Case Summary: P0012 Error – Toyota Corolla 2NZ-FE (2009 E140, 180,000+ km)
Symptoms:
DTC P0012 (Camshaft Position – Timing Over-Retarded Bank 1) appears within 10–20 km after clearing.
Noticeable fuel consumption increase 10-11km/l
Tried multiple OBD apps — only Car Scanner reports P0012 consistently.
🧪 Steps Already Taken:
️ MAF Sensor & Air Intake:
MAF replaced with correct part (22204-31020) → readings improved to ~1.4–1.5 g/sec @ idle.
Fuel trims stabilized:
STFT B1: ~0.78%
LTFT B1: ~-6.25% previously at -26% replaced MAF with B series.
VVT System:
VVT-i solenoid cleaned thoroughly (externally and internally) & tested by applying direct 12V works smoothly.
VVT oil filter cleaned.
VVT gear cleaned internally by opening its gears
Timming marks recheck & cleaned timming plate as well
Engine oil: Fresh Havoline Pro DS 5W-40 (2,200 km old).
No oil sludge in head, but visible sludge on camshaft sensor and VVT solenoid which was cleaned throoughly.
Camshaft Position Sensor:
Removed and cleaned using degreaser.
Shows ~2.1 kΩ resistance.
No wiring fault, no short.
Scan Tool Observations (Latest):
MAF: 1.5 g/sec @ idle → normal.
Timing Advance: 7–8° @ idle, 30°+ @ 2500 RPM → seems active.
Coolant Temp: 96°C → normal.
Engine Load: ~30% @ idle → normal
Fuel Trims: STFT stable, LTFT mildly negative.
Issue: P0012 Returns Despite These Fixes
Experts please support, sharing OBD idle stats Thanks
