P239A — Diesel intake-airflow B position-sensor circuit — intermittent/erratic signal

P239A concerns diesel intake-airflow B position-sensor circuit. The monitor reports a signal or circuit condition that is intermittent or irregular, rather than continuously valid. The monitored signal is position feedback for airflow control B. The definition does not directly report the amount of air entering the engine.

Affected system: Diesel intake-airflow control

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: P239A-00, P239A00 (some scan tools add the fault-type byte, e.g. -00).