P2DD1: Control Pilot Charging Switch B Circuit High

What it means

The control pilot charging switch B reports a circuit high condition. SAE J1772 charging signal handshake may be compromised.

At a glance

• Usually lights the check-engine light

How it works

Control pilot charging switch B feeds a signal into the charging system's control pilot handshake circuit. P2DD1 sets when the module detects that signal above its expected range, which can indicate a wire shorted to battery voltage, an open switch, or a connection fault.

Common causes

Most likely first.

1. Wire shorted to B+
2. Switch open
3. Connector pins corroded - high contact resistance

Symptoms

• Charge status indicator shows fault
• Charging may not start or interrupts
• Slower-than-expected charge rate

How to diagnose it

1. Review freeze-frame and live switch B data during a charging attempt to confirm the signal is high when the fault sets.
2. Inspect the switch B harness for damaged insulation or contact with a power wire, and check the connector for corrosion or displaced pins.
3. With the circuit made safe according to service information, test the switch B signal wire for a short to battery voltage.
4. Check whether switch B is open when it should change state and test its contacts against the manufacturer's procedure.
5. If the switch and wiring test correctly, verify the charging controller input and connector.

Common fixes

• Repair a switch B signal wire shorted to battery voltage.
• Repair or replace corroded, loose, or displaced connector terminals.
• Replace switch B if testing confirms it is open or fails to change state.
• Repair the charging controller input only if testing isolates the fault there.

Can I keep driving?

The vehicle may still drive normally, but charging can fail or interrupt, so check that it charges reliably before depending on it for a journey. Do not probe charging circuit wiring while the system is energised.