2018 Crafter P0684 Error Glow Plug Control Module

[ColinK]

2018 Crafter

Sometimes turns over for about 15 to 20 seconds before starting. Then I got this error

P0684 Error Glow Plug Control Module to PCM Communication Circuit Range Performance

All I can find online are varied suggestions about:
cleaning glow plugs
replacing glow plugs
Replacing the Glow Plug relay

Can anyone give me more details

With an air temperature of 19 degrees are the glow plugs actually doing anything. Even if there is a fault should I expect a problem with starting?

Thanks

 

[ColinK]

Any help with this would be appreciated.

 

[mmi]

Would be more than helpful know what engine you have. Anyways, I guess it's one of these DASB, DAUA, DAVA.

Sometimes turns over for about 15 to 20 seconds before starting.

With an air temperature of 19 degrees are the glow plugs actually doing anything. Even if there is a fault should I expect a problem with starting?

Correct, at 19 °C the glow plugs barely flash, if at all. I don't think long cranking relates to glow plugs - I would check fuel pressure build-up at fuel rail first - with proper diagnostic tool, e.g. VCDS.

---

P0684 - Glow Plug Control Module (J179) - Implausible Signal

Any dash lights?

Sounds like a communication (wiring?) problem or non-functioning controller?

Well, using a proper tool you could try to catch the signalling of the controller at start-up.
It should be something like this - glow status below (although not a Crafter - instead a Transporter but similar engine than the mentioned ones)

 

[ColinK]

@mmi

Sorry I missed your reply.

2018 - Engine is 2.0 130bhp I think.

To clarify, this was a sudden error. Starts OK while warm.

It appears that a faulty relay is quite common.

Van has not gone far since my post. Only getting back to this now.

I don’t have VCDS

Could you tell me where the Glow Plug relay is located? I have searched several forums and videos.

Does anyone have a diagram for the relay pins so I can test it.

 

[mmi]

Could you tell me where the Glow Plug relay is located?

3 - Automatic glow period control unit -J179-

Does anyone have a diagram for the relay pins so I can test it.

I'm afraid it's not a simple thing to do. It's not just a relay - it's driven by two lines from ECU (Engine Control Unit)
Anyways, the part number for the unit should be 04L 907 281 B - for googling for the pins. Crafter wiring diagram shows their functionality.

Most likely also this ECU has a built-in test for the glow period control unit - which can be run with a proper diagnostic tool.

It appears that a faulty relay is quite common.

Perhaps then just replace with a new one?

2018 - Engine is 2.0 130bhp I think.

So possibly the engine code is DAUA? Assuming it's front wheel driven.

 

[ColinK]

Thanks for your detailed reply @mmi

Just checked. Yes DAUA engine. 2018 van.

Sorry I missed part of your earlier reply - about fuel pressure.

I don’t have VCDS. Will VCDS Lite do this diagnosis for me?

If no, will any universal diagnostic tablet do this diagnosis. Eg Autell or Launch? I would prefer to invest in some universal diagnostic tool. Even a model updated to around 2020 would be useful for most cars I would have.

Is low fuel pressure likely to only be present at startup? This always starts ok after running.

Regarding glow plug relay location. If that image shows location of glow plug relay above left wing under the bonnet, I don’t see any electronics there. See image.

Am I missing something obvious or could it be somewhere else?

Back to diagnostics.

 

[mmi]

about fuel pressure.

I don’t have VCDS. Will VCDS Lite do this diagnosis for me?

I'm afarid VCDS Lite doesn't help. Per Ross-Tech it won't do CANbus diagnostics - see link below

Ross-Tech: VCDS Lite

If no, will any universal diagnostic tablet do this diagnosis.

I don't know.

Is low fuel pressure likely to only be present at startup? This always starts ok after running.

The fuel pressure purges down to zero in seconds when engine is stopped (even for Stop/Start shutoffs).

Regarding glow plug relay location. If that image shows location of glow plug relay above left wing under the bonnet, I don’t see any electronics there. See image.

Am I missing something obvious or could it be somewhere else?

Well, the snippet was from VW workshop manual for engine DAUA so it was there from factory.

This one doesn't look OEM (especially the wiring without wrapper, no connectors?) - does it have any part numbers or some kind identifier. Where do the four cables from the left side go?

 

[ColinK]

@mmi
Thanks for your detailed answers again.

Based on your fuel pressure answer, if I understood correctly, a fuel pressure issue is unlikely to affect only cold start / first start, so still suspecting the glow plug relay. I will make some arrangements to get connected to diagnostics.

Regarding the black box with black and red wires. I will need to look again when I next see the van (with my son at the minute). I opened the box, it appears to have very heavy duty fuses in it. Van was owned by a fruit merchant, it had internally mounted aircon before my son purchased. So cables could relate to that. Lots of redundant cables in back of the van.

