What it means
The 5 V supply rail D is above the expected level. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The powertrain control module supplies certain sensors from a regulated 5 V reference rail labeled D and checks that rail’s voltage. This code sets when rail D reads higher than the module’s allowed range, which can affect every sensor sharing that supply.
Common causes
Most likely first.
- Reference wire shorted to a B+ supply
- Internal 5 V regulator failed
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light may be on
- One or more sensor readings may be implausible
- Rough running or reduced power may occur
How to diagnose it
- Use a scan tool to record freeze-frame data and compare live readings from sensors on reference rail D to find which readings became implausible when the fault set.
- Check the battery and charging system for abnormal voltage, since an overvoltage condition can affect monitored supplies.
- With the ignition off, inspect rail D wiring and sensor connectors for chafing, moisture, corrosion, loose terminals, or pins pushed back.
- With a wiring diagram, identify the sensors sharing rail D and disconnect them one at a time as directed by the manufacturer to see whether the rail voltage returns to range.
- Measure rail D at the specified test points and check for a short to battery voltage, then test the module’s 5 V regulator if the wiring and connected sensors are sound.
Common fixes
- Repair chafed or damaged wiring that lets rail D contact a higher-voltage circuit.
- Clean or repair corroded, loose, or pushed-back terminals at the affected connectors.
- Replace a sensor that is pulling rail D high, after confirming the fault follows that sensor.
- Repair or replace the control module if its 5 V regulator is confirmed faulty.
Can I keep driving?
If the engine runs normally, drive only as needed to reach a safe place for diagnosis; implausible sensor data can cause rough running or reduced power. Stop if the engine becomes difficult to control or power drops sharply.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.