P0697

Code

Generic P — Powertrain

Sensor Reference Voltage C Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 33 EN: 110 RU: 70

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Page language: EN

Causes

Open circuit in sensor reference C wiring (broken wire, disconnected connector)
Short to ground in the reference C circuit
Short to battery/ignition voltage in the reference C circuit
Corroded/loose sensor or PCM connector pins
Faulty sensor that draws excessive current or internally shorts
Blown fuse or damaged wiring harness (water intrusion, abrasion)

Symptoms

Check Engine Light (MIL) illuminated
Reduced engine performance, rough idle or stalling (if affected sensor is critical)
Incorrect or missing sensor data shown on a scan tool
Intermittent drivability issues when harness is moved or heated/cooled
Some sensors that use the C reference may not operate (fuel injection, ignition timing, boost control, etc.)

What to check

Retrieve all stored codes and freeze frame data with a scan tool; note related sensor codes
Identify which sensor(s) use Reference Voltage C from the vehicle service manual/wiring diagram
Visually inspect wiring and connectors for damage, corrosion, loose pins, or evidence of rodent/abrasion damage
Back-probe the sensor connector and measure reference voltage with key ON, engine OFF
Check continuity between the sensor reference pin and the PCM reference output pin (expect near 0 ohms)
Check for short to ground (low ohms to ground) or short to battery (voltage present with sensor disconnected)

Signal parameters

Expected reference voltage: approximately 5.0 V (typical acceptable range 4.5–5.5 V or 4.75–5.25 V depending on manufacturer)
Open circuit: no reference voltage (0 V or floating) at the sensor connector with key ON
Short to ground: reference voltage near 0 V with connector connected or harness grounded
Short to battery/ignition: reference voltage equal to battery voltage (~12 V) at sensor connector

Diagnostic algorithm

Step 1 — Confirm code and context: read DTCs and freeze frame; check for multiple reference circuit codes. Identify which sensors use Reference Voltage C via wiring diagrams.
Step 2 — Visual inspection: inspect harness, connectors, pin condition, and nearby components for damage, corrosion, water, or aftermarket modifications. Repair obvious damage.
Step 3 — Measure reference voltage: back-probe the sensor connector with key ON (engine OFF). If ~5 V is present at the PCM connector and not at the sensor when plugged in, suspect connector/terminal problem or damaged contact.
Step 4 — Check harness continuity: with battery disconnected, measure continuity between sensor reference pin and PCM reference output pin. High resistance or open indicates a broken wire or bad connector.
Step 5 — Check for shorts: with connector disconnected, measure resistance from the reference wire to ground (should be infinite/very high). If low, locate and repair short to ground. Also check for short to battery (presence of ~12 V with ignition off might indicate short).
Step 6 — Isolate sensors: disconnect the suspect sensor(s); re-test voltage at harness connector. If voltage returns to normal when sensor disconnected, the sensor may be shorted and should be replaced.
Step 7 — Repair and retest: repair wiring or connector faults, replace the sensor if confirmed faulty, clear codes and perform road test. If wiring and sensors check good and problem persists, consider PCM-level diagnosis or replacement only after verifying harness and sensor integrity.

Likely causes

Damaged wiring between PCM and the affected sensor(s)
Connector pins pushed out, bent, corroded or contaminated
Aftermarket accessory or repair that disturbed the wiring harness
Sensor failure causing internal short or open
Loose or missing harness retainer allowing connector movement and intermittent contact

Fault status

⚠️ Status

Open or short detected in Sensor Reference Voltage C circuit. PCM has lost the expected reference supply (approx. 5V) to one or more sensors; diagnostic and repair of wiring, connectors, or sensor required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2 hours