P0791 - Intermediate Shaft Speed Sensor A Circuit Malfunction
The P0791 code indicates a problem with the intermediate shaft speed sensor 'A' circuit. This sensor monitors the rotational speed of the intermediate shaft within the transmission, which is critical for proper shift timing and torque converter lockup. When the Powertrain Control Module (PCM) detects an abnormal signal or no signal from this sensor, it sets code P0791. Common causes include a faulty sensor, damaged wiring or connectors, low transmission fluid, or internal transmission mechanical issues.
01. Most Common Causes
- Faulty intermediate shaft speed sensor
- Damaged or corroded wiring/connectors
- Low or contaminated transmission fluid
- Internal transmission mechanical failure
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or erratic shifting
- Transmission slipping or delayed engagement
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect transmission fluid level and condition.
Step 3: Visually check sensor wiring and connectors for damage or corrosion.
Step 4: Test sensor resistance and signal output with a multimeter.
Step 5: If sensor and wiring are okay, check for internal transmission issues (requires professional diagnosis).
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the transmission may shift erratically or fail, potentially causing a safety hazard.
How much does it cost to fix?▼
Replacing the sensor typically costs $50-$150 for parts and labor. If internal transmission damage is found, costs can exceed $1,000.