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P codepowertrainMedium severity

P2208NOx Sensor Heater Sense Circuit (Bank 1)

There is a general fault in the circuit the control module uses to monitor (sense) the Bank 1 NOx sensor heater's operation.

Definition

In addition to driving the NOx sensor heater, the system monitors a heater sense circuit that feeds back heater voltage or current so the module can verify the element is actually working and regulating temperature. P2208 sets when that feedback signal on Bank 1 is missing or implausible, meaning the module can no longer confirm heater performance even if the heater itself still works. The MIL illuminates and the NOx and SCR monitors will not run to completion, which causes an emissions-test rejection and can eventually affect DEF dosing accuracy on diesel applications.

Common causes

  • Internal NOx sensor fault in the heater feedback circuitry
  • Open or shorted heater sense wire in the harness
  • Corroded or loose connector terminals
  • Water intrusion into the sensor module housing
  • Control module input circuit fault (rare)

Common misdiagnoses

  • SCR catalyst
  • DEF pump or injector
  • Fuses/relays replaced repeatedly without finding the sense-circuit fault
  • Oxygen sensor

Troubleshooting steps

  1. 1.Record freeze frame and companion codes

    Heater control codes (P2205-P2207) stored alongside point to a common power or ground problem rather than the sense line alone.

  2. 2.Inspect the sense circuit wiring

    Check continuity of the heater sense wire end to end and verify it is not shorted to ground or to the heater supply.

  3. 3.Verify sensor power and ground under load

    Confirm solid battery voltage and ground at the sensor module; marginal grounds commonly corrupt the feedback signal.

  4. 4.Monitor heater feedback PIDs

    With a capable scan tool, compare commanded heater duty against reported heater current or sensor temperature; feedback frozen at zero or full scale confirms the fault.

  5. 5.Replace the NOx sensor if wiring checks pass

    The feedback circuitry lives inside the smart sensor module, so a verified-good harness means the sensor assembly is at fault.

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