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P2064 — Reductantregeneration Supply Control Circuit High

Manufacturer-specificPowertrain (engine & transmission)

P2064 indicates the powertrain control module has detected higher-than-expected voltage on the electrical circuit that controls the reductant (Diesel Exhaust Fluid) supply pump or valve. This "circuit high" condition typically signals a short to power in the wiring or an internal fault within the pump assembly itself.

Symptoms

What causes it — most likely first

1. Short to voltage in control circuit wiring

The harness connecting the reductant pump to the control module has chafed or degraded, allowing the control wire to contact a voltage source and raise circuit potential above calibrated limits.

2. Faulty reductant supply pump assembly

Internal electrical failure within the DEF pump creates a short-to-power condition or incorrect resistance, causing the control circuit voltage to remain high when it should be low or pulsed.

3. Corroded or damaged electrical connectors

Moisture intrusion at the pump or control module connector causes terminal bridging or resistance changes that mimic a short-to-voltage condition on the supply control line.

4. Internal failure of tank valve/heater unit

On integrated systems, failure of the tank heater or valve assembly can feedback high voltage onto the supply control circuit through shared harness routing or internal shorts.

5. Control module output driver failure

Rarely, the powertrain or dedicated emissions control module driver circuit may fail in a high state, continuously supplying voltage rather than switching it. Consider only after wiring and component testing.

How it's diagnosed

  1. Visually inspect the wiring harness between the reductant tank and control module for chafing, melting, or exposed wires contacting voltage sources
  2. Disconnect the pump connector and measure voltage on the control circuit with a multimeter; battery voltage present when commanded off indicates a short to power
  3. Perform continuity testing between the pump control wire and known power feeds to isolate the short location in the harness versus inside the pump
  4. Measure resistance across the pump control terminals and compare to specifications; out-of-spec resistance indicates internal pump failure
  5. If no wiring or component faults are found, scope the control module output to verify it is not stuck high; replace module only if it fails to pull the circuit low when commanded

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationManufacturer-specific (P1/B1/C1/U1)
Related codesP2060 — Reductant Injection Air Pump Control CP2061 — Reductant Injection Air Pump Control CP2062 — Reductantregeneration Supply Control CP2063 — Reductantregeneration Supply Control CP2065 — Fuel Level Sensor B CircuitP2066 — Fuel Level Sensor B Performance

Frequently asked

Is it safe to drive with P2064 active?

Short trips are usually possible, but the vehicle may soon enter a reduced power mode or speed limitation to protect the SCR system; continued operation risks catalyst damage and hard starting once the DEF system depletes or locks out.

Do I need to replace the engine computer (PCM) to fix this?

Almost never. This code indicates a circuit high condition almost always caused by wiring shorts or pump failure. The control module should be the last component suspected after the wiring, connectors, and pump assembly have been thoroughly tested and ruled out.

What exactly is 'reductant'?

Reductant is Diesel Exhaust Fluid (DEF), a urea solution injected into the exhaust stream to break down nitrogen oxide emissions in the selective catalytic reduction (SCR) catalyst.

Can I just clear the code and see if it returns?

You can clear it to verify the repair, but if the underlying short or pump failure remains, the code will reset immediately or after the next drive cycle when the system performs its circuit integrity test.