P2740
Transmission Fluid Temperature Sensor "B" Circuit
- Severity
- Medium
- Driving
- Drivable — book it in
A fault in the transmission fluid temperature sensor "B" circuit. The module uses fluid temperature to decide when to lock the torque converter and how firmly to shift, so without a believable reading it takes a cautious default.
Possible causes
- CommonFailed temperature sensor - often part of the internal solenoid pack
- CommonCorroded or fluid-contaminated case connector
- CommonWiring damage between the transmission and the module
- PossibleInternal transmission harness failure
- PossibleLow fluid level leaving the sensor uncovered
What you might notice
- Harsh or delayed shifts, especially when cold
- Torque converter not locking up
- Higher fuel consumption
- Transmission temperature reading implausible
- Check engine light on
What to check, in order
- Compare the reported fluid temperature with ambient on a vehicle that has stood overnight. A reading far from ambient on a cold car proves the sensor wrong without any dismantling.
- Pull the transmission case connector and look for fluid inside it. Fluid wicking up the harness corrodes the pins and can reach and destroy the control module itself.
- Check the wiring between the case connector and the module.
- Check the fluid level and condition first. It is the cheapest check and it explains more transmission complaints than every electrical fault combined.
- On many transmissions this sensor is part of the internal solenoid pack, so replacing it means dropping the pan. Confirm the fault properly before starting.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Transmission
P2700P2701P2702P2703P2704P2705P2706P2707P2708P2709P2710P2711P2712P2713P2714P2715P2716P2717P2718P2719P2720P2721P2722P2723P2724P2725P2726P2727P2728P2729P2730P2731P2732P2733P2734P2735P2736P2737P2738P2739P2740P2741P2742P2743P2744P2745P2746P2747P2748P2749P2750P2751P2752P2753P2754P2755P2756P2757P2758P2759P2760P2761P2762P2763P2764P2765P2766P2767P2768P2769P2770P2771P2772P2773P2774P2775P2776P2777P2778P2779P2780P2781P2782P2783P2784P2785P2786P2787P2788P2789P2790P2791P2792P2793P2794P2795