What Does P1170 Mean?
This code is closely related to P1169 and also indicates the heated oxygen sensor (HO2S) on bank 1, sensor 1 has a fixed or non-switching output. Depending on the manufacturer, this may represent a secondary monitor or a different detection method for the same condition. The PCM has determined that the upstream O2 sensor is not providing the expected oscillating voltage signal needed for closed-loop fuel control, resulting in the fuel system potentially reverting to open-loop operation.
Common Causes
30%
Aged or degraded HO2S with slow response time below threshold
25%
Sensor element contaminated by engine oil consumption or coolant leak
20%
Intermittent wiring connection causing signal dropouts interpreted as a fixed reading
15%
Vacuum leak on bank 1 causing a persistent lean condition that prevents sensor switching
10%
Fuel delivery problem on bank 1 (low pressure, restricted injector) preventing normal mixture oscillation
Diagnostic Steps
1
Monitor bank 1 sensor 1 voltage and cross-count (number of rich/lean transitions) over a 30-second window at steady 2,000 RPM; healthy sensors typically show 8+ cross-counts per 10 seconds.
2
Check bank 1 short-term fuel trim during the test; if STFT is pegged at a high positive or negative value, address the underlying fuel/air issue before condemning the sensor.
3
Inspect the sensor connector for a secure connection; perform a wiggle test while monitoring live data for signal intermittency.
4
Check for vacuum leaks on bank 1 using a smoke machine; even small leaks can prevent the sensor from seeing rich excursions.
5
If the sensor has over 80,000 miles and other causes are ruled out, replace it with an OE-specification sensor.
Estimated Repair Cost
$120 - $350
Parts + labor, varies by vehicle and location
This code is closely related to P1169 and also indicates the heated oxygen sensor (HO2S) on bank 1, sensor 1 has a fixed or non-switching output. Depending on the manufacturer, this may represent a secondary monitor or a different detection method for the same condition. The PCM has determined that ...
The most common cause of P1170 (HO2S Bank 1 Sensor 1 Circuit Fixed (Bank 1 Sensor 1)) is: Aged or degraded HO2S with slow response time below threshold
Typical repair costs for P1170 range from $120 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A non-switching O2 sensor forces the engine into open-loop fuel management, which typically runs richer than optimal. This increases emissions and fuel consumption but does not pose an immediate safety hazard unless combined with other faults.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1170 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel / Air Metering
Difficulty
Type
Manufacturer
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