OBD-II Code B1299: Power Supply Circuit Short to Ground

What Does B1299 Mean?

B1299 means the Body Control Module (BCM) or Parking Aid Module (PAM) detects a short circuit in the power supply wire for a body electronic system. The power sent to a group of sensors is leaking directly to the vehicle's metal frame (ground) instead of powering the components. This fault almost exclusively affects the parking assist sensors located in the bumpers, causing the entire system to shut down.

Technical definition: The SAE/OBD-II definition is "Power Supply Sensor Circuit Short To Ground". The Parking Aid Module (PAM) sends a shared reference voltage (typically 8 volts) to multiple sensors on a single circuit. If that circuit shorts to ground at any point—in the wiring harness, a corroded connector, or inside a failed sensor—it pulls the entire circuit's voltage to zero, disabling all connected sensors and triggering the code.

Can I Drive With B1299?

Yes, But With Caution. For most vehicles, this code disables convenience features like parking sensors and does not impact the engine, transmission, or braking systems. However, on 2019-2020 Ram 1500s, a related fault causes the park assist system to unexpectedly apply the brakes when no object is present, creating a low-speed safety risk. Disable the park assist system via the dashboard menu until the fault is repaired.

Common Causes

• Damaged or Corroded Bumper Wiring Harness (Very Common) — Parking sensor wiring lives inside the bumpers, exposed to water, road salt, and collision impacts. Insulation frays, moisture penetrates the harness, and previous improper collision repairs (like unsealed wire splices) corrode, causing the 8-volt power wire to short directly to the chassis.
• Failed Parking Sensor (Common) — The electronic components inside a parking sensor fail and create an internal short circuit. Because the sensors share a single power supply line, one internally shorted sensor pulls the voltage down for the entire system.
• Corroded Electrical Connector (Common) — Plastic connectors attaching the wiring to the sensors or the main body harness crack and allow water entry. The metal pins inside corrode, creating a high-resistance short to ground. The main bumper harness connector behind the wheel well liner 🎬 See how to inspect and clean corroded sensor connectors. is the most frequent culprit.
• Control Module Software Glitch (Less Common) — On 2019-2020 Ram 1500s, the B1299 code triggers erroneously due to corrupt sensor data rather than a physical short. Manufacturers issue Technical Service Bulletins (TSBs) to update the Parking Aid Module's software to resolve these false codes.
• Low Battery Voltage (Less Common) — A weak vehicle battery causes low system voltage during startup, triggering random fault codes across various modules, including B1299. Always verify battery health before chasing a wiring short.
• Faulty Trailer Wiring (Less Common) — On trucks and SUVs, damaged wiring on a connected trailer back-feeds into the vehicle's electrical system. A short in the trailer's lighting circuit is sometimes interpreted as a sensor fault by the body control module.
• Failed Control Module (PAM or BCM) (Rare) — The computer module controlling the sensors fails internally. This is rare and must only be considered after thoroughly testing and ruling out all wiring, connectors, and sensors.

Symptoms

• Parking Assist System Inoperative — The parking sensor system shuts down completely. It will not beep or display objects on the infotainment screen when parking.
• Dash Warning Message or Light — A "Check Park Assist" or "Service Parking System" message appears on the instrument cluster, or a dedicated parking aid warning light illuminates.
• Immediate Loud Beep on Selecting Reverse — Systems in vehicles like Volkswagen emit a single, long, loud beep when shifting into reverse to indicate a system fault before disabling it.
• False/Phantom Obstacle Detections — An intermittent short or software glitch causes the system to detect non-existent objects or unexpectedly apply the brakes on certain Ram trucks.
• Check Engine Light (also visible on scanner) — A fault in a body module occasionally triggers the main Check Engine Light or a general malfunction indicator lamp, though this is less common for a 'B' code.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Replace a Failed Parking Sensor — Parts: $20-$150, Labor: $75-$300, ~1.5 hr book time (DIY)
• Repair or Replace Bumper Wiring Harness — Parts: $50-$200, Labor: $150-$400, ~2.5 hr book time (Professional)
• Clean or Replace a Corroded Connector — Parts: $20-$80, Labor: $75-$200, ~1.2 hr book time (Intermediate)
• Control Module Software Update — Parts: $0, Labor: $100-$250, ~1 hr book time (Professional)
• Replace the Parking Aid Module (PAM) — Parts: $150-$600, Labor: $120-$300, ~1.5 hr book time (Professional)

