OBD-II trouble code
P0393: Camshaft Position Sensor 'B' Circuit High (Bank 2)
The Bank 2 exhaust camshaft signal line is sitting above its upper limit. This is also the cam sensor position most likely to have been supplied with the wrong or a poor-quality replacement part.
Quick facts
- System
- Powertrain
- Category
- Camshaft / Timing
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $110 – $700
- DIY difficulty
- Intermediate DIY
What does P0393 mean?
P0393 says the voltage on the Bank 2 exhaust camshaft signal circuit has climbed above the window the engine control module accepts and stayed there. As with any high-side circuit code, the module is describing an electrical level and nothing else. Camshaft timing, oil condition and chain wear are irrelevant to it.
There is one thing about P0393 that its three Bank 1 counterparts cannot claim, and it is a parts-supply argument rather than an electrical one. Of the four camshaft position sensors a dual overhead cam V engine can carry, the 'B' sensor on Bank 2 is the lowest-volume position in the catalogue. It is the one a parts counter is least likely to stock, the one most often substituted with a 'fits multiple positions' aftermarket unit, and the one where a superseded part number is most likely to slip through. That matters diagnostically: when a freshly installed sensor sets P0393 immediately or within a day, the odds strongly favour a wrong or poor-quality part over a wiring fault that appeared at the same moment as the repair. Verify the part number against the vehicle identification number before condemning any harness on a car that has just had this sensor replaced.
The second area worth checking on a high-side code is the module end of the circuit rather than the sensor end. If the signal reaches the ECM connector at the correct level but the module still reports it as high, the input pin itself is a legitimate suspect. Pins lose tension after repeated connector cycles, and a terminal that no longer grips makes intermittent contact that a module reads as a floating, pulled-up line. Test terminal drag with a matching probe pin rather than by eye — a terminal can look perfect and hold almost nothing.
Beyond those two, the ordinary causes apply: a signal wire open somewhere along its length, a short to a voltage source running alongside it in the loom, a lost ground reference that lets the pulled-up line float, or a sensor that has failed with its output stage stuck high. Whatever the cause, the driving consequence is mild. The module abandons the Bank 2 exhaust phaser, holds it at default, and the engine runs on with slightly worse economy and no ability to complete its emissions monitors.
Common causes
- Wrong or superseded part number fitted at a recent sensor replacement
- Low-quality aftermarket sensor with an out-of-specification output
- Open circuit in the signal wire between the sensor and the ECM
- Signal wire shorted to a nearby supply voltage inside the loom
- Lost or high-resistance sensor ground allowing the line to float high
- Loose or low-tension terminal at the ECM connector
- Connector not fully latched after previous work on that side of the engine
- Internally failed sensor with its output stuck high
Symptoms
- Check engine light on with P0393 stored
- Code that appears immediately after a camshaft sensor was replaced
- Reduced fuel economy
- Loss of Bank 2 exhaust cam phasing and a modest drop in midrange response
- Occasional long crank before start-up
- Emissions monitors that will not set to ready
Diagnostic steps
- 1.Ask what was done to the car most recently. If this sensor has just been replaced, verify the part number against the vehicle identification number before any electrical testing.
- 2.If an aftermarket sensor is fitted, consider substituting a known-good original equipment unit as a test. On this position specifically, a wrong part is a common cause rather than an outside chance.
- 3.Back-probe the signal wire at the sensor connector with the key on. A reading at or near supply voltage with the sensor connected suggests the sensor or the circuit is pulled high.
- 4.Unplug the sensor and re-measure. A line that still reads high with the sensor removed puts the fault in the harness or the module, not the sensor.
- 5.Check the sensor ground with a voltage drop measurement while the circuit is live. A poor ground lets a pulled-up input float toward supply.
- 6.Perform a continuity check on the signal wire end to end to find an open, and inspect anywhere the loom crosses a power feed for chafe between the two.
- 7.Test the terminal drag at the ECM connector pin for this circuit with a matching probe. A pin that no longer grips reads as an intermittent open to the module.
- 8.Confirm the connector is fully latched and the seal is intact before closing up, and clear the code and drive to verify rather than relying on a bay idle.
Repair cost
$110 – $700
If a wrong or failing sensor is the cause, $110 to $320 covers it on an accessible engine, rising toward $700 where Bank 2 sits against the firewall. Harness repair for an open or a short to power is typically $150 to $400. Repinning or replacing a failed terminal at the ECM connector is usually $100 to $250 if the shop has the correct terminal on hand.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with camshaft position sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.