Intermediate Shaft Speed Sensor C Circuit
P2749 indicates a problem with the intermediate shaft speed sensor C circuit in the transmission. This sensor monitors transmission fluid flow and gear ratios; when its circuit malfunctions, the transmission cannot properly manage shift timing and fluid pressure.
What You Might Notice
- Hard or delayed shifting between gears
- Multiple warning lights on dashboard
- Rough idle or unstable engine speed
- Poor acceleration and driveability
- Transmission slipping or erratic behavior
Most Common Causes
- 1
Defective intermediate shaft speed sensor
The sensor itself has failed or become damaged, preventing accurate transmission fluid flow and speed readings to the transmission control module.
- 2
Wiring or connector issues
Corroded, damaged, or loose electrical connections between the speed sensor and transmission modules interrupt the signal circuit.
- 3
Low or dirty automatic transmission fluid
Contaminated or insufficient ATF reduces sensor accuracy and causes shifting problems; fluid should be checked and serviced per manufacturer specifications.
- 4
Transmission control module malfunction
An internal ECM or TCM failure prevents proper processing of sensor signals, or related solenoids and input/output shaft sensors may be defective.
How to Diagnose It
- 1
Check Defective intermediate shaft speed sensor — The sensor itself has failed or become damaged, preventing accurate transmission fluid flow and speed readings to the transmission control module.
- 2
Check Wiring or connector issues — Corroded, damaged, or loose electrical connections between the speed sensor and transmission modules interrupt the signal circuit.
- 3
Check Low or dirty automatic transmission fluid — Contaminated or insufficient ATF reduces sensor accuracy and causes shifting problems; fluid should be checked and serviced per manufacturer specifications.
- 4
Check Transmission control module malfunction — An internal ECM or TCM failure prevents proper processing of sensor signals, or related solenoids and input/output shaft sensors may be defective.
How to Fix It
- 1
Inspect and replace intermediate shaft speed sensor
Locate the sensor on the transmission, test its resistance and continuity, and replace if defective. Ensure proper installation and connector seating.
- 2
Check and repair wiring and connectors
Inspect the wiring harness between the sensor and transmission modules for corrosion, damage, or loose connections. Clean corroded connectors or replace damaged wiring.
- 3
Service automatic transmission fluid
Drain and replace the ATF according to manufacturer specifications; check fluid level and condition. Use the correct fluid type for your vehicle.
- 4
Diagnose transmission control module
Use advanced diagnostic equipment to scan for related transmission codes and test TCM function. If TCM or related solenoids are faulty, professional transmission service may be required.
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