What Does P2742 Mean?
The transmission control module has detected an abnormally low voltage signal from transmission fluid temperature sensor B circuit. This indicates either a short to ground, faulty sensor, or wiring issue causing readings below normal operating range.
Common Causes
40%
Transmission fluid temperature sensor B internal short circuit or failure
30%
Wiring harness short to ground or damaged insulation on sensor circuit
20%
Corroded or damaged sensor connector pins causing poor connection
10%
Failed transmission control module (TCM) internal circuit
Diagnostic Steps
1
Step 1: Inspect transmission fluid temperature sensor B connector for corrosion, damage, or moisture intrusion
2
Step 2: Measure resistance of sensor B at various temperatures and compare to manufacturer specifications
3
Step 3: Check wiring from sensor to TCM for short to ground using multimeter (should read infinite resistance to ground with sensor disconnected)
4
Step 4: Monitor live sensor data with scan tool during warm-up to verify erratic or stuck-low readings
5
Step 5: If wiring and sensor test good, suspect TCM failure and verify with known-good sensor swap
Estimated Repair Cost
$150 - $450
Parts + labor, varies by vehicle and location
The transmission control module has detected an abnormally low voltage signal from transmission fluid temperature sensor B circuit. This indicates either a short to ground, faulty sensor, or wiring issue causing readings below normal operating range.
The most common cause of P2742 (Transmission Fluid Temperature Sensor "B" Circuit Low) is: Transmission fluid temperature sensor B internal short circuit or failure
Typical repair costs for P2742 range from $150 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may experience harsh shifting, transmission may not shift properly, or enter limp mode. Safe to drive cautiously to repair facility but avoid highway speeds or heavy loads.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2742 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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