Cummins X15 CM2450 X124B (2018 & Newer) Fault Code: 2556 PID: S70 SPN: 729 FMI: 4/4 Engine Intake Air Heater 1 Circuit – Voltage Below Normal or Shorted to Low Source

Lamp:
Amber

Reason:
Low voltage detected at the intake air heater signal circuit.

Effect:
The intake air heaters can be ON or OFF all the time.

Circuit Description:
The intake air heater improves starting and white smoke control in cold ambient conditions. The Engine Control Module (ECM) controls relays that switch power to the intake air heater. Air heaters on 12 volt systems will have two relays while 24 volt systems only require one relay.

Component Location:
The intake air heater is located at the air inlet connection to the intake manifold. The location of the intake air heater relays will vary by vehicle and engine configuration.

Conditions for Running the Diagnostics:
This diagnostic runs when the keyswitch is in the ON position and when the Pulse-Width Modulated (PWM) device is getting energized or de-energized. In some cases, the diagnostics can also run at some fixed intervals.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the intake air heater circuit Pulse-Width Modulated (PWM) signal was not system voltage when the PWM signal was on.

Action Taken When the Fault Code is Active:
1. The ECM illuminates the amber check engine lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
2. The intake air heater operation will be disabled.

Conditions for Clearing the Fault Code:
1. To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
2. The fault code status displayed by the diagnostic tool will change to inactive immediately after the diagnostic runs and passes.
3. The ECM will turn off the amber check engine lamp immediately after the diagnostic runs and passes.
4. For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after four consecutive trips where the diagnostic runs and passes.
5. The reset all faults command in the diagnostic tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk:
Possible causes of this fault code include:
1. A shorted intake air heater relay.
2. Intake air heater relay supply wire shorted to ground.