System Too Rich Bank 1
P0172 — System Too Rich Bank 1. It is a high-severity fault: you should avoid long trips until it's fixed. The most common cause is contaminated or clogged fuel injector — spray pattern degraded. Typical fix: clean/replace the mass air flow (maf) sensor.
"Your car is telling you it's not okay. Believe it before it proves the point."
The Check Engine Light has come on and you find yourself in a dilemma. With your OBD-II scanner, you can figure out what’s going on. So, what should you do when you see the P0172 code?
- Fuel consumption: >20% above spec — verify with: fuel economy test over 100 km
- Upstream O2 voltage at idle: 0.7–0.8V continuous (normal: 0.4–0.6V) — verify with: OBD2 live data
- STFT (Short Term Fuel Trim): >+10% — verify with: OBD2 scanner freeze frame
- Black smoke on acceleration — verify with: visual inspection
- test drive
- Rough idle and hesitation 1
| # | Cause |
|---|---|
| 01 | Contaminated or clogged fuel injector — Spray pattern degraded |
| 02 | fuel cone breaks down, causing unatomized fuel puddles in cylinder,MAF sensor drift or contamination — Typically reads airflow >8 g/s at idle (normal: 3–7 g/s) |
| 03 | ECM compensates with excess fuel,Fuel pressure regulator malfunction — Pressure exceeding 58–60 psi |
| 04 | fuel overflow through return line insufficient,Upstream oxygen sensor slow response — Response time >100 ms |
| 05 | ECM cannot react to mixture changes in real-time,Intake system air leak — Unmeasured air bypasses MAF |
| 06 | ECM leans out calculation, fuel trim increases |
Typical operations: O2 Sensor - Upstream, Fuel Injector - Single · avg labour ≈ 1.1 h.
| Workshop labour by country | Hourly rate | Est. labour |
|---|---|---|
| IT | €45/h | €51–€207 |
| ES | €55/h | €62–€253 |
| FR | €75/h | €85–€345 |
| UK | £80/h | £90–£368 |
| DE | €95/h | €107–€437 |
| US | $120/h | $136–$552 |
| Parts & total | DIY | Pro |
|---|---|---|
| System Too Rich Bank 1 | €50–120 | €170–240 |
Our departments
Everything you need, picked by us
Spare parts comparator, new and usedfrom the fault code to the part
Tools and diagnosticsfor repairing it yourself
Tyres for car, motorbike, scootertyres and wheels, in 15 countries
Accessoriesinside and outside the cabin
Tuningsuspension, turbo, exhausts
Batteriesstarting and charging
Coming soonDealership car, motorbike, scootervehicles for saleFord Motor Company (Ford) is recalling certain 2018 Ford Expedition, F-150, and Lincoln Navigator vehicles equipped with 3.5L GTDI V6 engines. These vehicles have high pressure fuel pump assemblies with welds that can fracture, which may cause an oil or fuel leak.
In our database P0172 is recorded across 2884 vehicle models — most frequently on the Chevrolet Camaro, Ford F-150, Pontiac Bonneville.
A Honda Cr-V owner reported to NHTSA: “Idling rough code popping up P0172 dealer said it could be fuel injector bank 1 is to rich”
NO — REPAIR FIRST — get it diagnosed as soon as possible.
Typically €50–120 as a DIY repair and €170–240 at a workshop — the final figure depends on the actual cause and your vehicle.