29F5

What 29F5 Means

29F5 belongs to the emissions control system fault group (EGR/DPF/SCR) and often shows up together with 29F4. The source data stresses that despite these codes the car's performance stays normal: 0–60 mph in 8.7 s, which matches the factory figure for the automatic-transmission version. Throttle response is intact, so the author doubts the catalytic converter is actually failing.

The code points to a possible drop in catalytic converter efficiency, but a final diagnosis requires checking other factors that affect the fuel mixture and engine operation.

Symptoms

• The Motorwarnleuchte (MKL) warning light comes on; after clearing the codes it returns within a few drives.
• Increased oil consumption: 0.5 L per 62 miles.
• An additional fault is logged: 2AAC Variable Sauganlage (DISA mechanical defect).
• Subjectively, throttle response is intact and 0–60 mph matches the factory figure.

Diagnosis and Repair

1. Check the mass air flow sensor (LMM): the source data notes that replacing the LMM fixed the negative LTFT on bank 2. Check the LMM readings and replace it if needed.
2. Look for a vacuum leak on bank 1: the author considers checking the brake booster and the vacuum line to it as a possible cause of the negative LTFT on bank 1.
3. Diagnose the DISA system: with 2AAC present, check the mechanical condition of the Variable Sauganlage (DISA) actuator.
4. Assess the catalytic converter: given that performance is intact, don't rush to replace the catalytic converter; check its efficiency and the causes of a possible rich/lean mixture.

A common diagnostic mistake is ignoring vacuum leaks and LMM faults, which can mimic a drop in catalytic converter efficiency.

Secondary Problems

The BMW tech links high oil consumption to catalytic converter clogging: “der hohe Ölverbrauch, wodurch sich der Kat zusetzt.” Ignoring increased oil consumption can lead to further contamination of the catalytic converter and lower efficiency, which will eventually require more expensive repairs. Fix the cause of the oil consumption and check the catalytic converter's condition.