OBD-II trouble code
P0694: Fan 2 Control Circuit High
The second fan's control circuit stayed at voltage when the module told it to pull down — an open somewhere. Because fan 2 is only ever asked to run under heat and air conditioning load, this break can sit in the harness for months before anything reveals it.
Quick facts
- System
- Powertrain
- Category
- Cooling / Electrical
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $40 – $700
- DIY difficulty
- Intermediate DIY
What does P0694 mean?
The module switches the second fan by pulling its control circuit down to ground and then checks that the voltage actually went where it was sent. When the circuit stays up at supply voltage despite that command, the current has nowhere to go. Something in the path is open: a broken control wire, a relay with an open coil, a terminal that has backed out of its housing, a connector so corroded that it no longer conducts, or a fan lead left unplugged. There is no ambiguity about what the fan will do afterwards, and that is one of the few merciful things about this code. A circuit pulled low can leave a fan running constantly; an open circuit can only leave it not running at all.
What deserves more attention than the electrical theory is when this fault becomes visible, because the gap between the break happening and anybody finding out is unusually long. The second fan is a demand-driven device. It is commanded when refrigerant head pressure rises, when coolant temperature crosses an upper threshold, when the vehicle is towing or climbing, or when ambient temperature is high enough that the primary fan alone cannot keep up. On a cool day, in ordinary driving, without the air conditioning on, the module may go weeks without asking for it. A wire that broke during a February bumper repair produces no code, no symptom and no clue until the first genuinely warm afternoon.
This is why so many of these arrive described as a sudden failure that is nothing of the sort. The vehicle did not develop a fault in June; it revealed one. That reframing matters practically, because the highest-yield diagnostic question is not what changed recently, it is what work has been done to the front of the vehicle at any point since the weather was last hot. Bumper covers, condensers, radiators, headlights, intercoolers and grille trim all sit on top of this harness, and a connector left half-latched during that work behaves perfectly until something asks the circuit to conduct.
An open circuit also draws no excess current, which removes the one warning a vehicle normally gives itself. A short to ground blows a fuse and announces the problem. An open blows nothing, trips nothing, and leaves the module with a stored code and an inert fan. So the first tangible evidence tends to arrive as a consequence rather than as a warning: a temperature gauge climbing in traffic on the hottest day of the year, or an air conditioning system that has been quietly running its compressor against unrelieved head pressure. A stored P0694 found before either of those things happens is the cheap version of this problem, and it is worth acting on while it still is.
The functional check is refreshingly simple because of how absolute an open is. Warm the engine, switch the air conditioning to maximum, and watch. With bidirectional scan tool control, command the fan directly and watch for movement. In either case, a fan that never turns while the circuit is being commanded confirms the fault without a meter, and from there the work is tracing where the path is broken rather than deciding whether there is a fault at all.
Common causes
- Fan 2 control wire broken, cut or pulled apart between the module and the relay
- Relay coil open, or the relay missing from its socket entirely after previous work
- Fan motor connector left unlatched or unplugged during front-end repairs
- Terminal backed out or spread inside the relay socket or fan connector
- Corroded connector no longer conducting despite looking connected
- Open winding inside the second fan motor
- Damaged ground for the fan 2 circuit
- Harness pulled hard enough to break conductors inside intact-looking insulation, typically after a minor front impact
- Failed module driver for the fan 2 output, rare and to be confirmed last
Symptoms
- Check engine light with P0694 stored and often nothing else wrong that the driver can feel
- Second fan never running under any condition, including with the air conditioning at maximum
- Air conditioning performance falling away at idle and in slow traffic
- Coolant temperature rising in traffic on hot days on vehicles where fan 2 assists engine cooling
- Fault appearing for the first time in the first warm spell after months of normal driving
- No blown fuses anywhere, because an open circuit draws no current
- Normal cooling and normal air conditioning at road speed, which masks the fault most of the time
Diagnostic steps
- 1.Warm the engine fully, switch the air conditioning to maximum and watch the second fan. An open circuit means it cannot run, so a fan that never moves confirms the functional side without instruments.
- 2.If the scan tool supports bidirectional control, command the fan 2 output directly. This removes any doubt about whether the module ever asked for it.
- 3.Ask specifically what work has been done to the front of the vehicle since the last hot weather. Bumper, condenser, radiator, headlight and cooler jobs sit directly over this harness and an unlatched connector is a leading cause here.
- 4.Confirm the relay is physically present and fully seated before testing it. Relays borrowed for diagnosis elsewhere and never returned are a real cause of this code.
- 5.Swap the relay for a known-good identical one, or bench-test its coil for an open.
- 6.With the output being commanded, measure voltage along the control circuit from the module toward the relay. The point where the expected drop disappears brackets the break.
- 7.Inspect the relay socket and fan connector for spread, corroded or backed-out terminals, pulling gently on each wire at the back of the connector to find one that has released.
- 8.Measure the fan motor winding resistance to rule out an internal open before condemning the harness.
- 9.Wiggle-test the front harness with the circuit commanded, since a break inside intact insulation after an impact will read fine at rest and open under movement.
Repair cost
$40 – $700
The best case here is genuinely cheap: an unlatched connector or a missing relay costs the diagnostic time and nothing else, roughly $90 to $160. A replacement relay is $15 to $80 in parts. Repairing a broken control wire runs $120 to $350 depending on whether the front of the vehicle has to come apart to reach it. A fan motor with an open winding, or a fan-and-shroud assembly where the motor is not sold separately, is $250 to $700 fitted. Because this fault stays hidden until a hot day, the costs actually worth avoiding are downstream — an overheating event at $1,500 and up, or an air conditioning compressor worked against high head pressure at $900 to $1,800.
Estimate your repair
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Open the Repair Cost Estimator with cooling fan relay replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.