P1670 — Output Circuit Check Signal Low

What does OBD2 code P1670 mean?

P1670 — Output Circuit Check Signal Low. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, corroded, loose or damaged connector, faulty sensor or actuator of the affected circuit.

How much does it cost to fix P1670?

Control module repair — $300–$1,000; Replace the faulty sensor or actuator — $150–$500; Repair wiring or connectors — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Is it safe to drive with P1670?

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.

Will P1670 clear itself?

Sometimes P1670 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.

How do I diagnose P1670 myself?

Start with a scan: confirm P1670, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the output circuit check, and verify the suspect component against live data before buying parts.

When your vehicle's engine computer detects a problem with the signal voltage on the output circuit check circuit, it logs OBD2 code P1670. This diagnostic trouble code falls under the powertrain category, which means it relates to the engine, transmission, or their associated sensors and actuators. The specific condition that triggers P1670 is a signal voltage that remains abnormally low — essentially pulled down toward ground — instead of staying within the normal operating range the manufacturer specifies.

The output circuit check circuit plays a monitoring role within your vehicle's electronics. The control module continuously evaluates whether this circuit is receiving proper voltage and delivering expected signal levels while you drive. When something drags that signal low — whether a wiring short, a failing component, or a power supply problem — the module registers the abnormality. Once the fault persists through enough consecutive drive cycles to confirm it's a genuine defect rather than a momentary glitch, the ECU stores P1670 and illuminates the Check Engine light. The freeze frame data captured alongside the code is valuable: it records exact engine conditions at the moment of failure, including RPM, load, temperature, and vehicle speed, giving you a precise snapshot for diagnosis.

Understanding why P1670 sets requires recognizing the difference between a complete failure and a degraded signal. The circuit isn't necessarily dead — it's simply reporting a voltage level that doesn't match what the computer expects. This could stem from a direct short to ground somewhere in the wiring, a supply voltage that never arrives, or a faulty component pulling the signal down. Each cause points to a different repair path, which is why systematic diagnosis matters before spending money on parts.

Common symptoms of P1670

• The Check Engine light remains illuminated on the dashboard
• The affected system may operate intermittently or fail completely, depending on which circuit is involved
• Reduced engine performance or limp-home mode activation in some vehicle applications
• Fuel consumption may increase compared to normal driving patterns
• Auxiliary systems controlled by the affected circuit could stop functioning

What causes P1670?

• A failed output circuit check driver inside the control module pulling the signal low
• Supply voltage missing from the output circuit check circuit due to a blown fuse or relay issue
• The signal wire shorted to ground, often caused by chafed insulation rubbing against metal
• Corrosion, looseness, or physical damage at the electrical connector
• An inadequate ground connection at the component or module
• A defective sensor or actuator that drags the signal voltage down
• An internal driver fault within the engine or transmission control module

How to diagnose P1670

1. Connect an OBD2 scanner to the vehicle's diagnostic port, retrieve code P1670, and record the associated freeze frame data — these conditions must be replicated during the verification drive later.
2. Search for any related diagnostic trouble codes that accompanied P1670, as secondary codes often reveal the root cause faster. Check manufacturer TSB databases for your specific make and model, since many P0xxx codes have known factory fixes or software calibrations documented.
3. Perform a thorough visual inspection of the wiring harness and connectors tied to the output circuit check, looking for damaged insulation, corrosion, pushed pins, or loose connections.
4. Test for supply voltage at the output circuit check connector using a multimeter; then measure resistance from the signal wire to ground — a reading near zero ohms confirms a short to ground in the harness.
5. Check reference voltage, ground integrity, and signal continuity directly at the component's connector to isolate whether the fault lies in the wiring or the part itself.
6. Conduct a wiggle test on the harness while monitoring live data parameters — any signal dropouts or interruptions expose broken wires inside the insulation.
7. Clear P1670 from the ECU, drive the vehicle through a complete drive cycle including the specific conditions from the freeze frame data, and verify the code does not return.

How to fix P1670

Approach repairs from least expensive to most expensive to avoid unnecessary spending:

• Wiring harness repair or connector replacement: $80–$250
• Replacement of the faulty sensor or actuator in the affected circuit: $150–$500
• Control module diagnosis and repair or replacement: $300–$1,000

How much does it cost to fix P1670?

The total repair bill varies significantly depending on which component is actually at fault. Based on typical parts and labor rates at independent repair shops in the United States, expect to pay between $80 and $250 if the issue turns out to be wiring or connector related. Sensor or actuator replacement generally runs $150 to $500. The most expensive scenario involves the control module itself, where repair or replacement falls in the $300 to $1,000 range. An accurate diagnosis before purchasing parts is essential — in most cases the problem is far simpler and cheaper than the worst-case scenario, so work through the cheap possibilities first.

Can you drive with P1670?

In most instances, the vehicle remains drivable with P1670 stored, though you may experience reduced performance, a disabled auxiliary feature, or limp-home mode depending on which circuit is affected. If the malfunction causes stalling, prevents the engine from starting, or triggers warnings related to braking or steering systems, treat the situation as urgent and have the vehicle towed rather than driving it. For minor symptom cases, schedule repair at your earliest convenience without undue delay.

Related OBD2 codes

• P1600: Throttle Control Unit Malfunction
• P1601: Throttle Control Unit Throttle Position Malfunction
• P1602: Throttle Control Unit Modulated Command Malfunction
• P1603: Throttle Control Unit Detected Loss of Return Spring
• P1604: TCU Unable To Control Desired Throttle Angle
• P1605: Loss of KAM Power; Open Circuit