Tier 4 Interim Lamps and Operation

Most of the time, operating a Cummins Tier 4 Interim/Stage IIIB off-highway engine requires no operator action. Under certain circumstances, an operator-initiated active regeneration may be needed to clean the Diesel Particulate Filter (DPF). Indicator lamps on the instrument panel light up to show system status and alert the operator when action is needed.

HEST lampHigh Exhaust System Temperature (HEST) Lamp
Higher-than-normal exhaust temperatures may exist due to active DPF regeneration. Operator should make sure the exhaust pipe outlet is not directed at any surface or material that may become hazardous.

DPF LampDiesel Particulate Filter (DPF) Lamp
Lamp on when the DPF is starting to overfill with soot because the system is unable to undertake an automatic active regeneration. Operator should check to make sure the Regeneration Inhibit Switch is in the “Off” position, and continue working until it is convenient to perform a Stationary (parked) Regeneration.

DPF LampDiesel Particulate Filter (DPF) Lamp
When the DPF is nearly full, the DPF Lamp will start flashing. A reduction in power may be noticed. Operator should ensure that the Regeneration Inhibit Switch is off. Work may continue, but a Stationary Regeneration must be performed as soon as possible.

DPF and Check Engine LampDiesel Particulate Filter (DPF) and Check Engine Lamps
Lamps on indicate DPF is full and engine power has been significantly reduced until regeneration has occurred. Stationary Regeneration should be performed as soon as it is safe to do so.

Stop engine lampStop Engine Lamp
Lamp on indicates that continued operation could result in damage to the DPF. Shut down the engine as soon as it is safe to do so and call for service or risk damage to the DPF.


Regeneration lampRegeneration Inhibit Switch/Lamp
Pressing the Regeneration Inhibit Switch allows the operator to prevent active regeneration. Should be used only when high exhaust temperatures present a hazard. Excess use will result in need to service/replace DPF. Lamp on indicates that the Inhibit Switch is set to the “On” position.


View the Tier 4 Interim Operator Tips Card for more information [pdf, opens in new window].

DPF 3-Way Inhibit Switch

Exhaust switchAutomatic Active Regeneration Enabled
The switch remains in the standard mid-position during normal operations. This means DPF active regeneration is enabled and allows the DPF to clear any build-up of soot in the filter by initiating an active regeneration. Active regeneration is initiated automatically by a preset timer at 96-hour intervals and takes around 15 minutes to complete. No operator action is required and the equipment continues to work as normal during the active regeneration.

The HEST lamp may illuminate during active regeneration to indicate higher than normal exhaust temperatures and safety considerations apply.

Start Manual Active Regen
Pressing the switch into the top position starts a manual (parked) active regeneration. This is required on rare occasions due to very unusual duty cycle conditions. A manual (parked) active regeneration may be needed when the DPF Lamp illuminates to indicate the soot loading in the filter is increasing.

The HEST lamp may illuminate during the manual (parked) active regeneration to indicate higher than normal exhaust temperatures and safety considerations apply. The switch returns to the standard Mid-Position after pressing the Manual active regeneration.

Inhibit ON (Stop Active Regen) Function
Pressing the switch into the Bottom Position prevents active regeneration from occurring. Stopping the active regeneration function is required only for safety reasons to avoid higher than normal exhaust temperatures. When the switch is pressed the DPF Inhibit Lamp illuminates  to indicate active regeneration is disabled. The switch remains engaged in this position until pressed back to the standard mid-position to restore the automatic active regeneration function.

Active regeneration should not be left disabled for long periods of time as this results in the DPF soot loading increasing and a manual (parked) active regeneration will eventually be needed.