P1621

DTC P1621

CIRCUIT DESCRIPTION
This diagnostic applies to internal microprocessor integrity conditions within the engine control module (ECM).

Condition for Running the DTC
- The battery voltage is between 10-16 volts.
- The ignition switch is ON.

Condition for Setting the DTC
- The ECM detects that the calculated checksum does not agree with the ECM internal registered checksum.

Action Taken When the DTC Sets
- The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Freeze Frame/Failure Records.
- The ECM limits fuel injection quantity within 70%.
- The ECM limits fuel rail pressure within 17400 psi (120MPa).
- The ECM inhibits the cruise control.
- The ECM inhibits the PTO control.

Condition for Clearing the MIL/DTC
- The ECM turns OFF the MIL after 3 consecutive driving cycles when the diagnostic runs and does not fail. (12,000 lbs GVW)
- The ECM turns OFF the MIL when the diagnostic runs and does not fail. (Except 12,000 lbs GVW)
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic after the ECM turns OFF the MIL.
- Clear the MIL and the DTC with a scan tool.

P1621