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DTC codes / P06xx · Computer and output circuits / P06A5

P06A5Sensor Reference Voltage D Circuit High

P06A5 indicates that the powertrain control module (PCM) has detected a voltage on the sensor reference voltage D circuit that is higher than the expected 5-volt (or 3.3-volt) supply. This reference voltage is shared by multiple sensors, so an abnormally high reading points to a short to voltage, an open ground, or a faulty sensor pulling the line up.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Illumination of the check engine light (malfunction indicator lamp) with no other noticeable symptoms
  • Rough running or misfire if the affected sensors include the throttle position or manifold absolute pressure sensor
  • Reduced engine power or limp mode if the PCM deems the fault critical
  • Erratic or delayed transmission shifting when the reference voltage feeds a transmission sensor
  • Poor fuel economy or increased emissions due to incorrect sensor readings
  • In some cases, the engine may stall or hesitate during acceleration

Common causes, most likely first

  1. Short to voltage on the sensor reference voltage D circuit (e.g., chafed wire contacting a 12-volt source)
  2. Faulty sensor internally shorted and pulling the reference voltage high
  3. Open or high-resistance ground circuit for a sensor sharing the reference voltage
  4. Corroded or damaged connector pins at the PCM or sensor harness
  5. PCM internal fault causing incorrect reference voltage output
  6. Aftermarket accessories improperly wired into the reference circuit

How to diagnose and fix it

  1. Use a scan tool to retrieve all stored codes and freeze-frame data to identify which sensors share the reference D circuit.
  2. Visually inspect the harness and connectors for signs of chafing, corrosion, or loose pins, especially near hot or moving components.
  3. Disconnect sensors one at a time and monitor the reference voltage with a digital multimeter (DMM) to see if the high voltage disappears, isolating the faulty sensor.
  4. Measure resistance to ground on the reference circuit with the PCM disconnected to check for an open ground or high resistance.
  5. Check for voltage on the reference circuit with the ignition on and sensors disconnected; it should be close to 5 volts (or 3.3 volts) and stable.
  6. If the voltage remains high with all sensors disconnected, suspect a short to voltage in the harness or a faulty PCM; perform a voltage drop test on the circuit.
  7. Repair or replace the faulty sensor, harness, or PCM as needed, then clear codes and verify the repair with a test drive.

Shared Reference Circuits Can Mislead

  • The reference voltage D circuit often feeds multiple sensors, so a single shorted sensor can pull the entire circuit high and set codes for other sensors as well.
  • A common mistake is replacing the sensor that the code points to without checking the shared circuit; the fault may lie in a different sensor or in the wiring.
  • High reference voltage can also be caused by a poor ground at the sensor, which raises the voltage drop across the sensor and confuses the PCM.
  • Aftermarket electrical accessories tapped into the reference circuit can backfeed voltage and cause this code, so always check for non-factory wiring.
  • The PCM itself rarely fails, but when it does, it can output an incorrect reference voltage; confirm all other possibilities before replacing it.

Can I keep driving with P06A5?

If the vehicle drives normally, you can cautiously drive to a repair shop, but avoid heavy acceleration or towing. If the engine runs poorly or enters limp mode, stop driving and have the vehicle towed to prevent damage or unsafe operation.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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