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DTC codes / P06xx · Computer and output circuits / P0693

P0693Fan 2 Control Circuit Low

P0693 indicates that the powertrain control module (PCM) has detected a low-voltage condition on the control circuit for fan number two, which is typically the second electric cooling fan or the high-speed relay circuit. The PCM commands the fan on by supplying a ground or voltage to the control circuit, and when the feedback voltage stays below the expected threshold, the code is stored.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Engine overheating or higher-than-normal coolant temperatures, especially in traffic or when the air conditioning is on
  • The second cooling fan fails to run when commanded, while the primary fan may still operate normally
  • Air conditioning performance may degrade because the condenser relies on proper fan operation
  • In some vehicles, the PCM may disable the air conditioning compressor to protect the engine from overheating

Common causes, most likely first

  1. A faulty fan control relay or solid-state fan control module that has failed open or has high internal resistance
  2. Damaged, corroded, or disconnected wiring or connector pins in the fan control circuit, particularly at the fan motor or relay
  3. A short to ground or a chafed wire in the control circuit between the PCM and the fan relay or fan motor
  4. A failed cooling fan motor that draws excessive current or has an open winding, causing the control circuit to read low
  5. A faulty powertrain control module (PCM) driver circuit, though this is less common than wiring or component failures
  6. Poor ground connection at the fan motor or chassis ground point, leading to incorrect voltage feedback

How to diagnose and fix it

  1. Verify the code with a scan tool and command the second fan on and off using bidirectional controls to confirm the fault is present.
  2. Inspect the fan control relay, fuse, and wiring harness for obvious damage, corrosion, or loose connections, and test the relay with a multimeter.
  3. Measure resistance and voltage on the control circuit at the fan motor and at the PCM connector to check for shorts to ground or open circuits.
  4. Test the fan motor directly by applying battery voltage and ground to confirm it operates smoothly and does not draw excessive current.
  5. Check the ground circuit for the fan motor and the PCM, cleaning and tightening any suspect connections.
  6. If all wiring and components test good, substitute a known-good relay or fan control module to see if the code clears.
  7. As a last resort, diagnose the PCM driver circuit with an oscilloscope or replace the PCM only after confirming all other possibilities are eliminated.

Fan Control Circuit Low: Common Misdiagnosis Traps

  • A low-voltage code on a fan control circuit is often caused by a short to ground in the wiring rather than a failed fan motor, so always inspect the harness for chafing before replacing parts.
  • Some vehicles use a single fan with multiple speed windings, and the second fan control circuit may actually control the high-speed winding, so a failed fan motor can set this code even though the fan still spins at low speed.
  • The PCM may set P0693 intermittently if the fan relay coil is failing when hot, so a cold-weather diagnosis might not reproduce the fault until the engine bay reaches operating temperature.
  • A weak or corroded ground at the fan motor can cause the control circuit to read low, and this is frequently overlooked when technicians focus only on the positive side of the circuit.
  • After repairs, the code may remain stored until the PCM completes a full drive cycle with the fan commanded on, so clearing the code and verifying the repair requires a proper test drive.

Can I keep driving with P0693?

You can drive the vehicle short distances with this code, but avoid heavy traffic, prolonged idling, or towing until the fan operation is restored, because the engine may overheat and the air conditioning may stop working. If the temperature gauge climbs above normal, pull over and shut the engine off immediately.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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