P1666

What it means

On GM vehicles P1666 is defined as 'Driver 3 Line 6', which points to a fault in one of the control module's internal output driver circuits (driver group 3, line 6). The module saw a driver output that did not behave as commanded, for example a short, open circuit or wrong voltage on that line. Which component sits on that line depends on the model, engine and year, so confirm it in the vehicle-specific wiring information.

Symptoms

• Engine warning light on
• Possible poor running, hesitation or reduced performance if the affected output is engine-related
• Component fed by that driver not working or working intermittently
• Other related codes stored at the same time
• Intermittent fault that comes and goes with vibration or heat

Possible causes

• Wiring fault (short to earth, short to voltage or open circuit) on the circuit controlled by driver 3 line 6likely
• Faulty or shorted actuator, solenoid or relay connected to that driverlikely
• Corroded, loose or damaged connector terminals at the component or control modulepossible
• Low or unstable supply voltage or poor earth to the control module or the componentpossible
• Internal fault in the control module output driverpossible
• Outdated or faulty control module calibration, where a manufacturer update addresses this code for the specific modelrare

How to diagnose

1. Read all stored codes and freeze frame data, note any other driver or circuit codes, then record and clear the code to see if it returns.
2. Look up in the model-specific wiring information which component and circuit are on driver 3 line 6 for this vehicle.
3. Visually inspect the related wiring and connectors for chafing, heat damage, water ingress, corrosion or pushed-out pins.
4. Check battery condition, charging voltage, fuses and the module power and earth connections.
5. Measure the resistance of the connected actuator or solenoid and compare it with the specification for that model.
6. With the circuit unplugged, check the wiring for shorts to earth, shorts to voltage and continuity back to the module.
7. Command the output with a diagnostic scan tool, if supported, and check the driver signal with a meter or oscilloscope.
8. Check for applicable calibration updates or technical bulletins for the vehicle before suspecting the module.

How to fix

• Repair or replace damaged wiring and restore proper insulation and routing.
• Clean or replace corroded or loose connector terminals.
• Replace the faulty actuator, solenoid or relay once confirmed by testing.
• Repair power supply or earth faults, and replace a weak battery if needed.
• Update the control module calibration only if a manufacturer update exists for this fault, and replace or repair the module if testing proves an internal driver fault.

Can I keep driving?

This code for other makes

• P1666BuickDriver 3 Line 6
• P1666CadillacDriver 3 Line 6
• P1666ChevroletDriver 3 Line 6
• P1666GMCDriver 3 Line 6
• P1666OldsmobileDriver 3 Line 6
• P1666SaturnDriver 3 Line 6

Nearby codes

• P1665GMDriver 3 Line 5
• P1667GMReverse Inhibit Solenoid Control Circuit