DIY vs Professional

• Replace a Failed Parking Sensor — Beginner: Maybe
  Tools: Trim removal tools, socket set, screwdriver.
• Clean or Replace a Corroded Connector — Beginner: No
  Tools: Wire cutters/strippers, waterproof butt connectors, heat gun, multimeter.
• Repair or Replace Bumper Wiring Harness — Beginner: No
  Tools: Full socket set, trim removal tools, wire routing tools, zip ties.
• Control Module Software Update / Replacement — Beginner: No
  Tools: Manufacturer-specific diagnostic tool (e.g., Ford IDS, Mopar wiTECH).

Used vs. New Parts: Buying Guide

When a used part is worth it: A used OEM sensor from a low-mileage vehicle is a reliable alternative to a new aftermarket part. A used wiring harness makes sense only if it comes from a vehicle with no collision damage and zero signs of corrosion.

Donor-vehicle mileage cap: roughly under 100000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Inspect harness connectors for corrosion and ensure all locking tabs are intact. Avoid harnesses from rust-belt states.
• Verify the part number matches exactly, as different trim levels use different harnesses.
• Ensure the sensor plastic housing is not cracked and the face is free of deep scratches.

Decision logic:

• If The part is a simple parking sensor and budget is a primary concern → Buy a used OEM or new aftermarket sensor; aftermarket sensors are inexpensive and widely available.
• If The part is the main bumper wiring harness → Buy a new OEM or high-quality aftermarket harness. A used harness carries a high risk of hidden corrosion.
• If The vehicle is newer and under warranty or the part is the control module → Always use new OEM parts to ensure compatibility and software integrity.

Warranty tradeoff: Used parts typically have a 30-90 day warranty. New aftermarket parts come with a 1-year to limited lifetime warranty. New OEM parts carry a 1-2 year warranty.

Worst-case if a used part fails: $200-$500 if a used sensor or harness fails after installation, requiring repeat labor costs for bumper removal.

What Happens If You Wait — Timeline

1. Immediate: Code B1299 sets, a 'Service Park Assist' message appears, and the entire parking sensor system disables as a fail-safe. (MPG impact: 0%% · Added cost: $0)
2. 0-3 months: Increased risk of minor parking incidents. Without the audible warning, the driver misjudges distance, leading to scuffs or dents on the bumper. (MPG impact: 0%% · Added cost: $150-$600 (Typical cost for minor bumper scuff or scratch repair).)
3. 3-12 months: On 2019-2020 Ram 1500s, an ignored fault leads to hazardous 'phantom braking' events. For all cars, a persistent short causes a parasitic battery drain. (MPG impact: 0%% · Added cost: $150-$300 (Cost of a new battery and potential tow).)
4. 12+ months: The continuous electrical fault overloads and damages the Park Assist Module (PAM) itself, turning a simple wiring repair into an expensive module replacement. (MPG impact: 0%% · Added cost: $450-$900+ (Cost to diagnose and replace the control module).)

Cost of Not Fixing It

• Immediate: The parking assist system shuts down completely, increasing the risk of low-speed collisions with objects, curbs, or other vehicles. (Added cost: $250-$2000+ (cost of repairing bumper scuffs or a minor collision).)
• 1-6 months: On 2019-2020 Ram 1500 models, ignoring the fault leads to unexpected, erroneous automatic braking events at low speeds. (Added cost: Negligible, unless an incident occurs.)
• 6+ months: A persistent short to ground places a continuous drain on the battery or damages the control module itself. (Added cost: $300-$900 (cost of a new battery and/or control module).)

