Sensor Reference Voltage Circuit Low
The P0698 code indicates that the Engine Control Module (ECM) has detected a low voltage condition on the sensor reference voltage circuit, typically the 5-volt reference. This circuit powers various sensors like the throttle position sensor, crankshaft position sensor, and manifold absolute pressure sensor. A low voltage can cause multiple sensors to malfunction, leading to drivability issues.
1. Most Common Causes
- Short to ground in the 5-volt reference circuit
- Faulty sensor drawing excessive current
- Damaged wiring or connectors
- Failed ECM (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine stalling or rough idle
- Poor acceleration or hesitation
- Multiple sensor-related codes present
3. Step-by-Step Diagnosis
Step 1: Use a multimeter to check voltage at the 5-volt reference pin of a sensor; should be around 5 volts.
Step 2: If voltage is low, disconnect sensors one by one to see if voltage returns to normal, indicating a shorted sensor.
Step 3: Inspect wiring and connectors for damage, corrosion, or shorts to ground.
Step 4: If no sensor or wiring issue found, test ECM output at the connector; if missing, ECM may need replacement.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended as low reference voltage can cause unpredictable engine behavior, stalling, or loss of power, which may be dangerous.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and repair, but costs can vary if the ECM needs replacement, which can be $500-$1000.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.