P0063 code: O2 Sensor Heater Control Circuit Low (Bank 2, Sensor 3)
P0063 means o2 Sensor Heater Control Circuit Low (Bank 2, Sensor 3). The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0063 means
P0063 sits at the intersection of two less-common conditions: it requires a Bank 2 (the cylinder bank opposite cylinder 1, present on V-type and flat engines but not most inline-4s) and a Sensor 3 (a third oxygen sensor mounted after a second catalytic converter, fitted only to some exhaust systems). That sensor's heater exists purely for speed — bringing the sensing element to working temperature in seconds so the computer can verify converter performance early in every trip. The 'low' in this code means the heater control circuit measured below the expected voltage, which points to a short to ground in the wiring or a heater element that has failed open inside the sensor. Given the sensor's position far down the underbody, its harness and connector face road spray, salt, and debris for years, so wiring faults are a stronger contender here than for engine-bay sensors, though a worn-out heater element still tops the list. There is no effect on how the vehicle drives; the consequences are the warning light and emissions-test eligibility.
P0063 symptoms
- Check-engine light and no other clues
- No drivability, idle, or economy changes
- OBD emissions-test failure while the code is present
What it costs to fix P0063
Typical range: $150–$425 · about ~0.5–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Third (downstream) oxygen sensor | $30–$200 | ~0.5–1.5 hrs |
| Wiring / connector repair | $10–$120 | ~0.5–1.5 hrs |
| Heater-circuit fuse | $1–$10 | ~0.1–0.3 hrs |
Labor and access dominate the estimate for this rearmost sensor — quick on a lift, slower on jack stands, slower still if the sensor has welded itself into a rusty bung. Part prices stay moderate since third sensors are conventional downstream types.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0063 for my exact vehicle →
How to fix P0063
Moderate — doable at home with common tools and patience
- Check the fuse, then the rearmost plug
A blown heater fuse leaves the circuit dead and can read low on ground-switched designs, so check it first along with any other heater codes. Then find the Bank 2 Sensor 3 connector near the back of the exhaust and look for a crushed or cracked body, pulled wires and salt between the pins.
- Read the control wire with the key on
With the sensor still connected, back-probe its control wire, key on and engine off. Where the engine computer switches the heater's ground, that wire should rest near battery voltage. Zero there means the circuit is open somewhere or grounded; the next readings tell you which.
- Check the heater and look for a grounded wire
Unplug the sensor and read the heater terminals; an open element is the most common finding. If it's fine, disconnect the engine computer as the service manual directs and test each heater wire to body ground. Continuity reveals a grounded wire, often where the long lead was pinched or scraped near the rear of the car.
- Repair underbody wiring the durable way
Splice damaged sections with solder and adhesive-lined heat-shrink rather than tape or quick-splice clips, which let water wick into the copper. Re-clip the lead along its original path so it can't hang onto the pipe or get snagged by debris again.
- Replace the sensor if the heater read open
Fit a new Bank 2 Sensor 3, using penetrating oil and patience on the old one since this far back it's usually rusted in. Clear the code, then confirm on the next cold start that it stays away.
DIY or shop? Basic meter work under the car covers almost every P0063: fuse, connector, element and a short-to-ground check. The obstacles are physical — the Bank 2 Sensor 3 sits at the very back of the exhaust where rust is worst, and finding a grounded wire along a long underbody run is tedious lying on your back. Take it to a shop if the short won't reveal itself section by section, or if the sensor is fused to the pipe and the bung threads are at risk.
Tools for the DIY steps: Multimeter with back-probe pins · Ramps or jack stands · Solder and adhesive-lined heat-shrink · O2 sensor socket · Penetrating oil
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0063.
Start a case with P0063 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P0063?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0063: common questions
What is a 'circuit low' fault in plain terms?
When the computer powers the heater, it expects to see certain voltages in the circuit. 'Low' means the voltage sagged below that expectation — usually because current is leaking to ground through damaged wiring, or because the heater element inside the sensor has burned open and broken the circuit.
The code came back after I fixed it — why?
The usual suspects: the real fault was a grounded wire or corroded connector rather than the sensor, the replacement sensor's heater spec doesn't match the original, or a marginal connection under the car reopened with vibration and moisture. Recheck the harness along its full run before replacing anything else.
What does P0063 cost to sort out?
Commonly a low-hundreds repair when the sensor is replaced at a shop; considerably less as a DIY part swap. Wiring repairs range from trivial (one chafed spot) to a couple hours of labor if the short hides somewhere along the long underbody run.
Is it fine to keep driving with P0063 in the meantime?
The code alone doesn't answer that. As a repair it's lower urgency, since this sensor doesn't participate in fuel control. The practical limits are failing OBD emissions testing and a warning light that can no longer warn you of anything new — so if it starts flashing, stop driving.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0063 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P0063 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.