VCDS fault code clearing

[n10n]

Sorry to hear about the troubles. Just a couple of thoughts from sidelines:

1. There’s too many issues with VCDS readings, I would not trust the values you get from partial blockmaps. Not sure what would be the best way to sort this. Do you happen to know someone with a VCDS that’s 100% known to work? If so, get a blockmap there and see if you get equal results.

2. Did you have battery disconnected with all the EGR / front service position work? If not, try a capacitive discharge reset: disconnect battery for 15 mins or so, reconnect, and see if anything changes after reconnecting. Current time and electric window single click functions will need to be set afterwards.

3. I’m not sure if this means anything but in your original DTC freeze frame exhaust temperature sensor 2 is showing up as zero - obviously incorrect

Exhaust gas temperature sensor 1: 54.7 °C
Exhaust gas temperature sensor 2: -0.0 °C
Exhaust gas temperature sensor 3: 27.6 °C
Exhaust gas temperature sensor 4: 23.8 °C

 

[mmi]

exhaust temperature sensor 2 is showing up as zero - obviously incorrect

Per workshop manual and wiring diagram CFCA engine does not have exhaust temperature sensor 2.

 

[n10n]

Per workshop manual and wiring diagram CFCA engine does not have exhaust temperature sensor 2.

Ah thanks, that explains!

 

[Hannu]

It seems that there is possibly three (3) issues with the wiring as the following sensors are on different circuits

(1)​

Charge air pressure sensor G31 is wired separately to the ECU​

View attachment 269722

(2)​

Also accelerator pedal has it's own wiring between the pedal and the ECU​

View attachment 269734

(3)​

Circuit D141 in wiring diagram has the following sensors (common 5 Volts with all sensors)​

(possibly the "Reference voltage circuit B"??)

G28 Engine speed sender​

Data seems to be ok.

---

G69 Throttle valve potentiometer​

View attachment 269732

---

G212 Exhaust gas recirculation potentiometer​

View attachment 269733

---

G247 Fuel pressure sender​

2000 bars ! Not plausible.

View attachment 269730

---

G584 Regulating flap potentiometer (turbo actuator)​

Couldn't identify related data labels - possibly mislabeled in VCDS. Anyways, suspect items missing on latest blockmap (30-31.12 logs)..

Having poured over the wiring diagrams this evening I note that there are connections between the items listed. Clearly the ECU, which I checked today with negative results, but also
283 Earth point 2 and D141 connection (5V) engine pre-wire. However I'm a bit bemused as to were they are ?
I'm now thinking a possible bad earth, I know, clutching at straws now

 

[mmi]

I would not trust the values you get from partial blockmaps.

Well, even the partial ones are consistent - no items are missing until totally cut off. Makes me think that either the ECU couldn't keep up with the requests or something very weird in the VCDS.

Surely there can be typos or mislabeled items in blockmap but that's a different issue. For example in the following there definitely is some confusion in the labels - the bottoms ones surely are not correct.

 

[Hannu]

Sorry to hear about the troubles. Just a couple of thoughts from sidelines:

1. There’s too many issues with VCDS readings, I would not trust the values you get from partial blockmaps. Not sure what would be the best way to sort this. Do you happen to know someone with a VCDS that’s 100% known to work? If so, get a blockmap there and see if you get equal results.

2. Did you have battery disconnected with all the EGR / front service position work? If not, try a capacitive discharge reset: disconnect battery for 15 mins or so, reconnect, and see if anything changes after reconnecting. Current time and electric window single click functions will need to be set afterwards.

3. I’m not sure if this means anything but in your original DTC freeze frame exhaust temperature sensor 2 is showing up as zero - obviously incorrect

Exhaust gas temperature sensor 1: 54.7 °C
Exhaust gas temperature sensor 2: -0.0 °C
Exhaust gas temperature sensor 3: 27.6 °C
Exhaust gas temperature sensor 4: 23.8 °C

Hi, Yes it does seem VCDS isn't great but unfortunately I'm not aware of anyone close who has the system, may get onto VCDS to see if there is an upgrade.
Didn't disconnect the battery at the time of repair but have since when checking the ECU connections.
Many thanks for your advice

 

[n10n]

Well, even the partial ones are consistent - no items are missing until totally cut off. Makes me think that either the ECU couldn't keep up with the requests or something very weird in the VCDS.

I agree most likely the ones read are correct, just no way to be sure without comparing to a fully fuctioning blockmap.

But I don’t really see how ECU would not be able to keep up: after all VCDS just requests one by one (and possibly multiple items in one group request). Slowness should be the result of not keeping up, not losing values. Therefore I also think something very weird in the VCDS but there’s no way to know if it’s something about operating system, installation, drivers or perhaps even something electric such as damaged cable or dongle, bad contact in diagnostic port etc.

 

[Hannu]

I agree most likely the ones read are correct, just no way to be sure without comparing to a fully fuctioning blockmap.

But I don’t really see how ECU would not be able to keep up: after all VCDS just requests one by one (and possibly multiple items in one group request). Slowness should be the result of not keeping up, not losing values. Therefore I also think something very weird in the VCDS but there’s no way to know if it’s something about operating system, installation, drivers or perhaps even something electric such as damaged cable or dongle, bad contact in diagnostic port etc.

