| 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 |
B1668 means the reverse lights may stay on, not come on, or act oddly when you shift. That creates a safety problem behind the vehicle and can cause an inspection failure. This is a Dodge manufacturer-specific body code, so the exact monitoring strategy can vary by platform. According to Dodge factory diagnostic data, this code indicates a “Reverse lamp control circuit high.” In plain terms, the body controller sees the reverse-lamp control circuit stuck at a higher-than-expected electrical state when it should not.
B1668 Quick Answer
On a 2007 Dodge Charger, B1668 points to the reverse lamp control circuit reading “high” when the module expects it to switch normally. Diagnose the reverse lamp output circuit, wiring, and lamp load before replacing any module.
What Does B1668 Mean?
Official definition: “Reverse lamp control circuit high.” What the module detected: the body-side reverse-lamp control circuit stayed in a high electrical state during a self-check or commanded operation. What that means in practice: the module cannot reliably control the reverse lamps, so lamp operation may be incorrect or inconsistent.
What the module is actually checking: on Dodge body systems, a controller such as the TIPM/BCM (varies by build) commands the reverse lamps and also monitors the output. It expects the circuit state to change when it commands the lamps on or off. A “circuit high” fault sets when the monitored point remains high due to a short-to-power, backfeed through another circuit, an internal driver fault, or an open on a switched-ground design that makes the monitor read high. Why that matters: the DTC identifies a suspected trouble area, not a failed part, so you must prove the circuit condition with tests.
Theory of Operation
Under normal operation, the transmission range input (and related network messages, depending on Dodge configuration) tells the body controller when Reverse is selected. The controller then energizes the reverse lamp output circuit. Current flows through the bulbs or lamp assemblies to ground, and the lamps illuminate.
For B1668, the controller sees the reverse lamp control circuit stuck high when it expects a different state. A short to battery voltage can force that reading. Backfeed from an aftermarket trailer harness can also hold the circuit high. On some designs, an open load or poor ground changes the feedback voltage and can mimic a high condition, so you must test the circuit under load.
Symptoms
You usually notice a reverse lamp problem first, then the stored body code during a scan.
- Reverse lamps stay on with the shifter not in Reverse
- Reverse lamps do not illuminate when Reverse is selected
- Intermittent operation reverse lamps flicker or work only sometimes
- Bulb-out message exterior lamp warning or chime, if equipped
- Battery draw parasitic draw if reverse lamps stay powered
- Scan result B1668 stored or pending in the body/TIPM-related module
- Related lighting faults other rear lighting DTCs if a shared harness or ground fails
Common Causes
- Short to voltage on the reverse lamp control circuit: Chafed wiring can contact a B+ feed and hold the control line high.
- Corroded or water-intruded rear lamp connector: Corrosion can bridge terminals and backfeed power into the reverse lamp control path.
- Incorrect bulb type or aftermarket LED backfeed: Some LED assemblies leak voltage and drive the monitored circuit high.
- Stuck relay or miswired trailer/aftermarket harness: An added harness can feed reverse power into the factory circuit continuously.
- High-resistance ground at the rear lamp assembly: A weak ground can force current to return through another circuit and create a false high signal.
- Harness damage in trunk hinge/loom area: Repeated flexing can cut insulation and create intermittent shorts to power.
- Internal fault in the module driver for reverse lamps: A shorted high-side driver can keep output voltage high even when commanded off.
- Wrong or shorted reverse lamp socket: A distorted socket can cross-contact power and control terminals when the bulb installs.
Diagnosis Steps
You need a scan tool with body/BCM data, a digital multimeter, and a test light. Use back-probes, not paper clips. Have wiring diagrams for the reverse lamp feed, grounds, and any splices. A fused jumper helps for load testing. If the Charger has aftermarket trailer wiring, plan extra time for isolation.
- Confirm B1668 sets as stored or pending, then record freeze frame data. For this circuit-high code, focus on battery voltage, ignition state, gear position (PRNDL), and reverse lamp command status. Freeze frame shows conditions when the DTC set. Use a scan tool snapshot later to capture intermittent voltage spikes during a wiggle test.
