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P0335, P0641, P1682 (2007 Avalanche)


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Old 03-09-2015, 12:54 AM   #1
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I suddenly have problems with my truck. It was running fine then started disengaging the transmission while driving. the check engine and stabilitrac lights came on so I stopped a shop and got the OBD-II checked. the codes generated were P0335 (crankshaft position sensor) P0641 (Volt reference 1 circuit) and P1682 (ignition 1 switch circuit 2).

I have already changed out the Crankshaft position sensor and things have not gotten better. I may still need to get the computer "flashed".

At times (most of the time) the truck will start fine and run at idle great. As soon as I put it into gear though it starts to run rough. it will back up fine but when I put it into a forward gear it either dies or runs rough for a little bit and dies.

I am trying to get this fixed as quickly and cheaply as possible because I am going to be moving for work and need the vehicle. Any help would be great, thanks.

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Old 03-09-2015, 01:31 AM   #2
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P1682 Chevrolet Description
There are 2 ignition 1 voltage circuits supplied to the Engine Control Module (ECM). The first ignition circuit is provided by the powertrain relay, through a fuse. This ignition 1 voltage circuit supplies power to all the internal ECM circuits associated with the throttle actuator control (TAC) operation. The second ignition 1 voltage circuit is supplied by the run/crank relay through a fuse, and is used to power the remaining internal ECM circuits. If the ECM detects a voltage difference between the 2 ignition 1 voltage circuits, DTC P1682 will set.


P0641 Chevrolet Description
The control module has 2 internal 5-volt reference buses called 5-volt reference 1 and 5-volt reference 2 . Each reference bus provided 5-volt reference circuit for more than one sensor. Therefore, a fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to the reference bus. The control module monitors the voltage on the 5-volt reference buses.

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1979 Monte Carlo with a 400hp+ 350ci.
1983 T10 w/2.8L getting parked till can restore and put a v8 in
1994 Blazer 4dr with the CPI(FOR SALE)
1995 Blazer 4Dr 4X4(FOR SALE)
2002 Trailblazer LT
2007 Envoy Denali

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Old 03-09-2015, 01:44 AM   #3
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To me it sounds like a bad ignition switch. But I would check your ECM connectors for any corrosion.

I hate Drive by wire. And electrical Gremlins are the bain of my existence.

The 5volt reference goes to multiple sensors. Before you pull that ECM check everything you can. I know Dealers that will hit that ECM and replace it and then bam same thing happens again. Oh then its a couple more grand to get things replaced.

Parts replacer is all most shops are these days. They really dont teach tech in college so they are just taught to keep replacing parts till you find the right one. There is not testing of the new stuff these days and many people didn't take enough time in the electrical part of tech as they don't teach it and are taught to follow what the computer says. Old Tech guys can't do much more on these new vehicles cause of all the intricate of all the electronics are, no way to narrow down the codes.

I believe that second code, does the TPS, Fuel pressure, oil pressure and a couple others are all on the same line but I dont have a chart to go off of, just my search foo.

_____________________________________________
1979 Monte Carlo with a 400hp+ 350ci.
1983 T10 w/2.8L getting parked till can restore and put a v8 in
1994 Blazer 4dr with the CPI(FOR SALE)
1995 Blazer 4Dr 4X4(FOR SALE)
2002 Trailblazer LT
2007 Envoy Denali

Independent AmsOil Dealer

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Old 03-13-2015, 03:55 AM   #4
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For the curious, the solution ended up being both the Cam shaft sensor. Plus there had been a service bulletin to change out the pigtail connector for that sensor. It caused the ECM to pick up a fault between the Cam shaft sensor and the Crank shaft sensor.

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