P0694 Cooling Fan 2 Relay Control Circuit High

The P0694 trouble code is a generic OBD-II diagnostic trouble code related to the second engine cooling fan relay control circuit.

P0694 – Cooling Fan 2 Relay Control Circuit High

This code means that the PCM/ECM has detected higher-than-expected voltage in the control circuit for Cooling Fan 2.

The cooling fan system is responsible for maintaining the correct engine coolant temperature and, on many vehicles, helping control the temperature of the air-conditioning condenser. Modern vehicles may use one or more electric cooling fans that operate at different speeds depending on coolant temperature, A/C demand, vehicle speed and engine load.

When the PCM commands Cooling Fan 2 on or off, it monitors the electrical circuit. If the voltage does not behave as expected and remains too high, the PCM can store P0694.

Importantly, P0694 does not necessarily mean that the cooling fan motor itself is bad. The problem can be located in the relay, wiring, connector, fuse, control circuit or PCM.

What Does P0694 Mean?

P0694 can be understood as:

P = Powertrain
0 = Generic OBD-II code
6 = Computer output/control-related fault
9 = Specific system identifier
4 = Cooling Fan 2 control circuit high

The key phrase is:

Cooling Fan 2 Relay Control Circuit High

The PCM has detected a voltage condition in the Fan 2 relay control circuit that is higher than the expected value.

What Is Cooling Fan 2?

Many vehicles use more than one electric cooling fan.

For example, a vehicle may have:

• Cooling Fan 1

• Cooling Fan 2

The fans can operate individually or together.

Depending on the vehicle, Fan 2 may be used for:

• Additional engine cooling

• High coolant temperatures

• Air-conditioning condenser cooling

• High engine load

• Low vehicle speed

• High ambient temperatures

Some vehicles do not use two physically separate fans. Instead, they may use multiple fan circuits or a multi-speed fan arrangement.

Therefore, "Fan 2" should always be identified using the specific vehicle's wiring diagram.

What Does "Circuit High" Mean?

The word High refers to the electrical condition of the control circuit.

It does not necessarily mean:

• The engine temperature is high

• The cooling fan is spinning too fast

• The fan motor has excessive RPM

Instead, it means the PCM sees more voltage than expected on the Fan 2 relay control circuit.

A circuit that should normally be pulled low by the PCM may remain at a higher voltage than expected.

Symptoms of P0694

Possible symptoms include:

• Check Engine Light

• Engine cooling fan not operating correctly

• Fan 2 not operating

• Cooling fan running continuously

• Engine temperature rising

• Engine overheating

• A/C performance problems

• A/C compressor cycling abnormally

• Fan operating at the wrong speed

• Cooling fan remaining on after the engine is switched off

• Reduced engine performance in severe overheating conditions

The symptoms depend heavily on how the vehicle's fan system is designed.

Can P0694 Cause Engine Overheating?

Yes.

If Cooling Fan 2 is required for adequate cooling and it does not operate, engine coolant temperature can rise.

However, P0694 itself does not mean the engine is overheating. The code identifies an electrical problem in the Fan 2 control circuit.

If the vehicle's cooling system depends heavily on Fan 2, overheating can occur quickly, particularly when:

• Idling

• Driving slowly

• Sitting in traffic

• Using the A/C

• Driving in hot weather

• Operating under heavy load

If the temperature gauge rises toward the overheating range, the vehicle should be stopped safely rather than continuing to drive.

Common Causes of P0694

Faulty Cooling Fan 2 relay

The relay may have an internal electrical fault or contacts that are stuck.

Relay contacts stuck closed

A relay can remain energized even when it should be switched off.

Short to battery voltage

The control wire may be receiving voltage directly from the battery or another power source.

Damaged wiring

Chafed or incorrectly repaired wiring can create an unintended voltage connection.

Corroded connector

Corrosion can alter circuit resistance and produce abnormal voltage readings.

Loose connector terminal

A poor connection can interfere with relay control.

Incorrect relay

Installing a relay with the wrong configuration can cause abnormal circuit behavior.

Blown or incorrect fuse

A fuse problem can affect the fan power circuit, although a blown fuse does not by itself explain every P0694 condition.

Faulty cooling fan motor

A defective fan motor can sometimes cause excessive current or other electrical abnormalities that affect the control system.

Faulty fan control module

Some vehicles use a dedicated electronic fan control module instead of conventional relays.