Diagnosis Steps

1. Read the Trouble Codes
   Use an OBD-II scanner capable of reading Body ('B') codes to confirm B1299 is active. Note any other 'B' or 'C' codes. Multiple sensor codes point to a harness issue, while a single sensor code points to an isolated failure.
   Tools: OBD-II Scanner (with B-code capability) (Beginner)
2. Pro Tip: The Stethoscope 'Click' Test
   Turn the ignition on (engine off), set the parking brake, and shift into reverse. Place a mechanic's stethoscope or your ear directly against each parking sensor. A healthy sensor emits a faint, rhythmic clicking. A silent sensor is internally shorted or disconnected.
   Tools: Mechanic's stethoscope (Beginner)
3. Visually Inspect and Clean Sensors
   Locate the parking sensors on the bumpers. Check for physical damage, pushed-in sensors, or paint bubbling. Clean them thoroughly with soap and water to remove heavy grime or ice causing erratic behavior.
   Tools: Soap, water, soft cloth (Beginner)
4. Inspect the Bumper Wiring Harness and Connectors
   Access the wiring behind the bumper. Unplug each sensor connector and the main bumper harness connector. Look for green or white corrosion, bent pins, or water entry. Inspect the harness for chafing or poorly repaired splices.
   Tools: Flashlight, safety glasses, trim removal tools (Intermediate)
5. Pro Tip: Sensor Swapping for Confirmation
   If the click test identifies a silent sensor, swap it with a known good sensor from a different position on the bumper. Clear the codes and re-scan. If the fault code follows the sensor to the new position, the sensor is definitively faulty.
   Tools: Basic hand tools, OBD-II scanner (Intermediate)
6. Check the System Fuse
   Consult the owner's manual to locate the fuse for the "Parking Aid Module" or "BCM." Visually inspect the fuse to confirm it has not blown due to the short circuit.
   Tools: Owner's manual, fuse puller (Beginner)
7. Pro Tip: Test the Sensor Power Circuit for a Short
   Disconnect the main harness connector at the Parking Aid Module (PAM). Identify the sensor power supply wire using a wiring diagram. Set a multimeter to resistance (Ω) and check for continuity between that pin and a clean chassis ground. A reading below 10,000 ohms (10 kΩ) confirms a short to ground.
   Tools: Multimeter, vehicle wiring diagram, probe adapters (Advanced)
8. Pro Tip: Isolate the Fault by Disconnecting Components
   If a short is confirmed at the PAM connector, keep the multimeter connected. Disconnect each parking sensor one by one. If resistance jumps to infinite (OL) after unplugging a specific sensor, that sensor is shorted. If the short remains with all sensors unplugged, the wiring harness is faulty.
   Tools: Multimeter, basic hand tools (Advanced)
9. Advanced: Test Sensor Voltage and Resistance
   With the ignition on, back-probe the sensor connector. The power supply wire must show a reference voltage (typically 8V). If voltage is absent, the problem is upstream. Disconnect the sensor and measure resistance between its pins; a reading of 0 ohms or infinite (OL) indicates a failed sensor.
   Tools: Multimeter, back-probe kit, vehicle wiring diagram (Advanced)
10. Advanced: Check Live Data PIDs
    Use an advanced scan tool to view the live data stream for the PAM. Monitor the 'Sensor Supply Voltage' PID. A healthy system reads a steady ~8V. A reading of 0V confirms the module detects the short. Monitor individual sensor status PIDs to identify a single malfunctioning unit.
    Tools: Advanced Bi-Directional OBD-II Scanner (Advanced)

When This Code Triggers (Freeze-Frame Conditions)

• System Voltage: 11.5-14.5V (During key-on, engine-off self-test or with engine running.)
• Gear Selector: Reverse (The code sets immediately when the system is activated by selecting reverse gear.)
• Vehicle Speed: 0 mph (Fault is detected during low-speed maneuvering or when stationary.)
• Parking Aid Module Status: Active (The fault logs when the module powers on and attempts to energize the sensor circuit.)

Related Codes

• B1297, B1298, etc. — These codes indicate faults in other sensors in the same system. Seeing a string of these codes together with B1299 strongly suggests a main wiring harness problem affecting the shared power circuit, rather than multiple sensors failing simultaneously.
• B1342 — On Ford vehicles, this code means "ECU is defective." Always diagnose the B1299 short circuit first. The short on the sensor circuit forces the module to falsely report its own failure. Fixing the B1299 fault clears the B1342 code.
• C1700 / C1703 — These are Ford-specific codes for individual sensor circuit failures. B1299 indicates the shared power supply wire is shorted to ground. A C-code points to an issue with a specific sensor's signal wire.
• B1078F0 — This is a Volkswagen-specific code for a parking aid sensor function error. It points to a specific failed sensor causing the entire system to shut down, producing symptoms identical to a B1299 fault.

