VW Fox 1.2 6V BMD camshaft position sensor 16725 P0341 implausible - intermittent

Gt_ii · Mar 14, 2019

Hello, I wonder if anyone can give any tips for diagnosing periods of rough running and power reduction in my son's 2009 VW Fox. This seems to happen sometimes after cold starts when the engine has cranked for a few seconds longer than normal before starting.

To investigate, this fault, I bought a VCDS kit and got the following auto-scan:

Code:

Saturday,16,February,2019,16:14:46:62523
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 18.9.1.0 (x64)  HEX-V2 CB: 0.4437.4
Data version: 20190114 DS296.0
www.Ross-Tech.com


VIN: WVWZZZ5ZZ94107765   License Plate: XX58XXX
Mileage: 76560km-47572mi   Repair Order: 



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Chassis Type: 5Z (5Z - VW Fox (2004 >))
Scan: 01 03 08 09 15 17 19 44 46 56
 
VIN: WVWZZZ5ZZ94107765   Mileage: 76560km-47572miles
-------------------------------------------------------------------------------
Address 01: Engine        Labels: Redir Fail!
   Part No: 03D 906 023 B
   Component: SIMOS91 1.2l 2V     1415  
   Revision: --H04---    Serial number: VWZ5Z0H9142097
   Coding: 0000031
   Shop #: WSC 00000 785 00200
   VCID: 1D67DA2B51AE8D5F95B-5184

1 Fault Found:
16725 - Camshaft Position Sensor (G40) 
            P0341 - 008 - Implausible Signal - Intermittent
             Freeze Frame:
                    RPM: 288 /min
                    Mass Air / Rev.: 414.2 mg/str
                    Bin. Bits: 00000010
                    Temperature: 10.5°C
                    RPM: 224 /min
                    Mass Air / Rev.: 441.5 mg/str
                    Bin. Bits: 00000010
                    Temperature: -3.0°C

Readiness: 0000 0000

-------------------------------------------------------------------------------
Address 03: ABS Brakes        Labels: 5Z0-907-379-ABS.clb
   Part No SW: 5Z0 907 379 F    HW: 5Z0 907 379 F
   Component: ABS 8.0 front   H05 0005  
   Revision: 00000000    Serial number: 00000000000000
   Coding: 0000004
   Shop #: WSC 00000 785 00200
   VCID: 48C95B7FAEACB8F716D-50F4

2 Faults Found:
01314 - Engine Control Module 
            013 - Check DTC Memory - Intermittent
             Freeze Frame:
                    Fault Status: 00101101
                    Fault Priority: 2
                    Fault Frequency: 7
                    Reset counter: 216
                    Mileage: 76408 km
                    Time Indication: 0

18265 - Load Signal 
            P1857 - 000 - Error Message from ECU - Intermittent
             Freeze Frame:
                    Fault Status: 00100000
                    Fault Priority: 2
                    Fault Frequency: 8
                    Reset counter: 216
                    Mileage: 76408 km
                    Time Indication: 0


-------------------------------------------------------------------------------
Address 09: Cent. Elect.        Labels:. 6Qx-937-049-C.lbl
   Part No: 6Q2 937 049 F
   Component: 0000 BN-SG.         2S36  
   Coding: 01038
   Shop #: WSC 00000  
   VCID: 3FDB40A3FE62FF4FA77-50F4

No fault code found.

-------------------------------------------------------------------------------
Address 15: Airbags        Labels: 6Q0-909-605-VW5.lbl
   Part No: 1C0 909 605 K
   Component: 1M AIRBAG VW51      0011  
   Coding: 12621
   Shop #: WSC 00000  
   VCID: 2C0107EF1F1474D7125-50F4

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments        Labels: 5Z0-920-xxx-V1.clb
   Part No: 5Z2 920 820 
   Component: KOMBI+WEGFAHRS. M73 0013  
   Coding: 00432
   Shop #: WSC 00000  
   VCID: 76B5E58791D87E07B41-50F4
   WVWZZZ5ZZ94107765     VWZ5Z0H9142097

No fault code found.

