P1670

Output Circuit Check Signal Low

Powertrain Emission Controls Output Control Circuit 🟡 Moderate — Fix within a week ⚠️ Drive with Care
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What This Actually Means

In plain language — no jargon

The ECU detected that an output control signal is reading lower than expected, similar to a dimmer switch stuck in the low position. This typically indicates a wiring, connector, or component issue preventing proper signal voltage from reaching the ECU.

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Symptoms You May Notice

3 known symptoms for this code
Check Engine Light illuminated
Rough idle or engine stumbling
Reduced engine performance or power loss
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECM monitors output control circuit voltages to verify proper signal transmission to actuators and solenoids. It compares the feedback voltage against expected thresholds to ensure commands are being executed correctly. When voltage remains below the normal operating range, the ECU logs this fault.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Output Signal Voltage 4.5-5.5V or vehicle-specific range Below 3.0V or open/short condition detected
Circuit Resistance Less than 10 ohms Greater than 50 ohms or infinite resistance
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Wire harness connectors
Inspect all connectors related to the output circuit for corrosion, loose pins, or debris and clean or reseat as needed.
2
Wiring and terminals
Check the circuit wiring for breaks, pinches, or damage using a multimeter in continuity mode.
3
Output solenoid or actuator
Test the suspect component with a multimeter for resistance and continuity to determine if replacement is necessary.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code P1670 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code P1670

What happens after you fix the fault

Once the fault is repaired, P1670 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.