What causes a SPN 4088 code?

SPN 4088 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a SPN 4088 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4088 active.

How do I fix SPN 4088?

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBDIY

J1939 SPN

SPN 4088

Cummins fault code 4088

What it means

Aftertreatment 1 DEF Pressure - Data Erratic, Intermittent or Incorrect. The ECM detects that the Diesel Exhaust Fluid pressure is not reaching the commanded setpoint or is fluctuating outside of normal parameters.