Volkswagen Polo, 2013, Kuopio

The fault is that the car sometimes requires long cranking to start; the next start can be completely normal.

Summary by Pörhö workshop.

Long cranking when starting.
- Cranking observed -> Most of the time it starts normally,
but sometimes it won’t start, only cranks.
- Battery charged
- Event memory printouts available
- Engine recorded event P034100, “Camshaft position sensor, implausible signal”
- No manufacturer bulletins related to this symptom or event code
- Camshaft position sensor and connector inspected visually -> Connector locking moulding broken and connector oily, probably some contact oil applied? -> Oil cleaned from connector -> Recommended to renew connector housing -> Replaced; pins a little stiff in connector.
- Camshaft position sensor signal inspected with oscilloscope -> Does not match the test guide image exactly, but looks normal to me -> Tester asks whether it matches the guide image -> If it does not, it reports: “No fault”, if it does it reports: “Replace camshaft position sensor G40”.
- Checked that camshaft position sensor has the correct VO number
- Question: Did the symptom or event memory change after sensor replacement or has it remained the same?
- According to the service book the timing chain kit was renewed at 171,000 km / 09/2025. Was the symptom present before that or did it appear afterwards?
- Timing checked -> Appears to be very close to correct
- Crankshaft sensor connector housing locking broken -> Recommended to renew connector housing -> Replaced
- Crankshaft has a Delphi aftermarket sensor -> Recommended to try original -> Replaced -> No effect
- Tried updating the engine control unit -> Updated 5152 -> 7106 -> No effect
- Tried resetting learned engine values -> No effect
- Measured wiring between ECU and camshaft position sensor G40 -> 0.2 ohm, no short to +/-, nor between wires, i.e. OK -> Loaded wiring with a 24 W lamp -> Voltage drop to the wire 0.2 V, i.e. OK
- Measured wiring between ECU and crankshaft position sensor G28 -> 0.3 ohm, no short to +/-, nor between wires, i.e. OK -> Loaded wiring with 24 W lamp -> Voltage drop 0.27–0.29 V, i.e. OK
- Measured compression -> OK, approx. 15 bar in each cylinder
- ECU was repaired at Elehuolto -> No effect, the same symptom persists
- Now engine has P020100, P020200 and P020300, “Fuel injector cyl. 1–3, electrical fault in circuit events” -> Likely appeared after the ECU repair??
-> Proceeded with guided diagnostics for the events -> Measure injector resistances (including wiring) from the ECU -> The check does not suit this car, it gives the wrong break-out box number and pin positions -> Checked injector wiring in circuit diagram -> Measured injector resistances (from the common power feed for injectors to the ECU) -> 12.5 ohm, sounds like a normal value. The tester's reference 1–9 ohm is probably incorrect because the test did not otherwise match the car.
- Previous workshop had spliced the engine wiring harness -> Camshaft sensor 2/3 connector pin replaced from another harness -> Joint looks neat externally -> Heat shrink opened -> Connection was not soldered, wires just twisted together and heat-shrinked. One wire had a cut and was taped with fabric tape -> Replaced with new pins (3 repair wires) and heat-shrink joints as required -> No effect on symptom
- Measured crankshaft sensor supply voltage when fault present -> OK, 5 V.
- Measured crankshaft position sensor signal with oscilloscope with and without fault. Swing always the same 5 V and pulse width varies; higher revs give wider pulses. In my view the crankshaft sensor signal is fully functional.
- Tried unplugging all engine control connectors one by one -> Disconnecting any single connector did not reproduce the symptom
- Checked earthing points in the engine bay, left front crossmember rear end -> OK, bolts tight and clean -> Removed even the smallest corrosion
- Importer / manufacturer recommends renewing the wires from the ECU to the crankshaft and camshaft position sensors including terminals -> Permission for this was not granted by the payer