Short to earth or to voltage on the shared sensor reference supply wiring; A faulty sensor on the reference C circuit pulling the supply down internally; Damaged, corroded or loose connector terminals or wiring (chafing, water ingress); Open circuit or high resistance in the reference supply wire or a splice; Poor engine control unit earth or power supply fault; Fault inside the engine control unit's reference voltage regulator.

P0697

Sensor Reference Voltage C Circuit/Open.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
6: AreaComputer and output circuits
97: FaultThe specific fault in that area

What it means

P0697 is the generic code for a fault in the sensor reference voltage 'C' circuit, or the circuit being open. The engine control unit supplies a regulated reference voltage (normally 5 V, sometimes 12 V on some systems) to a group of sensors, and it has seen that supply out of range or missing. Which sensors share reference C varies by model and engine, so the wiring diagram is needed to identify them.

Symptoms

Engine warning light on
Poor running, hesitation or reduced power
Limp mode or restricted throttle response
Rough idle or stalling
Hard starting or no start
Other sensor fault codes stored at the same time

Possible causes

Short to earth or to voltage on the shared sensor reference supply wiringlikely
A faulty sensor on the reference C circuit pulling the supply down internallylikely
Damaged, corroded or loose connector terminals or wiring (chafing, water ingress)likely
Open circuit or high resistance in the reference supply wire or a splicepossible
Poor engine control unit earth or power supply faultpossible
Fault inside the engine control unit's reference voltage regulatorrare

How to diagnose

Read all stored and pending codes and note which other sensor codes appear alongside P0697, as they point to the shared sensors
Review freeze frame data to see engine speed, load and temperature when the fault set
Use the wiring diagram to identify which sensors share reference C for this model and engine
Visually inspect the related wiring, connectors and harness routes for chafing, water, corrosion or previous repair damage
With ignition on, measure the reference voltage at the sensor connectors and compare with the specification
Unplug the sensors on the circuit one at a time and watch whether the reference voltage recovers, which identifies a faulty sensor
Test the reference wire for continuity, and for shorts to earth or voltage, with the control unit disconnected
Check the control unit power and earth connections for voltage drop

How to fix

Replace the sensor that is pulling the reference voltage out of range
Repair or replace damaged wiring and fix any short or open circuit found
Clean or replace corroded or damaged connectors and terminals
Restore poor power or earth connections to the control unit
Replace or repair the control unit only after the wiring and sensors are proven good, following the manufacturer's procedure

Can I keep driving?

Medium severity

The car may be driveable, but poor running, limp mode or stalling can occur without warning, so get it checked soon. Avoid driving if it stalls or loses power, as that is a safety risk.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.