What Does P1798 Mean?
DTC P1798 indicates the output speed sensor 2 circuit is reporting values outside its expected range or showing performance issues. The TCM uses this sensor to calculate output shaft speed for shift timing and torque converter clutch operation. Erratic or out-of-range readings prevent accurate transmission control.
Common Causes
30%
Faulty output speed sensor 2 (worn or contaminated)
25%
Damaged or corroded wiring/connector on the OSS2 circuit
20%
Excessive air gap between sensor and reluctor ring
15%
Damaged or missing teeth on the reluctor ring
10%
Internal TCM circuit issue on the OSS2 input
Diagnostic Steps
1
Compare output speed sensor 1 and output speed sensor 2 PIDs on the scan tool while driving; they should correlate closely.
2
Inspect the output speed sensor 2 connector for corrosion, bent pins, or moisture.
3
Measure the sensor's resistance and compare to specification (typically 200–2000 ohms depending on type).
4
Check the sensor air gap and inspect the reluctor ring for damaged, chipped, or missing teeth using a borescope if possible.
5
Monitor the AC voltage output from the sensor while spinning the output shaft (if accessible) and verify a clean, consistent waveform.
Estimated Repair Cost
$100 - $600
Parts + labor, varies by vehicle and location
DTC P1798 indicates the output speed sensor 2 circuit is reporting values outside its expected range or showing performance issues. The TCM uses this sensor to calculate output shaft speed for shift timing and torque converter clutch operation. Erratic or out-of-range readings prevent accurate trans...
The most common cause of P1798 (Output Speed Sensor 2 Circ. Range/Performance) is: Faulty output speed sensor 2 (worn or contaminated)
Typical repair costs for P1798 range from $100 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Inaccurate output speed data can cause harsh or delayed shifts, TCC shudder, and potential transmission overheating, which may lead to sudden loss of drive.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1798 to identify the root cause.
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