P2BD6

Code

Generic P — Powertrain

Motor Electronics Coolant Pump C Control Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 25 EN: 33 RU: 32

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Page language: EN

Causes

Short to battery voltage on the pump control wire (feed to control pin).
Failed coolant pump (internal short or diode/back-EMF issue).
Faulty pump driver / power stage inside the ECU/module.
Corroded, damaged or loose connector or wiring (pin contact high resistance or intermittent short).
Poor or missing ground(s) causing abnormal circuit voltages.
Blown or incorrect fuse/relay related to the pump circuit.

Symptoms

Malfunction Indicator Lamp (MIL) or warning on instrument panel.
Coolant pump may run continuously, erratically, or not operate as commanded.
Engine overheating or poor cooling performance if pump not operating correctly.
Battery drain or parasitic draw in some conditions.
Related HVAC or thermal-management warnings on scan tool.

What to check

Retrieve freeze frame and related live data with a scan tool; note pump commands and reported voltage/PID values.
Visual inspection of pump connector, wiring harness, fuses and relays for damage, corrosion or loose pins.
Check relevant fuses and relays for proper value and operation.
Measure static battery voltage at the pump connector with ignition ON and engine OFF and with connector disconnected.
Backprobe the control pin while commanding pump ON and OFF to verify voltage response (use DVM/oscilloscope).
Inspect and test ground integrity for engine/chassis and ECU ground points.

Signal parameters

Control circuit idle (pump OFF) typically at or near battery voltage if the ECU uses a low-side switch, or near 0V if a high-side switch—refer to manufacturer wiring diagram.
When commanded ON (low-side driver architecture): control pin should drop toward 0V or show PWM waveform; expected voltage
If the ECU uses a high-side driver the inverse applies: ON ≈ battery voltage, OFF ≈ 0 V. Check vehicle-specific documentation.
PWM commands (if used) typically show a modulated waveform; frequency and duty-cycle are manufacturer specific.
Fault stored when control pin voltage is above the ECU’s allowed threshold or inconsistent with commanded state.

Diagnostic algorithm

Read and record all stored codes, freeze frame and live data. Clear codes and see if P2BD6 returns.
Visually inspect the pump, connector and harness for damage, pin contamination, or melting. Repair any obvious physical issues.
With key ON (engine OFF), backprobe the pump control pin and measure voltage. Note voltage with connector connected and disconnected.
Use a scan tool to command the pump ON/OFF while monitoring the control pin. Confirm whether the ECU is commanding correctly and whether the circuit follows the command.
If the circuit is high when it should be low (or vice versa), isolate by disconnecting the pump connector: if voltage remains high at the ECU side, suspect ECU driver fault. If voltage changes only at the pump side, suspect wiring or pump.
Measure continuity/resistance between the pump control pin and the ECU pin; check for short to B+ or short to ground. Wiggle harness while observing to check for intermittent faults.
Inspect and test related fuses/relays, and check all relevant ground points for low resistance to chassis.
If available, use an oscilloscope to verify PWM waveform characteristics (frequency, duty cycle, amplitude) and to detect transient spikes or back-EMF.
If wiring and connector are good but abnormal voltages persist on the ECU output, consider replacing the ECU/power module or sending it for repair following manufacturer procedures.
After repairs, erase codes, perform functional test and road test while monitoring pump operation and temperatures; verify code does not return.

Likely causes

Short to B+ on the control harness between ECU and pump connector.
Defective ECU output transistor or driver for Coolant Pump C.
Damaged pump connector allowing battery feed onto control pin.
Internal pump motor fault producing unexpected voltage back to the control circuit.

Fault status

⚠️ Status

Control circuit voltage for Coolant Pump C exceeds allowable threshold (Control Circuit High). Fault stored when ECU detects voltage inconsistent with commanded state. May be logged as current or pending; MIL illumination possible.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours