P0146: The computer sees no signal from the oxygen sensor farthest downstream on bank 1 (sensor 3)
O2 sensor no activity, bank 1 sensor 3
Severity: Monitor
An oxygen sensor circuit fault mostly affects emissions and fuel economy, and TroubleCodes.net reports little or no drivability change, so book a repair rather than stopping.
P0146 in short
P0146 means the computer sees no activity from the third oxygen sensor on bank 1, the side with cylinder 1. Typical causes are a dead or contaminated sensor, damaged wiring or a blown fuse. Fuel use can rise, so have it checked soon.
The computer expects a changing voltage from each oxygen sensor. P0146 sets when it sees no signal activity from bank 1 sensor 3.
Bank 1 is the side of the engine with cylinder 1. Sensor numbering depends on the exhaust layout, so check a diagram for your engine.
TroubleCodes.net notes that some vehicles use air/fuel ratio sensors instead of conventional oxygen sensors, so use the procedure for your vehicle.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Failed or contaminated oxygen sensor
Common general cause- Why it ranks here
- TroubleCodes.net lists a defective sensor and silicone or oil contamination as causes.
- What would change this
- Discolouration or deposits on the removed sensor raise it.
Cause 2: Damaged sensor wiring, connector or blown fuse
Common general cause- Why it ranks here
- TroubleCodes.net lists damaged wiring and connectors and blown fuses in the heater control circuit.
- What would change this
- Visible damage, or an open circuit in continuity tests, raises it.
Cause 3: Oil or coolant entering the engine contaminating the sensor
Possible — needs testing- Why it ranks here
- TroubleCodes.net lists internal engine problems such as oil or antifreeze contamination.
- What would change this
- Signs of oil or coolant loss raise it.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read all codes and freeze-frame data and note any fuel trim, misfire, exhaust or other oxygen sensor codes stored with P0146
IfFuel trim, misfire or other sensor codes are also stored
It meansRepair those first; they can disturb this sensor.
IfP0146 is the only code
It meansInspect the sensor wiring next.
Step 2: With the exhaust cold, inspect the sensor wiring, connector and related fuses for damage, corrosion and routing near hot parts
Warning:Let the exhaust cool fully before touching the sensor or its wiring. Back-probe connectors gently, never pierce insulation, and follow the wiring diagram for your engine.
IfDamaged wiring, a corroded connector or a blown fuse is found
It meansRepair it.
IfWiring looks good
It meansTest the sensor electrically.
Step 3: Unplug the sensor and test its resistance and the circuit continuity, voltage and ground against the specification for your engine
Warning:Let the exhaust cool fully before touching the sensor or its wiring. Back-probe connectors gently, never pierce insulation, and follow the wiring diagram for your engine.
IfResistance or readings are out of specification, or the removed sensor is contaminated
It meansThe sensor has failed; replace it.
IfSensor and circuit test good
It meansLook at the remaining causes.
Points to: Oil or coolant entering the engine contaminating the sensor
Symptoms
- Check engine light
- Higher fuel consumption
- Hesitation or power loss in some cases
How to fix
Step 1: With the exhaust cold, inspect the sensor wiring, connector and related fuse, then clear the code and test drive.
Parts and cost context
- Oxygen (O2) sensor:Use the correct sensor for that bank and position on your engine; sensors in different positions are often different parts.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
ChevroletYour car
1997 · Astro Van
Supported by vehicle dataGM bulletin 030604051 is a revised entry on P0146 (HO2S circuit insufficient activity, bank 1 sensor 3) for the 1997 Astro. Whether it is still current is not verified.
030604051 (chevrolet)Status unverified
Revised P0146 diagnostic entry for the bank 1 sensor 3 oxygen sensor
1997astro-van · issued · NHTSA 10004313
Revised GM bulletin on P0146, the heated oxygen sensor circuit insufficient activity code for bank 1 sensor 3, on the 1997 Astro. Only the NHTSA summary was read; it does not give the repair.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
GMCYour car
1997 · Safari
Supported by vehicle dataGM bulletin 030604051 is a revised entry on P0146 (HO2S circuit insufficient activity, bank 1 sensor 3) for the 1997 Safari. Whether it is still current is not verified.
030604051 (gmc)Status unverified
Revised P0146 diagnostic entry for the bank 1 sensor 3 oxygen sensor
1997safari · issued · NHTSA 10004313
Revised GM bulletin on P0146, the heated oxygen sensor circuit insufficient activity code for bank 1 sensor 3, on the 1997 Safari. Only the NHTSA summary was read; it does not give the repair.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Related codes
No curated relationships for P0146 yet.
Sources and review
- P0146 trouble code page
- On-Board Diagnostic Trouble Codes (generic code title list)
- Chevrolet bulletin 030604051: Revised P0146 diagnostic entry for the bank 1 sensor 3 oxygen sensor
- Gmc bulletin 030604051: Revised P0146 diagnostic entry for the bank 1 sensor 3 oxygen sensor
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
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