VCDS fault code clearing

[n10n]

Great deep dive as usual @mmi !

Please clear and recheck the faults the EGR connector disconnected.

Just to highlight this is a very good suggestion. I mean they all are but I think this should be the first test - if the other DTC's don't come back during this test it points to a fault in the new EGR. And it is the new component in the equation after all, thus the most likely culprit.

 

[mmi]

Great deep dive as usual @mmi !



Just to highlight this is a very good suggestion. I mean they all are but I think this should be the first test - if the other DTC's don't come back during this test it points to a fault in the new EGR. And it is the new component in the equation after all, thus the most likely culprit.

Just edited the proposal to include a request to get a blockmap - connector unplugged - to see if it has any secondary effects.

 

[Hannu]

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​

View attachment 270184
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​

View attachment 270185

​

(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​

View attachment 270190

Wondering if there is something loading the circuit as the voltages seen by ECU are so low.
View attachment 270188
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.

---

View attachment 270186

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

View attachment 270192

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

Very confusing,
First block map 11.41hrs is with EGR value disconnected
Second block map 13.22hrs is with fuel sensor disconnected yet VCDS showed EGR pressure sensor?
both would clear and the original fault still present, although when retested the fuel pressure did not return even though still disconnected.
I have a cheap multimeter which automatically controls what it measures and when testing the battery shows 12.5 volt
However when testing the wire to the sensors measured in ohms
ERG
red / brown 1.1
red / earth 1.04
brown/ earth 7.4
Fuel sensor
red / brown 1.5
red/ earth 1.1
brown earth 7.4

 

[Hannu]

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.

So my thinking at the moment is that if something is "loading" the circuit, its unlikely to be TWO broken wires in a loom and more likely to be a sensor or connection ?
I'm not ofay with canbus wiring and did think at one point this afternoon that I should try testing each earth with the multimeter to the battery but that may send 12v up the line and do more harm than good.

 

[mmi]

First block map 11.41hrs is with EGR value disconnected
Second block map 13.22hrs is with fuel sensor disconnected

Did you make notes what additional fault codes were triggered?

with fuel sensor disconnected yet VCDS showed EGR pressure sensor?

Sorry, I don't understand?

a cheap multimeter which automatically controls what it measures and when testing the battery shows 12.5 volt

That's interesting kind of instrument. What does it show when testing a 1.5 Volt battery - Volts or ohms?

However when testing the wire to the sensors measured in ohms
ERG
red / brown 1.1
red / earth 1.04
brown/ earth 7.4
Fuel sensor
red / brown 1.5
red/ earth 1.1
brown earth 7.4

Well, possibly there was no voltage present and thus the multimeter selected to measure resistance (ohms).
However, the fuel pressure sender VCDS reports 4810 mV - as if sensor is seeing the 5V reference voltage.
Anyways, resistance measurement across live circuit can't be trusted - true 1.1 ohms between red and brown would indicate a short between the two, which contradicts the 4.8 Volts seen by fuel pressure sender.

The confusing part is why unplugging EGR connector doesn't change anything in the blockmap - is there a break in the wiring.

I believe you need to get a more traditional multimeter with manually selectable measurements - to trace the 5 Volt at each connector.

 

[n10n]

First block map 11.41hrs is with EGR value disconnected
Second block map 13.22hrs is with fuel sensor disconnected yet VCDS showed EGR pressure sensor?

There are no material differences between these two blockmaps, so testing with EGR plug disconnected didn't really change much. Good news is that the EGR is not causing all the mayhem - but the bad news is that it's something else and we don't know what.

