B1991

Code

Other B — Body

Pedal Forward / Rearward Potentiometer Feedback Circuit Short to Battery

Brand: Other

Type: B — Body

Views: UK: 17 EN: 37 RU: 20

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Shorted signal wire to vehicle battery voltage (pin contact with power source)
Damaged/chafed harness or pinched wiring contacting a 12V source
Corroded or loose connector terminal causing unintended connection to battery feed
Failed pedal module (internal potentiometer short)
Water intrusion or contamination in pedal connector
Aftermarket wiring or recent repairs that disturbed harness routing

Symptoms

Malfunction Indicator Lamp (MIL) or fault warning illuminated
Adjustable pedal may not move or will not store/recall position
Reduced pedal function or protective limp mode for adjustable pedal circuit (vehicle may reduce related features)
Stored B1991 code (and possibly related pedal or communication codes)
Pedal position displayed in scan tool may read high/constant near battery voltage and not change with pedal movement

What to check

Use a scan tool: read/record freeze frame and live data for forward/rearward pedal potentiometer values while operating the pedal
Visually inspect pedal module connector and wiring harness from pedal to body/ECU for damage, pinched areas, chafing, or corrosion
With ignition ON (engine OFF) measure voltage on the potentiometer signal wire — a healthy signal is typically a variable 0–5V range; a constant voltage near battery (~12V) suggests a short to battery
Backprobe connector with harness connected and operate pedal to observe signal change
If safe, disconnect pedal module connector and re-check voltage on harness signal: if high voltage remains, the short is in wiring/vehicle harness; if voltage drops or is absent, the module is likely faulty
Check continuity between signal wire and fused battery feeds; check for unintended continuity to power circuits

Signal parameters

Expected: variable analog signal typically ~0–5 VDC that changes smoothly with pedal movement
Fault condition: signal held at/near battery voltage (approx. vehicle battery voltage ~12 V) or a fixed high voltage above normal operating range
Good correlation: two or more potentiometer reference signals (if present) should change together; mismatch indicates internal sensor failure

Diagnostic algorithm

Read and record DTCs and freeze frame data with a scan tool. Note related codes.
Visually inspect pedal assembly, connector, and wiring for damage, corrosion, water entry, or loose terminals.
With ignition ON (engine OFF), backprobe the forward/rearward potentiometer signal wire at the connector and measure voltage while an assistant moves the pedal. Expect a variable 0–5 V signal; a steady high voltage near battery indicates a short to battery.
Disconnect the pedal module connector. Re-measure the harness signal wire voltage. If the high voltage remains with the module disconnected, trace and repair harness or connector short to a fused power source. If the high voltage disappears, suspect the pedal module is internally shorted.
Perform a continuity/resistance check (engine OFF, connectors disconnected) between the signal wire and vehicle battery feed to confirm unintended continuity. Also check for continuity to other power wires that could cause a short.
If harness/connector damage is found, repair or replace the wiring and restore proper routing and insulation. If the pedal module is at fault, replace the module per manufacturer procedure.
After repair, clear codes, retest with scan tool and perform functional test of adjustable-pedal operation. Verify no reappearance of the fault.
If replacement or major wiring repair was performed, follow any required calibration or relearn procedures for the pedal module per manufacturer instructions.

Likely causes

Insulation breach on the forward/rearward potentiometer signal wire contacting a 12V feed
Failed potentiometer inside the adjustable-pedal module creating an internal short to the module’s power supply
Connector contamination or bent terminal connecting signal to battery feed
Harness routed near high-voltage conductors or fused power lead that rubbed through

Fault status

⚠️ Status

Stored when the pedal forward/rearward potentiometer feedback circuit voltage is detected above the normal operating range (shorted to battery). The control module sets B1991, may disable adjustable pedal function, and will store related freeze-frame data.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.8-2.0 hours