B1991: Pedal Forward / Rearward Potentiometer Feedback Circuit Short to Battery

Definition

The OBD2 code B1991 indicates a malfunction in the pedal forward/rearward potentiometer feedback circuit, specifically a short circuit to the battery, which can affect the proper functioning of the accelerator or brake pedal position sensors

Common causes

Shorted wiring or connectors in the potentiometer circuit
Faulty pedal position sensor
Corroded or damaged electrical connections
Grounding issues in the circuit
Malfunctioning engine control module (ECM) or body control module (BCM)

Common misdiagnoses

Faulty accelerator pedal position sensor
Wiring issues or shorts in the harness
Malfunctioning engine control module (ECM)
Incorrectly calibrated throttle position sensor
Issues with the brake pedal position sensor
Problems with the vehicle's body control module (BCM)
Faulty connectors or terminals in the circuit

Troubleshooting steps

1. Scan Tool Verification
2. Use an OBD-II scanner to confirm the presence of the B1991 code. Check for any additional codes that may provide more context
3. Visual Inspection
4. Inspect the wiring and connectors associated with the accelerator pedal position sensor (potentiometer). Look for signs of damage, corrosion, or loose connections
5. Check for any frayed wires or shorts to the battery or ground
6. Check the Potentiometer
7. Test the accelerator pedal position sensor (potentiometer) for proper operation. This can often be done with a multimeter
8. Measure the resistance across the potentiometer terminals while moving the pedal. The resistance should change smoothly without any dropouts or erratic readings
9. Inspect the Circuit
10. Use a wiring diagram to trace the circuit from the potentiometer to the engine control module (ECM). Check for continuity and shorts in the wiring
11. Look for any signs of wear or damage in the harness that could cause a short to battery voltage
12. Check Power and Ground
13. Verify that the potentiometer is receiving the correct voltage from the power source. Use a multimeter to check for battery voltage at the sensor connector
14. Ensure that the ground connection for the potentiometer is solid and free of corrosion
15. Test the ECM
16. If the potentiometer and wiring are functioning correctly, the issue may lie with the ECM. Check for any software updates or known issues with the ECM related to this code
17. If possible, test the ECM with a known good unit to see if the problem persists
18. Clear Codes and Test Drive
19. After performing repairs or replacements, clear the trouble codes using the OBD-II scanner
20. Take the vehicle for a test drive to see if the code returns. Monitor the pedal position readings with the scanner to ensure they are within expected parameters
21. Consult Technical Service Bulletins (TSBs)
22. Check for any TSBs related to the B1991 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations
23. Professional Help
24. If the issue persists after following these steps, consider seeking assistance from a professional mechanic or dealership, as they may have specialized tools and knowledge to diagnose the problem further. By following these steps, you should be able to identify and resolve the issue related to the B1991 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Scan Tool Verification

2. Use an OBD-II scanner to confirm the presence of the B1991 code. Check for any additional codes that may provide more context

3. Visual Inspection

4. Inspect the wiring and connectors associated with the accelerator pedal position sensor (potentiometer). Look for signs of damage, corrosion, or loose connections

5. Check for any frayed wires or shorts to the battery or ground

6. Check the Potentiometer

7. Test the accelerator pedal position sensor (potentiometer) for proper operation. This can often be done with a multimeter

8. Measure the resistance across the potentiometer terminals while moving the pedal. The resistance should change smoothly without any dropouts or erratic readings

9. Inspect the Circuit

10. Use a wiring diagram to trace the circuit from the potentiometer to the engine control module (ECM). Check for continuity and shorts in the wiring

11. Look for any signs of wear or damage in the harness that could cause a short to battery voltage

12. Check Power and Ground

13. Verify that the potentiometer is receiving the correct voltage from the power source. Use a multimeter to check for battery voltage at the sensor connector

14. Ensure that the ground connection for the potentiometer is solid and free of corrosion

15. Test the ECM

16. If the potentiometer and wiring are functioning correctly, the issue may lie with the ECM. Check for any software updates or known issues with the ECM related to this code

17. If possible, test the ECM with a known good unit to see if the problem persists

18. Clear Codes and Test Drive

19. After performing repairs or replacements, clear the trouble codes using the OBD-II scanner

20. Take the vehicle for a test drive to see if the code returns. Monitor the pedal position readings with the scanner to ensure they are within expected parameters

21. Consult Technical Service Bulletins (TSBs)

22. Check for any TSBs related to the B1991 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations

23. Professional Help