# Engine Light On!



## Robby (Mar 1, 2013)

Well, I am well aware that it seems like half the car has been replaced but my first thought is the negative battery cable may be or has developed high resistance.

The 'Lost Comm.' code is often the result......keep in mind that this is a wag.

Rob


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## joshuab (Apr 16, 2014)

Robby said:


> Well, I am well aware that it seems like half the car has been replaced but my first thought is the negative battery cable may be or has developed high resistance.
> 
> The 'Lost Comm.' code is often the result......keep in mind that this is a wag.
> 
> Rob


Robby, I actually thought of this. I do know my battery cable hasn't been changed, I have never complained about it & I never had it serviced. So maybe during my next oil change I'll have them check this by telling them the special coverage ?


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## Robby (Mar 1, 2013)

joshuab said:


> Robby, I actually thought of this. I do know my battery cable hasn't been changed, I have never complained about it & I never had it serviced. So maybe during my next oil change I'll have them check this by telling them the special coverage ?


You certainly should ask.....we have learned the resistance in the cable at the battery clamp crimp increases as it ages and I know you have read all the weird electrical bugs that start showing up when this occurs.

Rob


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## joshuab (Apr 16, 2014)

I sure have, & I will be sure to ask them about this & have them update that cable if they will. Because its acting really weird as mentioned in my initial thread opening it will come on & stay on for about 5 restarts of the car & then its gone! Stays away for good while I want to say over a month & then it comes back & just sorta repeats so that is odd. 

Thanks robby I am due a oil change this month here so its good timing.


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## obermd (Mar 3, 2012)

I'd also guess the negative battery cable.


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## ChevyGuy (Dec 13, 2014)

joshuab said:


> P057C ( * Brake Peddle position sensor circuit low * )


It may be a failing brake pedal sensor. We have seen a few.




joshuab said:


> U0140 ( * Lost communication with body control module invalid serial data received * )


This one worries me more because it points to "random stuff". See what the battery cable does for you.


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## joshuab (Apr 16, 2014)

ChevyGuy said:


> It may be a failing brake pedal sensor. We have seen a few.
> 
> 
> 
> This one worries me more because it points to "random stuff". See what the battery cable does for you.


You have a good point in regards to the BPP sensor; however have you seen random codes on it come & go for a good bit of time? & in regards to the lost communication yeah this worries me too. I can only hope a battery cable works  If not looks like two parts will need full replacement.

The only thing that worries me is when I go the dealership & explain to them the situation; they are likely going to want to change both parts to remedy the problem then if that doesn't they will take me up on the cable change. So what is the best approach I should use w/ the dealership, just simply tell them to check the special coverage part?


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## ChevyGuy (Dec 13, 2014)

joshuab said:


> You have a good point in regards to the BPP sensor; however have you seen random codes on it come & go for a good bit of time?


At some point it just wears out and gets flaky. So it seems possible that it would go in and out.




joshuab said:


> The only thing that worries me is when I go the dealership & explain to them the situation; they are likely going to want to change both parts to remedy the problem then if that doesn't they will take me up on the cable change. So what is the best approach I should use w/ the dealership, just simply tell them to check the special coverage part?


Good question. I'd feel better if you could find more random stuff to happen. I'd have to check and see what (if anything) resets a U0140. If it requires manual clearing, I wouldn't rule out the possibility that it happened during prior work/troubleshooting.

I think I'd reset the system and see what comes back.


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## joshuab (Apr 16, 2014)

ChevyGuy said:


> At some point it just wears out and gets flaky. So it seems possible that it would go in and out.
> 
> 
> 
> ...


I remember when having the transmission checked at aamco they did a scan to check for any TCM codes & only found history codes of those two codes. They said none of them was active so they cleared them all for me upon request. I have since had new ones come back so this hasn't just started its been like this for awhile now, engine light coming on w/ those codes then light going off ( storing codes ); & its just a repeat after repeat. I don't have or had any other codes in the active/history bank. The light has since gone off.


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## obermd (Mar 3, 2012)

Clear the codes and then only report the random electrical issues such as various dash lights flashing at random.


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## ChevyGuy (Dec 13, 2014)

joshuab said:


> P057C


I've confirmed this code will set if the sensor is wearing out (opening up). It's a Type A DTC - the light turns off after 4 ignition cycles of no malfunction. The history will clear after 40 warm up cycles. Or if cleared by a scan tool.




joshuab said:


> U0140


This light will turn off after 4 ignition cycles with no malfunction. The history will clear after 50 cycles. No mention of it being cleared by a scan tool.

All of this from the 2013 shop manual.


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## joshuab (Apr 16, 2014)

ChevyGuy said:


> I've confirmed this code will set if the sensor is wearing out (opening up). It's a Type A DTC - the light turns off after 4 ignition cycles of no malfunction. The history will clear after 40 warm up cycles. Or if cleared by a scan tool.
> 
> 
> 
> ...



