Intermediate Shaft Speed Sensor A Circuit
P0791 indicates the intermediate shaft speed sensor circuit is not functioning properly, preventing the transmission control module from accurately monitoring transmission shaft speed. This sensor is critical for proper automatic transmission shifting and fuel economy calculations.
What You Might Notice
- Hard or delayed shifts
- Multiple warning lights on dashboard
- Poor fuel economy
- Erratic engine idle speed
- Transmission slipping or hunting between gears
Most Common Causes
- 1
Defective intermediate shaft speed sensor
The sensor may be internally failed, damaged, or worn out, preventing accurate speed signal transmission to the TCM.
- 2
Wiring or connector issues
Corroded, loose, or damaged wiring between the speed sensor and transmission control module can interrupt the signal circuit.
- 3
Dirty or low transmission fluid
Contaminated or insufficient automatic transmission fluid can cause sensor malfunction and affect transmission operation.
- 4
ECM or TCM malfunction
Internal controller issues or software problems may prevent proper sensor signal processing.
How to Diagnose It
- 1
Check Defective intermediate shaft speed sensor — The sensor may be internally failed, damaged, or worn out, preventing accurate speed signal transmission to the TCM.
- 2
Check Wiring or connector issues — Corroded, loose, or damaged wiring between the speed sensor and transmission control module can interrupt the signal circuit.
- 3
Check Dirty or low transmission fluid — Contaminated or insufficient automatic transmission fluid can cause sensor malfunction and affect transmission operation.
- 4
Check ECM or TCM malfunction — Internal controller issues or software problems may prevent proper sensor signal processing.
How to Fix It
- 1
Inspect and replace intermediate shaft speed sensor
Locate the sensor on the transmission, inspect for damage or debris, and replace if defective. Ensure proper installation and connector seating.
- 2
Check wiring and connectors
Inspect all wiring between the sensor and TCM for corrosion, damage, or loose connections. Repair or replace damaged wiring and clean corroded connectors.
- 3
Service transmission fluid and filter
Perform a transmission fluid and filter change to remove contamination and ensure proper fluid level and condition for sensor operation.
- 4
Reprogram or replace TCM
If sensor and wiring check out, the transmission control module may need reprogramming or replacement to resolve circuit recognition issues.
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