What Does B1629 Mean?
This code indicates that the Body Control Module (BCM) or Transmission Control Module (TCM) has detected an abnormal voltage condition on the PRNDL (gear position) reverse input circuit. Specifically, the reverse position sensor signal wire is reading battery voltage (typically 12-14V) when it should be reading a lower reference voltage or ground. This suggests the reverse circuit wire is shorted to a positive voltage source, preventing accurate detection of the transmission being in reverse gear.
Common Causes
45%
Damaged or chafed wiring harness causing the reverse position sensor signal wire to contact battery voltage
30%
Failed or internally shorted transmission range sensor (PRNDL switch) with reverse circuit compromised
15%
Corroded or damaged connector pins at the transmission range sensor causing short to adjacent powered circuits
10%
Faulty BCM or TCM with internal circuit failure on reverse input channel
Diagnostic Steps
1
Step 1: Perform a visual inspection of the transmission range sensor connector and wiring harness from sensor to control module, looking for damaged insulation, pinched wires, corrosion, or evidence of water intrusion
2
Step 2: Using a digital multimeter, backprobe the reverse signal circuit at the transmission range sensor connector with ignition ON and transmission in Park, measure voltage (should read 0-0.5V typically). Then shift to Reverse and verify the expected voltage change per manufacturer specifications
3
Step 3: Disconnect the transmission range sensor connector and measure resistance between the reverse circuit pin and battery positive terminal with ignition OFF (should read infinite/OL resistance indicating no short). If continuity exists, trace and repair the short in the harness
4
Step 4: If wiring tests pass, substitute or test the transmission range sensor by measuring internal resistance values across all position circuits per service manual specifications to identify internal short condition
5
Step 5: Clear codes, cycle through all gear positions multiple times, and monitor live data for reverse signal voltage to confirm repair. Verify backup lights, reverse lockout solenoid, and transmission shift behavior function properly
Estimated Repair Cost
$100 - $650
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) or Transmission Control Module (TCM) has detected an abnormal voltage condition on the PRNDL (gear position) reverse input circuit. Specifically, the reverse position sensor signal wire is reading battery voltage (typically 12-14V) when it shoul...
The most common cause of B1629 (PRNDL Reverse Input Short To Battery) is: Damaged or chafed wiring harness causing the reverse position sensor signal wire to contact battery voltage
Typical repair costs for B1629 range from $100 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is generally safe to drive but may experience transmission shift quality issues, backup lights may not function, and reverse inhibit safety features may be disabled. Repair within one week to restore proper transmission operation and safety systems.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1629 to identify the root cause.
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Quick Info
Category
Body
System
Transmission Control System / Shift Position Sensing
Difficulty
Type
Manufacturer
Recommended Tools
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