P0697
UniversalSensor Reference Voltage C Circuit / Open
High SeverityThe P0697 code indicates that the Powertrain Control Module (PCM) has detected an open circuit in the 5-volt reference circuit 'C' that supplies power to multiple sensors. This open circuit means sensors relying on this specific voltage supply are not receiving power, which can lead to various engine performance issues.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before performing any electrical work on your vehicle. Be cautious when working around hot engine components and moving parts. If the vehicle is experiencing severe drivability issues, avoid driving it until diagnosed and repaired.
Common Symptoms
- Check Engine Light illuminated
- Engine may not start
- Engine stalling
- Rough idling or misfires
- Transmission shifting problems
- Lack of power or poor acceleration
- Inaccurate sensor readings (e.g., coolant temperature, throttle position)
Common Causes
- Open circuit or short circuit in the sensor reference voltage 'C' wiring harness
- Faulty sensor (e.g., shorted internal circuit causing an open on the reference line)
- Corroded or loose electrical connectors
- Faulty Powertrain Control Module (PCM)
Frequently reported on: General/Universal
Diagnostic Steps
- Visually inspect all wiring and connectors related to the engine and transmission for signs of damage, corrosion, or loose connections.
- Check for any blown fuses, especially those related to the engine or PCM. Replace if necessary.
- If comfortable with electrical testing, use a multimeter to check for 5-volt reference voltage at various sensors connected to circuit 'C'. This requires a wiring diagram specific to your vehicle.
- Unplug sensors one by one that are on the reference 'C' circuit and recheck for the 5V reference. A faulty sensor could be shorting the circuit.
👨🔧 When to Call a Professional
If you lack experience with electrical diagnosis using a multimeter and wiring diagrams, or if initial visual inspections do not reveal the fault, it is best to consult a professional mechanic. Diagnosing an intermittent open circuit can be particularly challenging.
Commonly Asked Questions
What does "Sensor Reference Voltage C Circuit / Open" mean?
It means the computer (PCM) isn't detecting the necessary 5-volt power signal on a specific circuit (labeled 'C') that's supposed to supply various sensors. An "open" circuit means there's a break preventing the flow of electricity.
Can I drive with a P0697 code?
It is generally not recommended to drive with a P0697 code as it indicates a critical electrical fault. Loss of sensor function can lead to unpredictable engine behavior, stalling, or damage to other components.
How do I find which sensors are on "Circuit C"?
You'll need your vehicle's specific wiring diagrams. These diagrams will show which sensors share the same 5-volt reference circuit. Common sensors might include MAP, TPS, or cam/crank sensors.
Is it possible for a bad sensor to cause this code?
Yes, an internal short within a sensor connected to reference circuit 'C' can sometimes draw too much current, causing the PCM to detect it as an open circuit to protect itself, or it can blow a fuse, leading to an open.
What's the most common cause of P0697?
The most common causes are damaged wiring or connectors leading to an open circuit. Less common but possible causes include a faulty sensor shorting the circuit or, in rare cases, a defective PCM.