Toyota Camry P0173: Fuel Trim Malfunction (Bank 2) diagnosis
Code verification standard
P0173 is published with SAE J2012 / ISO 15031-6 code structure plus Toyota Camry diagnostic context.
This page covers meaning, symptoms, first checks, live data, misdiagnosis risk, and repair verification.
What does this mean?
Code P0173 indicates a general fuel trim malfunction on Bank 2. The Powertrain Control Module (PCM) has detected that it cannot maintain the proper 14.7:1 air-fuel ratio by adjusting the short-term and long-term fuel trims within its programmed parameters for Bank 2. This suggests a consistent rich or lean condition specific to the engine bank that does not contain cylinder #1, leading to inefficient combustion, increased emissions, and potential long-term damage to the catalytic converter.
How serious is this code?
Driving with a P0173 code can lead to reduced engine performance, decreased fuel economy, and increased exhaust emissions. Prolonged operation with an incorrect air-fuel mixture can cause significant and costly damage to the catalytic converter on Bank 2. It is advisable to diagnose and repair this issue promptly to prevent further damage and ensure optimal engine operation and emissions compliance.
Diagnostic system: Fuel trim and air metering
On a Toyota Camry, the P0173 code should be diagnosed as part of the fuel trim and air metering group. Related codes and live data from this same system can change the repair priority, so avoid replacing parts from the code name alone.
Most Common Causes for Toyota Camry
- Vacuum leak in intake system
- Dirty or contaminated MAF sensor
- Clogged or faulty fuel injector
- Faulty oxygen (O2) sensor
- Faulty fuel pressure regulator
- Damaged, chafed, or broken wiring harness
- Corroded or loose electrical connector
- PCM/ECM software needs update (TSB)
- Internal PCM/ECM failure
Symptoms to Watch For
- Check Engine Light is illuminated
- Rough or unstable idle
- Decreased fuel economy
- Hesitation or stumble during acceleration
- Significant loss of engine power
- Poor acceleration or sluggish response
Before replacing parts, check these first
- Read short-term and long-term fuel trims at idle and cruise.
- Inspect intake boots, vacuum hoses, PCV plumbing, and MAF sensor contamination.
- Check fuel pressure if trims suggest a lean condition under load.
- Check for blown fuses, weak battery voltage, and damaged connectors before buying major parts.
Live data to compare
- STFT/LTFT at idle and 2500 RPM
- MAF grams per second
- Fuel pressure under load
How to Diagnose
Common Mistakes
Replacing oxygen sensors because they report lean/rich exhaust when the real cause is air, fuel pressure, or MAF data. Always confirm the fault with freeze-frame data, live data, visual inspection, and circuit checks before spending money on parts.
Repair verification
After the repair, clear P0173, complete a drive cycle, and confirm the monitor runs without the code returning. Save the before/after scan report if the vehicle needs emissions inspection.
Frequently Asked Questions
Can I drive with the P0173 code?
If the check engine light is solid, you can usually drive to a safe location or mechanic. If the light is flashing, pull over immediately to prevent catastrophic engine or catalytic converter damage.
Will the P0173 code clear itself?
Once the underlying problem is fixed, the engine computer will run its self-checks. If it passes over several drive cycles, the light will turn off automatically. You can also clear it immediately using an OBD2 scanner.
Will this code fail an emissions test?
Yes. If the Check Engine Light is on due to the P0173 code, your Toyota will automatically fail an OBD2 plug-in emissions or smog test.
What should I check first for P0173?
Read short-term and long-term fuel trims at idle and cruise. Inspect intake boots, vacuum hoses, PCV plumbing, and MAF sensor contamination. Check fuel pressure if trims suggest a lean condition under load.
Join the Discussion
Repair Estimate
Vacuum leak repair, MAF cleaning, or PCV hose repair
Major component replacement after live data and circuit tests confirm failure
Vacuum leaks and cleaning are cheap; fuel pump, injector, or MAF replacement costs more and should be verified.
DIY Difficulty
Can usually be performed at home with basic hand tools.