juice.

3) Was going to paste a page from the owner's manual after reading the OP, but you figured it out yourself.

 

[Martinjmpr]

Issue 1) Replace the oxygen sensor. It's a $30 part, and will take you about 10 minutes.

Do you have a link by any chance? Is it fairly easy to access this part?