I warmly welcome, I recently tried to connect my sharan to a computer using CDIFA and unfortunately I get a communication error. I started to check the cable - the K line and it turns out that everything is fine from the ODB socket to the meter and from the immobilizer plug to the ECU. Is there...

You only have no communication with the engine controller? The K line for the engine controller goes through the immo box. If there is a problem there should be communication with the immo box. Short-circuit K and W to immo forest and diagnosis should return. They are probably gray-white or white-gray wires.

Check the voltage on the K line. Under the cockpit, somewhere in the upper left corner there were connectors where all the K line wires come together. Unpin all in turn until you find what is blocking.

with the meter, you check in the socket whether the 12V is?

I checked, it's 12v. I also tried to connect for a short time - I connected pin16 with ecu directly with pin 7 of the OBD socket and then connects but only to the engine itself.

Eg additional heat and its rotten beam.

maybe something is happening with the cables because when I bought it, there were no 2 pieces in the fuse socket (there were empty spaces) and when I refilled them, the battery discharged after the night ... Added after 2 [minutes]: I have a total lack of communication. Only when connecting for a short time, as I mentioned before, I connected to the engine controller, I could not cope with others.

Thank you very much for the hints. As soon as I find a little more time I will start checking everything you write about and I will keep you updated on the results.

I finally found time to review the installation. It turned out that someone was already looking for something and the beam insulation was cut open. 4 yellow-black welded cables protruded from the cut insulation - visible in the photo. In addition, the gray cable with a white K line strip from the OBD socket is also welded to 4 others - also visible in the picture. These welds are factory or are they someone's makeover?

These heated wires from the first photo are connected K lines. I unraveled them all and it turned out that the connection was blocked by one of them - most likely from reheating (most likely because I have not checked yet and the computer can not connect now only with reheating).

Buddy, and where is the bundle and if I follow the cable from the obd lines k lines will I find the cable connections k lines

it is in a thick hanging behind the fuse box and relay box which is on the left side of the steering wheel. tracking the k line from obd you will reach it.

[Solved] VW Sharan 2003: Communication Error with Computer, OBD, CDIFA, K Line & ECU Troubleshooting

zuberek7 22989 15

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#1 17044840 18 Feb 2018 00:17

zuberek7 zuberek7

Level 9

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Post #1
17044840 18 Feb 2018 00:17

I warmly welcome,
I recently tried to connect my sharan to a computer using CDIFA and unfortunately I get a communication error. I started to check the cable - the K line and it turns out that everything is fine from the ODB socket to the meter and from the immobilizer plug to the ECU. Is there anything on the meter clocks that can block the connection?
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#2 17044855 18 Feb 2018 00:48

sagem173 sagem173

Level 9

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Post #2
17044855 18 Feb 2018 00:48

with the meter, you check in the socket whether the 12V is?
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#3 17044950 18 Feb 2018 07:16

zuberek7 zuberek7

Level 9

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Post #3
17044950 18 Feb 2018 07:16

I checked, it's 12v. I also tried to connect "for a short time" - I connected pin16 with ecu directly with pin 7 of the OBD socket and then connects but only to the engine itself.
#4 17044953 18 Feb 2018 07:29

ociz ociz

VIP Meritorious for electroda.pl

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Post #4
17044953 18 Feb 2018 07:29

zuberek7 wrote:
is there anything that can block the connection?

Eg additional heat and its rotten beam.
#5 17045494 18 Feb 2018 12:27

sagem173 sagem173

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Post #5
17045494 18 Feb 2018 12:27

or ecu freaks out
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#6 17045602 18 Feb 2018 13:14

grala1 grala1

VAG group specialist

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Post #6
17045602 18 Feb 2018 13:14

You only have no communication with the engine controller?
The K line for the engine controller goes through the immo box.
If there is a problem there should be communication with the immo box.
Short-circuit K and W to immo forest and diagnosis should return. They are probably gray-white or white-gray wires.
#7 17047468 19 Feb 2018 00:13

zuberek7 zuberek7

Level 9

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Post #7
17047468 19 Feb 2018 00:13

ociz wrote:

zuberek7 wrote:
is there anything that can block the connection?

Eg additional heat and its rotten beam.

maybe something is happening with the cables because when I bought it, there were no 2 pieces in the fuse socket (there were empty spaces) and when I refilled them, the battery discharged after the night ...

