P1271 and random unknown driver in DIC

[Rudeawakening]

Ok, I know theres alot of threads that talk about p1271 and the unknown driver with all the ses lights and brake lights coming on while beeping and than going away. I have the p1271 code and my TB will go into Reduced engine power mode with the Service engine soon light on. Ill pull over turn the car off and on again and drive away with the SES light on. The SES light aways resets its self and requires me to go view the history of trouble codes the have been shot in order to see what codes were fired. I replaced the APP sensor with an aftermarket one and it seemed to have fixed the problem for about a month. Iv checked almost every forum and some said that you should replace the APP with an OEM one and not an after market one. This would make sense to me considering the problem was fixed for a while, if it was something else like the wiring harness or fan clutch it wouldnt have fixed the problem for any length of time. Im hoping that the p1271 code being thrown is what also cause my TB to wig out and show unknown driver in my DIC and light up my lights and beep at me Ill keep everyone posted on what happens. Im doing this so hopefully it will save many people alot time and money. Iv seen people replace all kinds of stuff just to find out that it only needed an OEM APP sensor, so im hoping this answer will solve 90% of everyones problem with the dreaded p1271 code followed by SES / REP mode. Wish me luck

 

[The_Roadie]

Sometimes, the beeping and DIC issues are caused by a bad/loose instrument panel ground.

Base of the console on the right side of the transmission tunnel

View attachment 18170

 

[Rudeawakening]

Im kind of a newbie with cars and this is a stupid question but your talking about on the driver side of the car correct? is there a picture a that shows more of the area so I know where to look?

 

[The_Roadie]

It's sort of down here:

View attachment 18171

 

[Rudeawakening]

Okay, great I see. It looks like i have to take console off to get to it im guessing.

 

[Rudeawakening]

While im waiting for the part, from you experience what seems to be the most common cause of the SES/REP with code p1271 and fix?

 

[The_Roadie]

In general, SES/REP events are caused by a shared sensor reference voltage circuit. The PCM sends out a precise 5V signal that goes to two sensors on the accel pedal, two sensors on the throttle body butterfly valve, and one RPM sensor on the fan clutch. A fault in any of these three items OR the wiring harness between them and the PCM can cause an REP event. The most common cause in my experience is the last 12" or wiring harness going from the fan shroud to the fan clutch. It gets frayed and shorts out. That can be checked by visual inspection. The other items usually get shotgunned if the owner doesn't have a meter and know how to use it on the 5V reference wire.

 

[Rudeawakening]

Awsome, thanks. Do you have a picture you could post? id really appreciate it.

 

[The_Roadie]

Picture of what? The way the fan clutch plugs into the harness? It's sort of obvious when you look. Here's a picture of a replacement unit from autowarehouse.

View attachment 18181

 

[Rudeawakening]

Thank you for the pic, I just like to have an idea what im looking at/for considering this is my first time messing with a vehicle on my own,Sorry, should have been more specific. Im becoming more and more of a fan of TBs so after i get my repairs done I would like to slap an SS bumper on it down the road , but well see

 

[The_Roadie]

Making friends with a local mentor would be my advice. No substitute for somebody who can point at things and say what it is. Internet forums are no substitute for that. Buy beer.

 

[Rudeawakening]

Thanks for the advice. Ill keep everyone updated on what i find.

 

[Rudeawakening]

Ok, I took the floor trim off on the driver side door cuase i my carpet gets soaked when it rains and I saw this wire. Could these wires sitting in a wet environment possibly be the cuase of one if not both problems? Heres a picture of it. I have a different thread that talks about my leaks and getting my driver side carpet wet. (See Water soaking the carpet on the drivers side, do not have a sun roof. So we dont get off topic)

View attachment 18212

 

[Rudeawakening]

I changed out my doorman brand APP sensor for an OEM APP sensor so hopefully that is my problem so well see. Iv noticed that the OEM was much more responsive than my after market one. Id have to press the pedal down alot more to get it to do anything. I checked the fan clutch wire harness and notice anything. Looks like ill be playing the waiting game to see if i get the SES/REP again. In the mean time ill check out the possible poor ground connection. Ill keep you guys posted on what I find.

