What it means
The upstream and downstream oxygen sensor signals on bank 1 do not correlate as expected. This code alone does not establish whether the cause is a sensor fault, wiring issue, or catalyst problem.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 1 has an upstream oxygen sensor (sensor 1) before the catalytic converter and a downstream sensor (sensor 2) after it. The control module compares their signals and sets P00D5 when the two bank 1 readings do not follow the expected relationship; this alone does not identify a failed sensor or catalyst.
Common causes
Most likely first.
- Bank 1 upstream or downstream oxygen sensor inaccurate
- Exhaust leak affecting oxygen sensor readings
- Oxygen sensor wiring or connector fault
- Catalytic converter efficiency problem
Symptoms
- Check engine light on
- Fuel economy may worsen
- Possible rough running or hesitation
- Emissions test may be affected
How to diagnose it
- Record freeze-frame data and review live readings from both bank 1 oxygen sensors alongside fuel-trim data to see how their signals differ.
- Inspect both bank 1 sensor connectors and wiring, including sections near the exhaust, for damage, corrosion, or loose connections.
- Check the bank 1 exhaust path around both sensors for leaks that could distort oxygen readings.
- Use live data to assess whether bank 1 sensor 1 responds to engine mixture changes and whether sensor 2 shows the expected response after the catalyst.
- Evaluate catalytic-converter operation and test both sensors and circuits against the manufacturer's specification before replacing parts.
Common fixes
- Repair an exhaust leak affecting the bank 1 oxygen sensor readings.
- Repair damaged or loose wiring or connectors for bank 1 sensor 1 or sensor 2.
- Replace a bank 1 oxygen sensor that fails testing.
- Replace the catalytic converter only if testing confirms it is not functioning properly.
Can I keep driving?
If the engine runs smoothly, gentle driving is usually possible, but fuel economy and emissions may worsen. Get it diagnosed soon, and stop if it develops severe hesitation, stalling, or a flashing check-engine light.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.