-------------------------------------------------------------------------------
Address 19: CAN Gateway        Labels: 6N0-909-901-19.lbl
   Part No: 6N0 909 901 
   Component: 0000 GATEWAY CAN    2S36  
   Coding: 00014
   Shop #: WSC 00000  
   VCID: 70B9D39FF3BC50376ED-50F4

No fault code found.

-------------------------------------------------------------------------------
Address 44: Steering Assist        Labels: 6Q0-423-156.clb
   Part No: 6R0 423 156 
   Component: LenkhilfeTRW        V272  
   Coding: 10140
   Shop #: WSC 00000  
   VCID: 6D87CAEBE48EBDDF45B-50F4

No fault code found.

-------------------------------------------------------------------------------
Address 56: Radio        Labels: 1K0-035-1xx-56.lbl
   Part No SW: 5Z0 035 152 E    HW: 5Z0 035 152 E
   Component: Radio 9NK           0004  
   Revision: 00001000    Serial number: VWZ4Z4H9280875
   Coding: 0020201
   Shop #: WSC 00000 785 00200
   VCID: 34311F8FC2242C174A5-50F4

No fault code found.

End----(Elapsed Time: 01:40, VBatt start/end: 12.1V/12.1V. VIgn 0.0V)------

I have found the engine runs perfectly after I've cleared the fault memories. However, the 16725 P0341 fault code comes back every so often, always immediately after starting the engine, particularly when the engine is cold. The roughness and reduction in power then come back.

The ABS fault codes only appear after the brakes are first used after the 16725 P0341 fault has been logged. This makes me think they are not faults in themselves, just a by-product of the engine ignoring the camshaft position sensor signal and putting the engine into some kind of limp mode.

Reading around on the internet, it seems this might be a symptom of timing chain stretch, which can cause timing issues. It seems the 3 cylinder 1.2 Polo/Fox engines seem quite prone to this. Are there any measuring blocks I can look at or log to find out whether this could be be an issue?

Or could there any more straightforward things I should check out first?

Any suggestions would be very welcome, particularly if backed up by experience!

DrPeter · Mar 14, 2019

Hello,

Welcome to the Ross-Tech forum and thank your for posting your question with an Auto-Scan.

Are there any measuring blocks I can look at or log to find out whether this could be be an issue?

Or could there any more straightforward things I should check out first?

You can have a look at the measuring Value Block group [012] in the [01-Engine] with the engine at idle, (AC off, lights, etc off).

- Field 3 = Number of teeth of the sender wheel on the crankshaft when Camshaft Hall sender signal changes from negative(-) to positive(+)
--> Normal range is (26 to 31)

- Field 4 = (86 to 90) - Number of teeth of the sender wheel on the crankshaft when Camshaft Hall sender signal changes from positive(+) to negative(-)
--> Normal Range is (86 to 91)

If the values above are correct, there is no fault(concern) present at this time.

If the values are not correct, verify the G40-Camshaft sensor is not loose or damages. Check wiring as per the Official Factory Repair manuals, verify the engine is mechanically sound and you could try a new G40-Camshaft sensor.

Hope this helps,

drpeter

Jack@European_Parts · Mar 14, 2019

Vehicle Identification No.	WVWZZZ5ZZ94107765
Model	Fox FO
Date of production	03.12.2008
Year	2009
Sales type	5Z11J4
Engine Code	BMD
Transmission Code	JHN

In addition to Peter's aforementioned excellent detailed post and recommendations.

Check the connector & verify harness integrity to G40 is not dirty/faulty, corroded, improperly seated in VC or if W-crimp pushed back from a harness assembly failure, in addition check that the CAT is not restricted or if over filled with oil causing a slight bump or misfire or faulty fueling.

In some more recent cases observed cams may wear in a bearing journal and float changing reluctor ref point further causing such a deviation from fuel contaminated in oil!

Always observe for FOD! & JPPSG!

Gt_ii · Mar 16, 2019

Many thanks both. This is very helpful, particularly the information on Measuring Block 12. The values I have seen in Fields 3 and 4 over several sessions are 28, 29, 30, 58, 59, 60, so all within the acceptable range. At first the low number was in Field 3 and the high number in Field 4, but in later measurements this pattern reversed. I assume this varies depending on the orientation of the crankshaft when the OBD first picks up a signal from the camshaft.

