B1628

PRNDL Reverse Input Open Circuit

Body Transmission Control Gear Position Sensor 🟢 Low — Fix at next service ✅ Safe to Drive
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What This Actually Means

In plain language — no jargon

The transmission control module can't detect when you shift into Reverse because the electrical connection to the reverse gear sensor is broken or open. It's like a light switch with a disconnected wire—the signal never reaches the dashboard.

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Symptoms You May Notice

3 known symptoms for this code
Reverse gear not engaging or shifting improperly
Check Engine light or transmission warning light illuminated
Transmission stuck in limp mode or safe mode
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The TCM monitors voltage from the PRNDL (Park, Reverse, Neutral, Drive, Low) position sensor to identify gear selection. When Reverse is selected, the sensor should report a specific voltage signal. An open circuit means zero or no signal is detected.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
PRNDL Reverse Voltage 4.5-5.5V (signal present) <0.5V or no signal detected
Circuit Resistance <10 ohms >10k ohms (open circuit)
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
PRNDL sensor connector
Inspect the connector at the transmission range sensor for corrosion, loose pins, or water damage and reseat firmly.
2
PRNDL wiring harness
Check the wiring between the sensor and TCM for cuts, breaks, or pinched areas along the routing path.
3
PRNDL position sensor
If wiring and connectors are intact, replace the transmission range sensor itself as it may have failed internally.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1628 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code B1628

What happens after you fix the fault

Once the fault is repaired, B1628 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.