What Does P2740 Mean?
The TCM has detected a fault in the secondary Transmission Fluid Temperature Sensor B circuit. This indicates an electrical problem preventing the TCM from receiving accurate transmission temperature data from the backup sensor.
Common Causes
40%
Failed transmission fluid temperature sensor B with internal open or short circuit
25%
Damaged or corroded wiring harness between sensor B and TCM
20%
Corroded or loose connector at temperature sensor B causing intermittent connection
10%
Broken or damaged sensor mounting causing sensor failure
5%
TCM internal circuit failure affecting sensor input channel
Diagnostic Steps
1
Step 1: Locate transmission fluid temperature sensor B (typically in valve body or transmission case)
2
Step 2: Disconnect sensor connector and measure sensor resistance at various temperatures, compare to specifications
3
Step 3: Check for proper reference voltage (typically 5V) at sensor connector from TCM
4
Step 4: Inspect wiring harness for damage, shorts to ground, or opens using continuity and resistance tests
5
Step 5: If sensor and wiring test good, monitor TCM signal input using scan tool and verify TCM is properly grounded
Estimated Repair Cost
$100 - $400
Parts + labor, varies by vehicle and location
The TCM has detected a fault in the secondary Transmission Fluid Temperature Sensor B circuit. This indicates an electrical problem preventing the TCM from receiving accurate transmission temperature data from the backup sensor.
The most common cause of P2740 (Transmission Fluid Temperature Sensor "B" Circuit) is: Failed transmission fluid temperature sensor B with internal open or short circuit
Typical repair costs for P2740 range from $100 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Loss of temperature sensor B reduces transmission protection redundancy. TCM may use sensor A only or default values, potentially allowing transmission to overheat without proper warning.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2740 to identify the root cause.
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Quick Info
Category
Powertrain
System
Automatic Transmission Monitoring System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
