P1684 — Electronic Feedback Signal Not Detected

OBD2 code P1684 flags a problem with the sensor and actuator circuits (electronic feedback signal not detected). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit.

For Ford vehicles

metering oil pump position sensor circuit Mazda

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P1684 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 P0xxx 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 electronic feedback signal not for damage, corrosion, chafing or poor contact.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P1684 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P1684 (parts and labor, USD, independent shop rates): Repair wiring or connectors: $80–$250; Control module repair: $300–$1,000; Replace the faulty sensor or actuator: $150–$500. Overall, fixing P1684 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What are the symptoms of P1684?

Drivers most often notice: Check Engine Light on, possible limp mode depending on the affected component, increased fuel consumption in some cases, the affected system operates intermittently or not at all.

What is the most common cause of P1684?

The most common causes are: control module driver fault, faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit.

Is it safe to drive with P1684?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How do I diagnose P1684 myself?

Start with a scan: confirm P1684, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the electronic feedback signal not, and verify the suspect component against live data before buying parts.

What does OBD2 code P1684 mean?

When your scanner pulls code P1684, it tells you that the engine computer has lost contact with an electronic feedback signal somewhere in the powertrain circuitry. The term sounds technical, but the idea is straightforward: the module sent a command or expected a response, and the return signal never showed up. This places P1684 squarely in the powertrain category of OBD2 diagnostics, which covers everything from fuel injection to transmission operation depending on which circuit triggered the fault.

The control module constantly validates these feedback loops while the engine runs. It compares actual sensor or actuator behavior against stored parameters. When those readings disappear or fall outside acceptable limits for enough consecutive drive cycles, the ECU logs P1684 and turns on the check engine light. The accompanying freeze frame snapshot captures engine speed, load, temperature, and vehicle speed at the exact moment the fault occurred — invaluable data when you're tracking down an intermittent problem.

How you approach fixing P1684 depends entirely on where the signal dropped out. The sections below walk through symptoms, common culprits, and practical steps to pinpoint the root cause without replacing parts you don't need.

Symptoms of P1684

The check engine lamp is the most obvious indicator. Beyond that, you may notice one or more of the following:

Activated limp-home mode, which limits RPM and throttle response to protect the drivetrain
Noticeable spike in fuel consumption due to closed-loop operation being interrupted
The affected circuit acting sporadically or shutting down entirely
In rare cases, rough idle or hesitation under acceleration if the fault impacts a critical sensor

Common Causes of P1684

Wiring and connector problems top the list of triggers for this code. More specific culprits include:

Broken, frayed, or pinched wiring creating an open circuit
Corrosion, moisture intrusion, or loose pins at the affected connector
A blown fuse or failed relay feeding the circuit with power or ground
The control module's internal driver for that circuit has failed
The sensor or actuator itself has stopped producing or responding to the expected signal

Diagnosing P1684

Follow these steps in order to avoid unnecessary part swapping:

Connect your scanner and confirm P1684 is active. Save the freeze frame data before clearing anything — that snapshot tells you the driving conditions (load, temperature, speed) when the fault triggered.
Pull all stored codes, not just P1684. Related codes pointing to a specific circuit often point you directly to the failed component. Check for any manufacturer TSBs covering your make and model, as some P0xxx codes have known factory fixes or software updates.
Inspect the wiring harness and connectors associated with the affected circuit. Look for torn insulation, corroded terminals, rubbed-through wire, or connectors that aren't fully seated.
Check reference voltage and ground at the component's harness side. Use a multimeter to verify the sensor or actuator is receiving the power and ground it needs to operate.
Perform a wiggle test on the harness while watching live data on your scanner. Any signal dropouts or wild fluctuations during the test indicate a broken wire or intermittent connector.
Clear the code and complete a full drive cycle that replicates the freeze frame conditions. If P1684 returns, the fault is still present and you'll need to dig deeper into the circuit.

Repair Options and Costs

Labor rates vary by region, but the following ranges cover parts and workmanship at independent shops (USD):

Wiring harness repair or connector replacement: $80–$250 depending on accessibility and whether terminals need repinning
Control module diagnosis and repair: $300–$1,000 if the ECU's internal driver circuit is bad and can be rebuilt, or if the module needs replacement and programming
Sensor or actuator replacement: $150–$500 for most throttle position sensors, mass airflow sensors, and related actuators, including installation

Fixing P1684 typically runs between $80 and $1,000 depending on the actual failure point. The key is getting a solid diagnosis before purchasing components — the worst-case scenario (a failed module) is rarely where you should start.

Driving Safety Verdict

In most vehicles, P1684 does not leave you stranded. You can continue driving with the check engine light on, though reduced performance or a disabled辅助系统 may make the car feel sluggish. Treat it as urgent, however, if the fault causes stalling, hard starting, or affects braking and steering systems — stop driving and have it towed.