P1666

Code

CHEVROLET P — Powertrain

Driver 3 Line 6

Brand: CHEVROLET

Type: P — Powertrain

Views: UK: 16 EN: 51 RU: 20

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Page language: EN

Causes

Open or short in the wiring harness to the driven component
Corroded, loose, or damaged connector at the actuator or module
Blown fuse or tripped/failed relay in the circuit
Failed actuator or module being driven
Faulty PCM/BCM output transistor or internal driver
Aftermarket accessories or previous repairs that altered wiring

Symptoms

Malfunction Indicator Lamp (MIL) or dash warning lamp illuminated
Related component not operating (depends on which actuator is driven)
Intermittent operation of the associated system
Possible limp mode or degraded performance if a critical system is affected
No-start or drivability problems if the driver controls essential components

What to check

Read freeze frame and live data with a capable scan tool; note conditions when the code set
Inspect fuses and relays for the circuit related to the affected driver
Visually inspect wiring and connectors from the PCM to the actuator for damage, corrosion, or exposed conductors
Check battery voltage and chassis/engine grounds for good connection
Backprobe the driver circuit at the PCM and at the actuator while monitoring with a multimeter/oscilloscope
Perform wiggle tests on harness while monitoring signal to reproduce fault

Signal parameters

Expected driver output: switched ground or switched +12 V depending on circuit (0 V to ~12 V when active)
If PWM: duty cycle range 0–100% and frequency typically in the tens to low hundreds of Hz (vehicle-specific)
Open-circuit: infinite resistance; short-to-ground: near 0 ohms; short-to-battery: near 0 ohms to +12 V
Typical actuator coil/solenoid resistance: commonly 1–30 ohms (check component spec)
CAN/LIN communication lines (if used): idle voltages ~2.5 V differential (CAN) or 0–5 V (LIN)

Diagnostic algorithm

Connect a professional scan tool. Record freeze frame, pending codes, and live data. Note conditions when P1666 set.
Identify which component/actuator is controlled by "Driver 3 Line 6" from vehicle wiring diagrams or dealer information.
Visually inspect harnesses, connectors, and the actuator for damage, corrosion, or signs of overheating.
Verify battery voltage and main grounds. Low supply or poor ground can cause false driver faults.
With key on (engine off) and/or engine running as appropriate, backprobe the driver lead at the PCM and at the actuator. Observe voltage, switching behavior, and response to commanded inputs from the scan tool.
Measure resistance between PCM driver pin and actuator pin with power disconnected to check for opens/shorts. Also check for short-to-ground and short-to-battery conditions.
If the driver output appears shorted at the PCM (low resistance to ground or battery with connectors disconnected), suspect internal driver fault — confirm by isolating the harness and re-testing.
If the actuator is faulty (open or short), repair or replace the actuator and re-test.
Repair any damaged wiring or connectors; secure grounds and power connections. Use proper connector replacement and protective measures.
After repairs, clear codes, perform relearn procedures if required, and road test to verify the fault does not return.

Likely causes

Broken/shorted wire between PCM and the actuator on Driver 3, Line 6
Connector corrosion or bent pins at the actuator or module
Actuator (solenoid, valve, relay coil, etc.) internally shorted/open
PCM driver stage failure due to overcurrent or heat
Intermittent ground or poor battery voltage causing false detection

Fault status

⚠️ Status

Manufacturer-specific Diagnostic Trouble Code indicating a fault detected on PCM/BCM output Driver 3, Line 6. The module reports abnormal behavior on that driver circuit (open, short, or unexpected feedback). Inspect wiring, connector, fuse/relay, and the driven component; consider module testing if wiring and device check good.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours

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