B1629 — PRNDL Reverse Input Short To Battery

OBD2 code B1629 flags a problem with the body electrical system (PRNDL reverse input short to battery). The car is usually drivable while you plan the repair. Common culprits: body control module (BCM) fault, damaged wiring in door jambs or wet areas, blown fuse or failed relay.

body electrical

Is it safe to drive?

Short-term driving is OK Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm B1629 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many B0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the body electrical system for damage, corrosion, chafing or poor contact.
Subsystem check Operate the affected function while watching its switch and motor PIDs in live data.
Subsystem check Inspect connectors and wiring at flex points (door jambs, tailgate hinges) — wires break there first.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm B1629 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1629 (parts and labor, USD, independent shop rates): Repair wiring or connectors: $80–$250; Replace the switch or actuator: $120–$450; BCM repair or replacement: $300–$900. Overall, fixing B1629 usually costs between $80 and $900. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

Will B1629 clear itself?

Sometimes B1629 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

Is it safe to drive with B1629?

Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

How much does it cost to fix B1629?

Repair wiring or connectors — $80–$250; Replace the switch or actuator — $120–$450; BCM repair or replacement — $300–$900. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What are the symptoms of B1629?

Drivers most often notice: warning light on the dashboard, no impact on engine operation in most cases, the affected function (locks, windows, lighting, wipers) works intermittently or not at all.

What is the most common cause of B1629?

The most common causes are: body control module (BCM) fault, damaged wiring in door jambs or wet areas, blown fuse or failed relay.

B1629 is a body electrical fault code that specifically indicates a short-to-battery condition on the PRNDL reverse input circuit. When the body control module or instrument cluster detects that a signal line is receiving battery voltage when it should be grounded (or vice versa), it logs this code after confirming the condition through multiple test cycles. This isn't a one-and-done detection—the module needs to see the fault appear consistently under specific operating conditions before it triggers the warning light and stores the failure in memory.

The PRNDL designation refers to the gear position indicator circuit—essentially the wiring and switches that tell the computer which gear you've selected, including reverse. A short to battery means that somewhere in this circuit, a wire carrying a low-level signal has come into contact with full electrical power. The result is a damaged signal path that the module can no longer interpret correctly. When the ECU logs B1629, it also captures freeze frame data showing engine load, RPM, temperature, and vehicle speed at the moment of failure. Use that snapshot wisely—it tells you exactly what conditions to recreate during your diagnosis.

Common Symptoms of B1629

The check engine light or a dedicated body system warning lamp turns on in the instrument cluster
Reverse lights fail to illuminate when the gear selector is moved to the reverse position
The backup camera display may go blank or show no signal when reverse is engaged
The PRNDL display on the dashboard shows incorrect gear information or goes blank
In most cases, engine performance and drivability remain unaffected
Intermittent operation is common—the problem may come and go before becoming constant

What Causes B1629?

The most frequent culprit is damaged wiring in areas that flex constantly, particularly door jambs and around rear hatch or trunk hinges. Repeated opening and closing causes wire insulation to crack, exposing conductors that eventually short against each other or against chassis ground. Corroded or loose connectors also trigger this code frequently, especially in vehicles exposed to moisture, rain, or car washes where water infiltrates the wiring harness. Faulty switches or actuators within the affected circuit—such as a defective reverse light switch or a worn gear position sensor—can internally short and cause the module to detect battery voltage where it shouldn't exist. Blown fuses and failed relays interrupt the circuit's normal operation and produce similar symptoms. Less commonly, the body control module itself develops an internal fault that produces false short-to-battery readings.

How to Diagnose B1629

Start by connecting an OBD2 scanner and retrieving all stored codes along with their freeze frame data. Document everything before clearing—B1629 and any related codes tell a story about what failed and when. Next, search for technical service bulletins specific to your make, model, and year using your VIN on the manufacturer's website or nhtsa.gov. Many B0xxx code patterns have known factory defects with documented solutions or software updates. Perform a thorough visual inspection of the wiring harness in the rear of the vehicle, focusing on the flex points at door jambs, tailgate hinges, and any areas where wiring passes through metal panels. Look for cracked insulation, burned or melted wires, pushed-out connector pins, and the greenish-white residue of corrosion. Operate the affected function while monitoring relevant PIDs in the scanner's live data stream—watch for proper voltage changes when the circuit activates. If the visual inspection reveals no obvious damage, probe the circuit with a multimeter to check for unexpected resistance or shorts to ground. Finally, clear the code, complete a drive cycle that reproduces the conditions from your freeze frame data, and verify that B1629 does not return before considering the repair complete.

Repair Options and Costs

Tackle the most common and least expensive repairs first before investing in major component replacement. Wiring harness repair or connector replacement typically runs $80 to $250 for parts and labor at an independent shop. Replacing a faulty switch, actuator, or gear position sensor usually costs between $120 and $450 depending on the specific component and vehicle. If diagnosis points to the body control module itself, expect to pay $300 to $900 for BCM repair or replacement, including programming if required. Labor rates vary by region and shop, so these ranges reflect typical US market pricing at independent repair facilities. An accurate diagnosis before purchasing parts is essential—the $80 wiring fix is a much better outcome than an unnecessary $900 control module replacement.

Can You Drive with B1629?

In most vehicles, B1629 does not create an immediate safety hazard since body electrical faults rarely affect engine operation, steering, or braking. However, losing your reverse lights reduces visibility to other drivers when backing up, and a non-functional backup camera adds genuine risk in tight parking situations. There are no drivability concerns such as stalling, poor acceleration, or shifting problems. Use caution in reverse until the underlying cause is identified and repaired, especially at night or in poor weather conditions.