- Inspect the reverse lamp circuit path before any meter work. Check both reverse bulbs, sockets, rear lamp connectors, and the trunk hinge harness area. Look for rubbed insulation, water intrusion, green corrosion, and signs of trailer harness taps.
- Check all related fuses in the power distribution center and interior fuse panel. Verify each fuse has proper feed on both sides with the circuit commanded on. Do not rely on visual checks. A partially open fuse link can pass a meter test and fail under load.
- Verify module power and ground integrity under load. Turn the reverse lamps on with a scan tool output control if available, or command reverse with the wheels safely chocked and the brake applied. Perform voltage-drop testing on the module ground circuits while the lamps operate. Keep ground drop under 0.1V with the circuit loaded.
- Use the scan tool data list to compare command versus feedback. Watch reverse lamp command, gear position input, and any reverse lamp sense or output status items the BCM reports. If the BCM commands OFF but the feedback stays ON, treat it as a true circuit-high condition until proven otherwise.
- Isolate the rear load to see if the high condition comes from the lamp side. Disconnect both rear lamp connectors, then clear the code and cycle the ignition. If B1668 returns immediately with the lamps unplugged, suspect a short to voltage in the harness forward of the lamp connectors or a module driver issue.
- Check for backfeed from aftermarket equipment. Disconnect any trailer module, splice-in converter, remote start, or alarm wiring tied into rear lighting. Repeat the key cycle and reverse lamp command test. A removed backfeed that stops the code points to the add-on circuit, not the Dodge module.
- Test the reverse lamp control wire for unwanted voltage. With the lamps commanded OFF, measure voltage at the lamp connector control terminal to ground. Then wiggle the trunk hinge harness and rear body harness while watching the meter. A jump toward battery voltage during movement confirms an intermittent short to power.
- Load-test the suspected control circuit. Use a test light or a fused jumper load to ground at the lamp-side connector while the lamps command OFF. If the circuit cannot pull low or the voltage stays high, a power short exists upstream or the driver remains powered internally. Do not use continuity alone, since high resistance faults hide without load.
- Confirm the repair. After correcting wiring, grounds, connectors, or add-on harness issues, clear DTCs and run an operate-and-wiggle test. Verify reverse lamps work only in reverse and stay off in other ranges. Recheck for pending codes after a complete key cycle and a short drive.
Professional tip: If B1668 comes back immediately at key-on with the reverse lamps unplugged, treat it like a hard fault on a continuously monitored circuit. That result narrows the problem to a short to voltage in the body harness or a stuck module output. Prove the harness first by isolating sections and load-testing. Only then evaluate the module driver.
Need wiring diagrams and factory-style repair steps?
Body-system faults often involve switches, relay drives, inputs, actuators, and module-controlled circuits. A repair manual can help you trace the circuit and confirm the fault path.
Possible Fixes
- Repair short-to-voltage wiring damage: Restore insulation and routing in the trunk hinge loom or rear body harness, then secure to prevent repeat chafe.
- Clean, repair, or replace corroded rear lamp connectors and terminals: Remove water intrusion sources and correct terminal tension to stop backfeed.
- Remove or rewire aftermarket LED, trailer, or alarm backfeed sources: Correct the add-on interface so it cannot energize the factory reverse lamp control line.
- Restore rear lamp grounds and ground attachment points: Clean the ground eyelet and body contact, then verify low voltage drop with the lamps loaded.
- Replace damaged bulb sockets or incorrect bulb assemblies: Correct cross-contact issues that feed voltage into the control path.
- Replace the responsible module only after circuit proof: If isolation shows the driver stays high with the harness disconnected and powers/grounds verified, replace and configure the module as required.
Can I Still Drive With B1668?
You can usually drive a 2007 Dodge Charger with B1668, but treat it as a safety-related body fault. This code points to the reverse lamp control circuit reading “high.” Reverse lamps affect visibility when backing up. They also act as a warning to others. If the lamps stay on, other drivers may misread your intent. If they stay off, you lose rear illumination at night. Park where you can back out safely. Use a spotter in tight areas. Do not ignore this code if you tow or park in crowded lots.
