Dodge-specific code — factory diagnostic data| DTC Data Sheet | |
| System | Body |
| Standard | Manufacturer Specific |
| Fault type | Circuit High |
| Official meaning | Reverse lamp control circuit high |
Definition source: Dodge factory description · Autel MaxiSys Ultra & EV. Diagnostic guidance is based on factory-defined fault logic for this code.
B1668 means your Dodge Charger has a problem controlling the reverse lamps, and the backup lights may stay on or act wrong. That matters for safety because other drivers rely on your reverse lights. This is a Dodge manufacturer-specific body code, so its exact logic can vary by platform. According to Dodge factory diagnostic data, this code indicates the reverse lamp control circuit is reading “high.” In plain terms, the body controller sees the reverse lamp control line sitting higher than it. That points to a wiring, connector, lamp, or module driver issue, not an automatic parts failure.
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B1668 Quick Answer
B1668 on a Dodge Charger means the reverse lamp control circuit is stuck high when the module expects it to be low. Start by checking reverse lamp operation, then verify the control wire for a short to power or a failed driver.
What Does B1668 Mean?
Official definition: “Reverse lamp control circuit high.” The module that controls body lighting has detected an abnormally high signal on the reverse lamp control circuit. In practice, the reverse lamps may stay on, come on at the wrong time, or the system may disable the output to protect the circuit.
What the module checks and why it matters: The controller monitors the commanded state of the reverse lamp output versus the electrical feedback it “sees” on that control line. A “circuit high” fault sets when the line remains high when the module expects a low state. That usually points to a short to battery voltage, backfeeding through a bulb/socket issue, high resistance on the ground side that raises the circuit voltage, or an internal output driver problem. Use circuit tests to prove which condition exists before replacing any parts.
Theory of Operation
Under normal conditions, the body controller supplies or switches power to the reverse lamps when the vehicle reports Reverse selected. Depending on Dodge platform design, the controller may switch power on the feed side or switch the ground side. The module also monitors the output for plausibility so it can detect shorts, opens, and overloads.
With B1668, the controller sees the reverse lamp control circuit stay at a high electrical state when it should sit low. A short to power can hold the line high even with the lamps commanded off. Backfeed can also do it, especially with incorrect bulbs, damaged sockets, or trailer wiring splices. A failed output transistor inside the module can also keep the circuit high, but only after you verify wiring integrity and load behavior.
Symptoms
These symptoms match a reverse lamp control circuit that the module interprets as stuck high.
- Reverse lamps stay on with the shifter not in Reverse
- Reverse lamps come on intermittently, especially over bumps
- No reverse lamps if the module shuts the output down for protection
- Message/indicator body or lamp warning displayed, depending on cluster strategy
- Battery drain from reverse lamps staying powered
- Trailer lights behave abnormally if a trailer harness backfeeds the circuit
- DTC pattern B1668 resets immediately after clearing if the circuit remains high
Common Causes
- Short to battery voltage on the reverse lamp control wire: Contact with a B+ feed or chafed insulation forces the control circuit high even when the module commands it off.
- Backfeed through a damaged bulb, socket, or lamp assembly: Melted terminals or incorrect internal connections let another lighting feed energize the reverse circuit.
- Incorrect bulb type or aftermarket LED without proper load control: Some replacements create unintended backfeed paths or voltage behavior that looks like a stuck-high circuit.
- Water intrusion at the rear lamp connector: Moisture and corrosion bridge terminals and raise the control circuit voltage unexpectedly.
- Harness damage at the trunk hinge or rear body pass-through: Repeated flexing breaks insulation and lets the circuit touch adjacent power wires.
- Reverse lamp relay stuck closed (if equipped on the platform): A welded relay contact keeps the lamps powered and holds the control side high.
- Miswired trailer wiring or splice-in towing connector: Poor aftermarket splices often tie the reverse feed into another circuit and drive the control line high.
- Module output driver fault (BCM/TIPM logic varies by platform): An internal driver can fail and bias the output high, but only after you prove the external circuit integrity.
Diagnosis Steps
You need a scan tool that reads Dodge body codes and shows data and output controls. Use a DVOM, a fused test light, and basic backprobe leads. Have wiring diagrams for the Charger lighting circuits. A pin-fit tool and contact cleaner help at the rear lamp connectors. Plan to perform voltage-drop tests with the lamps commanded on.