Damaged fuse/relay box

Heat, corrosion or water intrusion can damage the relay control circuitry.

PCM driver problem

The PCM contains an electronic driver that may control the relay.

If this driver fails, the circuit may remain at an incorrect voltage.

Poor PCM ground

A poor ground can cause abnormal control-circuit behavior.

Aftermarket electrical modification

Remote starters, alarms, accessories or previous electrical repairs can interfere with cooling fan circuits.

Is P0694 Serious?

It can be serious.

The electrical fault itself may be relatively simple, but the consequences can be significant if Fan 2 is required to maintain engine temperature.

A cooling fan problem can eventually lead to:

• Engine overheating

• Coolant boiling

• Cylinder-head damage

• Head-gasket damage

• Warped components

• Severe engine damage

Do not ignore P0694 if the engine temperature is rising.

Can You Drive With P0694?

It depends on whether the cooling system is still operating correctly.

If the engine maintains normal temperature and the primary cooling fan continues to operate, a short trip to a repair facility may be possible.

However, avoid driving if:

• The temperature gauge is rising

• The engine is overheating

• Cooling fans do not operate when required

• Coolant is boiling

• The temperature warning light is on

• Steam is coming from the engine compartment

An overheating engine can suffer expensive damage very quickly.

P0694 vs. P0691

P0691 – Cooling Fan 1 Relay Control Circuit Low

The PCM detects an unexpectedly low condition in Fan 1's relay control circuit.

P0694 – Cooling Fan 2 Relay Control Circuit High

The PCM detects an unexpectedly high condition in Fan 2's relay control circuit.

P0694 vs. P0692

P0692 – Cooling Fan 1 Relay Control Circuit High

Concerned with Fan 1.

P0694 – Cooling Fan 2 Relay Control Circuit High

Concerned with Fan 2.

Both describe a high control-circuit condition, but they refer to different fan circuits.

P0694 vs. P0693

P0693 – Cooling Fan 2 Relay Control Circuit Low

The Fan 2 relay control circuit is detected as too low.

P0694 – Cooling Fan 2 Relay Control Circuit High

The Fan 2 relay control circuit is detected as too high.

This distinction is useful when diagnosing whether the control circuit is being pulled down correctly.

Can a Bad Cooling Fan Relay Cause P0694?

Yes.

A defective relay is one of the first components worth checking.

The relay may have:

• Stuck contacts

• Internal shorting

• Incorrect resistance

• Heat damage

• Corrosion

• Internal mechanical failure

However, the relay should be tested according to the manufacturer's specifications rather than replaced automatically.

Can a Short to Battery Cause P0694?

Yes.

A short to battery voltage is a particularly important possibility when the PCM detects a high control-circuit voltage.

The control wire may be receiving voltage from an unintended source.

Can a Bad Fan Motor Cause P0694?

Potentially.

The fan motor itself is not the primary definition of P0694, but a motor fault can affect the overall fan circuit.

A seized or partially seized motor can also cause excessive current draw and damage relays, fuses or wiring.

Can a Bad PCM Cause P0694?

Yes, but this should not be the first assumption.

The PCM controls the relay through an electronic driver.

If the driver transistor or internal control circuit fails, the PCM may be unable to control the relay correctly.

Before replacing a PCM, verify:

• Relay operation

• Wiring

• Power supply

• Ground

• Connector condition

• Fan motor

• Control-circuit voltage

Can a Blown Fuse Cause P0694?

A blown fuse can cause cooling fan problems, but a simple open power fuse does not necessarily explain a "circuit high" control code.

The complete fan circuit should be tested rather than assuming that the fuse is the cause.

Can a Bad A/C System Cause P0694?

Indirectly, potentially.

Cooling fans often operate when the A/C system is running because airflow across the condenser is necessary.

However, an A/C problem does not automatically cause P0694.

The fan control system should be diagnosed separately.

Can P0694 Cause the A/C to Stop Working?

Yes, potentially.

If the vehicle cannot properly control the cooling fan, the PCM or climate-control system may disable or limit A/C operation to protect the system.

The exact behavior depends on the vehicle.

Can P0694 Cause the Fan to Run Constantly?

Yes.

If the relay is stuck or the control circuit is receiving an unintended voltage, the fan may remain operational when it should be switched off.

Can P0694 Cause the Fan Not to Run?

