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·Honda
P0122 on Honda: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeverityNot safe to driveHonda
P0122 on a Honda 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 Honda?
Honda Civic
2006-2015 (R18A 1.8L, 8th and 9th gen)Uncommon on the Civic, but when it appears the throttle body assembly (Honda part 16400-RNA-A01) is the usual culprit. Honda requires the idle learn procedure (ignition on 2 minutes, then 5 minutes at operating temp) after any throttle work.
What causes P0122 on a Honda?
Beyond the generic causes listed on the main P0122 page, these are the Honda-specific patterns we see most often:
Honda CivicCarbon buildup preventing the throttle plate from returning to true closed position
Honda CivicCracked solder joint on the TPS board inside the throttle body
How to diagnose P0122 on a Honda 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 Honda? (EUR)
Estimated repair costs on a Honda (Honda parts and labour typically run 10% below 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 Honda
These codes commonly cluster with P0122 on Honda vehicles:
FAQ: P0122 on Honda
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 · Honda
Diagnosing P0122 on your Honda?
Your car logged {code}. Skanyx reads it on any standard Bluetooth OBD2 adapter, tells you whether it is safe to keep driving, and shows the {costRange} repair range so you know the number before a shop quotes you.
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