P20B7 — Reductant metering-unit heater control circuit — low electrical level

P20B7 concerns reductant metering-unit heater control circuit. The monitor reports an electrical level below its expected range. The monitored item is the metering-unit heater circuit. A low electrical level is not a direct measurement of reductant temperature.

Affected system: Reductant dosing and SCR aftertreatment

Symptoms

• Warning light may illuminate
• Related system function may be impaired
• Vehicle-specific symptoms vary

Possible causes

• Implausible sensor or switch signal, poor ground, connector corrosion, or wiring damage
• Related wiring, connector, power or ground fault
• Vehicle-specific mechanical or control issue

What to check

• Record stored and pending codes and freeze-frame data
• Compare the named sensor or switch signal with actual operating conditions; inspect the connector, reference supply, ground and harness.
• Confirm measured values against the vehicle service information
• Retest under the conditions that set the code
• Compare the named sensor or switch signal with actual operating conditions; inspect the connector, reference supply, ground and harness.
• Repair the verified cause and confirm the code does not return

Also written as: P20B7-00, P20B700 (some scan tools add the fault-type byte, e.g. -00).