Comprehensive diagnostic guide for OBD-II code P0695 Fan 3 Control Circuit Low

What This Code Means

• What the code means:
  • P0695 is defined as a fault in the third cooling fan control circuit. In other words, the engine control module (ECM/PCM) is detecting a low signal on the third fan control circuit when it expects a commanded signal to energize the cooling fan. This is typically associated with the third fan relay/actuator circuit in many modern vehicles (the exact function can vary by model). Source notes: Open Source definition states ; Wikipedia's OBD-II sections categorize P0695 under Powertrain Codes as a DTC related to the engine cooling/fan system.
• Where in the system:
  • This is a powertrain/engine cooling issue tied to the third fan circuit, often used for condenser cooling or high-speed radiator cooling, depending on vehicle design. The issue is detected by the PCM based on the expected control signal and actual circuit activity.

Symptoms and real-world complaints (what buyers often report)

• Engine temperature concerns:
  • Engine runs hotter than normal or overheats, especially at idle or low-speed when the third fan would be expected to run but does not.
• Cooling/A/C interaction:
  • Reduced cooling performance when the A/C is on or when heat load increases (condensor or radiator cooling is compromised by the third-fan fault).
• Illuminated warning indicators:
  • Check Engine Light (MIL) is commonly present with P0695, though some vehicles may show pending or stored codes first.
• Other observed behavior:
  • In some cases, fans may appear to operate intermittently or not at all when commanded by the PCM, leading to concern about sudden overheating during hot days or heavy load.

Diagnostic Approach

• Confirm the DTC with a scan tool and check freeze/short-term data for the third fan circuit (live data if available).
• Gather model-specific details:
  • Vehicle year/make/model, engine type, whether fan 3 is used for A/C condenser, radiator cooling, or both, and the location of the third fan relay in your vehicle's fuse/relay box.
• Inspect for obvious issues first:
  • Fuses related to cooling fans.
  • The third fan relay and its connector.
  • Wiring harnesses and connectors for damage, corrosion, or moisture.
• Perform electrical tests:
  • Check power supply and ground circuits for the fan relay coil and the fan motor circuit.
  • Verify PCM/ECM command signal to the relay coil (or to a driver transistor) when the engine coordinator calls for fan 3 operation.
  • If the relay and wiring test good, consider testing the fan motor itself.
• Test logically and safely:
  • If possible, manually energize the third fan to confirm the motor and airflow are functional.
  • Swap a known-good relay with the third-fan relay to see if the fault clears.
  • Check for PCM fault or software/firmware issues only after all harness/fuse/relay tests are complete and no wiring fault is found.

Step-by-Step Diagnosis

1) Verify code and data

• Use a scan tool to confirm P0695 is active and to review any related freeze-frame data (engine temp, road speed, AC use, etc.). Confirm whether there are any additional codes (P069x family or related fan codes) that could point to a common node (relay, wiring, or PCM).

2) Inspect fuses, relays, and vacuum/controls (physical inspection)

• Check all fuses related to cooling fans and the third-fan circuit per the vehicle's fuse box diagram.
• Inspect the third fan relay and its socket for corrosion, looseness, or heat damage.
• Inspect the wiring harness and connectors for the third fan circuit for signs of abrasion, bent pins, moisture intrusion, or loose grounds.
• Observed symptoms often begin with a relay or wiring fault; a simple fuse/relay issue is a common cause.

3) Electrical checks (relay coil and circuit)

• With the ignition on and the engine off, test the third fan relay coil for ~12 V at the coil input and verify the coil ground is solid.
• When the PCM commands the third fan (via scanner live data or a test drive and anticipated signal), verify if the coil receives voltage and if the coil is dropping to ground as expected.
• If there is 12 V on the coil input when commanded and a solid ground, the PCM/driver is likely functioning; if not, check the wiring between PCM/driver and the relay coil or a PCM fault.
• Also check for chassis ground integrity on the fan motor ground and the relay ground path.

4) Fan motor and circuit tests (coil activation vs. motor operation)

• If the relay energizes (coil clicks or coil shows voltage when commanded) but the fan does not run, test the fan motor circuit directly:
  • Measure the fan motor supply voltage at the fan connector when the relay is energized.
  • Check the fan motor resistance and grounding path; a seized wind or open windings will prevent operation.
• If energizing the fan directly (bypassing the ECM/relay) runs the fan, the issue is likely the PCM control signal or relay logic rather than the motor itself.

5) PCM/ECU and control logic considerations

• If all harnesses, fuses, and relay tests are good and the fan still does not operate when commanded, consider PCM/ECU control logic or wiring harness faults between the PCM and relay.
• In some cases, software/firmware updates or calibration changes to the PCM are needed, but such steps should be pursued only after verifying the hardware path and after ruling out typical harness/relay faults.
• Note: The sources describe P0695 as a card-coded fault in the powertrain codes and discuss the general concept of DTCs and powertrain control logic; specific PCM failure modes are not detailed .

6) Confirm by re-scanning and test drive

• Remove any temporary wiring or bypasses; recheck all circuit tests after repairs.
• Take the vehicle on a typical drive (including idle, stop-and-go traffic, and highway/steady high-speed) with the engine at operating temperature and the A/C on if applicable to trigger third-fan activity.
• Re-scan to ensure P0695 is cleared after the fault is repaired and verify that no new codes have appeared (e.g., related to the fan or ECU).

Common Causes

Note: The following probabilities are approximate and vehicle-model dependent. They reflect typical field experience rather than a published frequency from NHTSA complaints. If you have access to NHTSA complaint data for your specific year/make/model, prefer that data.

• Faulty third fan relay or driver (PCM output/relay driver) wiring fault:

  • Estimated probability: 35-45%

• Open/short in the third fan control circuit wiring or connector (including harness damage, pin corrosion, or bent terminals):

  • Estimated probability: 25-30%

• Faulty third fan motor (condenser/radiator or dedicated third fan) or a seized motor:

  • Estimated probability: 10-20%

• Blown fuse or degraded power supply to the fan circuit:

  • Estimated probability: 5-10%

• PCM/ECU fault or misinterpretation of the fan control signal:

  • Estimated probability: 5-10%

Diagnostic references from sources

• Definition and scope:
  • P0695 is described as a "Fan 3 Control Circuit Low" issue in the OBD-II framework (Powertrain Codes) per Wikipedia's OBD-II sections. This aligns with the concept of a third cooling fan circuit fault.
• Code description in open-source resource:
  • The open-source entry states , which matches the general diagnostic interpretation of P0695.
• The general idea of DTCs and how OBD-II monitors and reports faults is captured in the Wikipedia OBD-II sections (Diagnostic Trouble Codes). This guides how the P0695 code is used to diagnose engine cooling/fan control issues.

Safety Considerations

• Disconnecting electrical components with power applied is hazardous. Always disconnect the battery or isolate power before performing in-harness electrical tests to prevent shock, short circuits, or unintended energizing of fans while working near hot engine components.
• Fans can generate high currents and continue to spin after power is removed; secure the area and ensure the fan is isolated during testing.

What to document when returning the vehicle to the customer

• Code(s) retrieved and freeze-frame data (engine temp, fan status, A/C status, etc.).
• The exact location and type of third fan relay, fuse, and connectors inspected.
• Any repair performed (relay replacement, wiring repair, fan motor replacement, PCM check, software update).
• Results of all tests (voltage readings, resistance measurements, and whether the fan runs when directly energized).
• After-repair test results (scanned codes cleared, drive test performed, no reappearance of P0695).

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

---