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Discussion Starter #1
So I've own my 2009 I5 Canyon just about 3 months now. It has just over 100K miles and it's starting to act like every chevy I've ever owned... It randomly doesn't start like I'm not getting fuel. Then when it finally starts I get "service traction control" and "reduced power" and of course it runs rough. I get out my handy code reader and this is what I get:

P0171 - System too lean (This has been happening since day one, I guess it's the K&N)
P0651 - Sensor Reference Voltage "B" Circuit/Open (no idea what this means)
P0336 - Crankshaft Position sensor A Circuit Range/Performance

When I clear these codes and restart, the truck runs completely fine and shows no problems.

Today it got worse while I was driving down the road (in traffic), every time I pressed the gas pedal, it would try to die but it would idle fine. I shut it off and restarted it while rolling in traffic and it started fine and ran like it was normal.

I've been searching and here's what I plan on doing this weekend:

Getting the battery load tested (might be a low voltage screwing with BCM)
Eliminating ground blocks (I hear these can corrode over time)

Does anyone have any advice on this situation? I'm desperate here...
 

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..Getting the battery load tested (might be a low voltage screwing with BCM) Eliminating ground blocks (I hear these can corrode over time)
...
At a glance it seems you're on the right track, particularly the ground blocks (but makes sense to start with the battery).

Why? These are all electrical problems across several otherwise unrelated circuits.


...P0651 - Sensor Reference Voltage "B" Circuit/Open (no idea what this means)
P0336 - Crankshaft Position sensor A Circuit Range/Performance
..
"Sensor Reference Voltage.." is the voltage supply to a sensor. It comes from the ECM (or BCM in some cases) to supply a sensor which provides a precision measurement.
To do so the supply voltage to the sensor must be regulated to an exact voltage as the sensor's starting-point.
So where the overall system voltage is nominally 12 volts DC, there is a circuit in the ECM that reduces that to something like 5 volts, but it maintains that 5 volts very steadily to give the sensor a reliable reference point. (as the overall system voltage fluctuates up-down-up)
 

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The K&N itself is probably not causing the P0171, but it could be the installation of it that is creating the issue. Check to insure that all connections are secure and all hoses properly connected.
P0651 relates to one of the two 5 volt circuits that the ECM uses as reference signal to multiple sensors. The sensors on the "B" or "2" circuit are: Accelerator Pedal Position, Throttle Position Sensor 1 & 2, Crankshaft position sensor, and Secondary Air Injection pressure. The circuit apparently has a short somewhere.
With two of the codes (P0651 & P0336) pointing to the Crankshaft Position Sensor, that might be a good place to start.
 

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Discussion Starter #5
I will start my checking there. I forgot to mention that I was getting extremely hard shifts from 1st to 2nd this morning when my truck was acting up. Does this play into the 5v circuit at all?
 

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Discussion Starter #6
With two of the codes (P0651 & P0336) pointing to the Crankshaft Position Sensor, that might be a good place to start.
So I don't know much about these engines, can you tell me where the crankshaft position sensor is? Pictures are helpful... ;)
 

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... The circuit apparently has a short somewhere.
With two of the codes (P0651 & P0336) pointing to the Crankshaft Position Sensor, that might be a good place to start.
If it had a "short-circuit" then those circuits wouldn't work at all.
And those sensor circuits are all separate from each other.

The commonality between the sensor circuits you listed are the ground (common) connections and the ECM itself.
We haven't seen many ECM failures, have we? I don't recall ever seeing a post on that.

On the other hand, if I suddenly recall correctly, those sensor circuits don't go to ground. The reference voltage out from the ECM, thru the sensor (in the case of the TPS it's a potentiometer) and back to the ECM. I don't have a schematic in front of me though.


Other than that, low battery voltage tends to make the ECM go a bit spastic.
 

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Discussion Starter #8
Now your mind is working in circles like mine does! ;) haha... well I at least have a start and if this doesn't fix the problem, I'll at least prevent the next problem.
 

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From the 2009 GM Service Manual for Canyon/Colorado 3.7:

The engine control module (ECM) has 2 internal 5-volt reference busses called 5-volt reference 1 and 5-volt reference 2. Each reference buss provides 5-volt reference circuits for more than one sensor. A fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to that reference buss. The ECM monitors the voltage on the 5-volt reference buss.

The 5-volt reference 1 buss provides 5 volts to the following sensors:

• The manifold absolute pressure (MAP) sensor

• The fuel tank pressure (FTP) sensor

• The air conditioning (A/C) refrigerant pressure sensor

• The accelerator pedal position (APP) sensor 2

• The exhaust camshaft position (CMP) sensor

• The intake CMP sensor

The 5-volt reference 2 buss provides 5 volts to the following sensors:

• The APP sensor 1

• The throttle position (TP) sensor 1 and 2

• The crankshaft position (CKP) sensor

• The secondary air injection (AIR) pressure sensor
 

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Discussion Starter #11 (Edited)
So I'm in some more hot water with this truck. Two weekends ago I replaced the Crankshaft position sensor (thanks @rshadd for pointing out I put camshaft), eliminated ground blocks on each fender, and had my battery tested at autozone. This morning I had more codes than usual. Here is the run of them now.

