What Does P0698 Mean?
The PCM has detected that the 5-volt sensor reference voltage bus "C" is reading lower than the expected 5V threshold. A low reference voltage means all sensors on this bus are providing inaccurate (lower than actual) readings to the PCM. This can cause incorrect fuel mixture calculations, erratic idle, poor acceleration, and potential stalling. The driver may notice significant performance issues and multiple sensor-related codes.
Safety Warning
Low sensor reference voltage causes the PCM to receive inaccurate data from multiple sensors, leading to poor engine performance, potential stalling, and unpredictable behavior. Do not drive the vehicle until the fault is resolved, as sudden loss of power or stalling could occur in traffic.
Common Causes
30%
Short to ground in the 5V reference "C" wiring harness due to insulation damage
30%
Failed sensor on the "C" bus internally shorting the reference line to ground
20%
Corroded connector allowing moisture ingress and creating a low-resistance path to ground
15%
Internal PCM 5V reference "C" regulator failure producing insufficient voltage
5%
Damaged ground wire touching the reference wire at a splice or harness bundle
Diagnostic Steps
1
Measure the 5V reference "C" voltage at the PCM connector with all sensors connected; if below 4.5V at the source, the PCM regulator may be weak. If it is 5V at the PCM but low at sensors, the fault is in the harness.
2
Disconnect all sensors on the "C" reference bus one at a time while monitoring reference voltage; if voltage returns to 5V when a specific sensor is disconnected, that sensor is shorting the bus to ground.
3
With all sensors disconnected, measure resistance from the 5V reference wire to ground; it should be greater than 10k ohms. A low reading indicates a wiring short to ground.
4
Inspect connectors and harness routing for the "C" reference circuit, checking for water damage, chafing against metal brackets, or melted insulation near heat sources.
5
If a shorted sensor is found, replace it, clear codes, and verify the 5V reference returns to specification across all sensors on the bus.
Estimated Repair Cost
$75 - $600
Parts + labor, varies by vehicle and location
The PCM has detected that the 5-volt sensor reference voltage bus "C" is reading lower than the expected 5V threshold. A low reference voltage means all sensors on this bus are providing inaccurate (lower than actual) readings to the PCM. This can cause incorrect fuel mixture calculations, erratic i...
The most common cause of P0698 (Sensor Reference Voltage "C" Circuit Low) is: Short to ground in the 5V reference "C" wiring harness due to insulation damage
Typical repair costs for P0698 range from $75 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Low sensor reference voltage causes the PCM to receive inaccurate data from multiple sensors, leading to poor engine performance, potential stalling, and unpredictable behavior. Do not drive the vehicle until the fault is resolved, as sudden loss of power or stalling could occur in traffic.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0698 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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