Transmission Fluid Temperature Sensor Circuit Low
The P2742 code indicates that the transmission control module (TCM) has detected a voltage signal from the transmission fluid temperature (TFT) sensor that is lower than the expected range, typically below 0.5 volts. This can be caused by a short to ground in the sensor circuit, a faulty sensor, or issues with the wiring or connector. The TFT sensor is a thermistor that changes resistance with temperature; a low voltage reading suggests either a very high temperature (which is unlikely) or a circuit fault. This code can lead to improper transmission shifting and potential damage if not addressed.
1. Most Common Causes
- Faulty transmission fluid temperature sensor 'B' (internal resistance out of spec or internal short)
- Short to ground in the sensor circuit wiring
- Short to ground in the sensor connector or terminals
- Excessive resistance in the sensor ground circuit
- Intermittent wiring harness failure due to vibration or heat damage
- Rare TCM/ECM failure (less likely)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed transmission shifts
- Transmission may go into limp mode
- Poor fuel economy
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other related codes.
Step 2: Visually inspect the TFT sensor wiring and connector for damage, corrosion, or loose connections.
Step 3: Measure the voltage at the TFT sensor signal wire with the ignition on; compare to manufacturer specifications (typically 0.5-4.5V).
Step 4: Test the sensor resistance at different temperatures using a multimeter; replace if out of spec.
Step 5: Check for a short to ground by disconnecting the sensor and measuring resistance between signal wire and ground.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can cause transmission shifting issues and potential internal damage. If the transmission goes into limp mode, you may have limited speed and should have it repaired immediately.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the sensor or wiring needs replacement. The sensor itself is usually inexpensive, but labor costs vary by shop.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.