Like @mmi mentioned, many of the sensors outputting weird values (G31, G79, G185) have an independent wiring to the ECU. In addition we have G212 showing too low voltage (pointing to a positive feed issue) and G247 showing too high voltage (pointing to a ground issue). Putting these together I see these possible causes:

• Powering / grounding issue to the ECU itself - as the ECU is delivering both the positive (eg D141) and negative (eg 283) rails to the sensors ECU powering could affect multiple sensors at once. However ECU reports healthy voltages through IDE00019 and IDE01834.
• Unexpectedly high load / short that pulls some of the ECU voltages down
• Major wiring issue affecting many circuits from ECU
• Cooked ECU

This is still a very wide range of possibilities and I don't see easy ways to narrow the issues down without some rather extensive multimeter work and having the full wiring diagram as a reference. Personally I think the major wiring problem as the lowest probability of the above because many of the sensors have an independent wiring. My next steps with the diagnosis would be pulling the e-box open, taking a look at the ECU connector and starting unplugging / measuring individual ECU pins and wires from thereof. This is fairly involved undertaking but I think that's what it will take to pinpoint the issue - I may be wrong but seems to me blockmaps will not be able to help much more.

 

[Robert]

I have a cheap multimeter which automatically controls what it measures and when testing the battery shows 12.5 volt
However when testing the wire to the sensors measured in ohms

That's interesting kind of instrument. What does it show when testing a 1.5 Volt battery - Volts or ohms?

I use this one

UNI-T UT123D Smart True RMS Multimeter Digital AC/DC Current Volt Ohm Cap Test | eBay

This product does not include batteries. â Data Hold. Product Introductionï¼.

www.ebay.co.uk

and it is surprisingly good quality and high accuracy.
Unfortunately I never used measurement AUTOSELECTION mode as I don't trust it.

 

[Hannu]

Did you make notes what additional fault codes were triggered?


Sorry, I don't understand?


That's interesting kind of instrument. What does it show when testing a 1.5 Volt battery - Volts or ohms?


Well, possibly there was no voltage present and thus the multimeter selected to measure resistance (ohms).
However, the fuel pressure sender VCDS reports 4810 mV - as if sensor is seeing the 5V reference voltage.
Anyways, resistance measurement across live circuit can't be trusted - true 1.1 ohms between red and brown would indicate a short between the two, which contradicts the 4.8 Volts seen by fuel pressure sender.

The confusing part is why unplugging EGR connector doesn't change anything in the blockmap - is there a break in the wiring.

I believe you need to get a more traditional multimeter with manually selectable measurements - to trace the 5 Volt at each connector.

No additional fault codes triggered

I'll try the fuel sensor again tomorrow, my heads spinning but I'm sure it triggered a different fault.

Multimeter on order

 

[Hannu]

There are no material differences between these two blockmaps, so testing with EGR plug disconnected didn't really change much. Good news is that the EGR is not causing all the mayhem - but the bad news is that it's something else and we don't know what.

Like @mmi mentioned, many of the sensors outputting weird values (G31, G79, G185) have an independent wiring to the ECU. In addition we have G212 showing too low voltage (pointing to a positive feed issue) and G247 showing too high voltage (pointing to a ground issue). Putting these together I see these possible causes:

• Powering / grounding issue to the ECU itself - as the ECU is delivering both the positive (eg D141) and negative (eg 283) rails to the sensors ECU powering could affect multiple sensors at once. However ECU reports healthy voltages through IDE00019 and IDE01834.
• Unexpectedly high load / short that pulls some of the ECU voltages down
• Major wiring issue affecting many circuits from ECU
• Cooked ECU

This is still a very wide range of possibilities and I don't see easy ways to narrow the issues down without some rather extensive multimeter work and having the full wiring diagram as a reference. Personally I think the major wiring problem as the lowest probability of the above because many of the sensors have an independent wiring. My next steps with the diagnosis would be pulling the e-box open, taking a look at the ECU connector and starting unplugging / measuring individual ECU pins and wires from thereof. This is fairly involved undertaking but I think that's what it will take to pinpoint the issue - I may be wrong but seems to me blockmaps will not be able to help much more.

Sadly I think this is were my talent may prove lacking, I've convinced myself its something I've touched whilst replacing the EGR. I'm going to start by cleaning the chassis earths and the connections I have had off. Also double checking the block maps and faults when disconnecting the sensors