 

[Rudeawakening]

Its been 4 days since i changed out the old sensor and so far everythings been fine. So far so good.

 

[Rudeawakening]

Yesturday, the beeping and unknown driver started happening again, its really annoying Fortunatly I still have not had issues with the SES/REP mode. Im gonna investigate the ground connection when I have time. Im going to be busy moving all this week and weekend so I probably wont be able to get to it till the next weekend seeing that im gonna have to take my console off to get to it from where roadie suggested. Ill keep you guys posted. Let me know if you have other ideas where to check.

 

[Rudeawakening]

Since moday, all my gauges and the DIC would not work. All the gauges dont move including my speedometer and nothing displays in the DIC. However, it goes on and off. Like yesterday driving home it was fine but this morning it wasnt working. When my gauges arent working the beeping and lights flashing doesnt happen, so at least its a quiet ride.

 

[Rudeawakening]

Hey guys, sorry its been a bit since iv been on here. I havent got around to checking that ground yet, iv been really really busy. Im hoping to get to that this weekend. Ill keep you guys posted.

 

[Rudeawakening]

*UPDATE

Ok, yesterday I removed my center console and to get to the ground. It looked clean, but the area it was making contact to is painted which is not good. But the connection should still be making contact with frame throught the bolt which threads into the frame, but I cleaned the paint off down to clean bare metal anyways to make sure the connection is good. In another post I have had water leaking issues and my carpet getting soaked. See " Water soaking the carpet on the drivers side, do not have sunroof" for more info. I found and sealed the leak a month ago, but I just got to drying out the carpets yesterday. After doing all that, I have had no noise or any nonsense and its awsome! I drove it around yesterday and today and have not heard anything! :wootwoot: Now, its only been 24 hours since i did this so problems could still occur. But heres a run down of things I did to help anyone whos going through the same nightmare I have had :

-For the P1271 code and going into Reduced Engine power mode with the Service Engine Light Soon:

I replaced the APP sensor with an aftermarket doorman one back in November, however, that only worked for about a month. After doing a bit of some reading I found that aftermarket APP sensors are junk and only the orginanl manufacture part should replace it. So I got an orginal manufacture part and installed it. Its been a month now and still no problems with that. If your having this problem and are going to replace the APP sensor i would highly recommend the orginal manfacture part,its worth the extra money in this case.

-For the Unknown Driver and Service lights/Brake Lights and Beeping going off every 5 seconds:

Check to see if your carpets are wet or gets wet after it rains. If they do, you have a leak somewhere and it should be found and sealed. I found mine leaking on the drivers side top corner windshield (I do not have a sun roof).

Check the instrument panel ground. I took mine off and saw the mating sureface was painted, the paint acts as an insulator. Clean off of the paint down to clean bare metal and clean the the ground terminal ring as well and reattached it. The center console has to be removed in order to do this.

I hope this helps anyone who needs help on this. Ill keep ya posted on how things are going, I hope they say fine.

 

[Rudeawakening]

Ok, I dried out my carpets sunday and have not had a problem untill today. It was raining this morning and sure enough my lights started going crazy, I checked the driver side carpet again and it was getting wet. I noticed that the carpet was hardly damp near the door but it seemed soaked on the other side like near the gas pedal which i thought was weird. Anybody have any idea where the leak could be coming from now? My crazy beeping lights problem looks like its definatly related to my carpet getting wet. When i dried it out the first time it was totally fine. I hope someone knows where the leak is at, i just want this thing fixed lol

 

[WHY]