- Confirm B1668 and record freeze frame data. Focus on battery voltage, ignition state, gear selector state, and any related lighting or transmission range codes. Freeze frame shows conditions when the fault set. Use a scan tool snapshot during a road test to capture an intermittent spike that does not set a code.
- Check fuses and power distribution first, then do a fast visual inspection of the reverse lamp circuit path. Look at reverse lamp fuses, any lighting relays, trailer wiring taps, and the rear lamp housings. A circuit-high fault often comes from a rub-through near power feeds. Do not start by unplugging modules.
- Verify module power and ground under load before chasing the output. Turn the reverse lamps on with a scan tool output control or by selecting reverse safely with the wheels blocked. Perform a voltage-drop test on the module ground path while the circuit operates. Keep ground drop under 0.1V during operation, or repair the ground connection first.
- Check the reverse lamps for abnormal behavior. Note if they stay on with the ignition off, flicker, or come on with other lamps. That pattern points to a stuck relay, a backfeed, or a cross-short. Document exactly when the lamps illuminate.
- Inspect the rear lamp connectors and sockets on the Charger closely. Pull the connectors and look for green corrosion, overheated terminals, spread pins, or water trails. Tug lightly on each wire near the connector. Repair any pin-fit issues before electrical testing.
- Isolate the load to see if the fault clears. Disconnect both reverse lamp connectors, then clear codes and cycle the ignition. If B1668 returns immediately with the lamps unplugged, the issue sits in the harness, relay control, or module output. If the code stays away, a lamp assembly, socket, or bulb choice likely backfeeds the circuit.
- Test the control circuit for a short to B+. Keep the reverse lamps commanded off. Measure voltage on the reverse lamp control wire to ground at an accessible connector in the rear harness. A steady battery-level reading with the command off indicates a short to power or a stuck feed path. Unplug intermediate connectors and any trailer harness to find the section that drops the voltage.
- Load-test the suspect wire instead of relying on continuity. With the circuit off, connect a fused test light from the control wire to ground to provide a load. If the test light glows strongly, the wire receives power from an unintended source. Wiggle the harness at the trunk hinge and body pass-through while watching the light for changes.
- If the platform uses a relay for reverse lamps, verify relay control and contacts. Remove the relay and check whether the lamps go out. If they stay on, power backfeeds through wiring or lamp assemblies. If removing the relay stops the lamps, test for a welded contact and check why the relay coil receives power when it should not.
- Verify the command and feedback logic with scan data. Use the scan tool to monitor the reverse lamp command state and any available output status PID while switching between reverse and other ranges. If the module commands off but the circuit voltage stays high, the circuit has an external feed or a stuck driver. If the command toggles incorrectly, investigate the range input source that the module uses on this Dodge platform.
- Confirm the repair. Clear codes and run the same conditions shown in freeze frame. Command the lamps on and off several times and perform a short drive to cover bumps and harness movement. Make sure B1668 stays out of pending and stored memory. If the code sets as pending only, repeat the drive cycle to confirm it does not mature into a stored fault.
Professional tip: Many Dodge reverse lamp “circuit high” problems come from backfeed, not an open wire. A corroded socket can connect two lamp circuits internally. Unplugging the lamp assemblies early saves time. Always use a loaded test, because a high-resistance short can hide on a DVOM.
Possible Fixes
- Repair chafed wiring and restore proper routing: Fix rubbed insulation at the trunk hinge, rear body pass-through, or near splices, then secure the harness away from sharp edges.
- Clean or replace damaged rear lamp connectors and sockets: Remove corrosion, correct terminal tension, and replace overheated pigtails that create backfeed paths.
- Correct bulb and lamp assembly issues: Install the proper bulb type and repair or replace a lamp assembly that internally shorts or cross-feeds circuits.
- Remove or rewire faulty trailer wiring splices: Eliminate backfeed by repairing poor taps and using correct isolation methods for towing connections.
- Replace a stuck reverse lamp relay when testing proves it: Replace the relay only after you verify welded contacts or improper coil control.
- Address module output driver concerns only after circuit proof: If the control wire stays high with loads unplugged and harness isolated, follow Dodge service information for module output testing and replacement steps.
Can I Still Drive With B1668?
You can usually drive a Dodge Charger with B1668, but you should treat it as a safety-related body fault. This manufacturer-specific Dodge code means the reverse lamp control circuit reads “high,” so the vehicle may lose reverse lights or leave them on. Either condition creates risk. Other drivers may not see you backing up, or they may think you are backing up when you are not. Park using extra caution. Use mirrors and a spotter when possible. Avoid backing in dark areas until you confirm proper reverse lamp operation.
