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Discussion Starter #1
Ok. I am at a loss... 2003 beetle TDI, 5-speed. I can not get the scan tool to connect to the OBD II port. I have a factory radio, so it is not a shorted K-Line behind the radio (I did take it out and try without the radio) I tried resetting the computer (disconnected battery). I removed the gauge cluster. And of course I tried the scan tool on another vehicle and it worked fine. I know that this scan tool works on VW's because I have used it on several others. I tested Pin's 4 to 7 and got 12v with the ignition on. I tested same pins with radio disconnected and still got 12v with the ignition on. With the ignition off I get about 3v. I don't know what else to try. I have searched and searched and keep coming up with the same things... Check fuse 12 (good, but replaced anyway, also cleaned contacts), cut k-line on back of radio (again, factory, but tried it unplugged). Help, please, before I get more grey hairs...
 

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Discussion Starter #4
The scan tool is an Actron CP9145. It does power up when I hook it up to the OBD plug. I assume that this is THE factory radio because I did not have the code for it and was able to get it from the VW dealer with the VIN and the radio S#. I have no idea of the history of this car. I just bought it...Not running... It runs great now, but the CEL is on. I have cleaned the EGR (dirty), Cleaned the N75 valve, checked all vacuum lines, and still no change.
 

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Not sure what to tell you?

I would pull the radio out and disconnect if you think the OBD connectors are not bent or being pushed out of the connector.

Also someone may have had an aftermarket radio at one point and butchered the radio harness?

Removing the radio and disconnecting may be a start?
 

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At a bit of a loss to suggest the next move.

Check fuse #12.

Read this as well - http://newbeetle.org/forums/questio...-new-beetle/56062-obdii-port-doesnt-work.html

Maybe make sure the OBD terminals in the actually under dash connector are not bent, spread or partially backed out?

The under dash connectors need to bite or grab the male pins on the tool.

Also verify they wiring is in the proper cavity as well. Maybe also check the color code as well.

Not sure if you can connect to the OBD bus some other way to make sure there is not a cut or damaged wire?

I have not removed the underdash connector, but it should come down.

Also might try a loaner tool from the local auto parts store just to see what happens.
 

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Discussion Starter #8
Well, I bought a VAG-COM plug and software and it still will not talk to my beetle. I am going to try unplugging the SRS module and see what happens. I guess I am going to have to replace the computer if that doesn't work. What really sucks is that the car runs and drives great, but can't clear error lights, or get a clue as to what is wrong.
 

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From the original post it sounds like it may have the shorted K-line problem even if the radio is not the cause. The voltage between pins 4 and 7 should be less than 9 volts with the ignition on and 12 volts was measured. Try the resistor test between pins 4 and 7 as described in the linked post.
 

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Discussion Starter #11
Update.. Replaced the computer, still won't communicate. Tried all of the things that Ross-Tech said to try. No good. I have been told that it is probably the gauge cluster. I removed it but they said it will not talk if there is no gauge cluster, so I guess I am on the hunt. Problem is it has to be for a TDI...
 

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Leaving the battery off for an hour or more should reset the CEL, too.

03 is immobilized. No idea how that will play into your cluster search :/
 

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Usually the ECM will keep the CEL status for much longer than 1 hour.

You can disconnect the battery adn turn the headlights on an hope for the best, but do not be surprised if it does not clear/reset the CEL.

Any years the 2003 has an immobilizer and the cluster has a lot to do with the overall personality of the vehicle.
 

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Leaving the battery off for an hour or more should reset the CEL, too.

03 is immobilized. No idea how that will play into your cluster search :/
5 minutes of the battery disconnected, is about 4 minutes too long. Just disconnect the negative cable for about 1 minute, and don't worry about the headlights being on either. They don't even work with the battery disconnected! :)

Sent from AutoGuide.com App
 

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5 minutes of the battery disconnected, is about 4 minutes too long. Just disconnect the negative cable for about 1 minute, and don't worry about the headlights being on either. They don't even work with the battery disconnected! :)

Sent from AutoGuide.com App
OBDI would clear with the battery disconnected for only a few minutes, however, OBDII was specifically designed differently that OBDI not to allow the ECU/codes to be cleared with a quick disconnect of the battery. There may be a few OBDII ECU's out there that may clear with the battery disconnected for a short time, but this is not what OBDII mandated.

This was to keep the Freeze Frame and Emission Readiness Monitors from getting lost/reset and keeping people from trying to bypass faults for Emission Inspections easily.

As for turning the headlights on with the battery disconnected, no they will not and should not work. What is does is similar to holding the battery cables together when disconnected from the battery. The purpose of turning the headlights on, works over 95% of the time, or touching the battery cables together for 30 seconds is to drain all the modules capacitors in the car to get them back to a default logic an baseline state.

OBDII does have volatile RAM that will loose its memory after a lengthy period of time, but it is not likely 1-5 minutes and typically is not even after 1 hour. The headlight trick along with disconnecting the battery may speed up the process on some cars, but it still may take a LONG time.
 

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I don't think clearing the EEPROM for the ECU will help to establish comms.

The problem could be faulty running code, disconnecting the battery and turning on the lights to discharge the caps would fix this. But this does not (or should not) clear the EEPROM storing fault codes, if disconnecting the battery does clear the fault codes on a car it's only because the car is not designed correctly and is sending an electrical charge through the EEPROM and clearing it.

In computers the first issue is like when a computer won't boot, you unplug it and an hour later it just magically works when you get it to a fellow like myself. Or if you called me first, I would tell you to unplug and press the power button which fixes the issue.

The second part, clearing that EEPROM is like flipping the CMOS clear switch/jumper on the system board. The CMOS/BIOS is on EEPROM, it has to be hit with an electrical charge to wipe it first, and then it can be reprogrammed. The data in the EEPROM remains regardless of whether it has power or not. Only by electrically erasing the programmable read only memory can it be cleared. So I don't know how the fault codes on the car could be cleared by simply disconnecting power, for any length of time. Perhaps there is confusion on the part of the user in regards to the display of the fault code relative to the stored information in the EEPROM. The CEL seems to come on for current fault codes, so maybe we're just confused, not actually clearing the fault history and just turning off the idiot light?

Kind of went off track. /ramble


Communication failure is likely due to a damaged OBDII port, the cabling to the port from the ECU, a loose connection at the ECU or the comm port on the ECU was fried by an electrical event which did not also destroy the ECU.

If this was a server I would plug a new cable into the computer that I knew was good and test it. But how do you do that with an ECU? (I'm not even sure where the ECU is located to be honest, never had to fix it yet)
 
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