What Does P0399 Mean?
This code falls in the reserved range between the camshaft position sensor codes and the EGR system codes. When defined by manufacturers, it typically relates to a camshaft or crankshaft position system rationality fault. The ECM has detected a discrepancy in the engine position sensing system that does not match expected operational parameters. The driver may notice drivability issues including rough idle, hesitation, or reduced performance.
Common Causes
35%
Crankshaft or camshaft position sensor signal degradation
25%
Timing system mechanical fault — stretched chain or worn belt
20%
Wiring or connector issue in the engine position sensor circuits
12%
Reluctor wheel/tone ring damage or contamination
8%
ECM software or calibration issue
Diagnostic Steps
1
Review all stored and pending codes — check for companion camshaft or crankshaft position codes that help isolate which sensor or system is the root cause.
2
Using an oscilloscope, capture crank and cam signals simultaneously and verify correct phase relationship and signal quality at idle and 2,500 RPM.
3
Inspect all engine position sensor connectors and wiring for physical damage, moisture intrusion, or proximity to high-voltage ignition wiring that could cause EMI.
4
Verify timing mark alignment if accessible — remove timing cover inspection plugs and confirm marks align at TDC per manufacturer procedure.
5
Check for applicable TSBs, as this code is not universally defined and the manufacturer may have specific diagnostic guidance.
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
This code falls in the reserved range between the camshaft position sensor codes and the EGR system codes. When defined by manufacturers, it typically relates to a camshaft or crankshaft position system rationality fault. The ECM has detected a discrepancy in the engine position sensing system that ...
The most common cause of P0399 () is: Crankshaft or camshaft position sensor signal degradation
Typical repair costs for P0399 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Drive cautiously to a repair facility if the engine runs normally. If rough running, misfires, or unusual engine noises are present, have the vehicle towed to avoid potential internal engine damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0399 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Timing / Variable Valve Timing
Difficulty
Type
Generic (SAE)
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