Internal short or fault in the bank 1 sensor 2 oxygen sensor heater element; Heater control wire chafed and shorted to a voltage supply; Damaged, corroded or contaminated sensor connector or terminals; Fault in the heater relay or fuse supply circuit, where the heater is fed through one (varies by model); Wiring harness damage near the exhaust from heat or rubbing; Faulty engine control unit heater driver.

P0038

HO2S Heater Control Circuit High Bank 1 Sensor 2.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
38: FaultThe specific fault in that area

What it means

P0038 means the engine control unit has detected a high voltage or a short to voltage in the heater control circuit of the heated oxygen sensor fitted after the catalytic converter (sensor 2) on bank 1. Bank 1 is the side of the engine with cylinder number one. The control unit monitors the heater driver and sets the code when the circuit state does not match what it commanded, which points to a fault in the sensor heater, its wiring or the control unit driver.

Symptoms

Engine management light on
Usually no noticeable change in driveability
Possible failed emissions test or readiness monitors not completing
Slightly slower catalyst monitor or sensor readiness after a cold start
Occasionally other oxygen sensor or catalyst efficiency codes stored alongside

Possible causes

Internal short or fault in the bank 1 sensor 2 oxygen sensor heater elementlikely
Heater control wire chafed and shorted to a voltage supplylikely
Damaged, corroded or contaminated sensor connector or terminalspossible
Fault in the heater relay or fuse supply circuit, where the heater is fed through one (varies by model)possible
Wiring harness damage near the exhaust from heat or rubbingpossible
Faulty engine control unit heater driverrare

How to diagnose

Read all stored codes and freeze frame data, noting engine temperature and conditions when the code set, and check for other oxygen sensor codes
Inspect the sensor wiring and connector for melting, chafing, water ingress, corrosion or bent pins, especially near the exhaust
Confirm which sensor is bank 1 sensor 2 on this engine, as layout varies by model
Check the heater fuse and relay if fitted, following the wiring diagram for the specific vehicle
Measure the heater element resistance at the sensor and compare it with the manufacturer's specification
Check the heater supply and control wires for a short to voltage with the ignition on and the connector unplugged, using the wiring diagram
Check the heater control signal at the connector with the engine running, following the manufacturer's procedure
Clear the code and road test to see if it returns, confirming the repair

How to fix

Replace the bank 1 sensor 2 oxygen sensor if the heater element is faulty
Repair or replace shorted or damaged wiring and secure it away from hot or sharp edges
Clean or replace damaged connector terminals and the connector housing
Replace a faulty heater relay or correct a supply fault in the heater circuit
Replace or repair the engine control unit only after the wiring and sensor have been proven good, and only where the driver fault is confirmed

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as the downstream sensor mainly monitors the catalyst. Get it checked soon, because an unresolved wiring short could blow fuses or cause further faults, and the car may fail an emissions test.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.