2010 Cadillac SRx code P0641

norman52

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#1
i have a 2010 SRX 3.0 V6, 35K miles. I went to pick it up at the airport and it started and barely ran. It was like a car with a massive vacuum leak. The engine would barely idle and if you stepped on the gas
nothing happened. Sometimes it would rev a little but then go back to a very low lopey idle and usually die. Towed it home and pulled the code. Code P0641, Sensor Reference, Voltage A circuit open.
Per the shop manual this is the fuel pressure sensor back by the fuel tank. Does this sound right. I thought these cars had a limp home mode? No other codes.
Out of curiosity I disconnected the battery to clear the memory and the codes to see if the computer might relearn. I started the car and let it run (Between dying) for 20 minutes to see if any other codes would pop. P0641 right off the bat, then a while later I got a P0131 and a P0152 which I thin are the oxygen sensors then the P0300 which is the cylinder misfire. So any ideas? Could it be a bad PCm just going bad and throwing codes? By the way my freeze frame data showed MAP at 28.9 and fuel pressure at 70.0. Some of the freeze frame data is all over the place. The temp shows 32 and then 88 and the MAP goes between 28.9 and 32.1. Just trying to throw out as much data as I have.
 

kev2

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#2
A 2010 cadi I would suspect is under warranty.
Anyway this is a problem with the 5v reference circuit, The 2 o2 sensor codes are voltage issues with the sensors B1S1 and B2S1...

I will need to get the trouble tree for P0641.... not a code I see often.
P0131 - observe the B1S1 voltages- is it fixed low >200mV?
P0152 - observe B2S1- is it above > 750mV?

> Was there any evidence of high water (flood) that could have affected vehicle?
> check the o2 connectors for evidence of water or damaged wiring -
> Will your scanner access ALL codes- I am thinkiing the P0641 will have accompaninig Manufactures ....specific codes above P0999
 

norman52

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#3
! A/C refrigerant sensor

The codes p0131 & P0151 only came up after letting it run for about 20 minutes while I checked wires, watched it die and restarted etc. I think it was running so bad it was getting a lean signal. Same with the P0300 misfire.Of course it is just out of warranty.51 months but only 35K miles. Maybe I will get lucky and it will be an emissions issue and that might be covered. I talked to the service rep at Dougs Cadillac here in Seattle (Real Nice guy) and he told me that code P0641 is either B150 Fuel Tank pressure sensor, B17 BARO sensor, B47B fuel rail sensor, B1 A/C refrigerant pressure sensor or B23 all four camshaft sensors. He said the other 5 volt circuits would throw another code. Figuring the A/C issue should make the engine run bad. I have been trying to figure out where each of theses sensors are and how to check them. or possibly the ECM. He also said I can buy all the other sensors or the parts they check and replace them myself but if I buy a replacement ECM they have to program it to match the vehicle.

Thanks for the help. If I can bring up the rest of the data I will post it.
 

kev2

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#4
I am not getting access to this info as this is a cadi - not your normal fleet vehicle,
the code is for a problem with voltage on 1 of the, 2, 5v referance circuits
what we needed to know- WHAT is on the 5v driver circuit... and you found out-
FTP -
BARO -
Fuel RAIL-
AC snnsor-
CMP sensors-

Any one of these sensors or the wiring to them may be the issue- What does the scanner show as the voltage on them? I would one by one unplug a sensor and retest- taking a swag 1st ac sensor, then Baro, fuel rail, and CMP, - look for damage at sensor connector back to main harness.

If I cam I will post the exact locations BUT again a late model cadi is stumping me- hopefully a colleague will help out...
 

billr

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#5
I would emphasize the "emissions" angle with them. Virtually anything related to the engine can affect emissions, so should fall under the blanket of how long that stuff is mandated to last. Ignore their standard warranty.
 

norman52

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#6
I appreciate all the help. no matter what we would have tried we never would have found the problem.I gave in and had it towed to Doug's. Then found the wiring harness that goes back to the fuel tank under the drivers seat was severely corroded. They said they had a TSB for a leaky sunroof on these cars but they don't show a service record of this car every having the problem. I never had a wet floor that is for sure. Anyway, I guess I could have found the sensor that wasn't working, bought a new one and it still wouldn't be working. It would have taken me hours and hours to figure this out, even with all the help on here. I am out the tow bill and two hours of shop time and they will order me a new harness to fix the issue. Looks like around $1,000 out the door (ouch) but it will be fixed right and the problem shouldn't recur.
 

nickb2

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#7
backpressure is important to check. If all o2's unbolted and it rides like a nascar :ROFL. Would check resistance of heaters. Hard to do on these modeles, but cats where a problem, not the home kind. Easy way, for codes like this, is scan and check data and when code set and acceleration conditions and o2 switching, will help pin point problem. But with a 641 code check for a bad o2 on switchting, bad pcm, circuit in these cars is known. A 5vlt reference is to be for peizoelectric if menory serves well. So scann data is important to see how fast thay switch. If all 5v are there, o2s are fine but heaters need to be chekcked with multimeter. I must say, I a from canada so all I say here is subject to american laws that do not apply here.
 

kev2

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#8
gotta love it - "proprietary' information, yeah we know we fucked up but its our secret...
As always a day late and a dollar short- funny how fast they found it, yeah you (or I ) would still be checking

TSB: 10-08-45-002D
 
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#9
A corroded wiring harness on a very expensive four year old vehicle like this sounds a bit outrageous. Would be talking to one of those Cadillac executives.