Yes.

A circuit fault can prevent the PCM from correctly activating Fan 2.

How to Diagnose P0694

A proper diagnosis should begin with the electrical control circuit rather than immediately replacing the fan motor or PCM.

1. Scan all modules

Check for additional codes relating to:

• Cooling fan

• Engine coolant temperature

• A/C pressure

• Power supply

• PCM communication

• Other fan circuits

Additional codes can provide important clues.

2. Check engine coolant temperature

Use the scan tool to compare:

• Actual coolant temperature

• Dashboard temperature indication

• PCM coolant temperature

If the coolant temperature sensor is reporting an unrealistic value, fan operation may also be affected.

3. Check whether Fan 2 operates

Determine:

• Does Fan 2 operate at all?

• Does it operate continuously?

• Does it operate at the correct speed?

• Does it activate when commanded with a scan tool?

• Does it operate when the engine becomes hot?

• Does it operate when the A/C is switched on?

This immediately provides useful diagnostic information.

4. Test the fan using the scan tool

Many vehicles allow the technician to command cooling fan operation.

Command Fan 2 on and observe:

• Fan operation

• Relay operation

• Control-circuit voltage

• Current draw

If the PCM commands the fan but the fan does not operate, investigate the relay, power circuit, wiring and motor.

5. Inspect the Fan 2 relay

Check:

• Correct relay type

• Relay terminals

• Corrosion

• Heat damage

• Stuck contacts

• Coil resistance

• Switching operation

If the vehicle uses a solid-state fan controller instead of a traditional relay, follow the manufacturer's diagnostic procedure.

6. Check relay power supply

Verify that the relay receives the correct battery voltage where required.

Do not confuse the relay's power contacts with its control circuit.

7. Check the relay control circuit

Measure the voltage on the control side of the relay.

The expected voltage depends on the circuit design.

Some systems control the relay by switching the ground side, while others control it through the positive side.

Therefore, the wiring diagram is essential.

8. Inspect wiring

Look for:

• Short to battery

• Short to ground

• Open circuit

• Chafed insulation

• Melted wires

• Incorrect repairs

• Wiring routed too close to hot components

9. Inspect connectors

Pay particular attention to:

• Relay socket

• Fan connector

• Fan-control module

• PCM connector

Look for:

• Corrosion

• Water intrusion

• Burned terminals

• Loose pins

• Bent terminals

10. Check the fan motor

Verify that the motor:

• Rotates freely

• Does not bind

• Does not make abnormal noises

• Draws the correct current

• Receives the correct voltage

A seized fan motor can cause secondary electrical problems.

11. Check the fan control module

If the vehicle uses an electronic fan control module, verify:

• Power

• Ground

• Command signal

• Output

• Communication

A failed module can produce symptoms similar to a relay failure.

12. Check PCM power and grounds

A PCM ground problem can cause abnormal control-circuit voltage.

Voltage-drop testing is preferable to simply checking continuity.

13. Test for a short to battery

With the appropriate circuit isolated, check whether the control wire is receiving unintended battery voltage.

This is particularly important for a P0694 "High" condition.

14. Check the PCM control driver

If all external circuits are correct but the PCM cannot properly control the relay, the PCM driver may be defective.

PCM replacement should be considered only after the circuit has been thoroughly tested.

How to Distinguish a Relay Problem From a Wiring Problem

If the relay is removed and the control wire still has an unexpected voltage, the wiring or PCM driver may be responsible.

If the control circuit behaves correctly but the relay does not switch, the relay becomes more suspicious.

If the relay switches correctly but the fan does not operate, investigate:

• Fan power supply

• Fan ground

• Fan motor

• Fan wiring

This step-by-step approach prevents unnecessary replacement of expensive components.

How to Distinguish a Fan Motor Problem From a Control-Circuit Problem

A fan motor problem generally becomes more likely when:

• Correct voltage reaches the motor

• Ground is good

• The motor does not run

• Motor current is abnormal

• The fan physically binds

A control problem becomes more likely when:

• The motor works when powered correctly

• The relay does not operate

• Relay control voltage is incorrect

• PCM commands do not reach the relay

Can P0694 Be Caused by a Wiring Repair?

Yes.

Incorrect previous repairs are a surprisingly common source of electrical diagnostic problems.