 

[mmi]

Based on your fuel pressure answer, if I understood correctly, a fuel pressure issue is unlikely to affect only cold start / first start,

What happens if after cold start the engine is immediately stopped, and then restarted 2 minutes later. Again long crank or normal start?

 

[rod_vw]

On our 2023 model there are two relays mounted on the inner wheel arch below/behind the cable connection and fuse (black) box, You should also have a cover over the black box part number 7C0 955 737.
The red cover is over the +ve jump start connection, the -ve is on the right front wheel arch.

 

[Myzeneye]

Coin, did you resolve this issue? If so what was it and what did you do to fix it ?

 

[ColinK]

What happens if after cold start the engine is immediately stopped, and then restarted 2 minutes later. Again long crank or normal start?

Sorry for the delay in replying - I will explain in my update post in this thread in a minute.

On most occasions, the van turns over for about 3 to 6 seconds before starting - longer than I would expect, but I have not compared with another Crafter.

Sometimes after a warm start it starts immediately other times it still takes 3 to 6 seconds.

Sometimes form a cold start (summertime) it takes up to 30 seconds turnover before starting. same as it was when the battery was at a very low charge.

 

[ColinK]

Coin, did you resolve this issue? If so what was it and what did you do to fix it ?

No - see my update below

 

[ColinK]

@mmi @rod_vw
I hate reading fault threads where the OP fails to report outcome. This is not one of those threads. I will update when resolved.

I don't have access to this van very often (my son's) so posts are over an extended period.

=====

Update and summary of what I have done so far (two facts not previously mentioned).

The 2018 Crafter still has it's original battery. It sat for 2 months with only one battery charge with doors open frequently while accessories and storage was added - thus generally had a low battery. As I had read that battery issues can produce same symptoms I did not dig deeper until van was in regular use.

During this time it always took about 30 seconds to turnover and start but always started OK.

Yellow engine fault light was always on the dash

Using a cheap diagnostic tool I found the error

P0684 Error Glow Plug Control Module

The van has been driven daily for last two months.

Despite clearing all error codes the yellow engine fault light returned on next re-start

The starting issue is now somewhat different.

On most occasions, the van turns over for about 3 to 6 seconds before starting - longer than I would expect, but I have not compared with another Crafter.

Sometimes after a warm start it starts immediately.

Sometimes from a cold start (summertime) it takes up to 30 seconds turnover before starting. Same as it was when the battery was at a very low charge.

I bought Chinese OBD cable which came with VCDS which returns an "unknown Error Code" - see below

I know that a simple diagnostic might be to buy a new glow plug relay but I am not keen to recommend that my son spends ~£100 with an uncertain outcome.

Note I have changed some data below to xxxxxx as I am not sure if it identifies the specific vehicle. If full data required for any line please let me know.


Address 01: Engine (J623-DAUA) Labels:. 04L-907-309-V2.clb
Part No SW: 04L 906 056 NB HW: 04L 907 445 C
Component: R4 2.0l TDI H01 5239
Revision: 23201001
Coding: 001940106304010800000000000000000000000000000000
Shop #: WSC 00069 790 00013
ASAM Dataset: EV_ECM20TDI03004L906xxxxx 005003
ROD: N/A
VCID: 7AFB47EFFDDF5xxxxx-802E
VINID: 9E606AAAA8E9A9A240047146209Axxxxx

Unsupported vehicle. Please upgrade to a current Ross-Tech interface.
No ASAM data for: "EV_ECM20TDI0300xxxxxx" (VN54)
1 Fault Found:
15908 - ROD - Unknown Error Code
- 00 [00100111]
Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 1
Mileage: 151773 km

 

[mmi]

Yellow engine fault light was always on the dash

So it's the light with symbol of engine?

1 Fault Found:
15908 - ROD - Unknown Error Code

15908 = P0684

Despite clearing all error codes the yellow engine fault light returned on next re-start

Did the fault 15908 return also? Probably yes?

Perhaps you could log some engine data during engine starting?

VCDS > Select > Engine > Adv. Meas. Values >

Tick the following

IDE00021 Engine RPM​

IDE00347 Air mass: actual value:​

IDE00352 Main injection: duration of activation​

IDE00589 Fuel pressure​

• Click Log - Start
• Crank the engine till it starts
• Stop logging etc.
• The logfile will be in folder C:\Ross-Tech\VCDS\Logs
• Please post the logfile.

 

[ColinK]

@mmi

Thanks for your persistence with this.

I cannot quote your post so copied and pasted.

Yellow engine fault light was always on the dash

So it's the light with symbol of engine?

- Yes

15908 = P0684

- Yes

Did the fault 15908 return also? Probably yes?
Engine fault symbol did not return for about 5 days (which surprised me)
I now have a “no interface found” issue with VCDS

I did another post in the forum about that.

When I get that resolved or a new cable I will try to log some engine data during engine starting?