I've figured out how to log the measuring block data and have logged Block 12 on start up. So far, the figures look good and stable, although I haven't had an opportunity to log the point at which the fault comes back. I am feeling slightly reassured about the condition of the timing chain, but wondering if a problem with the tensioner could cause an intermittent timing error on start up.

The G40 connector and terminals look perfect and correctly assembled. I'd prefer to get some evidence suggesting a fault before fitting a new one, although at around £70 for the genuine part, that is a massively cheaper option to experiment with than getting the timing chain and tensioner replaced.

Jack@European_Parts · Mar 16, 2019

Costs no money to load light and verify the circuit.

Gt_ii · Mar 17, 2019

I've now been able to log Measuring Block 12 for both a "good" start and a "bad" start. The tables below show the first second of each engine start taken from VCDS logs in "Turbo" mode, ie at 16 measurements per second.

In the "good" start, the first camshaft signal is picked up within 0.2 seconds of starting to crank and the engine is running within 0.4 seconds:

Time	RPM	Load	Pos	Pos
s	/min	%	A	B
0.00	0	9	0	0
0.06	224	100	0	0
0.12	224	100	0	0
0.19	256	96	0	30
0.25	256	96	0	30
0.31	384	86	0	30
0.37	896	68	88	30
0.44	1152	51	88	30
0.50	1312	32	88	30
0.56	1344	21	88	30
0.62	1344	17	88	30
0.68	1312	14	88	30
0.75	1248	12	88	30
0.81	1184	18	88	30
0.87	1152	21	88	30
0.93	1088	22	88	30
1.00	1056	24	88	30

In the "bad" start, the first camshaft signal is not picked up until 0.5 seconds of cranking and the engine isn't running until around 0.9 seconds:

Time	RPM	Load	Pos	Pos
s	/min	%	A	B
0.00	0	9	0	0
0.06	224	100	0	0
0.14	224	100	0	0
0.19	224	100	0	0
0.26	224	99	0	0
0.31	224	99	0	0
0.38	288	98	0	0
0.44	288	98	0	0
0.50	320	93	0	90
0.56	320	93	0	90
0.63	320	84	28	90
0.69	320	84	28	90
0.75	320	83	28	90
0.81	320	83	28	90
0.89	704	73	28	89
0.94	896	65	28	89
1.01	960	51	28	89

So the 16725 P0341 trouble code that is being logged after a "bad" start seems to be caused by a temporary loss of the camshaft signal during cranking rather than incorrect timing.

Thank you Peter and Jack for getting me to this point. This gives me confidence that it is not a timing chain issue and that I can focus on the sensor and/or wiring, although I guess there could instead be something else is going on with the electrics to interfere with the camshaft signal or the ECU itself could be faulty.

Load testing the circuit is something I'd probably leave to the experts. Access to the ECU connector doesn't seem that straightforward on the Fox and I'd be scared of accidentally shorting something out and causing damage to the electrics.

So unless any other ideas crop up, I'll probably plump for the easy option and try a new camshaft position sensor. A bit of a risk I know, but if it doesn't solve the problem, I can always resell the sensor on ebay.

Gt_ii · Mar 21, 2019

Well, I fitted the new camshaft position sensor today, and things are looking positive. After 20 or more engine starts at various temperatures, not once has the fault recurred, and fault memories are clear.

Unexpectedly, unlike the genuine one I fitted, I discovered the sensor had the VW logo apparently scratched off, so I'm guessing an aftermarket replacement for the original. The new one is different in colour from the original, light grey with blue highlights, hopefully indicating a later and more durable design.

Thanks again Peter and Jack for specific advice given, which has narrowed down my search. If anything changes, I'll update the post for others to see. Otherwise I suspect I may be back soon with a question on checking the airbag settings.

VW Fox 1.2 6V BMD camshaft position sensor 16725 P0341 implausible - intermittent

Gt_ii

Verified VCDS User

DrPeter

Ross-Tech Employee

Jack@European_Parts

Gone But Not Forgotten

Gt_ii

Verified VCDS User

Jack@European_Parts

Gone But Not Forgotten

Gt_ii

Verified VCDS User

Gt_ii

Verified VCDS User