29CC and 2ABC Fault Codes: Multiple Misfire + Charge Pressure Sensor (BMW Guide)
29CC means combustion misfires on multiple cylinders, while 2ABC means an electrical fault on the charge pressure sensor. When they appear together the order matters: sensor first, misfire second.
— Tekin Code
29CC and 2ABC are two different codes from BMW's hex fault code system, both stored by the DME: 29CC means "combustion misfire on multiple cylinders", and 2ABC means "charge pressure sensor, electrical". You can see them separately, but on turbocharged engines such as N54, N55, N20 and B48/B58 they often arrive together — because the DME's cylinder charge calculation depends directly on that sensor's signal. Severity is high: the misfire itself threatens the catalytic converter.
What Do 29CC and 2ABC Mean?
2ABC is a signal code: the DME saw a voltage from the charge pressure sensor outside the plausible range — an open circuit, a short, a supply problem, or a signal that has gone flat. 29CC is a consequence code: the misfire counter derived from crankshaft speed fluctuation crossed its threshold on more than one cylinder.
Here is the link: the DME calculates the air mass entering each cylinder using the charge pressure sensor and meters fuel accordingly. If the sensor reads wrong, the mixture goes lean or rich, ignition timing is calculated from bad data, and misfires start across several cylinders. That is why, when both are present, you must resolve 2ABC first — starting with plugs and coils will most likely waste your money.
Code .............. 29CC
Definition ........ Combustion misfire - multiple cylinders
Module ............ DME
Generic equivalent P0300
Code .............. 2ABC
Definition ........ Charge pressure sensor, electrical
Module ............ DME
Related codes ..... 29CD-29D2 (per-cylinder misfire), 2C57 (boost too low),
3100 (boost control deactivated)
Severity .......... High - catalytic converter risk + limp mode
Common engines .... N54, N55, N20/N26, N63, B48/B58
Symptoms
• Shaking at idle, unstable RPM and jerky acceleration.
• Power loss and limp mode; some cars also show a "Drivetrain" warning.
• Check Engine light on steady; flashing when misfires are heavy.
• Distinctly poor running on a cold start, improving partially afterwards.
• Higher fuel consumption and a raw fuel smell from the exhaust.
• Inconsistent boost — normal on one drive, weak on the next.
• The code returning in damp weather or after a car wash (moisture in the connector).
Possible Causes
• Faulty or contaminated charge pressure sensor (TMAP) — drifting or completely dead. The most common cause of 2ABC.
• Corrosion in the sensor connector, oxidised pins, water ingress.
• Broken wiring or a chafed short in the harness, especially where engine vibration fatigues it.
• Hardened sensor O-ring — this creates both a signal issue and an air leak.
• Charge air leak (charge pipe, coupler) — even with a healthy sensor it upsets mixture and feeds the misfire.
• Worn spark plugs and weak ignition coils — the classic misfire-side cause.
• Low fuel pressure or a leaking injector; combined with a wrong air calculation, misfire becomes inevitable.
• Weak battery or a missing AGM registration — low voltage affects both sensor supply and coil output.
• Carbon buildup on the intake valves (direct injection engines).
Diagnostic Steps with OBDThink
With this pair, sequence is everything. Chasing the misfire before validating the sensor signal is the most common mistake.
• 1. Scan all modules and note which code repeats more often. A high 2ABC counter means the sensor is your starting point.
• 2. With the ignition on and the engine off, read the charge pressure sensor: it must equal ambient pressure (~1.00 bar). A reading of 0.00 bar or nonsense means there is no valid signal.
• 3. With the engine idling, watch the sensor value: it should track manifold pressure smoothly, without dropouts. Sudden drops to zero point to a connector or wiring problem.
• 4. Wiggle-test the connector by hand while watching live data — if the value jumps, the fault is in the wiring or pins, not the sensor.
• 5. Read the freeze frame: at what RPM and load was 29CC stored? Cold start versus full throttle narrows the cause considerably.
• 6. Watch per-cylinder misfire counters: spread across all cylinders points to a shared cause (air/fuel/sensor); concentrated on two cylinders points to the ignition side.
• 7. Check STFT and LTFT: clearly positive trims on both banks mean a leak or a wrong air measurement.
• 8. If the sensor checks out, move to the classic misfire path: coil swap test, spark plug inspection, fuel pressure measurement.
Reference values
Ignition on, engine off:
Charge pressure sensor . ~1.00 bar (equal to ambient)
Signal voltage ......... typically 0.5 - 4.5 V, not pinned at either rail
Idle (engine warm):
Manifold pressure ...... 0.35 - 0.45 bar absolute
Misfire counters ....... 0 on all cylinders
STFT / LTFT ............ -10% ... +10% / -8% ... +8%
EXAMPLE OF A FAULT:
Sensor 0.00 bar at key-on, voltage 4.98 V -> open circuit / supply problem
Sensor 1.00 bar but misfire Cyl3=52, Cyl4=47 -> sensor innocent, ignition side
Log the sensor value and the misfire counters in the same OBDThink recording. If the counters jump at exactly the moment the sensor signal glitches, you have proven cause and effect.
The Fix
• Connector and wiring repair: clean oxidised pins, tighten loose terminals, seal a connector that lets water in. Low cost and a surprisingly frequent permanent fix.
• Charge pressure (TMAP) sensor: replace if the signal cannot be validated, and always renew the O-ring. Low cost.
• Spark plugs: replace as a set every 25,000–40,000 miles on turbo engines. Low cost.
• Ignition coils: replace the culprit found in the swap test, or the whole set on a high-mileage car. Low to moderate cost.
• Charge pipe and couplers: replace if cracked and renew the O-ring. Low to moderate cost.
• Fuel side: low pressure means HPFP or filter; a leaking injector requires index coding after replacement. Moderate to high cost.
• Battery and AGM/IBS registration: fix this first if voltage is low. Low cost.
• Carbon cleaning (walnut blasting): on high-mileage direct injection engines. Moderate to high cost.
After replacing the sensor, clear the fault memory and take a short drive. If 2ABC stays away but 29CC keeps coming back, you are genuinely on the ignition or fuel side now — the diagnosis has narrowed by one step.
Can You Still Drive With These Codes?
If the Check Engine light is flashing, stop driving: an active misfire can melt the catalytic converter within minutes. If the light is steady and the car pulls normally, a short drive to the workshop is fine — avoid full throttle and long trips. If 2ABC is also pushing the car into limp mode, factor in the risk of sudden power loss.
Clearing codes is especially misleading with this pair: if 2ABC is an intermittent wiring fault it may stay away for days while misfire damage keeps accumulating. After the repair, clear the fault memory with OBDThink, then watch both the sensor value and the misfire counters over several drive cycles including a cold start and a full-throttle pull. If both stay clean, the problem is genuinely solved.