Climate & Environmental Factors

• Humidity and Rain: Moisture penetrates unsealed connectors or chafed wire insulation, causing copper wire corrosion. This corrosion creates an unintended path to ground, triggering the short circuit code. The fault often appears intermittently after rain or a car wash.
• Cold Weather and Road Salt: Road salt dramatically accelerates corrosion. Salty slush coats the bumper harness and works its way into compromised seals, making the B1299 code significantly more common in 'salt belt' regions.
• Physical Debris: Ice, mud, or heavy dirt buildup on the sensor face causes erratic behavior. While it does not cause a physical short circuit, it produces identical symptoms and must be ruled out by cleaning the sensors first.

How to Talk to a Mechanic About This Code

Say this: "I have an OBD-II code B1299 and my park assist system is inactive. Based on my research, it's likely a short in the bumper wiring harness or a single failed sensor. Can you please start by testing the sensor power supply circuit for a short to ground before recommending any part replacements?"

This signals to the shop that you are an informed customer. It directs them to perform a specific, efficient electrical test rather than starting with expensive, unnecessary steps. It focuses the diagnosis on the most common failure points—wiring and sensors—preventing a premature recommendation to replace the expensive control module.

Avoid saying:

• 'Just fix whatever's wrong'
• 'My park assist doesn't work, can you look at it?'
• 'My car is beeping, I think a sensor is bad.'

Questions to ask before authorizing the repair:

• Did the multimeter test confirm a short to ground on the sensor power circuit?
• How did you isolate the fault? Did the short disappear when you disconnected a specific sensor, or does the problem remain with all sensors unplugged?
• If you are recommending a wiring harness replacement, can you show me the damage or corrosion on the old one?
• If you are recommending a module (PAM/BCM) replacement, can you show me the tests that prove all the sensors and wiring are good?

Where to Take It: Dealer vs Independent vs Chain

• Dealer:
  Best for: Vehicles under warranty., Specific models with known software issues, like the 2019-2020 Ram 1500 which needs a TSB software update., Complex electrical issues requiring proprietary OEM diagnostic tools.
  Downsides: Significantly higher labor rates, often 1.5-2x more than an independent shop., Defaults to replacing an entire assembly (like a full bumper harness) when a simpler repair is possible. (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit for most cases. A reputable independent shop with good electrical diagnostic skills pinpoints a wiring short or bad sensor far more affordably than a dealer.
  Best for: Out-of-warranty vehicles where cost is a factor., Common electrical faults like a B1299, which a skilled technician diagnoses efficiently.
  Downsides: Diagnostic skill varies; vet the shop's reputation for electrical work., Lacks access to the latest manufacturer-specific software for TSB flashes. (Typical cost: +0% vs. baseline)
• Chain Shop: Use with caution. Acceptable for a straightforward sensor replacement, but avoid for diagnosing an unknown intermittent electrical fault.
  Best for: Simple, visible repairs like replacing a physically cracked sensor if you've already diagnosed it yourself.
  Downsides: Technicians lack the advanced electrical diagnostic training needed for an intermittent short., High pressure to upsell leads to recommendations for unnecessary work. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the repair cost exceeds 40% of the car's private-party value, pause. Since B1299 affects a non-essential convenience feature, leaving it unrepaired is a valid third option.

• Car worth $4000, fix is $500: Fix it. The cost is well below the threshold and restores a useful feature.
• Car worth $12000, fix is $900: Fix it. The repair cost is a small fraction of the vehicle's value.
• Car worth $2500, fix is $750: Borderline. Consider how much you value the park assist feature. If you don't need it, live with the fault and save the money.

What Scan Tool You Need for This Code

Minimum: An OBD-II reader that accesses and clears Body ('B') codes from the Body Control Module (BCM) or Parking Aid Module (PAM).

Basic $20 code readers only scan engine modules and will falsely report 'No Codes Found' when a B1299 is active.

Budget: Ancel BD310 or Motopower MP69033 (~$20) — These basic scanners read and clear the B1299 code, which is the first essential step. The Ancel BD310 offers both a corded display and a Bluetooth app.

Mid-range: Innova 5610 or TOPDON ArtiDiag Pro (~$300) — Provides access to live data PIDs from the park assist module, such as 'Sensor Supply Voltage'. This confirms if the voltage is dropping out. Some offer bidirectional controls to test components.