So you are assuming these codes are lighting up due to malfunctioning of the two?, Let say the two are actually starting to act up & need changing 

-- BPP sensor, I have seen on this forum that it isn't that hard to change this part?, The only thing I can actually see being hard is getting into that tight spot to change. Thoughts?

- Ok now the BCM I will not even attempt to resolve myself. I have been overlooking my coverage under Emissions I still have around 7K miles left on my warranty. So question is the BCM covered under the Emission warranty?


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## obermd (Mar 3, 2012)

joshaub, you have several indicators of an electrical issue here. If the brake pedal sensor doesn't get the right voltage it will trigger a CEL. If the BCM isn't getting correct voltage it will trigger a CEL. Get that Negative Battery Cable replaced before doing any other troubleshooting.


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## ChevyGuy (Dec 13, 2014)

joshuab said:


> So you are assuming these codes are lighting up due to malfunctioning of the two?


I think we should consider the possibility that the code are "real" and see where that takes us. Does the MIL light follow the pattern indicated? If it's erratic, then we should be considering this an erratic electrical problem.




joshuab said:


> BPP sensor, I have seen on this forum that it isn't that hard to change this part?, The only thing I can actually see being hard is getting into that tight spot to change. Thoughts?


It seems easy enough. The manual has you pulling the left dash trim cover and then the lower dash board, but it doesn't look all that hard. The manual calls for calibration with a scan tool after changing, but it sounds like some owners have been able to skip that step. You should verify the brake lights work properly.




joshuab said:


> Ok now the BCM I will not even attempt to resolve myself.


While it may not be hard to change, I'm sure it would have to be reprogrammed before the car could operate again. And the code may not indicate a problem with the unit. It's just loss of communication. It could be loss of power, shorted bus or something like that. It would be worth verifying that it's plugged in solidly and no signs of problems with the wiring. 




joshuab said:


> I have been overlooking my coverage under Emissions I still have around 7K miles left on my warranty. So question is the BCM covered under the Emission warranty?


I'm not sure. I could see the Engine Control Module being covered, but I highly doubt the Body Control Module would be. It has nothing to do with emissions.


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## obermd (Mar 3, 2012)

I believe the BCM handles the input from the clutch and brake position sensors. If it's not communicating properly the CELs for those two sensors may light up. The BCM handles basically everything in the car not related to the fuel, combustion, and emissions systems. Basically if it's not of the overall power train, which includes fuel and exhaust, the BCM handles it.


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## joshuab (Apr 16, 2014)

I am going to take the first route w/ the battery cable as this would be easiest route, if that fails to fix the issue. I am going after the fixing the BPP sensor. Then I am going to search my extended warranty provided by GM that was given to me due to the issue w/ my engine. 

Again my cover letter mentions the following & bold the section I want to see if this BCM is covered here , I am just wanting get brushed up on all this, I know i have a awesome dealership & I know I will be done right. But I still want to be prepared if someone try to maybe try take advantage of me if they see i am clueless  

I want to thank you'll so far for all the awesome responses.



> The following engine components will be covered: All internally lubricated engine parts; block; heads; manifolds; oil pan; mounts; seals; gaskets; starter; flywheel; harmonic balancer; belt tenisoner; water pump; the entire pressurized fuel system; injectors; all interal engine actuators; electrical components; *control modules and module programming;* diesel injection pump/glow plugs if applicable and throttle body.


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## ChevyGuy (Dec 13, 2014)

joshuab said:


> _The following *engine components* will be covered:_


Still doubtful. I doubt if the BCM is considered an engine component. I'd focus on the other issues, like the battery cable and the brake position sensor. Leave the BCM for last. It may clear up on it's own - especially if the battery cable is replaced. Lost communication is more of a symptom than a indication of what's failing.


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## joshuab (Apr 16, 2014)

Understood *@ChevyGuy* - I am going to have battery cable checked / changed if I can get the dealer moving on that. Then the BPP sensor is really simple to change I actually found the manual where to take the bottom part under the steering wheel off & then one bolt & then one clip very self doable. Just the calibration is fuzzy for me, I really don't want to short cut anything as it may come back to bite me later. Is there any tools available to hook to the car to do this?, or is this something only the dealers have? I am good w/ computers & software's so this part would be fine, I see there is some additional steps after that, but would it really hurt to skip the calibration step & would the car fix itself from that?


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## ChevyGuy (Dec 13, 2014)

joshuab said:


> Just the calibration is fuzzy for me, I really don't want to short cut anything as it may come back to bite me later. Is there any tools available to hook to the car to do this?, or is this something only the dealers have?


I'm not aware of any affordable tools that will do it. My guess is this is something that will calibrate itself over time - the calibration step is to insure everything is working properly when the car leaves the shop and a good customer experience. A big thing would be the brake lights. If they're working as expected, then the new sensor is probably close enough to the old sensor that you can get buy.


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