P2748 indicates the transmission control module (TCM) is receiving an intermittent or erratic signal from the intermediate shaft speed sensor B. This sensor monitors the rotational speed of the transmission input shaft, which is critical for proper shift timing and torque converter lock-up control. The intermittent nature suggests a loose connection, damaged wiring, or a failing sensor rather than a complete circuit failure.
The sensor itself is the most common source of an intermittent signal. Internal sensor degradation, contamination, or temperature-related failures can cause sporadic output.
Wires running to the sensor can be damaged by heat, road debris, or corrosion, causing intermittent open or high-resistance circuits.
The sensor connector may have loose pins, corrosion, or moisture intrusion, creating an inconsistent electrical connection.
The tone ring (magnetic ring on the shaft that the sensor reads) can accumulate debris, suffer from metal flake contamination, or become magnetically degraded.
Fluid level issues or degraded fluid can affect sensor operation and cause intermittent signal problems, particularly in vehicles where the sensor is submerged.
A fault in the transmission control module is possible but unlikely. Control module issues should be diagnosed only after all sensor and wiring possibilities are ruled out.
No. While some repair shops may recommend replacing the engine or transmission computer for this code, it is almost never the actual cause. The sensor, wiring, and connectors account for the vast majority of P2748 failures. Always thoroughly diagnose the sensor circuit before considering control module replacement.
Driving is possible but not recommended. The intermittent sensor signal can cause unpredictable shifting, transmission slipping, and may trigger a fail-safe mode. If the vehicle enters limp mode, driveability will be severely limited. Have it diagnosed promptly.
Costs vary significantly by vehicle. Sensor replacement often ranges from $100-$300 for parts and labor. However, if the issue involves transmission removal or extensive wiring repair, costs can be substantially higher. Simple connector cleaning or wiring repair is often much less expensive.
In most cases, yes. The intermediate shaft speed sensor is the most likely culprit. However, if the problem persists after sensor replacement, the wiring harness, connectors, or tone ring should be investigated before considering control module replacement.