What Does P0170 Mean?
The ECM has detected a malfunction in the heater circuit for the bank 2 sensor 3 oxygen sensor. This heater brings the O2 sensor to its operating temperature quickly, and when it fails, the sensor is slow to become active. On some manufacturer implementations, P0170 may alternatively indicate a fuel trim malfunction for bank 1. In the context of this code definition, the heater circuit malfunction prevents proper emissions monitoring at the third sensor position.
Common Causes
40%
Open O2 sensor heater element inside the sensor assembly
25%
Damaged wiring or connector in the heater circuit
15%
Blown O2 heater fuse or faulty heater relay
12%
Ground circuit fault causing excessive resistance in the heater path
8%
ECM heater driver circuit failure
Diagnostic Steps
1
Check the O2 sensor heater fuse first. If blown, inspect the heater circuit for short circuits before replacing.
2
Disconnect the bank 2 sensor 3 connector and measure heater resistance across the heater pins. Spec is typically 4–15 ohms; an open circuit means the sensor heater is burned out.
3
With the key on and the connector unplugged, verify battery voltage on the heater power supply pin. No voltage points to a fuse, relay, or wiring fault.
4
Check the ground side of the heater circuit — measure continuity from the ground pin at the sensor connector to a known good chassis or engine ground (should be < 1 ohm).
5
If all electrical tests pass, use an amp clamp on the heater feed wire with the engine running to confirm actual current flow. Typical heater draw is 0.5–2.0 amps.
Estimated Repair Cost
$100 - $300
Parts + labor, varies by vehicle and location
The ECM has detected a malfunction in the heater circuit for the bank 2 sensor 3 oxygen sensor. This heater brings the O2 sensor to its operating temperature quickly, and when it fails, the sensor is slow to become active. On some manufacturer implementations, P0170 may alternatively indicate a fuel...
The most common cause of P0170 (O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 3)) is: Open O2 sensor heater element inside the sensor assembly
Typical repair costs for P0170 range from $100 to $300, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving. A failed heater for the third O2 sensor only impacts emissions monitoring. No driveability or safety concerns, but the vehicle will fail emissions testing.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0170 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Fuel System / Emissions
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
