P0698 — Sensor Reference Voltage “C” Circuit Low #

Please note: The description of code P0698 may vary depending on the vehicle manufacturer (OEM). Always refer to your vehicle’s specific documentation for the most accurate definition.

• Sensor Reference Voltage “C” Circuit Low (Generic/SAE)
• Reference Voltage Circuit C Low Input (Chrysler/Jeep/RAM)
• Sensor Reference Voltage C Circuit Low Input (GM/Chevrolet/Buick)
• Sonde Tension de Référence “C” Circuit Bas (Peugeot/Citroën, French)

Summary of Code P0698 #

P0698 is an OBD-II trouble code that indicates the Powertrain Control Module (PCM), which is the vehicle’s central computer, has detected a low voltage condition in the reference voltage circuit “C”. This “reference voltage” is a stable 5-volt supply sent to certain sensors—such as temperature, pressure, or position sensors—so they can send accurate readings back to the PCM. When the voltage in circuit “C” drops below the expected threshold, it can compromise the accuracy of sensor data, which may affect engine performance, emissions, or drivability. This code is generic, but the affected sensors and circuits can differ between manufacturers and models. Prompt diagnosis is key to prevent cascading problems or safety issues.

Common Symptoms for DTC P0698 #

Vehicles with P0698 often show symptoms related to the malfunctioning sensor(s) supplied by reference circuit “C”. Sometimes, the only sign is an illuminated Check Engine Light. In other cases, the engine may run roughly or have performance issues. Here are the most common symptoms you might observe:

• Check Engine Light illuminated
• Engine hesitation or stalling
• Reduced engine power (limp mode)
• Poor acceleration or throttle response
• Hard starting or no-start condition
• Other sensor-related codes (e.g., for MAP, TPS, or ECT sensors)

Probable Causes for DTC P0698 (Ranked by Likelihood) #

Several factors can trigger a low voltage in the sensor reference circuit “C”. Generally, the most common causes are related to wiring issues, connector faults, or sensor malfunctions. Understanding the likely culprits helps prioritize your troubleshooting:

1. Damaged or corroded wiring in the reference circuit “C”
2. Loose, unplugged, or corroded connectors at the affected sensor(s) or PCM
3. Faulty sensor on the reference voltage “C” circuit
4. Short to ground in the reference voltage circuit “C”
5. Failed PCM (rare), unable to supply or regulate reference voltage

Step-by-Step Diagnosis for DTC P0698 #

Diagnosing P0698 requires a systematic approach to identify whether the issue lies with the wiring, the sensors, or the PCM itself. Here’s a step-by-step guide to help you pinpoint the root cause:

• Scan for additional codes: Check for other OBD-II codes that might point to a specific sensor or circuit fault.
• Identify affected sensors: Consult your vehicle’s wiring diagram to find all sensors powered by reference voltage circuit “C”.
• Visual inspection: Examine wiring and connectors on circuit “C” for damage, corrosion, or loose connections.
• Check reference voltage: With the ignition ON (engine off), use a multimeter to measure voltage at the sensor connector; it should read close to 5 volts.
• Test for shorts: Check for continuity between the reference wire and ground; there should be none.
• Sensor check: Unplug sensors on circuit “C” one at a time to see if voltage returns—if so, the unplugged sensor may be at fault.
• PCM check: If all else fails, verify PCM reference output at the source, and consider PCM diagnosis or replacement as a last resort.

Possible Repairs for DTC P0698 #

Once you’ve identified the cause, repairs can range from simple wiring fixes to component replacement. Always clear the code and retest after any repair:

• Repair or replace damaged wiring in the reference voltage circuit “C”
• Clean or secure connectors at sensors or PCM
• Replace the faulty sensor drawing down the voltage
• Fix any shorts to ground in the reference voltage “C” wiring
• Replace PCM if it cannot provide the correct reference voltage (rare; only after confirming all other causes)

Is It Safe to Drive with Code P0698? #

Limited: Use caution. Driving with P0698 may be possible in the short term if you only notice a Check Engine Light and no performance issues. However, if your engine runs poorly, stalls, or enters limp mode, continued driving could cause further damage or unsafe conditions. It’s recommended to diagnose and repair this code as soon as practical.

Vehicles Most Commonly Affected by DTC P0698 #

While P0698 is a generic code, it’s more frequently reported on certain makes and models—often those with complex sensor networks or known wiring vulnerabilities. The following brands and models appear most often in repair data:

• Chrysler, Dodge, Jeep, RAM (widely reported on 2000s–2010s models)
• General Motors (Chevrolet, GMC, Buick, Cadillac — especially mid-2000s trucks/SUVs)
• Fiat and Alfa Romeo (European models with shared PCM architectures)
• Peugeot and Citroën (for some Euro-market vehicles)

Frequent Mistakes & Best Practices for P0698 #

Misdiagnosis is common with this trouble code, often leading to unnecessary sensor replacement or overlooking simple fixes. Here’s how to avoid common pitfalls:

• Don’t replace sensors before checking the reference voltage supply and wiring.
• Always inspect connectors for corrosion or looseness before condemning a sensor or PCM.
• Consult the correct wiring diagram for your specific vehicle—sensor assignments to reference circuits can vary.
• Clear all codes and recheck after each repair to confirm the issue is fixed.

Quick FAQ about P0698 #

Here are answers to two of the most common questions drivers and technicians have about P0698:

• Q: Can one bad sensor on circuit “C” cause the reference voltage to drop for all sensors on that circuit?
  A: Yes. If a sensor fails internally and creates a short to ground, it can pull down the reference voltage for all sensors sharing circuit “C”, triggering multiple symptoms or codes.
• Q: How do I find which sensors are on reference circuit “C” in my vehicle?
  A: The best resource is the official wiring diagram for your specific make, model, and year. Most manufacturer service manuals or professional scan tools can provide this detail.