What Does P0393 Mean?
The camshaft position sensor B on bank 2 is reporting a high input signal to the ECM. The voltage on the signal wire exceeds the maximum expected threshold. For a Hall-effect sensor, the output may be stuck at the reference voltage; for a magnetic sensor, the amplitude may be excessively high. This prevents accurate camshaft position detection on bank 2. The engine may run with reduced performance, experience misfires, or enter limp mode with the check engine light illuminated.
Common Causes
30%
Open ground return wire for the CMP sensor B causing the signal to float to the reference voltage
25%
CMP sensor B signal wire shorted to the 5V reference wire or battery voltage
20%
Failed CMP sensor B with stuck-high output
10%
Sensor air gap too small causing excessively high voltage output (magnetic sensors)
10%
Corrosion or water intrusion at the ECM connector affecting the input circuit bias
5%
ECM internal pull-up or input protection circuit failure
Diagnostic Steps
1
With the sensor connected and ignition on, measure the signal voltage at the ECM connector. A constant 5V or battery voltage confirms a high-stuck condition. Compare to the expected resting state for your sensor type.
2
Disconnect the CMP sensor B and re-measure the signal voltage at the ECM connector. If the voltage drops to the expected bias level (typically 0-0.5V for Hall-effect), the sensor is the fault. If it remains high, the wiring has a short to voltage.
3
Verify the sensor ground circuit has continuity from the sensor connector ground pin to the ECM ground pin. An open ground forces the signal line to float to the reference voltage. Resistance should be <1 ohm.
4
Check for pinched or melted wires in the CMP B harness where the signal wire could contact the 5V reference wire or any B+ source. Separate and repair any damaged wires with proper splice techniques.
5
For magnetic sensors, verify the air gap is not too small. Reinstall the sensor to specification and recheck the signal amplitude with an oscilloscope. Excessive amplitude can overdrive the ECM input.
Estimated Repair Cost
$60 - $450
Parts + labor, varies by vehicle and location
The camshaft position sensor B on bank 2 is reporting a high input signal to the ECM. The voltage on the signal wire exceeds the maximum expected threshold. For a Hall-effect sensor, the output may be stuck at the reference voltage; for a magnetic sensor, the amplitude may be excessively high. This ...
The most common cause of P0393 (Camshaft Position Sensor B Circuit High Input (Bank 2)) is: Open ground return wire for the CMP sensor B causing the signal to float to the reference voltage
Typical repair costs for P0393 range from $60 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A high CMP signal causes loss of camshaft position data for bank 2. The engine will run in a degraded mode using backup timing strategies. The vehicle can be driven at moderate speeds to a repair facility. Not an immediate safety hazard, but performance is reduced and misfires can damage the catalytic converter over time.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0393 to identify the root cause.
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Quick Info
Category
Powertrain
System
Variable Valve Timing / Engine Timing System
Difficulty
Type
Generic (SAE)
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