What P0012 means (quick)

The ECM commanded the intake cam on Bank 1 to advance, but sensors show it’s stuck retarded. Most common culprits: oil quality/pressure, sticky phaser or OCV, timing wear/skip, or wiring/driver faults.

Symptoms (typical)

• Rough/low-power, poor fuel economy, cold-start rattle, stalling
  
  

• Check Engine Light; sometimes misfire or cam/crank correlation codes accompany it
  
  

Most common root causes

1. Wrong/dirty oil, low oil level, sludge restricting OCV/phaser
   
   

2. Low/hot oil pressure (worn pump/clearances, clogged pickup)
   
   

3. Stuck/weak OCV (VVT solenoid) or blocked OCV screen
   
   

4. Mechanical timing/phaser fault (chain stretch, jumped tooth, damaged phaser/tensioner/guides)
   
   

5. Wiring faults: OCV power feed, ECM low-side driver, CMP 5 V ref/ground/signal
   
   

6. Rare: ECM driver failure or incorrect software
   
   

Step-by-step troubleshooting (do in order)

1) Fast checks (no tools)

• Verify oil level/grade meets spec (e.g., 5W-30/0W-20 per vehicle). If wrong/dirty, change oil + filter first.
  
  

• Clear codes, road-test, re-scan. If P0012 returns quickly, continue.
  
  

2) Scan-tool data & sanity checks

• Look at freeze-frame: engine hot? RPM/load?
  
  

• Watch Desired vs Actual Intake Cam Angle at hot idle and while snapping throttle:
  
  

  • Healthy: Actual tracks Desired within a few degrees, settles quickly.
    
    

  • P0012 pattern: Actual lags/retards when ECM commands advance, or sticks near 0/retarded.
    
    

• Run bi-directional test: Command OCV on/off (or step duty). You should see RPM/angle respond.
  
  

3) Mechanical oil-pressure test (critical for P0012)

• Install a mechanical gauge at the engine’s test port.
  
  

• Check hot idle and 2,000 rpm against spec (rule of thumb ≈ ≥10 psi (70 kPa) per 1,000 rpm; use manufacturer spec if known).
  
  

• If low: address oil weight, pump, clearances, pickup, bearing wear before chasing electronics.
  
  

4) OCV (intake) electrical/hydraulic checks

• Unplug OCV; inspect for sludge on the filter screen. Clean or replace if clogged.
  
  

• Measure coil resistance (typical 6–14 Ω; check your spec). Out of range → replace.
  
  

• Key-On, engine off (KOEO):
  
  

  • One pin should have Battery voltage (B+) from IGN fuse/relay.
    
    

  • The other wire goes to ECM low-side PWM driver.
    
    

• With scan-tool active test or at warm idle, back-probe the ECM-side wire:
  
  

  • You should see pulsed ground (PWM); a test light to B+ should blink.
    
    

  • If no B+ at OCV A → check fuse/relay/wiring.
    
    

  • If B+ OK but no PWM → wiring to ECM or ECM driver fault (after ruling out shorts).
    
    

• If electrically OK but angle still slow/stuck → suspect sticking OCV or phaser/hydraulic issue; try swapping with bank/position (if identical) to see if fault follows.
  
  

5) CMP & correlation sanity

• CMP (intake) is typically 3-wire Hall (5 V ref, sensor ground, signal).
  
  

• KOEO checks:
  
  

  • 5 V ref present, sensor ground near 0 V.
    
    

  • Cranking/idle: square-wave on signal (scope best). Missing/flat signal → sensor/wiring issue.
    
    

• If any cam/crank correlation codes or noisy signal: proceed to timing inspection.
  
  

6) Timing/phaser inspection

• Listen for chain rattle at start/hot idle.
  
  

• If data shows unstable angle or permanent offset and oil/OCV are good:
  
  

  • Mechanical timing check (marks/locking tools as per service manual).
    
    

  • Inspect tensioner extension, guides, chain stretch, and the phaser (stuck internally).
    
    

  • Repair/retime as required; replace phaser/tensioner/chain components if worn.
    
    

7) Finalize

• After repairs: clear codes, perform warm idle & road test, confirm Actual vs Desired tracks, no pending codes.
  
  

• If all else checks and P0012 persists: ECM driver/software (rare) → follow OEM procedures.
  
  

Quick spec/reference (generic)

• OCV coil: ~6–14 Ω (typical)
  
  

• OCV power: B+ on one pin (IGN fuse/relay), ECM low-side PWM on the other
  
  

• CMP sensor: 5 V ref, sensor ground, square-wave signal to ECM
  
  

P0012 wiring circuit diagram

What it shows:

• Battery → Fuse/Relay → OCV (pin A = B+) → ECM low-side PWM driver (pin B)
  
  

• CMP (3-wire Hall): 5 V Ref & Sensor Ground from ECM, Signal back to ECM
  
  

• Test points TP1–TP5 for quick measurements (B+, OCV PWM, CMP 5 V/SGND, CMP signal).