29D2
Moderate29D2 — Cylinder 4 Misfire
Description
What the Code Means
Code 29D2 points to a misfire in cylinder 4. The fuel-air mixture in cylinder 4 either fails to ignite or ignites at the wrong time. The cause can be a faulty ignition component (spark plug, coil) or a problem in the engine control unit (DME). If replacing the coil and plug doesn't fix it, the ignition driver in the ECU is the likely culprit.
Symptoms
Symptoms
- Rough idle (engine stumble)
- Engine vibration and shaking
- Check Engine light on
- Loss of power
- Hesitation under load
Causes and fixes
Diagnosis and Repair
Step 1: Swap Components
Swap the ignition coil and spark plug from cylinder 4 into another cylinder. If the fault follows them, replace the faulty component.
Step 2: Check the ECU
If the misfire stays in cylinder 4 after the swap, the fault is most likely in the engine control unit (DME). Bench-test the ignition output circuits.
Step 3: Repair the ECU
If the ignition driver is confirmed faulty, repair or replace the ECU.
Possible secondary damage
Secondary Damage
Ignoring code 29D2 can lead to:
- Catalytic converter damage (from unburned fuel)
- Contaminated oxygen sensors (O2 / lambda)
- Higher fuel consumption
- Worse emissions