P0122 means the ECU is seeing an abnormally low voltage on throttle position sensor circuit A, typically under 0.2V when it expects 0.5V to 4.5V. Most cars drop into limp mode with capped throttle.
DTC/P0122·BMW
P0122 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeverityNot safe to driveBMW
P0122 on a BMW means the ECU is seeing an abnormally low voltage on throttle position sensor circuit A, typically under 0.2V when it expects 0.5V to 4.5V. Most cars drop into limp mode with capped throttle.
What does P0122 mean on a BMW?
BMW 3-Series
2006-2013 (N52, N54, N55)BMW uses dual redundant TPS in both the pedal and throttle actuator. P0122 usually pairs with P2135 and drops the car into a restrictive failsafe. Water leaks into the E-box under the cowl are a well-documented cause on E90s.
What causes P0122 on a BMW?
Beyond the generic causes listed on the main P0122 page, these are the BMW-specific patterns we see most often:
BMW 3-SeriesFailed throttle actuator (DME-controlled) on N54/N55
BMW 3-SeriesWater in the E-box corroding DME connector pins
How to diagnose P0122 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0122:
- Read all stored codes and note companion codes such as P0113, P0222, or P2135
- Watch live data for TPS1 voltage with key on, engine off. Below 0.2V confirms the low input
- Wiggle the throttle body connector and harness while watching live data to catch intermittent faults
- Backprobe the TPS signal, 5V reference, and ground pins with a multimeter. Reference should read 4.9 to 5.1V
- If reference and ground are good but signal stays near 0V, replace the TPS or throttle body
- If the 5V reference is missing, check the wiring back to the ECU for a short to ground
- After repair, clear codes and run the throttle body relearn per the manufacturer procedure
- Road test and confirm TPS voltage sweeps smoothly from ~0.5V at closed throttle to ~4.5V at WOT
How much does P0122 cost to fix on a BMW? (EUR)
Estimated repair costs on a BMW (BMW parts and labour typically run 40% above the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0122 on BMW
These codes commonly cluster with P0122 on BMW vehicles:
FAQ: P0122 on BMW
Can I just drive with P0122 until the weekend?
You can move the car short distances, but limp mode caps power and makes merging or overtaking dangerous. Fix it before any highway driving.
Will disconnecting the battery clear P0122 for good?
It'll clear the light, but if the sensor or wiring is faulty the code returns within minutes of driving. You're masking the problem, not fixing it.
Do I need a throttle relearn after replacing the throttle body?
Yes, on almost every drive-by-wire vehicle. Without the relearn the idle will hunt or stall. Most OBD2 apps with bidirectional control can run it in under a minute.
Why did P0122 appear right after I cleaned my throttle body?
The connector probably wasn't fully seated, or carb cleaner seeped into the TPS. Reseat the plug and let it dry overnight before condemning parts.
Can a weak battery or bad alternator trigger P0122?
Yes. If system voltage drops below about 10V during cranking or under load, the 5V reference can sag and log a low-input code. Load-test the battery before chasing sensors.
Looking for the full P0122 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0122 guideSkanyx · BMW
Diagnosing P0122 on your BMW?
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