What Does B1630 Mean?
This code indicates the body control module (BCM) or transmission control module (TCM) has detected an abnormal short-to-ground condition in the reverse position input circuit of the transmission range sensor (PRNDL switch). The PRNDL switch communicates gear selector position to various vehicle systems, and this fault specifically affects the reverse gear signal circuit. The control module detected voltage lower than expected on the reverse input circuit, indicating an electrical short to ground somewhere in the wiring or switch assembly.
Common Causes
40%
Damaged or chafed wiring harness between transmission range sensor and control module causing short to ground
30%
Failed or internally shorted transmission range sensor (PRNDL switch)
20%
Corroded or moisture-contaminated connector terminals at transmission range sensor
10%
Failed body control module or transmission control module with internal circuit fault
Diagnostic Steps
1
Step 1: Perform visual inspection of transmission range sensor connector and wiring harness from sensor to control module, looking for damaged insulation, pinched wires, corrosion, or signs of moisture intrusion. Pay special attention to areas where harness passes near sharp edges or heat sources.
2
Step 2: Disconnect transmission range sensor connector and inspect terminals for corrosion, pushed-back pins, or damage. Using a digital multimeter set to resistance mode, check continuity between the reverse circuit pin (consult wiring diagram for specific pin) at the sensor connector and known good ground - should read open circuit (infinite resistance).
3
Step 3: With sensor disconnected, check resistance between the reverse signal wire at the control module connector and chassis ground using multimeter - should read open circuit. If continuity to ground exists, locate and repair short in wiring harness between sensor and module.
4
Step 4: If wiring tests normal, reconnect sensor and measure voltage on reverse circuit wire at sensor connector with transmission in Park using multimeter - should see reference voltage (typically 5V or 12V depending on system design). Shift to Reverse and measure again - voltage should change per manufacturer specification.
5
Step 5: If voltage readings are abnormal with known-good wiring, replace transmission range sensor. If sensor and wiring test normal but code persists, perform control module power and ground circuit verification, then consider control module replacement as last resort.
6
Step 6: After repair, clear codes, cycle transmission through all gear positions multiple times, and road test vehicle to verify reverse gear engagement and backup lights function properly with no code return.
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the body control module (BCM) or transmission control module (TCM) has detected an abnormal short-to-ground condition in the reverse position input circuit of the transmission range sensor (PRNDL switch). The PRNDL switch communicates gear selector position to various vehicle sys...
The most common cause of B1630 (PRNDL Reverse Input Short Circuit To Ground) is: Damaged or chafed wiring harness between transmission range sensor and control module causing short to ground
Typical repair costs for B1630 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may not start in any gear or may start in gears other than Park/Neutral creating a safety hazard. Backup lights and reverse camera may not function, and transmission may exhibit improper shift quality or enter limp mode. Repair should be completed promptly to ensure proper transmission operation and safety system functionality.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1630 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Body
System
Transmission Control System
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
