What Does P1333 Mean?
P1333 indicates that the signal from knock sensor 4 is reading abnormally high, exceeding the expected voltage range. This typically occurs on V-configuration engines with multiple knock sensors. A high input can be caused by a shorted sensor, wiring fault, or excessive mechanical noise being interpreted as constant knock events.
Common Causes
35%
Shorted knock sensor 4 or internal sensor failure
25%
Wiring harness short to voltage in the knock sensor circuit
20%
Corroded or water-damaged connector at knock sensor 4
12%
Excessive mechanical engine noise (accessory belt, idler bearing) near sensor location
8%
ECU internal circuit fault on knock sensor input channel
Diagnostic Steps
1
Check for related knock control limit codes (P1331, P1332) that may indicate the ECU is over-retarding timing based on the faulty sensor input.
2
Disconnect knock sensor 4 and measure its resistance with a multimeter. Compare to the manufacturer specification (typically 500k-600k ohms for piezoelectric type).
3
Inspect the wiring harness from the ECU to knock sensor 4 for shorts to power, chafing, or damaged insulation.
4
Check the knock sensor connector for moisture intrusion, corrosion, or bent pins.
5
With the sensor disconnected, verify the ECU sees an open circuit (no signal). If the ECU still reads high, the fault is in the wiring or ECU.
6
Replace knock sensor 4 if sensor resistance is out of specification or the sensor is damaged.
Estimated Repair Cost
$80 - $350
Parts + labor, varies by vehicle and location
P1333 indicates that the signal from knock sensor 4 is reading abnormally high, exceeding the expected voltage range. This typically occurs on V-configuration engines with multiple knock sensors. A high input can be caused by a shorted sensor, wiring fault, or excessive mechanical noise being interp...
The most common cause of P1333 (Knock Sensor 4 High Input) is: Shorted knock sensor 4 or internal sensor failure
Typical repair costs for P1333 range from $80 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A faulty high-reading knock sensor causes excessive timing retard, reducing power and fuel economy. While not immediately dangerous, continued operation reduces performance and may mask real knock events.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1333 to identify the root cause.
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Quick Info
Category
Powertrain
System
Ignition System / Knock Control
Difficulty
Type
Manufacturer
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