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AUDI A3 8L, 1.6 Gasoline + LPG: Engine Fails to Start, Suspected ECU Damage

l1715s 20418 17
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Why won’t an Audi A3 8L 1.6 APF gasoline/LPG engine start and also won’t communicate with the ECU, even though the fuel pump, relay 167, and fuses seem OK?

Uszkodzony był przekaźnik nr 30 pod maską, przy akumulatorze, i po jego wymianie samochód zaczął normalnie odpalać [#17520153] Wcześniej sprawdzono, że na pinach 1 i 2 sterownika jest masa, a na pinie 62 pojawia się napięcie po włączeniu zapłonu, więc zasilanie ECU wyglądało na obecne [#16641351][#16639513] Mimo że pompa „na krótko” pracowała, sam jej dźwięk nie wystarcza — trzeba też sprawdzić, czy paliwo dochodzi do listwy wtryskowej oraz czy jest iskra [#16641371] Inny użytkownik potwierdził podobną awarię: przekaźnik pod maską miał zimny lut [#17549281]
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  • #1 16638312
    l1715s
    Level 9  
    Posts: 50
    Rate: 17
    Hello, I have AUDI A3 8L, 1.6 gasoline + LPG.
    I am asking you for help, I cannot start the engine.
    It started with the fact that for several months every few (naście) days I had problems firing the car. It was enough then that I waited a moment, about 10 to 30 minutes and the car was on fire.

    Now I can't fire at all.

    Things I checked:
    - the fuel pump does not start either when the ignition is switched on or when turning the starter.
    - the pump relay (167) works, after applying voltage the 'pyka' relay, the contacts inside the relay are clean.
    - after inserting the relay into its place, feel at hand when trying to start the engine that it turns on.
    - after applying voltage from the battery directly to the pump, the engine also does not start.
    - I can't start the engine, emergency on LPG
    - I don't think there is a spark on the cable going to the candle (I'm not sure if I checked it correctly, please give me a hint how to check it carefully).
    - I can't connect to the engine module via VCDS, with another module, e.g. ABS, the program connects without a problem, hence the conclusion that the interface and the cable itself are OK.
    - and of course I checked the fuses - they are OK.

    From what I read on the forum, the ECU driver probably fell.
    Please, tell me what else I can check - on Monday I want to check if there is voltage on the plug going to the ECU.
    Only now a question for you - I found the plug diagram (in truth to A2, but probably the same link ), is the link post scheme good and applicable to A3? Which means "relay power"
    If it turns out that the power supply in the plug is good, does it really mean that the driver is free?
    Is the diagram (from the link) sufficient to try to connect the ECU via a cable to the computer?

    I am asking for advice, what else can I check?
    Thanks in advance for your help, best regards.
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  • #2 16638328
    sulof1601
    Level 26  
    Posts: 598
    Help: 94
    Rate: 280
    Hello, enter the engine code.
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  • #3 16638347
    l1715s
    Level 9  
    Posts: 50
    Rate: 17
    sulof1601 wrote:
    Hello, enter the engine code.


    Engine code: APF
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  • #4 16638364
    sulof1601
    Level 26  
    Posts: 598
    Help: 94
    Rate: 280
    APF has the Simos 33 (Multi Point) driver and in the link you have the description of the Bosch driver. Go to Google and enter Simos 33 pin out.
  • #5 16638370
    jareckim
    Level 14  
    Posts: 70
    Help: 5
    Rate: 49
    Did you supply voltage to the fuel pump? This can be done by removing the relay and shorting the appropriate contacts. The pump should then work, if it can't be heard, I would bet on damage to the pump (burned, stuck pump motor).

    Added after 13 [minutes]:

    The 1.6 APF engine has a Bosch motronic.
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  • #6 16638650
    l1715s
    Level 9  
    Posts: 50
    Rate: 17
    jareckim wrote:
    Did you supply voltage to the fuel pump? This can be done by removing the relay and shorting the appropriate contacts. The pump should then work, if it can't be heard, I would bet on damage to the pump (burned, stuck pump motor).
    Added after 13 [minutes]:
    The 1.6 APF engine has a Bosch motronic.


    As I wrote at the beginning, the pump works. I connected the pump directly from the battery and it worked.

    The driver is SIEMENSA. Code 06A 906 033 A.
    Can someone send a description of the pins. I tried, but to no avail.
  • #7 16638795
    kanar2306
    Level 17  
    Posts: 708
    Help: 23
    Rate: 280
    Here is the diagram ....
    AUDI A3 8L, 1.6 Gasoline + LPG: Engine Fails to Start, Suspected ECU Damage
  • #8 16638906
    l1715s
    Level 9  
    Posts: 50
    Rate: 17
    Thanks for the diagram.

    If I combine well and understand the diagram, then I should definitely have mass on pins 1 and 2.

    Correct me if I'm wrong - the numbers in the upper left (30 and 15) and in the lower left corner of the diagram (31) indicate the numbers of pins in the controller, whether these are numbers not associated with it.

    Because if so, it means that I should have ground on pin 31, voltage 30 straight from battery, and voltage 15 after turning on the ignition?