Examples include:

• Incorrectly connected wires

• Added jumpers

• Poor crimp connections

• Exposed conductors

• Incorrect relay wiring

• Aftermarket accessory connections

Can P0694 Return After Clearing the Code?

Yes.

If the underlying electrical problem remains, the PCM will monitor the circuit again and may store P0694 after the appropriate operating conditions are met.

Clearing the code without repairing the circuit does not solve the problem.

Common Diagnostic Mistakes With P0694

Replacing the fan motor immediately

The fan motor may be perfectly good.

Replacing the PCM immediately

The wiring, relay and connectors should be tested first.

Confusing Fan 1 and Fan 2

The exact fan identification depends on the vehicle.

Ignoring the wiring diagram

Different vehicles use different relay-control strategies.

Testing only for continuity

A circuit can have continuity but still have a short, excessive resistance or an intermittent fault.

Ignoring relay-socket damage

A damaged relay socket can create intermittent or abnormal electrical conditions.

Ignoring coolant temperature data

An incorrect temperature signal can influence fan operation.

Ignoring the A/C system

The cooling fans often have an important role in condenser cooling.

What Is the Correct Repair for P0694?

The correct repair depends on the confirmed cause.

Possible repairs include:

• Replacing a faulty Cooling Fan 2 relay

• Repairing a short to battery voltage

• Repairing damaged wiring

• Repairing an open circuit

• Repairing corroded connectors

• Replacing damaged relay terminals

• Replacing a faulty cooling fan motor

• Replacing a faulty fan-control module

• Repairing fan power or ground circuits

• Correcting PCM power or ground problems

• Repairing the PCM control circuit

• Updating or reprogramming the PCM where applicable

• Replacing the PCM if its internal driver failure is confirmed

How to Test the Vehicle After Repair

After the repair, verify the cooling system under several conditions.

Check that:

• Fan 2 operates when commanded

• Fan 2 switches off when appropriate

• Fan speeds are correct

• Engine coolant temperature remains normal

• A/C operates correctly

• Relay control voltage behaves correctly

• Fan current draw is normal

• No overheating occurs

• No additional cooling-fan codes appear

• P0694 does not return

The vehicle should ideally be tested both at idle and under normal driving conditions.

Frequently Asked Questions About P0694

What does P0694 mean?

P0694 means the PCM has detected a high voltage condition in the Cooling Fan 2 relay control circuit.

Does P0694 mean the cooling fan is bad?

No. The relay, wiring, connector, control module or PCM may be responsible.

Can P0694 cause overheating?

Yes, if Fan 2 is required for adequate engine cooling and does not operate correctly.

Can P0694 cause the fan to run constantly?

Yes.

Can P0694 cause the fan not to run?

Yes.

Can a bad relay cause P0694?

Yes.

Can a short to battery cause P0694?

Yes. This is an important possibility because the code specifically identifies a high control-circuit condition.

Can a bad fan motor cause P0694?

Potentially, although the motor itself is not the direct definition of the code.

Can a bad PCM cause P0694?

Yes, but the external circuit should be tested before condemning the PCM.

Can P0694 cause A/C problems?

Yes, potentially, because the cooling fan may also be needed for condenser cooling.

Can I drive with P0694?

Only if the engine maintains normal temperature and the cooling system is functioning correctly. If the engine overheats or the temperature warning appears, stop driving.

Does P0694 mean the engine will overheat immediately?

No. The severity depends on the vehicle's fan configuration and whether another fan is still operating.

Does P0694 mean the cooling fan relay needs replacement?

Not necessarily. The relay should be tested before replacement.

Final Thoughts on P0694

P0694 – Cooling Fan 2 Relay Control Circuit High indicates that the PCM has detected an unexpectedly high electrical condition in the Cooling Fan 2 relay control circuit.

The fault can be caused by a relatively simple relay or wiring problem, but it can also involve the fan motor, fan-control module or PCM.

A logical diagnostic sequence is:

Scan All Modules → Check Coolant Temperature Data → Command Fan 2 On → Test Relay → Check Relay Control Voltage → Inspect Wiring → Check Fan Motor → Check Fan-Control Module → Verify PCM Power/Ground → Test PCM Driver

The most important point is that P0694 does not automatically mean the cooling fan motor or PCM is defective.

Because a cooling fan malfunction can eventually lead to engine overheating, the vehicle should be diagnosed promptly, particularly if the coolant temperature is rising or the fan does not operate when required.