P0175 Code: System Too Rich (Bank 2)
Bank 2 is still running rich even though the PCM is already cutting fuel on that side as far as it may.
Safety first · Consult a professional
- Fuel vapor is flammable. No smoking or open flames; work outdoors and fix fuel leaks before driving.
At a glance
Severity: Moderate
- Meaning
- System Too Rich (Bank 2)
- System
- Fuel & Air Metering · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $150–$1,400
- DIY difficulty
- Moderate
P0175 means the negative fuel trim limit has been reached on bank 2, the half of a V engine that does not include cylinder 1. The PCM is already subtracting a large share of fuel on that side and the bank 2 upstream sensor still reports rich. Because bank 1 has its own sensor and its own trims, comparing the two banks is the quickest way in. With P0172 also stored, extra fuel is reaching both banks from a shared source such as high rail pressure, an open purge valve or fuel-diluted oil. With bank 1 close to normal, either bank 2 is getting fuel it shouldn't, from a dripping injector on that side, or it is getting less air than the PCM assumes, or its sensor is biased.
Can I keep driving? Short, gentle trips to a shop are fine, but don't let it run for weeks. A rich bank 2 cooks its own catalytic converter first, so stop driving if the check engine light flashes, you smell raw fuel or the exhaust on that side glows or rattles.
How to read P0175
- P Powertrain
- 0 Generic (SAE)
- 1 Fuel & air metering
- 75 Specific fault
Symptoms
- Check engine light on, sometimes with P0430 for the bank 2 converter following later
- Fuel smell strongest from one tailpipe or one side of a dual exhaust
- Black soot inside the bank 2 tailpipe while the bank 1 side stays gray
- Hard hot restart, cranking longer after a short stop
- Rough idle and lower gas mileage
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Leaking or dripping injector on a bank 2 cylinder
- Shared fuel source with P0172 also set: fuel pressure too high, purge valve stuck open or gasoline in the oil
- Bank 2 upstream sensor biased rich: coolant or silicone contamination, or its signal wire shorted to the heater feed
- Bank 2 taking in less air than the PCM assumes: phaser stuck retarded, intake runner flap stuck or heavy carbon on bank 2 intake valves
- Upstream sensor plugs swapped between banks, or a sensor with the wrong characteristic fitted to bank 2
- Partly restricted bank 2 catalytic converter raising backpressure on that side
Diagnosis step by step
Check whether P0172 is present and compare trims
On a warm engine, read long-term trim on both banks at idle and at 2,500 rpm. Bank 1 within about 5% of zero while bank 2 sits at -15% or lower means the fault belongs to bank 2. Both banks similarly negative means a shared cause, so test fuel pressure, pinch the purge line and smell the oil before touching anything on bank 2.
Tools: OBD-II scanner
Read the bank 2 spark plugs
Pull the plugs from bank 2 and line them up next to one plug from bank 1. A single plug that is black, sooty or smells of fuel points straight at the injector for that cylinder. If every bank 2 plug looks equally dark, suspect air supply or the sensor instead.
Tools: Spark plug socket, Flashlight
Check fuel pressure hold with the engine off
Connect a gauge, run the engine, shut it off and watch the reading. A drop of more than a few psi within five minutes means something is leaking; clamp the return or supply line to separate the regulator from the injectors. Relieve pressure before disconnecting, keep sparks away and wipe up spills immediately.
Tools: Fuel pressure gauge
Test the bank 2 sensor for a rich bias
During a deceleration from 3,000 rpm with the throttle closed, fuel cut should drive a narrowband sensor below 0.2 V. A bank 2 sensor that stays high while bank 1 drops is lying. With the sensor unplugged, check for continuity between its signal and heater terminals: any reading means an internal short that feeds heater voltage into the signal.
Tools: OBD-II scanner, Multimeter
Compare how both banks breathe
Read actual versus desired cam angle for both banks and command any runner control flaps while watching them move. On direct-injection V engines, look at the bank 2 intake valves with a borescope through a runner if carbon is suspected. The MAF measures total air and the PCM splits fuel evenly, so a bank that breathes less ends up rich.
Tools: OBD-II scanner, Flashlight
Swap the upstream sensors side to side
Only if both sensors share a part number: swap them, clear the codes and drive. If the rich reading moves to bank 1 and P0172 appears, the sensor is at fault. If bank 2 stays rich, the sensor was telling the truth.
Tools: O2 sensor socket, OBD-II scanner
Where the parts are
- 1Ignition coil
- 2Spark plug
- 3Fuel injector
- 4Camshaft sensor
- 5Crankshaft sensor
- 6Engine computer (ECM)
- 7Intake manifold
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace leaking bank 2 injector(s), intake removal on many V engines | No | $300–$950 |
| Replace bank 2 upstream O2 or air-fuel sensor | Yes | $180–$450 |
| Replace bank 2 camshaft oil control valve or phaser | No | $200–$1,400 |
| Walnut-blast carbon from bank 2 intake valves (direct injection) | No | $400–$800 |
| Replace fuel pressure regulator (shared cause) | No | $150–$450 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Field data
| Chrysler | 2 | Town And Country | |
|---|---|---|---|
| Honda | 2 | Pilot | |
| Kia | 2 | Sedona, Stinger |
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
The lit check engine light fails the OBD-II portion of a smog check, and a rich bank drives up HC and CO where a tailpipe probe is still used. Repair first, then drive until the readiness monitors complete; a freshly cleared code shows up as not ready.
Frequently asked questions
Why does only bank 2 run rich if both banks share one fuel pump?
The pump is shared, but each bank has its own injectors, its own sensor, its own camshafts and its own exhaust. A dripping injector, a biased sensor or a sticking phaser on that side only affects bank 2, which is exactly what P0175 without P0172 tells you.
I replaced the bank 2 O2 sensor and P0175 came back. Why?
The old sensor was probably reporting a real rich mixture. Look for the extra fuel or the missing air on that bank: read the plugs, test pressure hold for a leaking injector and compare cam timing between the banks.
Will P0175 damage the catalytic converter?
It can. Surplus fuel from bank 2 burns inside that bank's converter and overheats it. On engines with one converter per bank, a P0430 that shows up later is often the bill for a P0175 that was ignored.
Can a bad coolant temperature sensor cause P0175?
It can make the engine run rich, but it affects both banks equally, so you would normally see P0172 as well. A coolant sensor is an unlikely cause of a rich condition on bank 2 alone.