What Does P0697 Mean?
The PCM has detected an open circuit on the 5-volt sensor reference voltage bus "C". This reference line provides the precise 5V supply that multiple engine sensors (such as TPS, MAP, fuel pressure, or EGR position) rely on for accurate readings. When this bus goes open, all sensors sharing the "C" reference may report incorrect data or fail entirely, potentially causing driveability issues, rough running, or a no-start condition.
Safety Warning
This code can cause severe driveability issues including stalling, rough running, loss of power, or inability to start. Multiple sensor inputs may be lost simultaneously. The vehicle should not be driven until diagnosed and repaired, as the engine may stall unexpectedly in traffic.
Common Causes
30%
Open or broken wire in the 5V reference "C" bus harness, often due to chafing or heat damage
25%
Failed sensor on the "C" bus creating an internal open that breaks the reference chain
20%
Corroded or disconnected connector at any sensor sharing the "C" reference bus
15%
Internal PCM failure in the 5V reference "C" regulator circuit
10%
Damaged splice or junction point in the shared reference harness
Diagnostic Steps
1
Identify which sensors share the 5V reference "C" bus using the vehicle wiring diagram; common sensors include MAP, TPS, fuel rail pressure, and EGR position sensors.
2
With key on engine off, backprobe the 5V reference pin at each sensor on the "C" bus; normal reading is 4.9-5.1V. An absent or very low reading at all sensors confirms the open reference.
3
Disconnect sensors on the "C" bus one at a time and check if the 5V reference returns at the remaining sensors; if it returns when a specific sensor is disconnected, that sensor has an internal open/short.
4
Inspect the wiring harness for the 5V reference "C" line, paying attention to areas near the exhaust manifold, sharp edges, and routing clamps where chafing commonly occurs.
5
Measure resistance of the 5V reference wire from the PCM connector pin to each sensor connector pin; should be near 0 ohms. An open reading indicates a break in the wire.
6
If all wiring and sensors test good, the PCM 5V reference "C" regulator may have failed internally.
Estimated Repair Cost
$75 - $600
Parts + labor, varies by vehicle and location
The PCM has detected an open circuit on the 5-volt sensor reference voltage bus "C". This reference line provides the precise 5V supply that multiple engine sensors (such as TPS, MAP, fuel pressure, or EGR position) rely on for accurate readings. When this bus goes open, all sensors sharing the "C" ...
The most common cause of P0697 (Sensor Reference Voltage "C" Circuit Open) is: Open or broken wire in the 5V reference "C" bus harness, often due to chafing or heat damage
Typical repair costs for P0697 range from $75 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This code can cause severe driveability issues including stalling, rough running, loss of power, or inability to start. Multiple sensor inputs may be lost simultaneously. The vehicle should not be driven until diagnosed and repaired, as the engine may stall unexpectedly in traffic.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0697 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Electrical / Sensor Reference
Difficulty
Type
Generic (SAE)
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