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Old 10-08-2016, 12:12 PM   #1
Blue Bowtie
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2003 Venture Warner Brothers

I am beginning to understand the full meaning of the "Warner Brothers" label on this vehicle. When things go wrong, they go really wrong, like a Wile E. Coyote caper using every Acme Manufacturing rocket sled, iron anvil, and Super Spring Shoes usually turns out.

The van is in theft mode. The transponder has power. The BCM is communicating. The PCM is getting a crank signal at C2/23 from the ignition switch but is not grounding the start relay via C2/76. The SECURITY message is scrolling in the DIC along with the alternator warning (of course) and any other expected message, such as door ajar, etc.

After several attempts to "learn" the key with the 10 minute on / 10 second off cycles it is clear the theft system is not happy. The instrument cluster is APPARENTLY communicating via the Class 2 bus since it detects the door switches, fuel level input, etc. I say "apparently" since I do not have a Tech II and cannot confirm this with a Snap On or other bi-directional scanner.

I have checked all the fuses I can find in the circuit in both fuse panels.

For further information, the fuel pump runs its normal 2 second prime cycle. I can manually enable the fuel pump to verify it is not a problem, and manually actuate the starter. The engine will run for about 2-3 seconds and die every time I do that. I suspect the PCM is terminating injector pulses after NOT seeing the key transponder signal within the 3- second window.

What am I overlooking, and what am I missing?

I had one of these about two years ago and I tracked down a chafed wire in the PCM harness in the engine compartment (two wires actually). From that experience I quickly went to the PCM signals to help diagnose this after checking the routine stuff like fuses, neutral switch, etc.
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Old 10-08-2016, 02:35 PM   #2
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Re: 2003 Venture Warner Brothers

Additional information is that the transmission range selector is reporting correctly according to the PCM data. I can run the lever through the quadrant and the PCM reports every position correctly.
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Old 10-08-2016, 02:37 PM   #3
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Re: 2003 Venture Warner Brothers

" I suspect the PCM is terminating injector pulses after NOT seeing the key transponder signal within the 3- second window. "

I'm no expert but how are you sure the PCM is not terminating the injector pulse because it is not getting a rotation signal from the cam or crank signal?

Perhaps a simple and quick test would be to wrap the plastic part of your ignition key with several layers of tin foil and then try to start the car. If it then does not start at all, that would show that the key transponder signal was present.
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Old 10-08-2016, 03:09 PM   #4
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Re: 2003 Venture Warner Brothers

Thanks for the reply. I appreciate your input and bringing up very viable reasons for the condition. I am not certain that your theory is not correct, but I do have some reservations.

First, the PCM requires input CMP/CKP pulses to fire the injectors at all. It is an SFI system, and not batch fire, so reference pulses must be present to sequence injectors. The engine runs for 2-3 seconds normally and then dies - Even with the fuel pump still running. That indicates to me that the PCM is getting the reference pulses.

Second, I did not want to dismiss your theory at all, so I removed the ignition lock cylinder completely. The column shroud was already removed to check the wiring and transponder/immobilizer module anyway, so it was easy. I shut off the ignition for about a minute while connecting the remote starter solenoid wiring, turned on the ignition to RUN with a large screwdriver, and used the bypass to crank. As before, the engine would fire and run for about 2-3 seconds and quit. It did this at least a half dozen times in succession, and did it even after the ignition was cycled off for a period of time.

For complete verification, cranking with the ignition off does not start the engine at all. However, after a couple seconds of cranking the fuel pump DOES run, probably in the oil pressure switch.

If you have any other theories I'd be happy to test them out.

My limited information on PK3 is that the engine WILL run in theft mode if it is cranked and the PCM has about 2-3 seconds to verify that a valid key is in the transponder range. That seems to coordinate with my current symptoms pretty closely.
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Old 10-08-2016, 06:09 PM   #5
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Re: 2003 Venture Warner Brothers

Furthermore, there is serial traffic on the GM-LAN bus and Class II bus to/from the Transponder/Immobilizer unit on the steering column (purple wires):



Not much left, is there?

I am beginning to believe the either the key pellet and/or the transponder/immobilizer has failed. I've read that other RFID devices can affect the system if they are near the steering column when a start attempt is made, but I've also read that the original PK3 key can be re-learned if that occurs.
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Old 10-08-2016, 06:34 PM   #6
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Re: 2003 Venture Warner Brothers

You seem very thorough in your work and are more skilled than I am. Hopefully someone else will come along with some more ideas.

I simply cannot understand why you did not find a diagnostic code being set if the car is starting and then shutting down after a few seconds. No doubt you have looked for these codes. If the PCM is not happy it should be setting a code to point you in the general direction of the problem?

When I recently had good cranking but a complete no start condition, I was getting NO code at all. Since you are getting a start up and then the shut-down I simply have no idea where to look without a code. However, the no code condition might be telling us that when the PCM is taking over it is doing it's job but there is a break in the circuit somewhere after the PCM takes over - and the signal needed to keep the engine running is not being received - to wherever that signal is suppose to be going?
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Old 10-08-2016, 07:45 PM   #7
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Re: 2003 Venture Warner Brothers

I looked for stored and pending DTCs in the PCM, BCM, transmission code, SIR codes, ABS codes, and all the data I could access. The ONLY data stream my scanners will not read is the VTS and raw data on the serial bus. Unfortunately, it seems that is the data stream I need to access to see VTS codes. From what I can determine the Tech II is about all that will read the data.
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Old 10-08-2016, 08:53 PM   #8
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Re: 2003 Venture Warner Brothers

UPDATE:

My daughter (her van) finally drove in the hour-and-a-half or so with the spare key. Since I had communication on the serial lines, all the critical signals from other systems at the PCM, and had checked every connector and wire terminal in the circuit I was down to a key or transponder, and doubted it was the transponder.

I stuck in the spare key, turned on the ignition and got only the charging system warning and door ajar message. Turned to crank and BAM! Starts like nothing ever happened. Somehow, somewhere, some way, something boned the RFID circuit/antenna foil in original key bow. We cannot do anything but guess what it may have been, but new blanks are on the way as we speak.

Thanks to all those who assisted.
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