Golf 4, 2000, APF, Secondary air pump - Faulty shift signal

Hello,

For the past few days, I've been trying to get my air pump working, but without success, and I'm not sure what the exact problem is.

I measured the control signal and the power supply as shown in the diagram. The red wire provides the power supply to start the pump; I'm measuring 12V, and when I bridge it, the pump also starts.

When the motor is running, the switching signal for the relay (green line) shows 12V; when the motor is off, it shows 0V.

So, it seems like the cables are in good condition up to that point?

Is the relay not defective either? I've already installed two other relays, and I even bought a brand new one directly from VW today to be sure.

The error code indicates that the secondary air pump's flow rate is too low (which makes sense, since it's not working), and the relay shows a short circuit to ground. That means there's nothing on the 12V line, but isn't everything supposed to be there?

Edit: Title description edited @Autoservice.

Hey CrÄsh!

"Huh?!"

What kind of vehicle or engine are we talking about?
What is the EXACT error message Autoscan?
Is the idle stable? Normal consumption?

According to your somewhat difficult-to-understand measurements, there seems to be voltage both at the coil and at the load contacts of the relay (by the way: RELAY! ). If the latter are shorted, the pump (valve) runs. The relay is also new, so I would look elsewhere, such as... AGR (if applicable to vehicles manufactured in 1999 or later), throttle body, air filter, etc.

Just think that the error message you described will likely have a different cause.

Best regards from Munich!

Hello,

Sorry, if I didn't express myself clearly .
It's a Golf 4 model from the year 2000 with the engine code APF.
The idle speed seems normal. I need to read the exact error code again.

I always thought the pump would turn on immediately when the engine starts (when it's cold)?

What surprises me is that, in the actuator diagnostics, shouldn't it be possible to activate the relay directly? "That's not the case for me, or in the last instance, it always shows "Error" in the actuator diagnosis."

Hey CrÄsh!

Are you sure it's APF and not ABF?
The latter would be the 2.0L 16V engine, starting with the Golf III.

Please investigate the error in detail.
It wouldn't hurt to remove the blower and inspect it for corrosion or moisture.
Here, you could also test the part's functionality. It's possible that a faulty valve could cause condensation and... Exhaust gases entered the pump in reverse and damaged or destroyed it.

Otherwise, measure the voltage at the relay again - preferably when it's plugged in!

Best regards from Munich!

Hello,

Here are the exact error codes:

17843 - Relay for secondary air pump (J299): Short circuit to ground.
P1435 - 35-10 - - - Intermittent.
17831 - Bank1: Secondary air system - insufficient airflow.
P1423 - 35-00 - -
18056 - Data bus drive failure.
P1648 - 35-10 - - - Intermittent.


It is an APF SIMOS33 1.6l 2V. 74KW, a good one.

I'm currently considering starting a completely new thread because I have two problems, or rather, one major problem.

1. The errors in memory.

The problem was with the pump. The voltage was always okay, at least when the relay wasn't plugged in. Even when bypassing the relay, the pump turned on. As I mentioned before, I even went the extra mile and bought a brand new relay from VW.

2. It jerks violently at full throttle between 1000 - 2000 rpm. It's already starting to exhibit misfires above 2000 rpm.

When you search for the problem on Google, you'll find that X people have encountered it, so it's not uncommon. Everyone had different approaches to solving it. I've also only had the vehicle for a few months and want to fix all the issues. Or, this error is really frustrating!

I have already exchanged:

- Spark plugs, spark plug wires, ignition module/coil.
- Both lambda sensors are new.
- New valve cover gasket.

It's also not possible to swap out all the parts, and that can also cost a significant amount of money .
Therefore, I'm wondering if we should start a separate thread for this issue.

Hey CrÄsh!

Hm, the spark plugs probably weren't free, but the rest apparently was .

Uncontrolled or haphazard parts swapping can also have serious consequences, especially if it leads to introducing errors yourself!
Why were the lambda sensors replaced? Did the secondary air injection fault occur AFTER the lambda sensors were replaced? If so, where did the probes come from?

If not: Do as I suggested: Remove the secondary air pump and take a look inside. It should be dry & delicious!

After that, clear the error codes and observe whether/when the secondary air error reappears; start the process with the engine at operating temperature.
The first one mentioned above. The error likely occurred because the motor was running without the relay being connected.

Best regards from Munich!

Hello DieselBär30x,

Thank you for your participation .
I replaced the lambda sensors because both of them were showing errors in the error memory when I bought the car (and they reappeared even after clearing the error codes). After that, I bought new sensors from Bosch as an accessory.
The problem with the secondary air pump, specifically the insufficient airflow, was already present before, along with the sensors.
If I bypass the control signal, the pump starts, so it should be okay, right? I'll take a look anyway.

