What it means
Same as P0651 with the reference rail shorted to ground. 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
- Affects emissions; the car can fail an emissions test
How it works
The powertrain control module supplies a shared reference-voltage rail called circuit B to sensors that need a stable voltage to report readings. It sets P0652 when it detects that this rail is below its expected range, commonly because the rail is shorted to ground or a connection is faulty.
Common causes
Most likely first.
- Reference rail shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
How to diagnose it
- Read freeze-frame data and scan for related sensor or module codes to identify which systems on reference circuit B were affected at the same time.
- With the circuit active, monitor the affected sensor readings and reference voltage on a scan tool to see whether the low condition is current or intermittent.
- Inspect circuit B wiring and connectors for chafing, moisture, corrosion, loose seals, or pushed-back pins that could pull the rail low.
- Wiggle accessible sections of the harness while watching live data to see whether the reference voltage or related sensor readings change.
- Use the vehicle wiring diagram to isolate the circuit B branches and test for a short to ground, then check connector continuity and contact condition against the manufacturer's specification.
Common fixes
- Repair chafed or damaged reference-circuit wiring.
- Clean or repair corroded connectors and restore pushed-back pins.
- Repair the identified short to ground in a circuit B branch.
- Replace a sensor only if testing shows it is pulling the shared reference rail low.
Can I keep driving?
Driving may be unreliable if sensors on circuit B provide incorrect readings; the engine may enter reduced-power mode or fail to start. Avoid unnecessary driving if it runs poorly, and address the fault promptly because multiple systems can be affected.
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.