P0652Sensor Reference Voltage B Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- The engine module feeds several sensors (camshaft, pedal, pressure sensors) from separate regulated 5 V reference circuits; 'B' is circuit 2. A short at one sensor pulls the whole reference down, so every sensor on it reports at once – unplug them one by one until the reference returns to 4.8–5.2 V. P0652 means reference B is too low – usually the 5 V line or a connected sensor is shorted to ground. GM's 6.6 L Duramax LB7/LLY (2004–05) sets it below 4.7 V for 2 s; GM Europe's 2.0 L turbo after 1 s or 10 s cumulative, each with the lamp in the first trip. Newer GM engines report it under the collective code P0651, and Ford does not use P0652. All sensors on the circuit then read low, with matching codes, limp mode and possibly starting problems.
- What you may notice
- Check engine light
- Several 'low' sensor codes at once
- Limp mode or reduced power
- Starting problems
- Likely causes
- Likely5 V reference wire shorted to ground (chafing)
- LikelySensor on the reference circuit shorted internally
- PossibleMoisture or corrosion in a connector
- RareModule
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.