Will check the cable tomorrow, I've just checked for updates and I have the latest version

 

[mmi]

Having poured over the wiring diagrams this evening I note that there are connections between them. Clearly the ECU, which I checked today with negative results, but also
283 Earth point 2 and D141 connection (5V) engine pre-wire. However I'm a bit bemused as to were they are ?
I'm now thinking a possible bad earth, I know, clutching at straws now

Both D141 and 283 start from ECU and separate out to different sensors. They are crimped together somewhere along the wiring loom.
I'm afraid there no other way than start chasing where the 5V disappears - that's what I was hoping to see using the VCDS data. Now it looks like the 5V is lost very close to the ECU. Of course it could be also on "283" harness.

 

[mmi]

Will check the cable tomorrow, I've just checked for updates and I have the latest version

Could you please also make a blockmap without engine running - just to see if it's any different?

 

[Hannu]

Per workshop manual and wiring diagram CFCA engine does not have exhaust temperature sensor 2.

Its been too wet and cold to do much today but here are the ignition on engine off log and blockmap carried out this afternoon

 

[mmi]

blockmap carried out this afternoon

Thanks - that's a full/complete one - a bit confusing it works engine off. Certainly a good thing

---

I then tested the system by pulling off the wiring to each sensor / wiring connection around the engine. Each one pulled up a further fault code

I did note that during this process the original fault that I'm trying to trace did clear but returned when tested again.

Just to clarify - the fault "Sensor reference voltage B" was also there always - besides the fault of disconnected sensor?

 

[mmi]

G28 Engine speed sender​

Data seems to be ok.

Well, having had another look it seems that I have to take that back. Obviously ECU is missing some of the crankshaft sensor signal - possibly running on timing signal from camshaft sensor?



Note: Logs from 30.12.2024 and 31.12.2024 were cut short - thus not included here.

 

[Hannu]

Thanks - that's a full/complete one - a bit confusing it works engine off. Certainly a good thing

---

Just to clarify - the fault "Sensor reference voltage B" was also there always - besides the fault of disconnected sensor?

No, Sensor reference B only came on after I replaced the EGR value / cooler

 

[Hannu]

Well, having had another look it seems that I have to take that back. Obviously ECU is missing some of the crankshaft sensor signal - possibly running on timing signal from camshaft sensor?

View attachment 270102

Note: Logs from 30.12.2024 and 31.12.2024 were cut short - thus not included here.

Would it get a reading if not running ?

 

[Hannu]

Thanks - that's a full/complete one - a bit confusing it works engine off. Certainly a good thing

---

Just to clarify - the fault "Sensor reference voltage B" was also there always - besides the fault of disconnected sensor?

Ill try one in the morning engine running, see what happens

 

[mmi]

No, Sensor reference B only came on after I replaced the EGR value / cooler

Sorry, I meant when you now disconnected the sensors and got respective faults - was the fault "Sensor reference fault" also present?

 

[Hannu]

Sorry, I meant when you now disconnected the sensors and got respective faults - was the fault "Sensor reference fault" also present?

Yes it was, it would clear on the 2nd try of "clearing fault codes" but came back on retest

 

[Hannu]

Thanks - that's a full/complete one - a bit confusing it works engine off. Certainly a good thing

---

Just to clarify - the fault "Sensor reference voltage B" was also there always - besides the fault of disconnected sensor?

Please find complete block map WITH ENGINE RUNNING. I fear those incomplete maps were operator error, I'm learning, Slowly

 

[mmi]

Please find complete block map WITH ENGINE RUNNING. I fear those incomplete maps were operator error, I'm learning, Slowly

Excellent! Well, "to err is human". I'd say it's definitely worth to learn how to use and exploit VCDS - even though we are still struggling to pinpoint the issue.

Below now the updated data items to look into - both engine idling and engine not running.
GREEN = good data
RED = implausible values

(1)​

Charge air pressure sensor G31 is wired separately to the ECU​

I find a bit confusing the voltage values now - almost at zero. Is there something loading the circuit? Would expect to see voltages close to 1 Volt.

(2)​

Also accelerator pedal has it's own wiring between the pedal and the ECU​

​

(3)​

Circuit D141 in wiring diagram has the following sensors (common 5 Volts with all sensors)​

(possibly the "Reference voltage circuit B"??)

G212 Exhaust gas recirculation potentiometer​

Wondering if there is something loading the circuit as the voltages seen by ECU are so low.

Can you access and measure EGR connector (disconnected)
See the picture above:
- should get 5 Volts between pin 1 (red wire) and pin 3 (brown wire)
- should get 5 Volts between pin 1 (red wire) and chassis ground
- should have continuity from pin 3 (brown wire) to chassis ground

Please clear and recheck the faults the EGR connector disconnected.
Ideally would also like to get a blockmap to see if anything else is affected.

---

Wondering if there is missing ground (for this sensor??) as the voltage is close to the reference voltage (5V).



Can you access the fuel pressure sensor connector?
On disconnected connector
- should get 5 Volts between pin 3 (red wire) and pin 1
- should get 5 Volts between pin 3 (red wire) and chassis ground
- should have continuity from pin 1 (brown wire) to chassis ground.

Please clear and recheck the faults the connector disconnected.
Ideally would also like to get a blockmap to see if anything else is affected.

---

Attached also collected blockmap data - parallel two maps before the faults, and two maps at the fault.
RED = not good