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Intermittent transmission slips

Tiny
VSSOUTLET
  • MEMBER
  • 2008 PONTIAC TORRENT
  • 3.4L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 111,000 MILES
This has been a problem since I got the car almost a year ago. Every now and then, the transmission would slip. This would generally happen in traffic. Around 3,000 miles ago, I had a charging issue so I replaced the alternator. Instantly, the problem was gone 99% of the time. Now it is back. When I run my Bluetooth odbii app, I see the power range from the ECM is around 14.5 volts to 16.1 volts. No changing issues yet, but I am perplexed that the problem has recurred. I also noticed that there is a loose wire that goes to the negative battery post. I am not sure where it is supposed to go or if it is impacting this problem. I have attached a photo to illustrate.

Be grateful for any advice or insight.
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Sunday, September 23rd, 2018 AT 10:43 PM

33 Replies

Tiny
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Good morning.

First, are there any codes? Current or history?

16.1 tells me you have a bad alternator. The regulator is no good. The voltage should be 14 to 14.5 volts only. Anything beyond that is no good for any of the modules.

As far as the wire, it does look like a ground but since you have no other issues, it may be nothing. you could run it to the body and see what happens but I doubt it will make any difference.

Roy

https://www.2carpros.com/articles/how-to-check-a-car-alternator
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Monday, September 24th, 2018 AT 4:34 AM
Tiny
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Roy,

Since this is a new alternator, is it possible that the ECM is telling the alternator to put out that much power?

Also, the wrapping around the wire and the length suggests that it goes into a wire bundle of some sort. Any idea which one?
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Monday, September 24th, 2018 AT 2:59 PM
Tiny
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The regulator is inside the alternator itself. The ECM just turns it on and off.

That is a bad alternator.

Is there any harness around there at all? I cannot see from the picture.

Roy
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Monday, September 24th, 2018 AT 3:02 PM
Tiny
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Attached a screen shot of my code scan.
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Monday, September 24th, 2018 AT 3:03 PM
Tiny
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None of them are related to the transmission.

I cannot see the Body Control codes, too small.

Can you post the Body Control codes?

Roy
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Monday, September 24th, 2018 AT 3:10 PM
Tiny
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B2625, P0455, C0899. I do not think there is anything wrong with the transmission. Since the problem stopped when I replaced the transmission 2,500 or so miles ago, the problem must be electrical or with a computer.
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Monday, September 24th, 2018 AT 3:31 PM
Tiny
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Okay, if the transmission is slipping then there is an issue.

The C2625 does not show as a valid code. Can you verify?

Roy

C0899

C0899
Descriptor
Probable Causes
Electronic Brake Control Module (EBCM)
Rear Differential Clutch Control Module (CCM)

p0455

P0455
Descriptor
Probable Causes
Fuel Filler Cap
Fuel Tank Pressure (FTP) Sensor
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Monday, September 24th, 2018 AT 3:44 PM
Tiny
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It is B2645. Does not this collection of codes - especially given the high voltage output, suggest an electrical issue?
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Monday, September 24th, 2018 AT 4:14 PM
Tiny
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No, it suggests you have issues with these systems.

B2645 is a possible BCM failure. That may be related to the issue you have since it controls all body functions.

Roy

B2645

B2645
Descriptor
Probable Causes
Ambient Light Sensor
Body Control Module (BCM)
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Monday, September 24th, 2018 AT 4:21 PM
Tiny
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Can that light be caused by a faulty alternator or a bad ECM? I am asking because I was getting BCM codes before replacing the alternator. I did not get them after replacing it for almost 3,000 miles. Now they are back.
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Monday, September 24th, 2018 AT 4:31 PM
Tiny
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The only way the alternator could cause it is if it is putting out AC voltage.

Put your voltmeter on the battery with the engine running and check for AC voltage at the alternator.

Roy
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Monday, September 24th, 2018 AT 4:35 PM
Tiny
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I will check. Is it possible for the ECM to command the alternator to output too much voltage? I am just trying to figure out why my new alternator is no longer working properly.
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Monday, September 24th, 2018 AT 4:50 PM
Tiny
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Yes, it is. You would need a scan tool that can read the PCM and see if it is commanding on the alternator.

Either way, the voltage regulator is inside the alternator and that is no good since the voltage is way high.

Roy
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Monday, September 24th, 2018 AT 4:54 PM
Tiny
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Attached is a live readout of power output. As you can see, the range is 13.595 volts to 16.1 volts on a five mile drive around the neighborhood. Lights, radio and A/C were on. This reading is in sync with my meter readings at the alternator itself. AC output was present, but very low. It fluctuated between 1/4 and 1/2 a volt.

Does this mean that a new alternator with less than 3,000 miles on it has a bad regulator or could it be that the ECM is commanding that much output? Until the voltage output issue is diagnosed, I think every other code is suspect.

Given this new data, what do you think?
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Monday, September 24th, 2018 AT 5:46 PM
Tiny
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You need a new alternator. There should be 0 AC volts. You have a bad alternator.

Roy
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+1
Monday, September 24th, 2018 AT 5:50 PM
Tiny
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Thanks Roy!
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Monday, September 24th, 2018 AT 10:22 PM
Tiny
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You are welcome.

Always glad to help.

Roy
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Tuesday, September 25th, 2018 AT 3:21 AM
Tiny
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Replaced the alternator. The thing makes noise. Sounds like bearings. Cheap Chinese-made junk. Looks like I will have to replace it again. "DuraLast" is a misnomer. :(

I am still concerned about that wire that hangs off the negative terminal of the battery. It must go somewhere and it is not long enough to attach to anything except the wiring bundle directly behind it. I flushed all of the codes out of the computer. Let's see what else shows up over the next day or so.
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Wednesday, September 26th, 2018 AT 10:15 PM
Tiny
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Yes, I would try another brand alternator. Have them upgrade you to a better alternator.

Roy
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Thursday, September 27th, 2018 AT 3:17 AM
Tiny
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  • 2008 PONTIAC TORRENT
  • 3.4L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 111,000 MILES
This is the never ending story of a car "ghost" that refuses to go away.

Bought the car in November 2017. A couple of weeks after I got it, the car start intermittently slipping gears. No real pattern of when. It just happened. One time it went into limp mode.

Fast forward to the summer of 2018. I get a charging system error and the car shows all signs of a bad alternator.

I install a new alternator - magic. The problem stops for a considerable number of miles - probably 3,000 and then it starts up again. Test the alternator and it is throwing out over 16 volts, so bad voltage regulator, right? Replaced the alternator again. Now all heck is really breaking loose. I am getting the following codes:

P1719
P0700
P0403
P0405
B2645
B3155
C0561
P1779

In addition to the transmission slips, it seems like the engine is revving too high. When I am at a light, it feels like my foot is lightly on the gas pedal. If I shift into neutral, RPM's briefly increase by 600 RPM's and then they go back to normal. When I shift into reverse, I can feel it wanting to bolt backwards and the car rumbles a bit.

I suspect that this is all electrical and related to one or two specific things. I am just stumped as to which ones.

I am getting about 15.5vdc on my Fluke at the battery. I am also attaching snapshots of the report and the live computer feed.

Help!
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Saturday, September 29th, 2018 AT 1:28 PM (Merged)

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