P1153
HO2S Insufficient Switching Bank 2 Sensor 1
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The P1153 code is the Bank 2 counterpart to P1133, specific to GM vehicles. It means the upstream oxygen sensor on Bank 2 (the side of the engine opposite cylinder #1) is not switching between rich and lean signals fast enough. The PCM counts these transitions over a 100-second window and flags this code when the count is too low.
The most common culprit is a worn or contaminated oxygen sensor, though exhaust leaks close to the sensor and vacuum leaks can also fool the PCM into thinking the sensor isn't switching properly. An often-overlooked cause on GM vehicles is silicone contamination — using the wrong type of RTV sealant during engine work can coat the sensor and ruin it.
This is not an urgent repair but should be addressed within the next month. Driving with this code long-term can reduce fuel economy and potentially stress the catalytic converter. Replacing the upstream O2 sensor is a common DIY repair, and aftermarket sensors for GM V6 and V8 engines typically cost $20–$80.
Severity
Symptoms
- •Check engine light is on
- •Reduced fuel efficiency
- •Rough or unsteady idle
- •Slight hesitation on acceleration
- •Occasional exhaust smell
Likely Causes
The Bank 2 upstream O2 sensor has degraded or become contaminated, reducing its ability to switch between rich and lean states at the expected rate.
An exhaust leak 6-12 inches from the HO2S allows ambient air into the exhaust stream, diluting readings and causing insufficient switching.
An unmetered air leak upsets the air-fuel ratio on the Bank 2 side, so the sensor doesn't see normal rich-lean cycling.
Certain RTV silicone gasket materials release vapors that coat the O2 sensor element, poisoning it and preventing proper switching. Silicone in fuel can cause the same issue.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the Bank 2 Sensor 1 upstream oxygen sensor
- Check for and repair exhaust leaks near the Bank 2 sensor
- Inspect and fix any vacuum leaks in the intake system
- Verify no silicone-based gasket materials have contaminated the sensor