What Does P0038 Mean?
The ECM has detected a high voltage condition in the heater circuit of the Bank 1, Sensor 2 (downstream) heated oxygen sensor. The circuit voltage exceeds the normal range, indicating an open heater element, open ground wire, or short to battery voltage. The sensor heater cannot warm the sensor, so catalyst monitoring will be delayed until the sensor reaches temperature from exhaust heat alone.
Common Causes
35%
Open (burned-out) heater element in the O2 sensor
25%
Open ground circuit in the heater wiring
20%
Heater circuit wiring shorted to battery voltage
15%
Corroded or backed-out connector pin preventing ground
5%
ECM heater ground driver failure
Diagnostic Steps
1
Disconnect the B1S2 O2 sensor connector and measure heater resistance across the heater pins — expect 2–15 ohms. An OL (infinite) reading confirms the heater element is burned out.
2
If heater resistance is within spec, verify the ground control wire has continuity back to the ECM — should be under 1 ohm. An open ground causes the circuit to float high.
3
Check for shorts to B+ by measuring voltage on the control wire with the sensor disconnected and key on. Battery voltage present indicates a harness short to a power source.
4
Inspect the downstream sensor connector for heat damage and corrosion. Backed-out pins are a common cause of open circuits in O2 sensor connectors.
5
Command the heater on via scan tool and backprobe the ECM connector to verify the ECM is providing a ground pulse. No ground activity suggests an ECM driver fault.
Estimated Repair Cost
$80 - $300
Parts + labor, varies by vehicle and location
The ECM has detected a high voltage condition in the heater circuit of the Bank 1, Sensor 2 (downstream) heated oxygen sensor. The circuit voltage exceeds the normal range, indicating an open heater element, open ground wire, or short to battery voltage. The sensor heater cannot warm the sensor, so ...
The most common cause of P0038 (Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 1 Sensor 2) is: Open (burned-out) heater element in the O2 sensor
Typical repair costs for P0038 range from $80 to $300, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive with no drivability impact. The downstream sensor is primarily for catalyst monitoring. The only concern is emissions testing compliance. Schedule repair at your convenience or before any emissions inspection.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0038 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System / Emissions
Difficulty
Type
Generic (SAE)
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