Professional: Autel MaxiCOM MK808S or Launch X431 Series (~$500-1200) — Provides full, dealer-level diagnostics. These tools offer advanced bidirectional controls, access to all manufacturer-specific codes, and module programming capabilities necessary if the PAM requires replacement.

Rent vs buy: Many auto parts stores rent OBD scanners, but you MUST verify their loaner tool reads Body ('B') codes. Buying a mid-range scanner that reads all system codes is a worthwhile investment for DIYers.

How to Clear the Code After You Fix It

1. Use an OBD-II scan tool to clear the code from the Parking Aid Module (PAM) or BCM.
2. Turn the ignition off, then on again.
3. Activate the park assist system by selecting reverse gear or pressing the system button.

Drive cycle (~5 minutes): A specific drive cycle is not required. Turn the ignition on (engine off), set the parking brake, and shift into reverse. If the 'Service Park Assist' message does not reappear and the system provides audible feedback, the repair is successful.

Readiness monitors affected: None

Watch out for:

• Using a basic OBD-II scanner that only clears engine codes (P-codes) will not clear a body code (B-code).
• The code returns immediately if the underlying electrical short is not repaired.
• Forgetting to plug a sensor or the main harness back in causes the code to persist.

Will This Fail Emissions / State Inspection?

No — by itself this code doesn't fail OBD inspection (but it can keep readiness monitors from setting, which causes a separate fail).

• California: A 'B' (Body) code like B1299 does not affect emissions and will not cause a smog check failure. The test focuses on engine (P-codes).
• New York: The NYS inspection checks for an illuminated Check Engine Light. Since B1299 only illuminates a park assist light, it will not cause an emissions failure.
• Texas: The OBD inspection fails a vehicle if the Check Engine Light is on. B1299 will not cause a failure on its own.

Most Commonly Affected Vehicles

• Ford Expedition / E-Series Vans (2009-2014) — Extremely common issue. Diagnosis almost always leads to a faulty bumper harness, a failed sensor, or a corroded main connector.
• Ram 1500 (2019-2020) — B1299 often has a manufacturer-specific meaning of "Signal Shape/Waveform Failure." TSBs 08-082-20 and 08-047-19 advise this code sets erroneously and requires a PAM software update to fix false detections and unexpected braking.
• Chevrolet Volt (2016-2019) — Indicates a circuit fault with a front park assist sensor. Dealer replacement exceeds $900, but DIY replacement is possible by removing the bumper cover.
• Ford Escape (2009-2012) — Shares the same system architecture as other Fords, making it susceptible to shorts in the parking aid sensor power circuit.
• Ford C-Max (2013-2018) — Owners frequently report failures of the rear sensors and wiring after minor rear impacts, leading to system deactivation.
• Lincoln Navigator (2007-2014) — Built on the Ford Expedition platform, it uses the identical Parking Aid Module (PAM) system and suffers from the exact same wiring and sensor faults.
• Volkswagen Tiguan / ID.4 (2018-Present) — A fault in a single parking sensor disables the entire system as a fail-safe measure. A silent sensor during a 'click test' is a strong indicator of the failed component.

Manufacturer-Specific Notes

• Ford / Lincoln / Mercury: Ford consistently defines this as "Power Supply Sensor Circuit Short To Ground" relating to the Parking Aid Module (PAM). Check resistance on the power supply circuit to ground; a reading below 10 kΩ confirms the short.
• Ram / Dodge / Chrysler: On 2019-2020 Ram 1500s, B1299-25 means "Signal Shape/Waveform Failure" and requires a dealer software update per TSB 08-082-20. This is a software glitch causing phantom braking, not a physical short.
• Jeep: On some Jeep models, B1299 refers to an Oxygen Sensor circuit fault. This is an engine management code completely unrelated to body electronics or parking systems.
• Volkswagen / Audi: These brands use other codes (like B1078F0) for a single sensor failure, but the symptom is identical: the entire park assist system shuts down. Diagnosis relies on the 'click test' to find the dead sensor.
• Honda / Acura: B1299 is not a commonly used code. A similar code, P1299, indicates an engine overheating condition. A "Check Parking Sensor System" warning on a Honda is often just a burned-out indicator bulb in the park assist switch.

Real Owner Stories

Ford Expedition with intermittent failure after collision repair

Owner reported B1299 code appeared weeks after the rear bumper was replaced and wiring was repaired by a dealer following a collision.

