[T6_measured] 01-Engine - Built-in tests for electrical coolant pumps

[mmi]

Yet another set of engine's built-in tests to try.

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HOW-TO run engine's built-in test for EGR cooler pump​

IGNition ON (engine not running)​

VCDS > Select > Engine > Output test > IDE00879-EGR cooler pump​

Select "Measuring Values" ​

Pick up e.g. the following data items for monitoring - the same set works for all the tests - thus all the tests can be run at one go.

Select "Log" (if so desired or just monitor the values)​

Select "Start" - the measuring value cycles at 5 second intervals from minimum to maximum​

Verify that the pump makes audible sound in engine bay.

When finished (NOTE: test won't run forever - it will eventually time-out)

Select "Stop"​

NOTE: EGR cooler pump runs always when ignition is ON - depending on coolant temperature somewhere in 70%...100%. The test will overtake normal operation and run the pump between OFF (indicated as 0 %) and MAXIMUM (100%) at 5 second intervals.

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Test for Air charge cooler pump​

> IDE01944-Coolant pump for charge pressure cooler​

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NOTE: The test will run the pump between OFF (indicated as 10%) and MAXIMUM (indicated as 95%) at 5 second intervals. This pump is the loudest one.

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Test for Heater support pump​

> IDE07243-Heater support pump​

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NOTE: The test will run the pump between OFF (indicated as 10%) and MAXIMUM (indicated as 95%) at 5 second intervals.

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I don't expect the data above to change even with a faulty pump - the fault diagnosis needs to be done based on other criteria - e.g. no audible sound from pump.

 

[mmi]

Reserved.

 

[mmi]

Reserved.

 

[Dellmassive]

Awesome

 

[Broadside]

Hi @mmi i have been told by a mechanic who has worked at a VW van centre that the EGR coolant pump can stop working but doesn’t show a fault code, possibly due to the motor spinning but the impeller not turning.

Do you have any ideas how to test this or is it something you’ve heard of before?

You may have seen in another thread that my recently replaced EGR has failed and I’m trying to work out why before getting a new EGR fitted.

 

[n10n]

Do you have any ideas how to test this or is it something you’ve heard of before?

Check out the PDF [1] attached to post [2] - EGR valve position and EGR temperatures graphs within



EDIT: missed a timescale - 130 - 150s into the drive. The cooling part shown takes roughly 14 seconds.


If you have VCDS available you could log IDE07757 (EGR valve position) and IDE04035 (EGR temperatures). If the coolant is not circulating you probably should see EGR input and output temperatures remaining much closer to each other and especially output temperature not cooling down effectively after the EGR valve position transitions from positive to negative.

IDE07757,Exhaust recirc.valve 1 bank 1: posit.feedback - Actual value,27.52, %

IDE04035,exh.gas recirc. temperature,EGRTemp 11/12:173/100 ?C / EGRTemp 21/22:---/--- ?C,

These were measured with CXEB (204) engine so might be little bit different for your engine, hope this helps!

[1] https://www.t6forum.com/attachments/2023-09-19-n10n-egr-polarity-pdf.214492/
[2] VW T6 Custom PID codes for DPF

 

[mmi]

Hi @mmi i have been told by a mechanic who has worked at a VW van centre that the EGR coolant pump can stop working but doesn’t show a fault code, possibly due to the motor spinning but the impeller not turning.

I have been told the same. Sounds credible.

Do you have any ideas how to test this or is it something you’ve heard of before?

As @n10n suggests above I would use VCDS to monitor EGR cooler input and output temperatures. When everything is working as should you would expect to have well cooled gases at fairly stable temperature at the output of the EGR cooler as below from 200 to 1100 seconds. Without proper cooling would expect to see something similar as from 1100 to 1800 seconds (here the cooler is actually bypassed).



The plot adopted from

[T6_measured] Winter specialities

Spot the winter specialities:

www.t6forum.com

 

[T6_FunBus]

My van has always had issues running these tests. It often says ‘refused by control unit’ when I want to run output tests on any of the pumps, whether engine is warm, cold, been running and stopped etc. not sure why.

It did it before when I was troubleshooting but persisting with trying and eventually it allowed me. But recently I’ve not been able to run any, always says ‘refused by control unit’. Any ideas?

Also, from my findings;

Charge cooler and EGR
12v supply and ground pins
2.9-3v control signal voltage (green / yellow wire)

Heater support pump
12v supply and ground pins
Previous testing showed anything from 0-10v on the blue / pink wire…
Today showed only 1-1.2v when testing

It seems the heater support pump is managed differently to the other two pumps, as when disconnecting egr or charge cooler, it shows open circuit, but that does not happen when disconnecting control wire from the heater support pump. It just shows ‘supply voltage error’.

Not really sure what this proves or means…

It would be beneficial if we could someone discover exactly how this third pump is controlled and operated, and therefore how to troubleshoot such issues with it.

 

[T6_FunBus]

Reporting back on this.

I have P16CB00 - heater support pump supply voltage error

Pump and wiring to ECU changed.

New pump and power, ground wires tested on EGR and Charge Cooler pump.

Always the same error.

The only difference is the control wire has low voltage compared to others on heater support pump. Heater support pump also does not report that the control circuit is open circuit when disconnected.

This is looking like an ECU fault.

However, heater support pump secondary activation circuit does run at 95% and can vary. All switches correct with ignition and overrun when ignition is off.

There are other VW owners all over different forums with the same problem.

As far as I can tell there are only two options once everything else is exhausted. Replace ecu (which seems a bit overkill considering the pump functions and output tests work) or as pump works find someone willing to remove dtc.