AGR Valve: Diagnostic Trouble Code Only?

On my Audi A4 AFN from 1997, the EGR valve only activates when I run a diagnostic test that checks its operation.
When I let the engine idle after it has warmed up, the EGR valve remains closed. Even with slight acceleration, nothing changes.

Therefore, measurement block 3 in the engine control unit also shows a fluctuating air mass value of 490 to 500 mg/stroke at idle (target is 285 mg/stroke).

What could that be, or is it normal?

Regards,
Thomas.

Hi, have you ever measured the voltage at the EGR valve? That would help determine whether the valve is stuck or not being activated at all.

Hey, have you ever measured the voltage at the EGR valve? That would determine whether the valve is stuck or not being activated at all.

I measured the voltage at idle without a valve connected to the connector: 13.6 volts.

When I apply 12V from the power supply to the valve, it opens and the EGR system activates.

I'm going to measure the voltage with the valve connected. It's possible that the voltage will drop when the valve is attached.

I find it amusing that the valve opens via the VAG-COM actuator diagnosis function.

Regards,
Thomas.

I just measured the voltage again with the valve connected.
During actuator diagnosis, the valve receives 12.7 volts.
In idle and partial load conditions, the EGR valve should open. However, the voltage remains constant at 7.7 volts.

Could the engine control unit be defective?

Regards,
Thomas.

In the idle and partial load range, the EGR valve should open. However, the voltage remains constant at 7.7 volts.


What does the duty cycle say? Is it related to the 7.7V?

At this voltage, the control valve should be approximately 60% open, which means that the EGR system should also be operating at a proportional level.

For your information: the valve is controlled using pulse-width modulation. In this process, the ground connection is switched. A 100% duty cycle would result in full voltage at the valve (= fully open). With a faulty EGR system, the duty cycle on my ALH engine oscillates between 84.5% at idle and partial load (attempting to reduce air mass - valve fully open) and 4.8% at full load (fully closed).

CU Gremlin.

In the idle and partial load range, the EGR valve should open. However, the voltage remains constant at 7.7 volts.


What does the duty cycle say? Is it related to the 7.7V?

At this voltage, the control valve should be approximately 60% open, which means that the EGR system should also be operating at a proportional level.

For your reference: The valve is controlled using pulse-width modulation. In this process, the ground connection is switched. A 100% duty cycle would result in full voltage at the valve (= fully open). With a faulty EGR system, the duty cycle on my ALH engine oscillates between 84.5% at idle and partial load (attempting to reduce air mass - valve fully open) and 4.8% at full load (fully closed).

CU Gremlin

Could the AGR function be disabled in the engine control unit (ECU)? Channel 03 shows a large tolerance range, but I'm not sure if anything changes with it when using a diagnostic command.

I'm sorry, but I can't translate that because it appears to be gibberish or a string of random characters. Please provide a valid German text for me to translate.

ttns4 wrote:

Could the EGR function be disabled in the engine control unit? Channel 03 shows a large tolerance, but I don't know if anything changes with it during a diagnostic test

.
Hello,

If the EGR valve can be opened during the actuator diagnosis, then the hardware is okay.

If the system is operating normally, the EDC will not see a need to open it because the target and actual values of the mass airflow sensor are close enough.

IMO, this could be due to the following reasons:

Adaptation of channel 3 to high/maximum air mass.
"Low Mass Air Flow (MAF) sensor reading indicates insufficient air mass -> therefore, a defect is likely."
3. Air is being drawn in behind the mass airflow sensor (MAF).
4. Combinations of 1, 2, and 3 in any order.

If everything is operating normally, the EDC sees no need to open it because the target and actual values of the mass airflow sensor are close enough to each other.

@Ulf:
According to his initial post, the target value is 285, but the actual value is 500. I don't think the EDC would consider this to be 'too close.'

@A2TDI:
Just to be sure:
- Is your engine control unit (ECU) original, or has it been modified with a chip tuning upgrade?
- Did you measure the 7.7V using an analog (pointer) meter, or a digital one?
- At 7.7V, was the EGR valve still in the same position as if it were not powered?
- Is the EGR valve easy to operate?

Just a few thoughts from my end...

Regards,
Private.

PrivatBereich wrote:

According to his initial post, the target value is 285, but the actual value is 500. I don't think the EDC considers this to be "too close".

That might be true...
I can think of one more possibility right now:

"The EGR valve is not closing properly, but in order for it to remain deactuated (without power), the mass airflow sensor (MAF) reading would have to be almost reached or exceeded."

5. The EGR valve is not closing properly - but in order for the EGR to remain deactived during this process, the MAF sensor's target value must already be nearly reached or exceeded.
Hmm... so, our A2TDI mentioned 7.7V... I wouldn't really consider that to be without current flow...
Furthermore, the air mass is too high at idle (it's above the target value), which means the EGR valve is more likely to be stuck in the closed position rather than the open position.

My interpretation: Either a faulty EGR valve or an EGR valve that is sticking and tends to remain closed.


@A2TDI:
Here's the translation:

'In addition to the previous four questions, how do you determine whether the AGR valve is currently open or closed?'

Regards,
Private matter; I need to go now.

First of all, thank you very much for the numerous responses!

- Your ECU is original, and no chip tuning has been performed?
ECU is unchipped. Only 10 cents (when turned off).

- Did you measure the 7.7V using an analog (pointer) meter and not a digital one?
No, it's a digital true RMS multimeter. I have the measurement range set to a fixed value.
Since the multimeter has a PC interface, I'm going to try logging the signal.

- At 7.7V, was the EGR still in the same position as when it's not powered?
Yes, it hasn't moved. I'm observing the membrane rod through the openings in the container.

- Is the EGR valve easy to operate?
I disconnected the hose and manually operated it with a pump. The AGR (Abgasrückführung - Exhaust Gas Recirculation) ran without any 'Slick Effect' (presumably referring to a specific type of behavior or issue).

Regards,
Thomas.

'Sometimes, a suggestion or comment isn't necessarily helpful in finding a solution to the issue.'

What do you have against a permanently closed AGR (Agricultural Land Reserve)? Other people do other things and take shortcuts that aren't entirely okay to get what they want. And you don't need it, and you still achieve the same effect.