What Does B1291 Mean?
This code indicates the body control module (BCM) has detected a short to ground condition in the potentiometer circuit of the right side air intake servo motor. The servo motor uses a potentiometer to provide position feedback while controlling airflow distribution in the HVAC system. The BCM detected abnormally low voltage on the feedback circuit, indicating the signal wire is shorted to chassis ground or the potentiometer itself has failed internally.
Common Causes
45%
Damaged or chafed wiring harness causing short to ground between BCM and servo motor potentiometer
35%
Failed servo motor with internal potentiometer short to ground
15%
Corroded or moisture-damaged connector terminals creating ground path
5%
Failed body control module with internal circuit fault
Diagnostic Steps
1
Step 1: Perform visual inspection of the right air intake servo motor location, wiring harness routing, and connectors for obvious damage, chafing against metal surfaces, water intrusion, or corrosion. Pay special attention to areas where harness passes through firewall or near sharp edges.
2
Step 2: Disconnect the right air intake servo motor connector and measure resistance between the potentiometer signal wire (consult wiring diagram for specific pin) and chassis ground using a digital multimeter. Reading should be infinite (open circuit). If resistance is low (under 10 ohms), wiring harness is shorted to ground.
3
Step 3: With servo motor still disconnected, measure resistance across the potentiometer terminals on the servo motor itself while manually rotating the actuator shaft through its range. Resistance should vary smoothly between approximately 1-5k ohms without dropping to zero. Also check resistance from each potentiometer terminal to motor housing ground - should be infinite. Low or zero readings indicate failed servo motor.
4
Step 4: If wiring and servo motor test good, inspect BCM connector terminals for corrosion, bent pins, or moisture. Measure voltage at BCM side of disconnected servo harness - potentiometer reference voltage should be present (typically 5V). If reference voltage is absent or shorts to ground when connector is plugged in, BCM may be faulty.
5
Step 5: After repairs, clear codes, operate HVAC system through all modes and temperature settings while monitoring live data for proper servo motor position feedback. Verify code does not return and right side air distribution operates correctly.
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the body control module (BCM) has detected a short to ground condition in the potentiometer circuit of the right side air intake servo motor. The servo motor uses a potentiometer to provide position feedback while controlling airflow distribution in the HVAC system. The BCM detec...
The most common cause of B1291 (Servo Motor Potentiometer Airintake Right Circuit Short To Ground) is: Damaged or chafed wiring harness causing short to ground between BCM and servo motor potentiometer
Typical repair costs for B1291 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This fault does not affect vehicle safety or drivability and the vehicle can be driven normally. HVAC air distribution on the right side may not function properly, potentially affecting cabin comfort and windshield defrost effectiveness on that side.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1291 to identify the root cause.
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Quick Info
Category
Body
System
HVAC Climate Control System
Difficulty
Type
Manufacturer
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