How Serious Is This Code?
B1668 rarely creates a drivability problem, but it can create a real safety problem. Reverse lamps help prevent backing collisions. A “circuit high” fault often means the module sees voltage when it should not. That can leave the lamps on, drain the battery, or trigger more body codes. In other cases, the module disables the output to protect the circuit. That can leave the lamps inoperative. The issue stays “mostly an inconvenience” only when the lamps still operate correctly and the code sets intermittently. Treat it as urgent if the lamps behave wrong, the battery drains, or the transmission range input looks inconsistent on the scan tool.
Common Misdiagnoses
Technicians often replace bulbs or lamp housings first and never load-test the circuit. That wastes time because B1668 targets the control side, not bulb brightness. Another common miss involves blaming the PCM or a “bad TIPM” without proving the output stays high with the connector unplugged. People also confuse a reverse-lamp issue with a backup camera problem. On Dodge platforms, shared grounds and rear harness splices create false “high” readings when corrosion backfeeds voltage. Avoid guesswork by verifying the lamp command on the scan tool, checking for unintended voltage on the control wire with the load disconnected, and confirming the range/PRNDL input agrees with the shifter position.
Most Likely Fix
The most common confirmed repair directions for B1668 involve wiring faults, not modules. First, repair a short-to-voltage or backfeed in the reverse lamp control wire near the trunk hinge, rear body harness, or lamp connector. Second, clean and repair corrosion at rear connectors or ground points that allows cross-feed from another lighting circuit. Do not call the module or TIPM failed until the output stays high with the rear harness disconnected and you verify the module has clean power and grounds under load. After repair, cycle key and shift through ranges to confirm the code stays cleared. Enable criteria vary, so confirm with service information.
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: Manufacturer-specific code for “Reverse lamp control circuit high.”
- Safety impact: Reverse lamps may stay on or fail to light, increasing backing risk.
- Root cause rule: The DTC flags a suspected circuit condition, not a failed part.
- Best first proof: Unplug the rear load and check for unintended voltage on the control wire.
- Common fix pattern: Harness damage, connector corrosion, or backfeed near the rear body wiring.
FAQ
What does “reverse lamp control circuit high” mean in practical terms?
It means the body control side sees the reverse lamp control circuit at a higher voltage than expected. That usually happens when the circuit gets fed power from the wrong place, or when the module output cannot pull the line low. Confirm it by checking if the reverse lamps stay on, then measure the control wire with the lamp connector unplugged.
Will clearing B1668 fix the reverse lights?
Clearing the code only resets the fault memory. It does not repair the electrical condition. If the circuit still reads high, the module will set B1668 again. Clear the code only after you repair wiring or connectors and confirm proper lamp operation. Then drive and recheck for pending codes after several key cycles and reverse events.
How do I confirm the repair is complete and the code will not return?
Verify three things: the reverse lamp command changes correctly, the lamps respond correctly, and the control circuit voltage behaves normally with the load connected. Then perform multiple key cycles and shift into Reverse several times. Drive conditions that allow the body controller to run its checks vary by vehicle. Use Dodge service information to confirm the exact enable criteria.
What wiring areas most often cause a “circuit high” on a Dodge Charger?
Start at the rear lamp connectors, trunk hinge harness flex points, and any trailer-wiring splices. Those spots commonly chafe insulation or corrode. Either issue can backfeed voltage into the reverse lamp control wire. Also inspect shared ground points near the rear body. A poor ground can force current to return through another circuit and create false voltage readings.
Do I need to program a module if a TIPM or body module ends up being the problem?
On this Dodge platform, replacement body control hardware often requires configuration or initialization to match the vehicle options. Many shops use a factory-level scan tool or equivalent to complete setup and confirm outputs. Do not replace a module based on B1668 alone. Prove the output driver stays high with the harness unplugged and confirm powers and grounds first.