    In addition, the voltage should appear on pin No. 3 after turning on the relay.
    The relay is turned on in turn from pin 23 or 62. So probably on the plug on pin 3 there will be no voltage?

    And the last thing I see is that voltage 62 will appear after switching on the ignition.

    Please let me know if what I wrote makes sense. If not, write which pins to check.

    Thanks again in advance.
  • #9 16639261
    jareckim
    Level 14  
    Posts: 70
    Help: 5
    Rate: 49
    It is strange that it is simensa, because according to AutoCom it should be in the APF bosch engine.
    The designations 15, 30, 31 do not apply to the controller, they are system designations according to DIN 72552

    Battery
    15 positive battery supply after switching on the ignition
    30 positive power supply directly from the battery
    30a plus power supply directly from the second battery via 12/24 V relay
    31 minus battery or weight
    31a minus the battery directly or ground via a 12/24 V relay
    31b minus the battery or weight through the switch
    31c minus the battery via a 12/24 V relay

    At 62 is given a plus after the ignition switch, and the relay control is from 23 and it is a relay to control the fan and has nothing to do with the lack of firing.
  • #10 16639442
    l1715s
    Level 9  
    Posts: 50
    Rate: 17
    The driver is Siemens, when I get home I will send a picture.

    So to sum up - on the plug for the controller on pins 1 and 2 I should have mass, and on pin 62 the voltage after switching on the ignition.
    What about pin 3, shouldn't there be voltage after switching on the relay (controlled from pin 23)? When is this relay turned on?

    On the other hand, voltage will not go to pin 3 as the controller will be disconnected, as I will check the pins: /

    So 1.2 - mass, 62 - voltage?
  • #11 16639513
    jareckim
    Level 14  
    Posts: 70
    Help: 5
    Rate: 49
    l1715s wrote:
    The driver is Siemens, when I get home I will send a picture.

    It does not matter, it is important what is in reality, not in the descriptions. AutoCom says that audi APF engines are motronic, but what is important is what should not be.

    l1715s wrote:
    So 1.2 - mass, 62 - voltage?

    Yes
  • #12 16641351
    l1715s
    Level 9  
    Posts: 50
    Rate: 17
    I checked and the weight is on pins 1,2. There is also 62 voltage on the pin. The car still doesn't smoke. Earlier when it stopped, it fired. I think it's good. What else could I check?

    I checked relay 167 once, after shorting the contacts the ammeter shows over 5A, the pump turns on.

    On Monday, I think I'll give it to someone wise if I can't find anything.

    In the attachment there is a photo of the driver.
    Attachments:
    • AUDI A3 8L, 1.6 Gasoline + LPG: Engine Fails to Start, Suspected ECU Damage IMG_20170814_083936.jpg (4.71 MB) You must be logged in to download this attachment.
  • #13 16641371
    jareckim
    Level 14  
    Posts: 70
    Help: 5
    Rate: 49
    In general, a gasoline engine requires fuel, air and a spark to function properly. It also needs a properly functioning timing system. Assuming that everything is ok with the timing gear, you should check if it is so-called spark and whether fuel is supplied. The spark can be checked by unscrewing one candle and after putting it on the pipe and applying to the mass someone must turn off the starter. There is a spark, damage must be sought in the fuel system, none in the ignition system (coil, coils, wires, computer, immobilizer, alarm, ignition cut off, etc.). In the fuel system, it should check whether it supplies fuel at all to the injection rail. Because the sound of a pump does not mean that it is pumping something. To check this, you need to remove the fuel line at the rail, place the container and turn it on with the starter.
  • #14 16641394
    l1715s
    Level 9  
    Posts: 50
    Rate: 17
    That's how I came to check the spark thoroughly, because I'm not sure of the previous check. I'll do it later.

    Is it possible that if the voltage is where it should be after switching on the ignition, then the ignition block may be damaged?
  • #15 16641490
    goldwinger
    VIP Meritorious for electroda.pl  
    Posts: 6900
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    Finally power this controller and see if there is communication
    What do you have on the third pin?
  • #16 16940424
    icpawel79
    Level 2  
    Posts: 2
    Rate: 9
    Hi,
    Buddy, you managed to overcome this bug with firing, because I have the same problem ....
  • #17 17520153
    l1715s
    Level 9  
    Posts: 50
    Rate: 17
    icpawel79 wrote:
    Buddy, you managed to overcome this problem with firing, because I have the same problem ...


    Probably the answer after such a long time will be of no use to you, but I will leave for posterity.
    Maybe someone will be useful and help something.

