What Does B1991 Mean?
This code indicates that the body control module (BCM) or seat control module has detected an abnormal voltage condition in the power seat's forward/rearward position potentiometer feedback circuit. The circuit is showing a voltage level consistent with a direct connection to battery voltage (typically 12-14V) when it should be reading a lower reference voltage (typically 0-5V). This suggests a short circuit condition between the signal wire and a power source, preventing accurate position sensing of the seat track.
Common Causes
45%
Damaged or chafed wiring harness in seat track mechanism causing signal wire to contact power wire
30%
Failed potentiometer sensor internal short to power supply within the seat position sensor assembly
15%
Corroded or damaged connector pins causing cross-circuit contamination between power and signal circuits
10%
Faulty seat control module with internal circuit failure causing voltage bleed to sensor circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of seat track wiring harness, checking for pinched, chafed, or damaged wires especially at seat mounting points and track rails where movement occurs. Look for exposed copper or damaged insulation.
2
Step 2: Disconnect the seat position potentiometer connector at the seat track and measure voltage on the signal wire terminal (vehicle side) with ignition on using a digital multimeter - reading should be 0V with connector disconnected; if battery voltage (12V+) is present, wiring harness has short to power
3
Step 3: With potentiometer disconnected, measure resistance between the signal pin (sensor side) and the power supply pin on the potentiometer - should read open circuit (OL) or very high resistance; low resistance indicates internal sensor short
4
Step 4: Inspect all connectors in the seat control circuit for corrosion, pushed-out pins, or moisture contamination using electrical contact cleaner and magnification; check connector pin tension and sealing
5
Step 5: If wiring and sensor test good, check for voltage bleed at the control module connector by backprobing the signal circuit with module connected and seat stationary - should read stable 0.5-4.5V range, not battery voltage
6
Step 6: Clear codes, cycle seat through full range of motion while monitoring live data for position sensor voltage; verify voltage remains within normal range (0.5-4.5V) and changes smoothly without jumping to battery voltage
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates that the body control module (BCM) or seat control module has detected an abnormal voltage condition in the power seat's forward/rearward position potentiometer feedback circuit. The circuit is showing a voltage level consistent with a direct connection to battery voltage (typica...
The most common cause of B1991 (Pedal Forward / Rearward Potentiometer Feedback Circuit Short to Battery) is: Damaged or chafed wiring harness in seat track mechanism causing signal wire to contact power wire
Typical repair costs for B1991 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 operation or safety and the vehicle can be driven normally. The power seat may not function correctly or may be stuck in position, which could affect driver comfort and proper seating position for airbag deployment.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1991 to identify the root cause.
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Quick Info
Category
Body
System
Body Control/Power Seat System
Difficulty
Type
Manufacturer
Recommended Tools
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