Ok, I dried out my carpets sunday and have not had a problem untill today. It was raining this morning and sure enough my lights started going crazy, I checked the driver side carpet again and it was getting wet. I noticed that the carpet was hardly damp near the door but it seemed soaked on the other side like near the gas pedal which i thought was weird. Anybody have any idea where the leak could be coming from now? My crazy beeping lights problem looks like its definatly related to my carpet getting wet. When i dried it out the first time it was totally fine. I hope someone knows where the leak is at, i just want this thing fixed lol

along where the wiper come through sometimes the seals/ can leak

 

[Rudeawakening]

Ok, sorry its been so long for an update but here it is. I fixed me leaks getting into my TB but that was not the problem. I decided to drop off my TB at a dealer ship around april. They found that my BCM was getting water in it and it was corriding inside so $900 later the BCM was replaced. Prior to this, everytime it would rain the TB could go crazy but now its totally quiet in any rain np.......until 2 weeks ago. I dropped it back of at the dealer ship and told them whats happening and they put the same mechcanic on it that repalced by BCM. The BCM looked ok, but on the instrument panel there was a short. They would have voltage in the input but nothing on the output. They also said there was 9 codes tripped and most of them were communication codes, which make sense. Soo $600 bucks later they repalced my instrument panel. Its been raining alot lately and still no problem. The dealer ship was thinking that the water got into the BMC and cuased the instrument panel to short out. Makes sense, but wouldnt it be going crazy all the time than and than rain would have nothing to do with it???? They said it was possibly just coincedental, but I find it hard to believe that every time it rained it goes crazy and its only coincendtal. Well, so far its working ill keep you guys updated every know and than. I hope that this is it and my problem is fixed, and I hope that this helps anyone else out with this total craziness

 

[The_Roadie]

Makes sense,

...no it doesn't. Communication issues from the BCM could not POSSIBLY take out the gauge cluster. It's just as likely to be a bad Onstar module under the rear seat, especially if you had a water problem with the BCM in the same location at the other side of the truck.

If the dealer didn't troubleshoot the issue by using a communication analyzer (the Tech II tool they all have) while removing modules from the data bus splice packs (SP205 or SP306) then they're guessing while spending YOUR money.

My guess would be the persistent wet layer under the carpet has created some soggy wiring, and if the insulation has any nicks, then all bets are off. Did you or they remove the carpet and check the many harnesses that are routed underneath?

Comm problems all require knowledge of the splice packs, where comm wiring is tied together precisely so you can remove one module at a time from the bus and see if the problem goes away. If it's too intermittent this is a challenge, I admit. But to claim the gauge cluster was "shorted out" by something the BCM did, now that's just ludicrous. Sorry you got victimized.

 

[Rudeawakening]

...no it doesn't. Communication issues from the BCM could not POSSIBLY take out the gauge cluster. It's just as likely to be a bad Onstar module under the rear seat, especially if you had a water problem with the BCM in the same location at the other side of the truck.

If the dealer didn't troubleshoot the issue by using a communication analyzer (the Tech II tool they all have) while removing modules from the data bus splice packs (SP205 or SP306) then they're guessing while spending YOUR money.

My guess would be the persistent wet layer under the carpet has created some soggy wiring, and if the insulation has any nicks, then all bets are off. Did you or they remove the carpet and check the many harnesses that are routed underneath?

Comm problems all require knowledge of the splice packs, where comm wiring is tied together precisely so you can remove one module at a time from the bus and see if the problem goes away. If it's too intermittent this is a challenge, I admit. But to claim the gauge cluster was "shorted out" by something the BCM did, now that's just ludicrous. Sorry you got victimized.

The wet carpet isnt a problem anymore. I found the leak and sealed it before I had the BCM changed out and its been dry since. I did check the wiring while I had the carpet pulled back though and i didnt see any nicks and the wiring looked fine. I guess if it does happen again ill go back and recheck it. I just hope the water leaking into the BCM and the shorted instrument cluster was the problem. Time will tell.