What Does P0142 Mean?
The ECM has detected a malfunction in the oxygen sensor heater circuit for Bank 1 Sensor 2 — specifically an electrical fault in the heater element or its control circuitry. While P0141 is the more commonly used generic code for this fault, P0142 may appear on certain OBD-II implementations as an alternative or supplemental heater circuit code. The heater is essential for rapid O2 sensor warm-up. Without it, the sensor takes much longer to reach operating temperature and may produce inaccurate readings during cold operation.
Common Causes
35%
Open or shorted O2 sensor internal heater element
25%
Blown heater circuit fuse or relay failure
20%
Wiring damage in the heater power or ground circuit (open, short, or high resistance)
15%
Corroded O2 sensor connector preventing proper heater circuit contact
5%
ECM heater control driver failure
Diagnostic Steps
1
Check and test the O2 sensor heater fuse. If blown, measure the heater element resistance before replacing the fuse to determine if a short caused the failure.
2
Measure the Bank 1 Sensor 2 heater resistance at the sensor connector — expect 2-15 ohms. An open circuit means the heater has burned out; very low resistance (<1 ohm) indicates a short.
3
Verify battery voltage at the heater power pin with KOEO (key on engine off). If no voltage, trace the circuit back through the fuse, relay, and harness.
4
Check the heater ground control — on PWM-controlled systems, use a lab scope to verify the ECM is toggling the ground. On simple systems, verify continuity to ground.
5
If wiring and fuse are intact but heater resistance is out of spec, replace the O2 sensor.
Estimated Repair Cost
$75 - $300
Parts + labor, varies by vehicle and location
The ECM has detected a malfunction in the oxygen sensor heater circuit for Bank 1 Sensor 2 — specifically an electrical fault in the heater element or its control circuitry. While P0141 is the more commonly used generic code for this fault, P0142 may appear on certain OBD-II implementations as an al...
The most common cause of P0142 (O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)) is: Open or shorted O2 sensor internal heater element
Typical repair costs for P0142 range from $75 to $300, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. The heater circuit fault only impacts cold-start emissions performance and OBD readiness monitors. No effect on engine power or driveability.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0142 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions / Exhaust
Difficulty
Type
Generic (SAE)
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