B1629: Reverse Position Switch Circuit Short to Battery
The B1629 code indicates that the vehicle's control module has detected a short to battery voltage in the input circuit for the reverse gear position switch or sensor (part of the PRNDL system). This circuit is responsible for informing the control module which gear the driver has selected. A short to battery means the circuit is receiving constant voltage when it shouldn't, often due to damaged wiring insulation or an internal fault in the transmission range sensor.
1. Commonly Affected Makes
2. Most Common Causes
- Wiring in the reverse input circuit shorted to battery power
- Damaged or internally faulty transmission range (TR) sensor
- Corroded, bent, or moisture-damaged pins in the TR sensor connector
- Faulty control module (rare but possible)
- Aftermarket electrical modifications interfering with the circuit
3. Symptoms You Will Notice
- Check Engine Light or Transmission Warning Light illuminated
- Reverse lights may stay on constantly or not work
- Transmission may not shift properly or get stuck in a gear
- Incorrect gear indication on the dashboard
4. Step-by-Step Diagnosis
Scan for codes and verify B1629 is present
Visually inspect wiring and connector for damage, corrosion, or shorts
Test the reverse switch/sensor circuit for voltage with key on, engine off
Check resistance of the TR sensor according to manufacturer specs
If wiring and sensor check out, test control module input/output
5. Frequently Asked Questions
Is it safe to drive?▼
It is moderately safe for short distances, but driving with this code can cause transmission shifting issues or incorrect gear indication. Have it diagnosed soon to avoid potential transmission damage.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, depending on whether it's a wiring repair (cheaper) or TR sensor replacement (more expensive).