P22B5: O2 Sensor Pumping Current Trim Circuit/Open (Bank 1 Sensor 2)

P22B5 flags an open trim line on the bank 1 downstream wide-band probe. Bosch LSU probes carry a trimming resistor in the connector module, wired to pin 5 (RT/IA), that sets each sensor's individual characteristic; the controller reads it to scale the measured pump current. Lose that line and the oxygen value can still move, but with the wrong gain. Chrysler's wording speaks of the pump cell current trim of sensor 1/2 and lists the code for 2010-2012 Ram 2500/3500 with the 6.7 Cummins; after the wiring repair its road test compares both sensors during 10-second fuel cut-offs and allows no more than 4 % difference. Saab's upstream analog P2626 is checked in overrun below 750 °C and sets above 4.81 V. P22B6/P22B7 are low/high, P22C2 bank 2.

Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank. Sensor 2 is the sensor after the catalytic converter.

Symptoms

• Check engine light
• Downstream oxygen reading disagrees with the upstream sensor during fuel cut-off
• Follow-up aftertreatment or catalyst faults possible

Most likely causes

• Corroded or loose trim-line terminal in the sensor connector
• Trim wire broken between sensor connector and ECM or sensor module
• Open trimming resistor in the sensor's connector module

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the wiring and connector of the sensor indicated
2. Check the continuity of the wire between the component and the control module.
3. Look for exhaust leaks
4. Check the signal in live data with the engine warm
5. Check the fuse and the heater resistance if the code mentions it
6. Replace the sensor if it has power and does not respond

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P22B5 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 2: Fuel injection
• B5: Specific fault in that system

Frequently asked questions

Can I keep driving with code P22B5?

Yes, you can normally drive in moderation, but get it repaired soon: you will use more fuel and the catalytic converter can be damaged over time.

What causes code P22B5?

The most common causes are: corroded or loose trim-line terminal in the sensor connector; trim wire broken between sensor connector and ECM or sensor module; open trimming resistor in the sensor's connector module.

Related codes

• P22B6O2 Sensor Pumping Current Trim Circuit Low (Bank 1 Sensor 2)
• P22B7O2 Sensor Pumping Current Trim Circuit High (Bank 1 Sensor 2)
• P22C2O2 Sensor Pumping Current Trim Circuit/Open (Bank 2 Sensor 2)
• P2626O2 Sensor Pumping Current Trim Circuit/Open (Bank 1 Sensor 1)
• P22ABO2 Sensor Positive Current Control Circuit/Open (Bank 1 Sensor 2)

Sources

• static.nhtsa.gov: MC 10128943 9999
• static.nhtsa.gov: MC 10139681 9999
• bosch-motorsport.com: Data Sheet 69034379 Lambda Sensor LSU 4.9
• saabwisonline.com: dtc p2237 p2239 p2243 p2251 or p2626

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.