What causes a P1235 code?

P1235 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 P1235 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1235 active.

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

OBD-II

P1235

Turbo Speed Plausibility fault

What it means

The Engine Control Module (ECM) detects that the turbocharger speed signal is inconsistent with other engine parameters like mass airflow, engine RPM, and boost pressure.