What Does P0343 Mean?
The ECM has detected that the camshaft position sensor A signal on Bank 1 is reading above the expected voltage threshold, typically exceeding 4.8V on a 5V reference circuit. This high input condition usually points to a short to voltage in the sensor wiring, a failed sensor with internal short, or a problem in the ECM's internal pull-down circuit. The engine may experience hard starting, misfires, or run in a degraded limp mode with retarded timing.
Common Causes
35%
Camshaft position sensor A (Bank 1) internal failure causing signal line to be pulled high
30%
Short to battery voltage in the CMP sensor signal wire due to chafed insulation contacting a power source
20%
Corroded or damaged connector pins at the CMP sensor or ECM causing high-resistance ground path
15%
ECM internal pull-down circuit failure on the CMP signal input
Diagnostic Steps
1
Disconnect the Bank 1 camshaft position sensor A connector and measure voltage on the signal wire with KOEO. If voltage remains above 4.5V, the short to power is in the harness between the sensor and ECM.
2
With the sensor disconnected, measure resistance between the signal wire and battery positive. A low reading (under 1K ohm) confirms a short to voltage in the wiring harness.
3
Inspect the CMP sensor wiring harness routing near the valve cover, exhaust manifold, and any harness clamps for chafed or melted insulation that could cause a short to a nearby power wire.
4
Check the CMP sensor connector pins for corrosion, pushed-back terminals, or oil contamination. Measure sensor resistance per manufacturer specifications (typically 500-1500 ohms for Hall-effect type internal coil).
5
If wiring checks pass, install a known-good CMP sensor and verify signal voltage with an oscilloscope at idle. The signal should produce clean square waves between 0V and 5V with consistent frequency.
Estimated Repair Cost
$75 - $350
Parts + labor, varies by vehicle and location
The ECM has detected that the camshaft position sensor A signal on Bank 1 is reading above the expected voltage threshold, typically exceeding 4.8V on a 5V reference circuit. This high input condition usually points to a short to voltage in the sensor wiring, a failed sensor with internal short, or ...
The most common cause of P0343 (Camshaft Position Sensor A Circuit High Input (Bank 1)) is: Camshaft position sensor A (Bank 1) internal failure causing signal line to be pulled high
Typical repair costs for P0343 range from $75 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A high CMP signal can cause incorrect ignition and fuel injection timing, leading to potential stalling at highway speeds or failure to start. The vehicle should be diagnosed promptly to prevent being stranded.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0343 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Timing / Variable Valve Timing
Difficulty
Type
Generic (SAE)
Recommended Tools
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