Added after 2 [minutes]:

grala1 wrote:
You only have no communication with the engine controller?

I have a total lack of communication. Only when connecting "for a short time", as I mentioned before, I connected to the engine controller, I could not cope with others.
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#8 17047605 19 Feb 2018 06:26

ociz ociz

VIP Meritorious for electroda.pl

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Post #8
17047605 19 Feb 2018 06:26

Check the voltage on the K line.
Under the cockpit, somewhere in the upper left corner there were connectors where all the K line wires come together. Unpin all in turn until you find what is blocking.
#9 17049566 19 Feb 2018 21:47

zuberek7 zuberek7

Level 9

» | Topic author Helpful post? (+2)

Post #9
17049566 19 Feb 2018 21:47

Thank you very much for the hints. As soon as I find a little more time I will start checking everything you write about and I will keep you updated on the results.
#10 17312249 04 Jul 2018 18:46

zuberek7 zuberek7

Level 9
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Post #10
17312249 04 Jul 2018 18:46

I finally found time to review the installation. It turned out that someone was already looking for something and the beam insulation was cut open. 4 yellow-black welded cables protruded from the cut insulation - visible in the photo. In addition, the gray cable with a white K line strip from the OBD socket is also welded to 4 others - also visible in the picture. These welds are factory or are they someone's makeover?

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#11 17322630 11 Jul 2018 05:59

zuberek7 zuberek7

Level 9

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Post #11
17322630 11 Jul 2018 05:59

These heated wires from the first photo are connected K lines. I unraveled them all and it turned out that the connection was blocked by one of them - most likely from reheating (most likely because I have not checked yet and the computer can not connect now only with reheating).
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#12 17323700 11 Jul 2018 18:39

dabrowski marek dabrowski marek

Level 11

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Post #12
17323700 11 Jul 2018 18:39

Buddy, and where is the bundle and if I follow the cable from the obd lines k lines will I find the cable connections k lines
#13 17323786 11 Jul 2018 19:24

zuberek7 zuberek7

Level 9

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Post #13
17323786 11 Jul 2018 19:24

it is in a thick hanging behind the fuse box and relay box which is on the left side of the steering wheel. tracking the k line from obd you will reach it.
#14 17324059 11 Jul 2018 21:42

dabrowski marek dabrowski marek

Level 11

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Post #14
17324059 11 Jul 2018 21:42

Thanks a lot or maybe you know what color cable goes to the additional heater and where its controller is located
#15 17324102 11 Jul 2018 22:05

zuberek7 zuberek7

Level 9

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Post #15
17324102 11 Jul 2018 22:05

all K lines are gray with a white stripe. only from the immobilizer is white. It is impossible to determine which is what without checking.
#16 17324448 12 Jul 2018 06:39

zuberek7 zuberek7

Level 9

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Post #16
17324448 12 Jul 2018 06:39

all K lines are gray with a white stripe. only from the immobilizer is white. It is impossible to determine which is what without checking.

Added after 8 [hours] 34 [minutes]:

Finally, it turned out that the connection blocks the reheating controller. Thank you all for the advice.
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Topic summary

✨ The discussion revolves around a communication error encountered when connecting a 2003 VW Sharan to a computer using CDIFA. The user confirmed that the K line and OBD socket connections are intact, but communication with the engine controller is absent. Suggestions included checking the voltage on the K line, inspecting the immobilizer box, and verifying connections under the dashboard. The user later discovered damaged wiring in the harness, which was blocking the K line connection. Ultimately, it was determined that the reheating controller was the source of the communication blockage.

FAQ

TL;DR: In a 2003 Sharan, after 8h34m of tracing, "all K lines are gray with a white stripe," and the additional‑heater controller was the K‑line blocker. Isolate the K‑line and test with that controller unplugged. [Elektroda, zuberek7, post #17324448] Why it matters: This FAQ helps VW Sharan 7M owners and techs fix no‑communication OBD issues by tracing K‑line faults fast.

