Comprehensive diagnostic guide for P0696

What This Code Means

• P0696 generally corresponds to a fault in the cooling fan 3 control circuit: a high . In OBD-II terminology this is categorized as a powertrain

Key clinical interpretation

• The PCM/ECM is detecting a sustained high signal on the circuit that drives the third cooling fan (either the PCM output is stuck high, a short to power exists, or the circuit is physically faulty). This does not always mean the fan itself is bad; it can be a fault in the control circuit, wiring, pin connections, relay, or PCM output.

What you may notice (symptoms)

• The cooling fan 3 circuit may stay commanded on (fan runs continuously or at higher speed than expected).
• Engine temperature may be elevated or difficult to manage, especially in hot ambient conditions or when the cooling load is high.
• You might observe abnormal fan behavior that correlates with engine temps (e.g., fan comes on at idle or remains on after shutdown in some configurations).
• DTC P0696 may be stored with or without accompanying related cooling/fan codes depending on OEM logic and the specific vehicle.
  Note: The symptom set is largely driven by the role of the fan control circuit and the PCM's interpretation of the circuit state.

Probable Causes

• Faulty fan 3 control relay or the relay drive circuit in the PCM (25-40%)
• Short to power or internal short in the fan 3 control circuit wiring or connector (20-30%)
• Faulty PCM output or PCM software calibration (15-25%)
• Wiring harness issues: poor/loose ground or poor multi-pin connector integrity (10-20%)
• Faulty fan assembly or internal feedback (rare but possible) (5-10%)

Notes:

• Since NHTSA complaint data specific to P0696 isn't provided , the above likelihoods are informed by common failure patterns seen in cooling fan control circuit faults in the field. If you have access to OEM service data or TSBs for a specific vehicle, those can shift the probabilities.

Diagnostics plan (step-by-step, practical and safety-focused)

1) Prepare and verify

• Safety: Disconnect or disable the battery only as needed for wiring checks; re-connect before live testing. Use proper PPE and follow vehicle-specific safety precautions for cooling systems.
• Confirm DTC: Use a capable scan tool to confirm P0696 is present and note any freeze-frame data (engine temperature, fan status, RPMs, vehicle speed, etc.). Check for related DTCs (other P0xxx codes or C/U/T codes) that might guide the fault (e.g., other cooling fan codes, short-to-ground/short-to-power codes, or PCM faults).

2) Quick visual and basic electrical checks

• Inspect look for obvious issues: damaged/worn wiring harnesses, melted insulation, exposed conductors near hot components, corrosion on connectors, and any aftermarket wiring that could affect the circuit.
• Check fuses and the three potential power/relay paths:
  • Power supply fuse for the fan circuit
  • Relay 3 (or equivalent) coil supply and contacts
  • The control circuit fuse/isolator if OEM design uses a separate control rail
• Inspect the fan 3 relay and its socket for corrosion, bent blades, and proper seating. Swap with a known-good relay if permissible in the vehicle's logic (document the swap for re-testing).

3) Electrical tests of the control circuit

• Backprobe or use a logic-compatible breakout to monitor the PCM output on the fan 3 control circuit while the engine runs and temperature changes.
• With ignition ON (engine off), check for a stable voltage on the fan 3 control circuit pin when the PCM is not commanding the fan (should be low or open-circuit depending on design). Then start/activate the cooling system (engine warming) to observe whether the PCM output ever commands the circuit high correctly and how the circuit responds.
• Check for shorts:
  • Short to power: If the control line reads near battery voltage unexpectedly.
  • Short to ground: If the line reads near ground while PCM is trying to drive it high or low (depending on design).
• Ground integrity: Verify the ground path for the PCM and the fan control circuit is solid. A poor ground can cause misreadings or erratic logic levels.

4) Relay and fan circuit testing

• Test the fan 3 relay coil resistance and verify it functions when energized with a known-good input. If the relay coil is weak or intermittently failing, it can create control circuit symptoms even if the PCM output is correct.
• If possible, supply a known-good 12V source to the fan via a test jumper or by swapping in a known-good relay/fan harness to determine if the issue is the relay or wiring vs. the PCM.
• If the fan 3 is an integral motor with a built-in controller, verify whether external control is required; some designs have a separate sensor/relay module.

5) PCM/output verification and software considerations

• If the wiring and relays check out, monitor the PCM output in live data:
  • Commanded fan state vs. actual circuit signal
  • Coolant temperature and other conditions that trigger fan control
• If the PCM output appears faulty or inconsistent over time, consider PCM reflash or software update if available (this is OEM-dependent). Some failures are software-related and fixed via reflash or calibration updates.

6) Correlate with vehicle-specific data

• If you have access to OEM repair data, service bulletins, or factory test procedures for your exact vehicle, consult them for the P0696 fault-often the OEM will document known relay/driver circuit issues, harness routing concerns, or particular connector pin problems that can apply to your case.
• If other cooling-related codes are present (e.g., P0690, P0693, or P0699 family codes), treat them as related indicators of circuit/relay/harness issues rather than isolated faults.

7) Troubleshooting decision tree (quick guide)

• If the fan 3 control circuit is read as high only when engine is at a certain temperature or condition and the actual hardware (relay, wiring, fan) tests good: suspect PCM or software calibration; consider OEM update.
• If voltage on the control circuit is high or near battery voltage at all times, and the relay coil is not energizing as expected: likely short to power or stuck output; inspect connectors and wiring for damage or pin misalignment.
• If the control circuit is intermittently high or shows fluctuating behavior: inspect for loose or corroded connectors, damaged wires, or grounds; verify harness routing not rubbing on metal edges; consider harness replacement if damage found.
• If the fan 3 circuit remains off when commanded on but the fan remains physically off or undercooling occurs: inspect the relay, the fan power feed, and the relay control path as primary suspects.

Repair Options

• Fix wiring/connectors: repair or replace damaged harness segments, clean/seat connectors, apply dielectric grease as appropriate, and ensure secure mating with proper torque.
• Replace faulty relay or the fan control module (if diagnosed as relay or PCM-related). If the PCM is suspect, verify service options (reflash, replacement, OEM module replacement) per vehicle and warranty status.
• Replace the cooling fan assembly if the motor itself is failed or if internal control circuitry is damaged and not recoverable via wiring changes.
• After repairs, clear the DTCs, recheck scan data, and run the engine to operating temperature, verifying that the fan control circuit behaves as designed (observer the commanded state vs. actual state in live data). Re-run any OEM diagnostic tests if available.
• If applicable, install any available OEM software/firmware updates to address known PCM/driver issues.

Post-Repair Validation

• Confirm cooling system operation across a range of ambient temperatures and driving conditions (idle, highway, high fan load).
• Ensure the DTC does not return after a cooldown period, and verify freeze-frame data shows expected parameters.
• Confirm no new codes are triggered during subsequent drive cycles.

Safety Considerations

• Work only on a cooled engine and cooling system when performing wiring/relay tests.
• Disconnect the battery before disconnecting or connecting electrical harnesses to avoid short circuits.
• Follow OEM procedures for any sensor/relay replacement and for reprogramming if needed.

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.

---