    The problem was caused by damaged relay no. 30, located under the hood, near the battery.
    I bought a replacement for PLN 20 and I still fly without problems today.
  • #18 17549281
    icpawel79
    Level 2  
    Posts: 2
    Rate: 9
    Hi, I was overtaken by an electro mechanic, the problem was the relay under the hood, cold solder ...
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Topic summary

✨ The discussion revolves around an AUDI A3 8L with a 1.6 gasoline + LPG engine that fails to start, suspected to be due to ECU damage. The user initially experienced intermittent starting issues, which escalated to a complete failure to start. Various checks were performed, including the fuel pump, relay functionality, and voltage at specific pins of the ECU. The engine code was identified as APF, and it was noted that the engine uses a Siemens driver. Users provided insights on checking the fuel system, ignition system, and the importance of verifying the relay and ECU connections. Ultimately, a solution was found where a damaged relay (relay no. 30) was replaced, resolving the starting issue.
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FAQ

TL;DR: 1 confirmed fix: replacing Relay 30. "The problem was caused by damaged relay no. 30." Symptoms included no pump prime, no spark, and no ECU comms. [Elektroda, l1715s, post #17520153]

Why it matters: This FAQ helps Audi A3 8L 1.6 (APF) owners quickly isolate a no-start without wasting time or parts.

Quick Facts

What usually causes an APF 1.6 A3 to crank but not start?

A failed Relay 30 under the hood near the battery was a confirmed cause. Replacing it restored starting immediately. Watch for no pump prime, no spark, and no ECU communication together. "The problem was caused by damaged relay no. 30." [Elektroda, l1715s, post #17520153]

Where is Relay 30 on this car and why should I check it first?

It sits under the hood near the battery. The thread’s solved case points to this relay as the root cause of no-start. It is cheap and quick to swap, making it a high-return first check during diagnosis. [Elektroda, l1715s, post #17520153]

How do I test the fuel pump and relay 167 quickly?

Remove relay 167 and bridge the correct contacts to feed the pump. The OP measured over 5 A and heard the pump run. This confirms circuit load and pump rotation, though it does not prove rail delivery. [Elektroda, l1715s, post #16641351]

VCDS won’t connect to the engine ECU, but ABS connects. What next?

Verify ECU power and grounds at the connector. Check ground on pins 1 and 2, and ignition-switched +12 V on pin 62. If present, investigate relays, wiring, or ECU health next. [Elektroda, jareckim, post #16639513]

Which engine control unit does the APF use: Bosch or Siemens?

Despite catalog confusion, the APF case here used a Siemens unit marked 06A 906 033 A. The owner confirmed this with the unit in hand. Search using Simos pin-out if you need wiring. [Elektroda, l1715s, post #16638650]

What do the DIN 72552 numbers 15, 30, and 31 mean on the wiring diagram?

15 is ignition-switched positive, 30 is battery positive, and 31 is chassis/battery negative. These standardized numbers identify power paths regardless of brand. Use them to trace feed and ground faults. [Elektroda, jareckim, post #16639261]

Which ECU pins should have power and ground on APF during cranking?

Expect ground on pins 1 and 2, and +12 V on pin 62 with ignition on. Confirm with a multimeter and clean probe contact. Loss at any of these points can block ECU wake-up. [Elektroda, jareckim, post #16639513]

My no-start was intermittent for months, then permanent. Is that relevant?

Yes. The OP reported intermittent starts after waiting 10–30 minutes, progressing to complete no-start. Intermittency often indicates heat- or vibration-related relay or solder faults. Document the pattern before testing. [Elektroda, l1715s, post #16638312]

How can I check for spark safely on this engine?

Remove one spark plug, reconnect to its lead, and ground the metal body to the engine. Have a helper crank and watch for a strong blue spark. If spark exists, focus on fuel delivery; if not, check ignition feed and ECU control. [Elektroda, jareckim, post #16641371]

Does hearing the pump mean fuel reaches the rail?

No. Pump noise does not guarantee pressure or flow. Disconnect the feed at the rail, aim into a safe container, and crank to verify delivery. Address leaks and fire safety before testing. [Elektroda, jareckim, post #16641371]

It won’t start on LPG either. What does that suggest?

Failure on LPG and petrol points toward shared systems: ECU power/ground, ignition, or immobilizer paths. Note concurrent symptoms like no pump prime, no spark, and no ECU link to narrow faults. [Elektroda, l1715s, post #16638312]

What edge-case should I watch for with Relay 30?

Cold solder joints inside the under-hood relay can cause intermittent or permanent no-starts. Resoldering or replacing the relay resolved a similar case. Inspect the board if you open it. [Elektroda, icpawel79, post #17549281]

How can I verify if the ECU wakes up at all?

Power the controller correctly and check for diagnostic communication. As one expert put it: "Finally power this controller and see if there is communication." Confirm feeds before condemning the ECU. [Elektroda, goldwinger, post #16641490]

How do I quickly confirm a bad Relay 30? (3-step How-To)

  1. Locate Relay 30 under the hood by the battery and inspect for heat marks.
  2. Swap in a known-good relay of the same type and attempt a start.
  3. If the car fires and VCDS connects, replace the relay permanently. [Elektroda, l1715s, post #17520153]

I’m confused by the diagram’s pin 3 and relay control—should pin 3 have voltage?

Understand the diagram first: 15/30/31 are DIN codes, not pin numbers. Relay control paths differ from ignition feed. Focus on verified basics—pins 1, 2 (ground) and 62 (+12 V)—before chasing relay-controlled lines. [Elektroda, jareckim, post #16639261]
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