Outcome: The permanent fix required replacing the entire rear bumper wiring harness to eliminate the faulty splice.

Lesson: After a collision repair, an intermittent electrical fault points to a poor-quality splice. Insist on a full harness replacement over a simple wire splice.

2019 Ram 1500 with B1299-25 and multiple sensor codes

Truck displayed a 'Service ParkSense' message. A scan revealed code B1299-25 (Signal Shape/Waveform Failure) alongside codes for adjacent sensors.

Outcome: The owner discovered a Ram Technical Service Bulletin (TSB) for erroneous sensor codes. A dealer software update for the Park Assist Module (PAM) resolved all codes without replacing parts.

Lesson: For 2019-2020 Ram 1500s, a B1299-25 code strongly indicates the need for a dealer software update per the TSB before attempting physical repairs.

2017 Chevy Volt with intermittent front sensor fault

The park assist system faulted intermittently, specifically when it rained or when the car's nose dipped during braking.

Outcome: The intermittent nature pointed to a failing sensor. The owner replaced the front left corner sensor, permanently fixing the problem.

Lesson: An intermittent fault that changes with weather (rain) is a classic sign of moisture in a connector or an internally failing sensor. The 'click test' confirms if a sensor is dead.

How to Prevent This Code From Triggering

• Regularly Clean Sensors (Monthly or after off-roading/snow) — Keeps the sensor faces free of mud, ice, and road grime. Dirt causes erratic behavior and phantom detections that mimic electrical faults.
• Apply Dielectric Grease to Connectors (Whenever a connector is unplugged for service) — Dielectric grease seals electrical connectors from moisture and oxygen, preventing water intrusion and corrosion—the primary cause of shorts in the bumper harness.
• Inspect and Secure Bumper Harness (During tire rotations or underbody service) — Ensures the wiring harness behind the bumper is properly secured. A dangling harness chafes against the vehicle frame, wearing through the insulation and causing a short.
• Use Waterproof Splices for Repairs (During any wiring repair) — Never use simple butt connectors or electrical tape. Heat-shrink butt connectors with an inner adhesive lining melt to create a waterproof seal, protecting the splice from corrosion.

Frequently Asked Questions

Can I fix a B1299 code myself?

Yes, this is a manageable DIY repair. Replacing a dirty sensor or blown fuse is a beginner-level fix. Removing the bumper cover to replace a sensor or harness requires intermediate skills to avoid damaging paint or clips.

How much does it cost to fix B1299?

A DIY fix costs under $30 for an aftermarket sensor. A professional repair shop charges $150 to $450 for diagnosis and replacement. Dealerships charge significantly more, with a single sensor replacement on a Chevy Volt exceeding $900.

Will clearing the code make it go away?

No. You can clear the code with a scanner, but it returns instantly the next time the module runs its self-test if the electrical short still exists.

What does the '-25' mean in a Ram B1299-25 code?

The '-25' is a Failure Type Byte (FTB) specifying a 'Signal Shape/Waveform Failure.' For 2019-2020 Ram trucks, this indicates corrupt sensor data rather than a physical short. This points directly to a software issue requiring a dealer update per TSB 08-082-20.

My parking sensors work sometimes and not others. Could this still be B1299?

Yes, an intermittent fault is a classic B1299 symptom. Loose connections, frayed wires touching metal on bumps, or moisture entering a connector after a car wash cause these temporary shorts.

Can a bad battery cause a B1299 code?

Yes. A weak battery causes low voltage conditions during startup, triggering glitches in electronic modules. Always verify battery health before performing complex electrical diagnostics.

What is the easiest way to test parking sensors?

Put the car in reverse with the engine off and ignition on, then listen closely to each sensor. A working sensor makes a faint, audible clicking or buzzing noise. A silent sensor is internally shorted or disconnected.

Key Takeaways

• Code B1299 indicates a direct short to ground on the 8-volt power supply line shared by the bumper parking sensors.
• Water intrusion and road salt corroding the main bumper wiring harness cause over 80% of B1299 faults.
• A B1299 code disables park assist and triggers unexpected automatic braking on 2019-2020 Ram 1500 trucks.
• Perform the 'click test' by listening to each sensor in reverse; a silent sensor instantly identifies the internally shorted unit.
• Owners of 2019-2020 Ram 1500s must check TSB 08-082-20, which resolves erroneous B1299-25 codes via a dealer software update.