P0699
UniversalSensor Reference Voltage C Circuit High
Medium SeverityThe powertrain control module (PCM) has detected that the reference voltage on circuit C, which supplies power to various sensors, is higher than its normal operating range. This high voltage can cause connected sensors to provide inaccurate readings, potentially leading to engine performance problems or difficulty starting.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before working on electrical components to prevent electrical shock or damage to the vehicle's systems. Ensure the vehicle is off and cooled down before attempting any repairs.
Common Symptoms
- Check Engine Light illuminated
- Engine performance issues (rough idle, misfires, stalling)
- Hard starting or no-start condition
- Transmission shifting problems
- Inaccurate sensor readings (e.g., fuel gauge, temperature gauge)
Common Causes
- Short to voltage in the reference circuit C wiring
- Faulty PCM/ECM (less common)
- Faulty sensor on reference circuit C (e.g., TPS, MAP, APP sensor)
- Corrosion or damage to wiring or connectors
Frequently reported on: General/Universal
Diagnostic Steps
- Check for other related diagnostic trouble codes (DTCs) and address them first.
- Visually inspect the wiring harness and connectors for the affected reference circuit C for any signs of damage, corrosion, or shorting.
- Using a multimeter, test the voltage at the reference circuit C pin at the affected sensors and at the PCM/ECM connector to identify if the voltage is indeed high.
- If a specific sensor is suspected, disconnect it and retest the circuit voltage. If the voltage returns to normal, the sensor may be faulty.
- If all wiring and sensors appear fine, test the PCM/ECM outputs, though this usually requires specialized equipment or professional help.
👨🔧 When to Call a Professional
If you lack experience with electrical diagnostics or do not have the necessary tools like a multimeter and wiring diagrams, it is best to consult a certified mechanic. Incorrect diagnosis or repair can damage sensitive electronic components.
Commonly Asked Questions
What does P0699 mean?
It indicates the powertrain control module detected a higher than normal voltage on the sensor reference voltage C circuit, which is used to power certain sensors.
Can I drive with a P0699 code?
It's generally not recommended to drive for extended periods. The high voltage can lead to inaccurate sensor readings, affecting engine performance, fuel economy, and potentially causing other components to fail. Address it as soon as possible.
How do I identify which sensor is on circuit C?
You'll need your vehicle's specific wiring diagrams to determine which sensors are powered by reference voltage circuit C. Common sensors on a reference circuit include throttle position, manifold absolute pressure, and accelerator pedal position sensors.
Is a faulty PCM always the cause of P0699?
No, a faulty PCM is less common. More often, the issue lies with a short to voltage in the wiring, a damaged connector, or a faulty sensor creating the high voltage condition.
What tools do I need to diagnose P0699?
A multimeter is essential for testing voltage and continuity. Access to your vehicle's specific wiring diagrams is also crucial for pinpointing the affected circuit and components.