P22B7: O2 Sensor Pumping Current Trim Circuit High (Bank 1 Sensor 2)

P22B7 is, going by its title, the high fault on the trim circuit belonging to bank 1's downstream wide-band probe. In GM's diesel tables (2016, 2018 and 2025 group 04) the code is a ceiling test on the oxygen value of the second NOx sensor: the 2016 table flags readings above 24 %, which is more oxygen than fresh air holds, in 100 of 200 samples. The test runs only while exhaust back-pressure stays below its limit, no exhaust brake is active and no NOx sensor pressure fault is pending; GM rates it Type B, two trips. GM bulletin 21-NA-149 lists it for the 3.0 Duramax LM2 alongside harness chafing. No public source gives a trim-resistor threshold. P22B5 is the open, P22B6 the low case, P22C4 bank 2. The lamp lights.

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 value above 21 % in live data

Most likely causes

• Faulty downstream NOx/oxygen sensor reporting excess oxygen
• Chafed engine harness affecting the sensor lines (GM 3.0 LM2)
• Trim or signal wire shorted to a voltage source

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 sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
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 P22B7 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 2: Fuel injection
• B7: Specific fault in that system

Frequently asked questions

Can I keep driving with code P22B7?

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 P22B7?

The most common causes are: faulty downstream NOx/oxygen sensor reporting excess oxygen; chafed engine harness affecting the sensor lines (GM 3.0 LM2); trim or signal wire shorted to a voltage source.

Related codes

• P22B5O2 Sensor Pumping Current Trim Circuit/Open (Bank 1 Sensor 2)
• P22B6O2 Sensor Pumping Current Trim Circuit Low (Bank 1 Sensor 2)
• P22C4O2 Sensor Pumping Current Trim Circuit High (Bank 2 Sensor 2)
• P2628O2 Sensor Pumping Current Trim Circuit High (Bank 1 Sensor 1)

Sources

• gsi.ext.gm.com: 16OBDG04 Engine Diagnostics
• gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
• gsi.ext.gm.com: 25OBDG04B
• static.nhtsa.gov: MC 10224856 0001

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.