What Does P2559 Mean?
The PCM is detecting an abnormally high voltage on the coolant level sensor circuit. This indicates the sensor circuit may be open, shorted to voltage, or the sensor is reading a constant 'full' condition.
Common Causes
35%
Open circuit in wiring between coolant level sensor and PCM
30%
Faulty coolant level sensor with open internal circuit or stuck float
20%
Disconnected or corroded sensor connector causing open circuit
10%
Wiring shorted to voltage source from another circuit
5%
PCM internal pull-up resistor or sensor input circuit fault
Diagnostic Steps
1
Step 1: Inspect coolant level sensor connector for proper connection and corrosion on terminals
2
Step 2: Check sensor wiring harness for breaks, cuts, or damaged connectors along entire length to PCM
3
Step 3: Disconnect sensor and measure resistance across sensor terminals to verify sensor continuity
4
Step 4: Test for voltage on sensor signal wire with sensor disconnected (should read battery voltage with pull-up)
5
Step 5: Perform wiggle test on wiring harness while monitoring sensor voltage to identify intermittent opens
Estimated Repair Cost
$85 - $380
Parts + labor, varies by vehicle and location
The PCM is detecting an abnormally high voltage on the coolant level sensor circuit. This indicates the sensor circuit may be open, shorted to voltage, or the sensor is reading a constant 'full' condition.
The most common cause of P2559 (Engine Coolant Level Sensor/Switch Circuit High) is: Open circuit in wiring between coolant level sensor and PCM
Typical repair costs for P2559 range from $85 to $380, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Low coolant condition will not be detected or reported to driver, risking engine overheating. Manually verify coolant level is adequate.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2559 to identify the root cause.
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Quick Info
Category
Powertrain
System
Cooling System Monitoring
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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