BMW 29D1 identifies cylinder 5 misfire on a six-cylinder DME. An E83 N52 or F25 N55 X3 has cylinder 5; an F25 N20 four-cylinder does not, so a raw 29D1 on an N20 requires DME/scanner identity checks. On a valid six-cylinder, preserve smooth-running data, inspect labeled plug/coil 5, then test injector delivery, rear intake leakage, compression and VANOS timing.
Match the symptom
Select the closest observation. The result changes the first test; it does not name a part to replace.
Stop loading to protect catalysts.
What can set 29D1—and how to separate it
The order below is evidence-driven, not a universal probability ranking. Vehicle year, repair history, companion codes and the operating condition in freeze frame change where diagnosis should begin.
| Possible cause | Evidence that supports it | First useful test |
|---|---|---|
| Worn/fouled plug or ignition fault | Cylinder leader and controlled swap follows | Labelled plug/ignition test |
| Injector or fuel-pressure fault | Contribution/pressure mismatch | Injector/fuel tests |
| Intake, purge or boost leak | Trim/smoke pattern | Smoke and purge test |
| Compression, valvetrain or timing fault | Count stays with mechanical weakness | Compression/leak-down/timing |
| Shared voltage or contaminated fuel | All cylinders or post-refueling | Voltage/fuel-quality test |
Confirm cylinder 5 exists
Decode VIN and engine before ordering a fifth coil. A four-cylinder code mismatch is diagnostic evidence.
Read complete module address and BMW fault text.
Test a valid six-cylinder fault
Capture cold/load smooth-running values, inspect plug 5 and move only the suspected coil.
If it stays, test injector and smoke-test the rear runner/CCV area.
Measure compression and timing
Use compression/leak-down and VANOS/cam data after fuel/ignition tests.
Verify no returning 29D1 under the original condition.
Save these scan-data clues
Freeze frame is a snapshot of conditions when the PCM matured the fault. It can distinguish an idle-only problem from a load, cold-start or monitor-completion problem. Clearing first throws that context away.
- Exact VIN, platform, model year and engine sales code
- All confirmed, pending and permanent companion codes
- RPM, load, coolant temperature and vehicle speed
- Relevant commanded and actual scan data
- Recent service, repairs and symptom conditions
- Manufacturer bulletin and current software/VIN status
A practical diagnostic workflow
- 01Identify engine and bank layout
Cylinder patterns differ.
- 02Preserve counters
Save cold/load evidence.
- 03Inspect plugs in order
Deposits direct testing.
- 04Target ignition
Use one controlled test.
- 05Test fuel and air
Graph pressure/trims and smoke paths.
- 06Prove mechanical health
Use compression/leak-down/timing.
- 07Verify original condition
Avoid a flashing-MIL road test.
Do not replace the most commonly named component from 29D1 alone. Confirm the exact engine, preserve evidence and complete the manufacturer test sequence before ordering parts.
Why the model year changes the test
BMW X3 diagnostics span E83, F25 and G01 generations with N52 naturally aspirated six-cylinder, N20 four-cylinder turbo, N55 six-cylinder turbo, diesel and newer B-series engines. A four-digit E-series fault may not be the native code on a later DME. Confirm VIN, chassis, engine designation, production date and complete ISTA fault text before choosing VANOS, boost, fuel or cylinder tests.
- N52/N55 has six cylinders; N20 has four and no cylinder 5.
- Verify DME/module on an N20 X3 displaying 29D1.
- N52 and N55 injector systems differ.
- 2A82/2A87 companions raise cam-control priority.
29D1 FAQ
Does P0300 mean all coils failed?+
No.
Can I drive?+
Not with flashing MIL or strong shaking.
Can bad fuel cause it?+
Yes.
Should I replace plugs first?+
Inspect and record them first.
Can vacuum leaks cause it?+
Yes.
Can timing cause it?+
Yes, especially with cam/crank codes.
Why save counters?+
They reveal cylinder and bank structure.
What confirms repair?+
Stable counters under original conditions.
Ford diagnostic references
These documents explain Ford monitor operation. Exact pinpoint tests, connector views and specifications must be selected for the truck's VIN and model year in current service information.
01BMW Technical Information SystemOfficial VIN-, engine- and ISTA test-plan information↗02BMW owner's manualsOfficial VIN/model operating, warning and maintenance information↗