How to Measure the Crankshaft Position Sensor of a Jetta?
3 Answers
The measurement method for the Jetta crankshaft position sensor is as follows: 1. Check the normal gap between the crankshaft position sensor and the pulse wheel (target wheel), which should be greater than 0.5mm and less than 1.2mm. If the pulse wheel is installed incorrectly, being too large or too small, it may cause signal deviation; 2. Turn off the ignition switch, disconnect the crankshaft position sensor connector, and measure the resistance between terminal 1 and terminal 2 of the sensor, which should be between 400 and 600 ohms. If the reading is not within this range, it can be determined that the crankshaft position sensor itself is faulty and should be replaced. The two signal wires of the crankshaft position sensor are insulated from the shielding wire; 3. Turn on the ignition switch and measure the voltage of the two signal wires to ground, which should be 1.4V. This is the preset voltage on the signal wires by the engine control unit. When starting the engine, the signal voltage of the crankshaft position sensor should be close to 1.6V. If there is an open or short circuit inside the sensor, in the signal lines, or inside the engine control unit, it will prevent the computer from receiving the crankshaft position signal, thereby causing the engine to fail to start.
Measuring the crankshaft position sensor on a Jetta is actually not difficult. Based on my experience repairing several old Jettas, here's the process: First, turn off the ignition switch and disconnect the sensor connector to prevent short circuits. Use a multimeter set to the resistance mode to directly measure the resistance between the two terminals on the sensor itself. The normal range should be between 500 and 2500 ohms, depending on the model year—I always keep a repair manual handy for reference. If the resistance is infinite, it means the internal coil is broken; if it's less than 10 ohms, there's a short circuit. After checking resistance, you also need to test the signal output. Start the engine and have a friend help press the accelerator while you measure the AC voltage at the connector with the multimeter. The needle should fluctuate with the engine RPM—if it stays still or the voltage is below 0.5 volts, replace the sensor immediately. Finally, remember to check for oil or metal debris near the sensor mounting position, as it's highly sensitive to gap interference.
Last time my car wouldn't start, I tested the crankshaft position sensor myself. First, I confirmed the trouble code was P0335 or similar crankshaft signal issue. Then I used a multimeter: disconnected the battery negative terminal for safety, located the sensor hidden on the engine side, and unplugged the 3-pin connector. To test power supply voltage - connect the red wire to ground and black wire to voltage setting, with ignition ON it should show 12V. No voltage means checking fuses and wiring. Next, test the signal wire by setting multimeter to AC mode and measuring the middle signal wire - during cranking, voltage should fluctuate between 0.3-3V. For static testing, directly measure resistance across sensor terminals - my reading was around 860 ohms, right within specification. If you find abnormalities, don't force repairs - these sensors are inexpensive, just replace with a new one to solve the problem.
