Intermediate Shaft Speed Sensor B Circuit Intermittent
P2748 indicates an intermittent electrical problem with the Intermediate Shaft Speed Sensor B circuit, which monitors transmission input shaft speed for transmission control. This sensor is critical for proper shift timing and transmission operation, and a fault causes the transmission computer to set this code when it detects inconsistent or missing signal data.
What You Might Notice
- Hard or delayed shifting between gears
- Check Engine Light and transmission warning lights illuminated
- Erratic engine speed or surging
- Poor fuel economy and reduced performance
- Transmission slipping or hunting between gears
Most Common Causes
- 1
Defective Intermediate Shaft Speed Sensor
The sensor itself may be failing intermittently or have an internal electrical fault. This is the most common cause as sensors can degrade over time due to heat and vibration.
- 2
Wiring or Connector Issues
Corrosion, loose connections, damaged wiring, or poor contact between the sensor and transmission control module can cause intermittent signal loss.
- 3
Low or Dirty Transmission Fluid
Contaminated or insufficient ATF can cause sensor fouling and electrical issues, affecting sensor signal quality and transmission operation.
- 4
Transmission Control Module (TCM) Internal Fault
A defective TCM or ECM may produce false readings or fail to properly read the sensor signal, though this is less common than sensor or wiring faults.
How to Diagnose It
- 1
Check Defective Intermediate Shaft Speed Sensor — The sensor itself may be failing intermittently or have an internal electrical fault. This is the most common cause as sensors can degrade over time due to heat and vibration.
- 2
Check Wiring or Connector Issues — Corrosion, loose connections, damaged wiring, or poor contact between the sensor and transmission control module can cause intermittent signal loss.
- 3
Check Low or Dirty Transmission Fluid — Contaminated or insufficient ATF can cause sensor fouling and electrical issues, affecting sensor signal quality and transmission operation.
- 4
Check Transmission Control Module (TCM) Internal Fault — A defective TCM or ECM may produce false readings or fail to properly read the sensor signal, though this is less common than sensor or wiring faults.
How to Fix It
- 1
Inspect and Test Speed Sensor B
Locate the intermediate shaft speed sensor B on the transmission and test it for proper resistance and signal output. Replace the sensor if it shows abnormal readings or fails continuity testing.
- 2
Check Wiring and Connectors
Inspect the sensor wiring harness and connectors for corrosion, damage, or loose connections. Clean corroded contacts with electrical cleaner and repair or replace damaged wiring as needed.
- 3
Change Transmission Fluid and Filter
Drain and replace the automatic transmission fluid and filter to remove contaminants that may be affecting sensor performance. Follow manufacturer specifications for fluid type and capacity.
- 4
Test Transmission Control Module
If sensor and wiring are confirmed good, have the TCM tested or reprogrammed by a professional technician to rule out internal module faults that may require replacement.
Need a deeper diagnosis?
Search for related repair guides or browse by system.