Quick Facts

OBD-II pinout: 7 = K-line (ISO 9141/14230), 16 = +12 V, 4/5 = ground. [“OBD-II Connector Pinout”]
Sharan K-lines are gray/white; the immobilizer’s K-line is white. [Elektroda, zuberek7, post #17324448]
K-line splice cluster sits in the thick loom behind the left fuse/relay box. [Elektroda, zuberek7, post #17323786]
Auxiliary heater controller can short the K-line and block diagnostics to all modules. [Elektroda, zuberek7, post #17324448]
To locate a K-line short, measure the line and unplug the splice connectors one by one. [Elektroda, ociz, post #17047605]

Why won’t my 2003 Sharan connect to CDiFA/VCDS?

A module is likely pulling the shared K-line down. In this documented case, the additional heater controller blocked communication across modules. Unplug the heater controller and retest diagnostics. If communication returns, repair or replace that controller or its harness. [Elektroda, zuberek7, post #17324448]

Where is the K-line junction I should check first?

Follow the gray/white K-line from the OBD socket to a splice cluster. It is inside a thick loom behind the fuse and relay box on the left of the steering wheel. Access the loom, open the wrap carefully, and expose the splice connectors for testing. [Elektroda, zuberek7, post #17323786]

How do I isolate a shorted K-line quickly?

Use this 3-step method:

Measure K-line voltage at OBD pin 7 with ignition on.
Unplug K-line splice connectors under the dash one by one.
After each unplug, retry the scan until communication returns; the last removed branch is faulty. [Elektroda, ociz, post #17047605]

Does the engine ECU’s K-line route through the immobilizer?

Yes. The engine ECU K-line passes through the immobilizer box. If that path fails, you may still talk to the immobilizer itself. As one expert put it: "Short-circuit K and W to immo forest and diagnosis should return." Verify the gray/white and white wires at the immo plug. [Elektroda, grala1, post #17045602]

What color are the Sharan’s K-line wires, including immobilizer?

All K-lines are gray with a white stripe. The immobilizer K-line is white. Trace and confirm before cutting, because multiple gray/white lines join in the loom, and identification requires testing continuity. "All K lines are gray with a white stripe. only from the immobilizer is white." [Elektroda, zuberek7, post #17324448]

Why did a direct jump to OBD pin 7 only talk to the engine ECU?

A direct wire connected your scan tool only to the engine ECU’s K-line, bypassing the shared splice. That isolated the engine module from the rest, so only the engine answered while other controllers remained unreachable on the faulty K-line branch. This behavior matches the reported test outcome. [Elektroda, zuberek7, post #17044950]

Can the additional heater (Webasto) block diagnostics on the K-line?

Yes. The additional heater controller can hold the K-line bus down and kill communication to all modules. Disconnect that controller and check if scanning resumes. If it does, repair the heater controller or its corroded harness before reconnecting it to the K-line. [Elektroda, zuberek7, post #17324448]

How many joined K-line wires might I find in the under-dash loom?

Expect multiple splices. In the documented teardown, the gray/white K-line from the OBD socket was welded to four other K-line wires in the loom. One of those branches blocked diagnostics until isolated from the bus. This shows how a single bad branch can affect all modules. [Elektroda, zuberek7, post #17312249]

How do I verify OBD-II power before chasing K-line faults?

Check for battery voltage at OBD pin 16 and good grounds on pins 4 and 5. Without stable +12 V and ground, no scan tool will connect, regardless of K-line integrity. Confirm power first to avoid misdiagnosing a communications fault. [“OBD-II Connector Pinout”]

Could a failed ECU cause total no-communication on the K-line?

It can. A malfunctioning ECU may disrupt bus communication and appear as a global no-comm condition. Rule it out by isolating ECU’s K-line branch at the splice and testing tool communication with other modules. Replace or repair the ECU only after confirming isolation results. [Elektroda, sagem173, post #17045494]

After adding missing fuses, my battery died overnight. Related to no-comm?

It can be related. Reinstalling missing fuses can re-energize a faulty retrofit or corroded circuit, such as the auxiliary heater harness. That can both drain the battery and load the K-line. Pull the suspect fuse, unplug the heater controller, and recheck current draw and diagnostics. [Elektroda, zuberek7, post #17047468]

If the immobilizer path is faulty, can I still run diagnostics?

Often, yes. You may retain communication with the immobilizer even if the engine ECU path via immo is broken. Bypassing or shorting the K and W lines at the immobilizer plug for testing can restore scan access, confirming a path fault. Proceed carefully and document wiring. [Elektroda, grala1, post #17045602]