FAQ
TL;DR: Octavia II 2.0 TDI BKD second-try starts were cured by replacing 1 relay (458); "the problem disappeared" and starts on touch. Fuel-pump swap alone didn't help. [Elektroda, arrrturek, post #17052893]
Why it matters: If your BKD starts only on the second try, this FAQ shows the exact fix and quick checks owners used.
Quick facts:
- Vehicle/symptom: Skoda Octavia II (2005) 2.0 TDI BKD; first crank fails, second attempt starts after a long stop. [Elektroda, arrrturek, post #17026173]
- Two codes were logged: 17978 “engine operation blocked” and 16618 “boost control limit reached.” [Elektroda, arrrturek, post #17036463]
- Cycling the ignition several times enabled starting before the repair. [Elektroda, arrrturek, post #17033822]
- Replacing the in-tank pump did not help; replacing relay 458 restored instant starts. [Elektroda, arrrturek, post #17052893]
- Cleaning relay 458 contacts worsened it to a no-start; new relay solved it. [Elektroda, arrrturek, post #17052893]
Quick Facts
- Vehicle/symptom: Skoda Octavia II (2005) 2.0 TDI BKD; first crank fails, second attempt starts after a long stop. [Elektroda, arrrturek, post #17026173]
- Two codes were logged: 17978 “engine operation blocked” and 16618 “boost control limit reached.” [Elektroda, arrrturek, post #17036463]
- Cycling the ignition several times enabled starting before the repair. [Elektroda, arrrturek, post #17033822]
- Replacing the in-tank pump did not help; replacing relay 458 restored instant starts. [Elektroda, arrrturek, post #17052893]
- Cleaning relay 458 contacts worsened it to a no-start; new relay solved it. [Elektroda, arrrturek, post #17052893]
What actually fixed the second-try start on this Octavia BKD?
Replacing relay 458 in the engine compartment fixed it. The in-tank pump was replaced earlier and did not help. After the relay swap, the car started immediately every time. The owner wrote it “fires every time you ‘touch’ it.” This points to a power-supply relay failure rather than fuel delivery hardware alone. Start by inspecting and replacing relay 458 if symptoms match. [Elektroda, arrrturek, post #17052893]
What were the exact symptoms before the fix?
After a long stop, the engine would not start on the first attempt. It would not light or fire even with a long crank. On the second attempt, it started by touch. The issue was sporadic at first and then worsened. This pattern suggests a power or priming problem that stabilizes after an initial key cycle. [Elektroda, arrrturek, post #17026173]
Why does turning the ignition on a few times help it start?
Fuel can drain back or pressure can drop between starts. Multiple key-on cycles let the in-tank pump re-prime the system. As one expert noted, “the pump in the tank tops up enough fuel.” If it starts after several primes, suspect supply or control of the pump. [Elektroda, robokop, post #17036922]
Is the ignition switch (‘cube’) the culprit here?
Unlikely if the dash powers and the starter spins strongly. As one reply put it, “If the ignition turns on and the starter is spinning, it’s definitely not a cube.” Focus diagnosis on fuel supply and control relays instead. [Elektroda, piotrekwoj1, post #17026338]
Which fault codes were logged, and what do they say?
Two fault codes appeared later in the thread: 17978, described as “Electronic control module engine operation blocked,” and 16618, “Boost Pressure Adjustment; the end of the control range has been reached.” These indicate an ECU block condition and a boost control limit event. [Elektroda, arrrturek, post #17036463]
Does replacing the in-tank fuel pump solve second-try starts?
Not in this case. The owner replaced the pump, but the issue persisted. The final resolution was replacing relay 458 in the engine bay. After that, starts were immediate and consistent. Use the pump as a check, but prioritize the relay if symptoms align. [Elektroda, arrrturek, post #17052893]
Where is relay 458 on this car?
In this case, relay 458 was in the engine compartment. The owner cleaned its contacts, which led to a no-start. Replacing the relay restored reliable starting. Inspect this relay if you experience similar second-attempt starts. [Elektroda, arrrturek, post #17052893]
Should I clean relay 458 contacts or just replace it?
Replace it. Cleaning the contacts made the car stop starting entirely in this case. After installing a new relay 458, the car started instantly. This edge case shows that contact cleaning can worsen an intermittent failure to a total no-start. [Elektroda, arrrturek, post #17052893]
Could the immobilizer be causing the no-start?
Yes, immobilizer faults can block the ECU and prevent starting. As one expert explained, “The controller is blocked when the immobilizer does not work properly.” If suspected, diagnose with a scan tool and check the key, immo loop, and ECU. [Elektroda, piotrekwoj1, post #17036793]
Were immobilizer faults shown during diagnosis here?
No immobilizer module errors were reported at the time of checking. Only the engine controller showed faults. This steered the repair away from immobilizer parts and toward power supply and relay checks. [Elektroda, arrrturek, post #17037021]
What should I test first when no errors appear?
Verify where power is missing during the first key-on. Use live data and a meter to check component activation. As one helper advised, “Now you need to locate where the power is missing.” Reproduce the symptom and re-scan immediately after the failed first start. [Elektroda, piotrekwoj1, post #17033948]
Does turning ignition on multiple times actually help a BKD start?
Yes. The owner confirmed that cycling the ignition a few times allowed the engine to start. This points toward fuel priming or relay-controlled power not establishing on the first cycle. Use this behavior as a diagnostic clue. [Elektroda, arrrturek, post #17033822]
How do I quickly check if the tank pump gets power on first key-on?
Try this three-step check:
- Turn key to ON and listen for pump prime near the tank.
- Backprobe the pump connector to verify voltage during the first prime.
- Compare first vs. second key-on. If power appears only later, suspect control/relay.
[Elektroda, misiekpb, post #17031676]