How Serious Is This Code?
B1668 ranges from an inconvenience to a real safety problem. If the reverse lamps simply do not work, the car still drives normally, but your visibility to others drops. If the reverse lamps stay on, the situation becomes more serious. It can confuse traffic behind you and cause unwanted battery draw when parked. On many Dodge platforms, the reverse lamp command comes from a body module that decides when to energize the lamp driver or relay. A “circuit high” fault points to an electrical condition, not a confirmed failed module. Treat it as urgent if lamps act abnormal, the battery drains, or multiple body codes appear.
Common Misdiagnoses
Technicians often replace the reverse bulbs first, then stop when the code returns. Bulbs rarely cause a “circuit high” condition at the control side. Another common miss involves checking only for power, not for an unintended power feed. A backfed voltage from trailer wiring, an aftermarket alarm/remote start, or a mispinned connector can hold the control circuit high. Shops also overlook testing under load. A corroded socket can pass a voltmeter check and still fail the circuit when current flows. Avoid wasted parts by verifying the module command state, then proving whether the circuit stays high because of wiring, a relay, or a driver output.
Most Likely Fix
The most frequently confirmed repair direction involves correcting an unintended voltage on the reverse lamp control circuit. Start at the rear lamp harness and any splices. Look for chafing, water intrusion, and non-factory taps. Many repairs end with cleaning and repairing the lamp socket or connector, then restoring proper grounds so the circuit no longer floats high. If the circuit stays high with the rear harness disconnected, focus forward. A stuck reverse lamp relay, a short to battery in the control wire, or a body module output held high by backfeed are common findings. Verify each with isolation testing before replacing any module.
Repair Costs
Repair cost depends on whether the confirmed root cause is a sensor, wiring, connector issue, or control module problem. Verify the fault electrically before replacing parts.
| Repair Type | Estimated Cost |
|---|---|
| Basic DIY inspection | $0 – $50 |
| Professional diagnosis | $100 – $180 |
| Wiring / connector repair | $80 – $350+ |
| Actuator / motor / module repair | $100 – $600+ |
Key Takeaways
- B1668 on Dodge: This manufacturer-specific code flags a reverse lamp control circuit that reads high.
- Safety first: Reverse lamps affect how others judge your vehicle movement.
- Prove the fault: Confirm whether the circuit stays high with loads disconnected.
- Backfeed matters: Aftermarket wiring and trailer adapters often hold the circuit high.
- Don’t guess modules: Verify wiring, relay logic, and grounds before any control module replacement.
FAQ
Can a bad reverse bulb cause B1668 on a Dodge Charger?
A failed bulb usually causes an open-load issue, not a “circuit high” condition. B1668 points to the control side reading higher than expected. Start by checking whether reverse lamps behave wrong. Then unplug the rear lamp connector and recheck the circuit state. If the circuit still reads high, the bulb and socket are not the root cause.
What quick test confirms whether the problem is in the rear of the car or forward wiring?
Disconnect the rear lamp assemblies or the rear harness connector, then command reverse and watch the reverse lamp output status on a scan tool. Also check the control wire for unwanted voltage with the load unplugged. If the circuit stays high with the rear unplugged, the fault sits forward, at wiring, a relay, or a module output.
Could trailer wiring or an aftermarket remote start set B1668?
Yes. Trailer adapters and aftermarket electronics can backfeed battery voltage into the reverse lamp circuit. That backfeed can hold the circuit high even when the module commands it off. Inspect for added splices near the trunk and left rear quarter area. Remove the adapter or disconnect the aftermarket device, then retest before replacing any factory parts.
How do I confirm the repair is complete after fixing the wiring?
After repairs, clear B1668 and run a functional check. Shift into reverse with the brake applied and verify proper lamp operation. Then drive and cycle several key-on/key-off events. Enable criteria vary by Dodge platform and body controller strategy. The code should not reset after repeated reverse engagements, and the reverse lamp output should toggle correctly.
Do I need to program a module if the reverse lamp driver inside the body controller tests bad?
If isolation tests prove the module output stays high with the circuit disconnected, a control module fault becomes likely. On Dodge platforms, body controllers often require configuration or programming after replacement. Plan on using a factory-level scan tool or an equivalent that supports Dodge body module setup. Confirm power, grounds, and network health first to prevent repeat failure.