What Does P0791 Mean?
The TCM has detected a general electrical malfunction in the intermediate shaft speed sensor A circuit. This sensor monitors the rotational speed of an intermediate shaft inside the transmission, which is critical for calculating gear ratios and shift timing. A circuit fault means the TCM cannot properly monitor internal transmission operation, which may result in harsh shifts or limp mode.
Common Causes
35%
Failed intermediate shaft speed sensor A
25%
Damaged or corroded wiring/connector to the sensor
15%
Excessive air gap between sensor and reluctor ring
15%
Damaged or missing reluctor ring teeth on intermediate shaft
10%
TCM input circuit failure
Diagnostic Steps
1
Monitor intermediate shaft speed sensor A PID in live data during driving — check for erratic readings, zero signal, or dropout.
2
Inspect the sensor connector and wiring for damage, corrosion, or contamination with transmission fluid.
3
Measure sensor resistance (typically 200-2000 ohms depending on type) and compare to manufacturer specification.
4
Check for AC voltage output from the sensor while spinning the shaft (if magnetic pickup type) or verify proper 5V reference supply (if Hall-effect type).
5
Inspect the reluctor ring for damaged, missing, or contaminated teeth if the sensor itself tests good.
Estimated Repair Cost
$150 - $600
Parts + labor, varies by vehicle and location
The TCM has detected a general electrical malfunction in the intermediate shaft speed sensor A circuit. This sensor monitors the rotational speed of an intermediate shaft inside the transmission, which is critical for calculating gear ratios and shift timing. A circuit fault means the TCM cannot pro...
The most common cause of P0791 (Intermediate Shaft Speed Sensor A Circuit) is: Failed intermediate shaft speed sensor A
Typical repair costs for P0791 range from $150 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The transmission may enter limp mode or exhibit harsh/erratic shifts. Driving at moderate speeds to a repair facility is acceptable, but avoid highway driving or heavy acceleration. Prolonged driving without repair can lead to transmission damage from improper shift timing.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0791 to identify the root cause.
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Quick Info
Category
Powertrain
System
Automatic Transmission
Difficulty
Type
Generic (SAE)
Recommended Tools
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