P0038: Ho2S Heater Control Circuit High (Bank 1 Sensor 2)
P0038 means the engine computer sees too much voltage or an open/high-resistance condition in the heater circuit for the downstream oxygen sensor on Bank 1, Sensor 2. The most common fix is replacing the oxygen sensor or repairing the wiring/connector, which usually costs about $150 to $400 at an independent shop.
- Severity
- Moderate
- Can I drive?
- Drive with caution
- DIY?
- Possible with some experience
- Repair cost range
- $80 – $900
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What does P0038 mean?
This code points to the heater circuit for the oxygen sensor located after the catalytic converter on Bank 1. The heater helps the sensor warm up quickly so the computer can monitor exhaust mixture and catalyst operation soon after startup. When the circuit reads too high, it usually means the heater circuit is open, shorted, or the sensor heater itself has failed. It can also happen from damaged wiring, corrosion, or a blown fuse in the heater circuit, depending on the vehicle.
Common symptoms
- Check engine light on
- Possible longer warm-up time before emissions system works correctly
- Poor fuel economy in some cases
- Rough running shortly after cold start in some cases
- Failed emissions test
Causes, fixes and costs
P0038: Ho2S Heater Control Circuit High (Bank 1 Sensor 2)
General guide for most cars. Your car may differ.
The car usually still drives, but the engine computer may not monitor emissions properly and fuel economy can suffer. Stop driving if the wiring is melted, the engine runs badly, or other warning lights and driveability problems appear.
Most likely causes
- 1
Failed Bank 1 Sensor 2 oxygen sensor heaterHigh
If the check engine light is on with no major drivability symptoms, the heater inside the sensor is often the problem. This is especially likely on high-mileage vehicles or when the code returns after clearing.
Quick check: Inspect the sensor wiring for damage, then test heater resistance with a multimeter or replace the sensor if the circuit tests out of range.
- 2
Open or damaged wiring/connectorHigh
A code for heater circuit high often comes from a broken wire, loose plug, melted harness, or corrosion at the connector. This is more likely if the code appeared after exhaust work, road damage, or animal damage.
Quick check: Visually inspect the harness and connector near the exhaust for melting, breaks, pulled pins, or green corrosion; wiggle-test the connector while watching live data if available.
- 3
Blown fuse or power feed problem to heater circuitMedium
If the heater has lost its power supply, the circuit can set a high/open fault even though the sensor itself is fine. This is more likely when multiple heater-related codes show up or the code sets immediately after start-up.
Quick check: Check the related fuse and verify battery voltage at the heater power wire with the key on, engine off.
- 4
PCM driver or control issueLow
If the sensor and wiring test good but the code keeps returning, the computer may not be controlling the heater correctly. This is less common and usually considered after all circuit checks pass.
Quick check: Confirm sensor power, ground, and resistance first; if everything checks out, have the circuit tested with a scan tool and wiring diagram.
Can you fix it yourself?
Possible with some experience
Difficulty: Moderate. A DIY owner with a multimeter and jack stands can inspect the wiring and sometimes replace the oxygen sensor, but exhaust-threaded sensors can be stubborn. You need the correct upstream/downstream sensor location, a scan tool if possible, and care not to damage the harness.
Show the stepsHide the steps
- Verify the code and clear it to see if it returns
- Locate Bank 1 Sensor 2 after the catalytic converter
- Inspect the connector and harness for heat damage, corrosion, or broken wires
- Check the related fuse and heater power feed
- Test heater circuit resistance and voltage if you have a multimeter
- Replace the sensor if the heater is open or out of spec
- Repair any damaged wiring and secure the harness away from the exhaust
- Clear the code and road test
Estimated repair cost
$150 – $350
Replace Bank 1 Sensor 2 oxygen sensor: parts ~$50-$180, labor ~$100-$170
- Repair oxygen sensor wiring or connector$100 – $250
- Replace fuse or repair heater power circuit$80 – $180
- PCM diagnosis or replacement$250 – $900
Prices vary by vehicle, rust level, and local labor rates, especially if the sensor is seized in the exhaust.
Frequently asked questions
Can I drive with P0038?
Usually yes, for a short time, because this code does not normally cause an immediate breakdown. Still, you should fix it soon because the car may run less efficiently and may fail an emissions test.
Will P0038 go away on its own?
Sometimes it can clear temporarily if the problem is an intermittent connection, but the fault usually comes back until the sensor, wiring, or fuse issue is fixed.
Is P0038 the same as a bad oxygen sensor?
Not always. The oxygen sensor heater is the most common failure, but damaged wiring, a blown fuse, or a control issue can set the same code.
Can I pass inspection with P0038?
Usually not if the check engine light is on or the OBD monitors are not ready. Most states will fail the car for an active emissions-related code.
Should I replace both oxygen sensors at once?
Not for this code alone. Start with Bank 1 Sensor 2 and inspect the wiring, since the upstream sensor and the other bank may be fine.
Related codes
- P0141 O2 Sensor Heater Circuit (Bank 1 Sensor 2)
- P0037 Ho2S Heater Control Circuit Low (Bank 1 Sensor 2)
- P0032 HO2S Heater Control Circuit High (Bank 1 Sensor 1)
- P0135 O2 Sensor Heater Circuit (Bank 1 Sensor 1)
- P0050 HO2S Heater Control Circuit (Bank 2 Sensor 1)
- P0140 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
Related problems
This guide covers most cars and is general advice, not an inspection. Prices are typical US independent-shop ranges and vary by region, car and shop. If your brakes, steering or a warning light feel unsafe, stop driving and contact a mechanic.