Update:

I took it for a short test drive today, and so far, the error hasn't appeared. The engine was warm, the coolant temperature was over 90°C, and the error hasn't been stored in the system yet. However, I haven't even seen the pump running once.

I also took the pump apart once, but you can't really see much inside except into the air duct. Everything looked dry.

I also measured the wiring. There's no continuity when the relay is plugged in? Okay, so when I hold the measuring device to both cables, it shows 0V. But when I do it without the relay, it shows 12V.

I then wanted to measure the cables individually. On one cable, I measured 12V when applying voltage to the blue/yellow wire, which, as far as I know, comes from the oxygen sensor. The other one goes to the engine control unit. If I connect it to the positive terminal of the battery there, should I have continuity? (Sorry, I'm not an electrical engineer, and I don't know if I'm expressing myself clearly ).


Regarding the issue with the misfires, I don't have any new information to report other than the fact that it is still present.

Hey CrÄsh!

If the piping to and from the pump is absolutely verschandeln and dry, I would temporarily stop troubleshooting in that direction and focus on the misfires.
Probably, the root cause lies here, and the secondary air leak is a known consequence.

Did he experience misfires before replacing the oxygen sensors?

It all reads to me like a vacuum leak, rather than a highly improbable simultaneous failure of the ignition system, lambda sensors, secondary air system, etc.
Buy some carburetor cleaner or brake cleaner and spray it on all the connections, especially those in front of and behind the throttle body, while the engine is running.
If the speed changes suddenly, there is a leak here!

What other parts were replaced or modified on the vehicle?

Best regards from Munich!

Hello,

I have already tried using brake cleaner, but it was unsuccessful.

That's a good question whether the jerking occurred before the data transfer. Based on my gut feeling, I would say no, but I haven't driven the vehicle much before the repairs. However, I had already disconnected the front oxygen sensor for testing purposes, and the misfires still occurred.

In the misfire detection, I see that the misfires are occurring on all cylinders. However, it resets the counter to 0 for cylinders 2 and 4 while the vehicle is in motion, but it doesn't do that for cylinder 1?

I have already exchanged the following:

- Spark plugs, spark plug wires, ignition module/coil.
- Both lambda sensors are new.
- New valve cover gasket.
- Seals on the oil inlet manifold.

What I know from the previous version is:

- New transmission.
- New steering gear.

Hey CrÄsh!

Good or bad, because that's where I run out of productive and meaningful ideas...

Here's what else you can do:
Close the secondary air vent on the exhaust side (securely!), then check again to see if the misfires persist.
If everything goes well then. O., Replace the valve.
If the problem persists, the cause lies elsewhere. If the intake manifold is sealing properly and is clean, I would investigate the wiring harnesses, (temperature) sensors, etc. Because, especially when installing or removing large/heavy components, a cable or hose can easily be damaged.

Do you still have the old Lambda sensors? Possibly, they might be reinstalled, because they probably weren't broken in the first place *I guess*.

Best regards from Munich!

Hello,

What do you mean by "securely and reliably closing"? Do those rubber hoses need to be sealed?
I unfortunately don't have the valve in front of my eyes right now.

Yes, unfortunately . These misfires were all over the internet...

I found elsewhere that someone else had the same problem, and it turned out to be the temperature sensor, which prevented the valve from opening. Which sensor are you referring to?

Update this morning:

This morning, I noticed that it was also slightly wobbling (50-100 rpm) when idling, and it feels like it has small jolts even when idling. Does this help with troubleshooting?

Quote:

and feels like it has small vibrations even when it's stopped. Does that help with troubleshooting? icon_cry.gif

You can hear it best from the rear of the car, almost from the exhaust.

If the misfires you described only occur at low RPMs and under full load, and disappear as soon as you reduce the load, then in 90% of cases, it's a "true" misfire and not a side effect of the EGR system or the air pump.

You completely replaced the high-voltage section of the ignition system, and hopefully you didn't damage any spark plugs during assembly on the insulator.

You might have a problem with the power supply to the ignition coil. I would check that and take a close look at the wiring harness.

Specifically, in the area where the wiring harness runs from the engine to the body. It's usually located next to the battery.

Hello AutoService,

Thank you for your participation as well. Everything sounds quite logical. However, what doesn't fit is that it only happens when he's warm. When it comes to an electrical problem, shouldn't it make no difference whether it's hot or cold?

But I'll still check the cables generally, just to be sure.

Hey CrÄsh!

Cr4sh wrote:

... what do you mean by "securely and firmly" closing? Do those rubber hoses need to be sealed? Unfortunately, I don't have the valve in front of my eyes right now, so I can't describe what it looks like ...

.
"A silver-colored, metal container" should be located above the secondary air pump and connected to it with hoses.

The exhaust outlet needs to be well and securely sealed because hot exhaust gases can otherwise flow backwards into the plastic components. Rubber, does it break?

Best regards from Munich!