Emissions code
P0038: Downstream oxygen sensor heater control circuit high (bank 1)
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $40 | $180 |
| Labor: 0.6 to 1 hours × $125 to $175 an hour | $75 | $175 |
| Fees: shop supplies, disposal, diagnostics | $0 | $15 |
| Total, rounded | $110 | $370 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in Boston, $31.54 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
This is the range for the most common fix, oxygen sensor replacement (one sensor). Which repair your car needs depends on a proper diagnosis.
The heater in the oxygen sensor behind the catalytic converter on cylinder 1's bank is drawing too much power, or the computer sees a voltage that is higher than it should on that wire. The heater may be shorted, or the wire may be touching another powered wire.
- Safe to drive?
- Usually yes, for now
- Most common cause
- Failed O2 sensor heater
Safe to drive. Emissions only.
What you may notice
- Check-engine light on
- No change in how the car drives
- May fail the emissions readiness check
Common causes, most likely first
- Failed O2 sensor heater
- Shorted wiring
- Bad connector
- Computer driver fault
Check this first
Inspect the sensor wiring near the exhaust for melted insulation, pinching or contact with another wire. Heat damage near the pipe is a common reason for high-circuit codes, and a wiring fix costs less than a sensor.
Other repairs that sometimes fix P0038
| Repair | Typical range, Boston |
|---|---|
| Diagnostic scan (check engine light) | $60 to $290 |
| ECU / engine control module replacement | $430 to $2,350 |
Before you pay
- Ask the shop what test showed this part is the cause, not just that the code appeared.
- Ask for parts and labor listed separately, and for the hours.
- Ask for a written OK before any extra work. Massachusetts rules require written authorization before repairs.
Got a quote already? Check it against the range. Want to see if your car has a recall tied to this problem? Check recalls by VIN.
Need to read a code yourself? OBD-II scanners on eBay (affiliate link, disclosure).
P0038 questions
Is this different from P0037?
P0037 means the heater circuit is reading low, such as a short to ground. P0038 means it reads high, such as a short to power. Both point at the same sensor and its wiring.
Can wiring cause it?
Yes. Melted or cracked insulation near the exhaust is a common cause, and a bare wire touching a powered wire creates a high reading. A visual check is quick and costs little.
Replace both sensors?
Only the faulty one, unless the shop finds more problems. The other sensors have their own codes, so replacing them adds cost without fixing this one.
How much does it cost to fix P0038?
The most common fix, oxygen sensor replacement (one sensor), has a typical range of $110 to $370 in Boston. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Related codes
- P0036: Oxygen sensor heater circuit fault (bank 1, after converter)
- P0037: Oxygen sensor heater circuit low (bank 1, after converter)
- P0141: Oxygen sensor heater fault (bank 1, after converter)
More emissions codes
Code meaning written in our own words. Some codes mean different things on different makes, so check your scan tool or manual. Not a repair shop, estimates only.