Got it — P0149 = Fuel Timing Error, and it’s very common on diesel engines.

What P0149 Means

The ECM commanded fuel injection timing, but the actual timing (from sensors) doesn’t match.

In simple terms: ➡️ The engine computer and the fuel system are not in sync.

This is not usually a wiring-only code — it’s often mechanical or fuel-system related.

Common Vehicles That Set P0149

Cummins (5.9 / 6.7)

Duramax

Powerstroke

VW / Audi TDI

Other common-rail diesels

Top Causes (Most Common First)

🌟 Injection Pump Timing Off

Pump installed one tooth off

Pump gear slipped

Pump replaced but timing not relearned / calibrated

📌 Very common after:

Timing belt/chain work

Injection pump replacement

🌟 Fuel Rail Pressure Problems

Weak high-pressure pump

Failing fuel pressure regulator

Restricted fuel supply

Air in fuel system

📌 ECM can’t control timing if pressure is unstable.

🌟 Camshaft / Crankshaft Sensor Issues

Sensor out of range

Sensor misaligned

Tone ring damage

📌 Even if no sensor code is present, timing correlation can still fail.

🌟 Timing Chain / Belt Stretch

Worn timing chain

Skipped tooth

Excessive slack

📌 Seen often on high-mileage diesels.

🌟 Faulty Injection Pump (Internal Failure)

Timing piston stuck

Internal wear

Cannot advance/retard timing properly

📌 Especially on older mechanical or CP3 systems.

Quick Diagnostic Flow (Shop Efficient)

✅ Step 1: Scan Data (Not Just Codes)

Look at:

Desired injection timing

Actual injection timing

Fuel rail pressure commanded vs actual

Cam/crank correlation

If desired ≠ actual → mechanical or pressure issue.

✅ Step 2: Check Fuel Supply

Fuel filter condition

Air in clear return lines

Lift pump pressure (if equipped)

Low supply = timing error.

✅ Step 3: Mechanical Timing Verification

Lock crank at TDC

Verify cam marks

Verify injection pump gear alignment

⚠️ This step fixes most P0149 cases.

✅ Step 4: Relearn / Calibration

Many engines require:

Injection timing relearn

Pilot injection calibration

Pump timing reset

Requires bi-directional scan tool.

✅ Step 5: Component Testing

Cam sensor signal quality

Crank sensor signal quality

Rail pressure regulator duty cycle

Important Note

❌ Do NOT replace injectors first ❌ Do NOT ignore mechanical timing ✔️ P0149 is rarely just electrical

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