VW T4 2.5 TDI Engine Control Unit

Hello, fellow tinkerers!

Key details: ACV 4/97, 460,000 km.

Today, my better half's T4 broke down.
Simply, the engine lost power.
The error memory contained 3 errors:
Sensor for control valve travel G149 35-00
Metering valve (N146) 18-00 upper limit value
Metering valve (N146) 19-00 lower limit value
The errors reappear immediately after being deleted, without any attempt to start the engine.
The pump was overhauled 50,000 km ago by a "specialized workshop" with a brand new metering valve. This was done as a precaution.
Unfortunately, the problems started then. Shortly thereafter, we experienced a breakdown, 800 km from home. The metering valve connection to the pump had come loose.
After the repair by the boss himself (I would have preferred an expert), the metering valve was set to too high a flow rate and started too early. Quote: "I thought they would appreciate a little extra power."
That's the background.
I therefore don't want to rule out the possibility that the pump doctor has further messed things up.
In a similar case, I read that the pump impeller had become skewed.
According to my initial inspection, at least the pump belt is very tight.

I would be very grateful for your ideas!
Thanks in advance!

Hello,

The regulator is quite simple, just remove the cover and check. Also, check the wiring!

See also:
/viewtopic.php?t=5517

Best regards, Rainer

Thank you, Rainer, for the quick response!

I will definitely remove the lid as soon as possible.

I was just wondering if the errors in the memory might indicate some kind of damage.

Hi,
could you also provide the values from MWB 019 (when the ignition is on)?
hg
Herbert

Absolutely!
Anything you want!
5.040 V Stop
5.040 V Start
And if it's convenient, I'll add another beer on top

Hi,

The voltage should be between 0.54 V and 0.88 V at the lower end, and between 4.1 V and 4.88 V at the upper end!

The motor should probably no longer be controllable.

Perhaps the sensor for the control lever is loose / hanging at the upper mechanical stop.

To be on the safe side before opening the metering valve, please post a Screenshot of MWB 001 and MWB 019 with the ignition on.

Best regards,
Herbert

I would also suspect that the fuel injector has come loose. Try setting the engine to 074-0.76 (MWB1) with the ignition on and see if that helps.

Here's a possible translation, keeping the HTML tags and URLs intact:

Could you describe a cable break in the area between the body and the engine? I've experienced this myself on a Golf III TDI and a Passat 35i TDI.

/viewtopic.php?t=27960&highlight=golf+tdi

Thanks for the interesting tip!

Actually, the bus had an accident once where all the cables to the control unit were cut.

I carefully repaired it back then,
but with this vibrating plate from the engine, you never know.
Unfortunately, I haven't had the chance to disassemble it yet, as I want to have it on our property first before opening the pump.
Hopefully, I'll be able to do that tonight.

Hi.
You can also measure directly on the pump connector to determine if the fault lies in the control panel area, or in the cable set or control unit.

The following values should be measured:
Pin 5 against 6: 0.4 - 1.0 Ohm (at 15 - 30°)
Pin 4 against 7: 1.2 - 4.0 kOhm (at 15 - 30°)(Temperature sensor, should be unimportant in this case)
Pin 1 against 2: 4.9 - 6.5 Ohm
Pin 2 against 3: 4.9 - 6.5 Ohm
Pin 1 against 3: 9.8 - 13.0 Ohm
Pin 3 against 5: Minimum 1.0 MOhm
Pin 6 against 7: Minimum 1.0 MOhm
All pins against ground: Minimum 1.0 MOhm

Measure all values with the pump connector disconnected.
Regards

While this provides static values, it is meaningless for the actual testing of the reactor.
hg
Herbert

Hey.

It's not enough to simply rule out, for example, a loose relay, as it can naturally be loose even with correct values.
An electrical problem in the control panel, such as a broken weld on the cable input, can be identified.
I have a control panel here, also from an ACV, that exhibits exactly the same symptoms. Errors in the STG (control system), which cannot be deleted. Return voltage around 5V, as far as I remember, exactly three errors related to the control panel.

If I pass current through it, I have no continuity between 1 and 3, and between 2 and 3. Also not between 5 and 6.
The motor received a new control panel after being fitted with the pump, and it is now running smoothly.

Since the error pattern closely matches, and we suspected a defect in the control panel through electrical measurements, and then identified it, I would definitely invest the few minutes in passing current.
Visually, you can't see the control panel itself, although it doesn't have the relay or the circuit board yet, only the black plastic cover. All the welds are present.

Best regards,
Matze

Okay,
You're right, the test before opening the MSW makes sense.
Best regards,
Herbert

Found an error. And "History repeats".
Apparently, the pump experts who had overhauled the pump weren't quite as good at soldering.
Once again, the workshop was to blame, and it was another faulty solder joint at the metering valve.
The first time, we had to have the car towed 800km and we had to take a rental car for a week. This time, it was only 80km.
If this had happened a month earlier, it would have cost us either our trip to Iceland and 2000€, or our stay in Iceland would have been extended:evil:
Anyway, I would have sued the pump workshop.
That's why, at 400,000km, I would proactively have the pump overhauled by a "professional" and have turned my car into an ADAC sponsor. There were a total of 3 breakdowns, once the cable from the shut-off valve had come loose due to being poorly attached.

I'm curious if there's anything I can do to prevent future open solder joints. Something that won't dissolve, so it won't be used in the pump.
Would shrink tubing over the solder joints be an option?
I want my bus to be reliable again.

Thanks to everyone for the great help!
There are real professionals with expertise and willingness to help!

Hi,

is the loose wire somehow under tension at the newly formed solder joint? Shouldn't happen, either something is vibrating that shouldn't be, or the wrong solder or something is being messed with.

Solder becomes brittle if it's constantly heated with the soldering iron.

Viele Grüsse, Rainer

Hi Rainer!

My speech!
I believe the wires shouldn't be under tension, but rather should be pressed together without being welded.
Unfortunately, the workshop owner didn't take me seriously when I told him this.
Unfortunately, it's now difficult to bend the wires, so I hope to find a way for them to create a permanent connection.