P0697: Sensor Reference Voltage C Circuit Open
What to do
Expect reduced power. As with the other reference faults, do not authorise replacing several sensors that failed together — they share a supply, and one shorted sensor or damaged wire explains all of them. Ask whether the reference voltage itself was measured.
What this code means
The third sensor reference voltage supply has failed open. Everything in P0641 applies: one regulated supply feeds several sensors, and when it collapses they all report nonsense together.
A third reference exists on engines carrying enough analogue sensors that two supplies cannot serve them all — commonly larger diesels with rail pressure, exhaust pressure, boost and throttle sensors to feed. Which sensors sit on reference C is engine-specific, so the codes stored alongside identify the circuit faster than tracing wiring.
Likely causes
Start here
- Shorted sensor dragging the reference down · moderate
- Failed sensor reference voltage supply · moderate
- Damaged wiring harness near exhaust heat · moderate
Less common
- Water ingress into connector · easy
- Failed control module · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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