P0171 - System too lean (This has been happening since day one, I guess it's the K&N)
P0336 - Crankshaft Position sensor A Circuit Range/Performance
P0651 - POwertrain
P2135 - Throttle/pedal position sensor/switch A/B voltage correlation
B2AAA - Body?

I noticed that when they tested my battery it was the original AC delco battery (truck is 2009). Can a battery cause this even when all tests are ok? I should also mention that this only happens when sitting overnight or after an 8 hour work day. After the truck studders and runs for a minute or so, I shut it off, clear the codes and it starts fine with no codes and runs like there is no problem.
 

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Do you have the original intake that you could reinstall to eliminate the lean condition? Just to test?

Battery could for sure cause the problems....happens frequently enough.

Did AutoZone 'load test' your battery as far as you know?
What are all of the test that were run on the battery?

I would not be too surprised if some of the codes are a result of others. Like perhaps it's running so rough that one code is causing a problem that another code is tripped.

I do not know a lot about it, but it seems that the CPS and TPS could be related. Don't trust me though, I can't say with any confidence they are related.

Maybe the body code is thrown because it feels neglected and it needs you to wash it?
 

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Discussion Starter #13
I do have my original intake. It was throwing the lean code with the original also but I had a K&N drop in filter in there. (it came that way when I purchased the truck)

Autozone tested the battery with the truck off. Then while it was cranking and then I asked him to load test it. So I think they did all the tests but since I wasn't holding the tester in my hand, I can't be sure.

And she definitely could use a wash but we've been getting rain here every other day, so she can be patient. :)
 

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So I'm in some more hot water with this truck. Two weekends ago I replaced the camshaft position sensor, eliminated ground blocks on each fender, and had my battery tested at autozone. This morning I had more codes than usual. Here is the run of them now.

P0171 - System too lean (This has been happening since day one, I guess it's the K&N)
P0336 - Crankshaft Position sensor A Circuit Range/Performance
P0651 - POwertrain
P2135 - Throttle/pedal position sensor/switch A/B voltage correlation
B2AAA - Body?

I noticed that when they tested my battery it was the original AC delco battery (truck is 2009). Can a battery cause this even when all tests are ok? I should also mention that this only happens when sitting overnight or after an 8 hour work day. After the truck studders and runs for a minute or so, I shut it off, clear the codes and it starts fine with no codes and runs like there is no problem.
From what I have experienced and going by posts here, yes the battery could cause this sort of behaviour. These trucks just do not respond well to low system voltage.

If it were me, I would go ahead and replace the battery anyway, as a preventive measure.
4+ years is a long time for a typical OEM battery.

(I got 6 years from my original battery, but that was pushing my luck beyond all sensible limits..)
 

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If the truck was lean before you swapped intakes, then it's unlikely the cause is your K&N. Just thought that may help eliminate that one thing from the list of potential problems.

Sounds as if the battery tests were thorough enough.
 

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Discussion Starter #17
You do understand the difference between the camshaft sensor and the crankshaft position sensor right? I don't understand why you replaced the camshaft sensor when you have a code that points to the crankshaft sensor.
Yes sir. I appreciate you pointing that out, it indeed was the Crankshaft Position sensor I replaced. I'm not sure why I had camshaft on the brain...
 

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There are grounds inside the cab under the seats as well, one under the drivers and two under the passengers.

Also it may be worth the effort to hit a dealership for a PCM/BCM flash and update to the later version just in case something is corrupted (the updates will fail and the unit in question will need replacing), and then have them run a CASE learn since that crank sensor supposedly needs one after a replacement is installed.
 

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Discussion Starter #19
So I just replaced the battery yesterday and the problem remains. This morning I couldn't get it to fix itself and so I just dropped it by the dealership. They read the code P0171 and say that the MAF sensor needs replaced. I asked why they think that and they said that's what the code tells them. WTF!!! Why am I wasting my time letting you look at it if all you're going to do is pull the codes? I've done that. They want $240 to replace the MAF sensor. This is the only gm dealer in with in 1 hour of me. I know I can do that sensor myself for $50 (amazon) but why the hell would the bad MAF cause all of the other codes for throttle and crankshaft position?

I'm at a loss. I've owned this truck since march and it's already turned into a money pit.

Summary-

Replaced Crankshaft Position sensor
Replaced Ground Blocks
Replaced Battery

Next up MAF sensor. (because the dealer won't diagnose any further with out a new one)
 

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Discussion Starter #20
So I hate when people don't follow up on their threads and I know it's been forever but I thought I'd give the solution.

I bought this truck in early spring (temperatures were still cold here) and it had a K&N setup on it. Well it seems that as it got warmer the K&N set up started to freak out. After changing the crankshaft position sensor, MAF sensor, ground blocks and buying a new battery, I still couldn't figure it out. I had always had a P0171 code that randomly popped up and so I thought, lets go back to stock air intake. Well I did that in Mid-July and here it is two months later and I haven't had a problem since. I've done more research on my K&N and it looks like the guy before me modified the 3.5L engine's K&N set up and put it in the 3.7L. I guess they aren't compatible...

Problem solved.
 
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