1.8 T Knock sensor problem

EMU BLACK / CLASSIC
1

Audi TT - 1.8T APY / E85 / Stock Knock Sensor - Emublack

DISCONNECTED KNOCK SENSOR.emublog (111.5 KB)

Hello everyone,

I’ve started working on my car again after a 2-year break. It’s an Audi TT with a 1.8T engine, APY code. The car has been sitting unused for quite some time, and I need to refresh my memory on a lot of things. The car was last tuned by a tuner in March 2022. Even during the initial tests back then, it seemed like there were some issues with the knock sensors. However, due to health problems, the car has been stationary since April 2022, and only now I am able to get back to working on it. The tuner is no longer in business, and I wouldn’t want to go back to him anyway because he did a terrible job. He’s the same person who also handled the wiring (unfortunately).

The knocking issues persist. From the logs I’ve taken over the past few weeks, the Emublack ECU continues to detect knocking. At the moment, I am following the lead of incorrect sensor configuration and/or wiring issues. If all the electrical/ECU components turn out to be fine, I’ll move on to investigating mechanical issues. (surely i’ll need to change engine mount)

Starting with the simple questions: If I disconnect both the signal wire from Knock Sensor 1 (PIN 3) and Knock Sensor 2 (PIN 16) from the ECU harness, the ECU still reads a voltage of about 0.40V. Is this normal? I haven’t disconnected the sensors from the engine, nor the connection from the sensor to the ECU. I’ve just pulled the pins of both sensors out of the ECU connector.

From this position, I ran some tests by switching between Knock Sensor 1 and Knock Sensor 2 from the “Sampling” section, but with little to no difference. However, as the RPM increases, the voltage signal also slightly increases, as you can see in the attached log.

In the log, you can see that from 0 to around 20 seconds, the Knock Sensor Value reads 0V. At that moment, the ECU was on but the engine was off. At around the 20-second mark, I started the engine. Both sensor wires were still disconnected from the ECU.

Regarding the wiring: the original Bosch sensor has 3 wires—one is the signal wire going from the sensor to the ECU, one is ground, and the third one? Is it a shielding?

Sorry for the long post, I tried to give as much information as possible all at once.

Thanks!

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First thing I’d check is that sensor ground and power/engine block ground are not joined somewhere. Sensor ground should be dedicated to sensors only, including knock, cam, crank, clt, tps etc. If done wrong this can induce noise into the sensor ground, which in my experience you can usually see in other sensors raw voltage.

If could upload the log here that would help us help you

Yes the 3rd wire will be shield. Often its a tin plated terminal vs the signal wires with are gold plated

I’d also advise dealing with any known mechanical issues right away. Many electrical and tune issues are symptoms of mechanical issues. Not likely the case given your results engine off here, but just general advice.

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Thanks @FloorItGarage for the answer.

A Ecumaster employee/owner (Jakub Kojder, maybe he’s also here) from Poland replied to me on Facebook, telling me that the type of open-circuit noise is normal since it’s a very high-impedance circuit, and it’s normal for there to be background noise when it’s not connected to the sensor.

The log was already attached to the first message.

The grounds should all be fine, but since I need to replace the ECU connector, I will take the opportunity to check them all again, thanks.
Since you are much more experienced than I am, do you think it’s possible to extend the existing wires that go to the ECU?
Let me explain: the previous tuner did a terrible job, leaving me with part of the original wiring and part of the new wiring, but the bundle of wires ends just after the accelerator pedal, where I placed the ECU. I’d like to move it further back, behind the brake pedal, to be clear. If I extend the existing wires by soldering them, is it a bad job?
Would it be better to use a connector to join the existing wiring, make an extension, and then connect it to the ECU with another connector?

4

whoops missed the file at the top, my bad

Moving the ECU is possible yes, so long as you maintain shielding and do quality connections. Soldering is not an acceptable method in my opinion, I build harnesses professionally and I only crimp. Crimping a mating connector (which I think I do have actually…) and making the wires longer might be neater, your call there depending on what there is room for.
If the work previous was as bad as you state would it be worth it to you to just re-make the entire loom? removes a lot of mystery and potentially piece of mind knowing its done correctly.

5

Yesterday I finished redoing and reassembling all the pins in the ECU connector from scratch to rule out any wiring or similar errors. This way, I know the connections are fine.

With the settings left by the previous tuner, the car continues to register knocking almost all the time, both at idle and when trying to accelerate. On the mechanical side, I strongly rule out real knocking (although I can’t be absolutely certain). The only issue I’ll need to address are the engine mounts, which I’ll have to replace since the current ones are quite worn out.

At the moment, I would focus more on a possible incorrect configuration of the parameters by the tuner. Is it normal for the gain to be set to 1.6? The knock sensor is the classic Bosch donut sensor, the one originally mounted.

The tuner had configured Knock Sensor 1 for all four cylinders.
If I try using Knock Sensor 2 instead, I get almost identical voltage values, which are always above the engine noise threshold.

When I pointed this out to the tuner at the beginning of 2022, he sent me a map with all the timing set to 4° to test and make a single recording. Even with this setup, I was logging almost continuous knock in the logs, meaning values always above the engine noise threshold (still with the gain set to 1.6).